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Source: https://theconversation.com/us/topics/astronomy-50/articles.atom

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<id>tag:theconversation.com,2011:/topics/astronomy-50/articles</id>
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<title>Astronomy – The Conversation</title>
<updated>2025-09-15T15:05:22Z</updated>
<entry>
<id>tag:theconversation.com,2011:article/255268</id>
<published>2025-09-15T15:05:22Z</published>
<updated>2025-09-15T15:05:22Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/information-collected-by-the-worlds-largest-radio-telescope-will-be-stored-and-processed-by-global-data-centres-255268"/>
<title>Information collected by the world’s largest radio telescope will be stored and processed by global data centres</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/689037/original/file-20250903-56-5b2stu.jpg?ixlib=rb-4.1.0&amp;rect=0%2C0%2C1919%2C1080&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>An artist&#39;s impression of the Square Kilometre Array telescope in South Africa.
<a class="source" href="https://skao.canto.global/v/SKAOMediaKit/album/OMQJL?display=curatedView&amp;viewIndex=0&amp;referenceTo=&amp;from=thumbnail&amp;column=image&amp;id=6vpstgj16l3n9e2r4t704o762v">(SKAO)</a></figcaption></figure><iframe src="https://audio.adauris.ai/v2/widget/RvjICRaqgSFBJozV1NoK/cWRNn9Ty6eqwkryvzWBq?distribution=true" style="width: 100%; height: 100px; border: none;" data-project-id="RvjICRaqgSFBJozV1NoK" allowfullscreen="false" allowtransparency="" allow="clipboard-read; clipboard-write" frameborder="0" id="ad-auris-iframe" scrolling="no" width="100%" height="400"></iframe>
When the Square Kilometre Array (SKA) Observatory goes <a href="https://www.skao.int/en">online later this decade</a>, it will create one of science’s biggest data challenges. The SKA Observatory is a global radio telescope project built in the Southern Hemisphere. There, views of our Milky Way are clearest and the SKA’s remote sites <a href="https://www.skao.int/en/explore/telescopes/322/telescope-sites">limit human-made radio interference</a>.
The project spans two sites: approximately 131,000 Christmas-tree-shaped antennas in western Australia and 200 large dish antennas in the Karoo region of South Africa. As part of this international collaboration, Canada has established a <a href="https://www.uvic.ca/research-innovation/office-vpri/announcements/13june24-ska.php">data-processing centre at the University of Victoria</a>.
<hr>



Read more:
<a href="https://theconversation.com/canadas-participation-in-the-worlds-largest-radio-telescope-means-new-opportunities-in-research-and-innovation-201341">Canada's participation in the world's largest radio telescope means new opportunities in research and innovation</a>



<hr>
The SKA Observatory will produce around <a href="https://alliancecan.ca/sites/default/files/2022-03/ndrio_white_paper_a_canadian_square_kilometre_array_regional_centre.pdf">600 petabytes</a> of data each year. That amount would take 200 years to download using an at-home internet connection of 100 megabytes per second. 
This data volume exceeds by a significant margin even what is produced by the <a href="https://home.cern/science/accelerators/large-hadron-collider">Large Hadron Collider</a>, often considered to be the world’s premier <a href="https://home.cern/science/computing">big data science project</a>.
<h2>Research aims</h2>
Among its many <a href="https://www.skao.int/en/explore/science-goals">science goals</a>, the SKA detects faint radio signals emitted during the <a href="https://www.colorado.edu/ness/science/cosmic-dawn">Cosmic Dawn</a>, roughly 50 million to one billion years after the Big Bang, when the very first stars and galaxies lit up the universe. 
The SKA will also test Albert Einstein’s theory of <a href="https://www.britannica.com/science/general-relativity">general relativity</a> by timing signals from pulsars (rapidly spinning neutron stars) with high accuracy. 
Another goal is understanding <a href="https://www.dunlap.utoronto.ca/observational-research/time-domain-science/fast-radio-bursts/">fast radio bursts</a> – brief, intense radio pulses from distant sources. The SKA is expected to detect fast radio bursts far more frequently than current instruments, providing a large dataset to help determine their cause, building on work done by facilities like Canada’s <a href="https://chime-experiment.ca/en">CHIME telescope</a>.
Initial data from the SKA is expected in 2027, with the start of major science operations in 2029 as the array is built and commissioned in phases.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/689977/original/file-20250909-64-32rsfb.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="an image of outer space showing the moon in the top right and dots of light throughout" src="https://images.theconversation.com/files/689977/original/file-20250909-64-32rsfb.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/689977/original/file-20250909-64-32rsfb.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=533&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/689977/original/file-20250909-64-32rsfb.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=533&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/689977/original/file-20250909-64-32rsfb.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=533&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/689977/original/file-20250909-64-32rsfb.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=670&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/689977/original/file-20250909-64-32rsfb.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=670&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/689977/original/file-20250909-64-32rsfb.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=670&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The first image from an early working version of the SKA Observatory’s SKA-Low telescope, which is currently under construction in western Australia.
<a class="source" href="https://skao.canto.global/v/SKAOMediaKit/album/P8F0I?display=curatedView&amp;viewIndex=0&amp;gSortingForward&amp;gOrderProp=name&amp;referenceTo=&amp;from=curatedView&amp;column=image&amp;id=u9u2oj88pt0mlb6vmt0nrsl10h">(SKAO)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
<h2>Canada’s role</h2>
Handling the large volume and complexity of SKA data requires a global network of specialized computing facilities, collectively known as SKA Regional Centres (SRCs). 
Canada became <a href="https://www.canada.ca/en/national-research-council/news/2024/05/canada-becomes-member-of-skao-radio-astronomy-project.html">a member of the SKA Observatory research project</a> in 2024. Shortly after joining, Canada committed to establishing one such centre. 
The Canadian SRC (CanSRC) will be the sole SRC in the Americas, serving as an important node for processing, storing and providing streamlined access to SKA data. It will allow researchers to focus on scientific analysis rather than data management hurdles.
<h2>Big Astronomy</h2>
The SKA is part of astronomy’s ongoing evolution toward “<a href="https://www.britannica.com/science/Big-Science-science">Big Science</a>,” where international collaboration becomes essential for scientific breakthroughs. This large-scale approach not only changes how science is funded, but also how it is conducted. 
While the SKA will still accommodate traditional investigator-led proposals — where individual scientists or small teams request specific telescope time and computational resources for more focused projects — most of its observing power will target ambitious, multi-year projects designed by large international teams.
Canadian researchers participate in all of the <a href="https://www.skao.int/en/science-users/science-working-groups">SKA Science Working Groups</a> and have co-chaired four of them in recent years. Canada is recognized as a world leader in <a href="https://casca.ca/wp-content/uploads/2020/04/AACS_final_Sept30.pdf">studies of pulsars, cosmic magnetism and transients</a>, as well as in low-frequency cosmology, areas where the SKA will make some of its most transformative discoveries.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/687605/original/file-20250826-56-cte44t.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="a red blotch against a grey background" src="https://images.theconversation.com/files/687605/original/file-20250826-56-cte44t.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/687605/original/file-20250826-56-cte44t.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/687605/original/file-20250826-56-cte44t.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/687605/original/file-20250826-56-cte44t.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/687605/original/file-20250826-56-cte44t.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/687605/original/file-20250826-56-cte44t.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/687605/original/file-20250826-56-cte44t.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The centre of our Milky Way galaxy as seen by MeerKAT, a South African radio telescope that will become part of the SKA.
<a class="source" href="https://www.sarao.ac.za/media-releases/new-meerkat-radio-image-reveals-complex-heart-of-the-milky-way/">(South African Radio Astronomy Observatory)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
<h2>Astronomical data management</h2>
Building, developing and managing CanSRC requires collaboration among <a href="https://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/">the National Research Council’s Canadian Astronomy Data Centre</a>, with four decades of experience in astronomical data management; the <a href="https://alliancecan.ca/en">Digital Research Alliance of Canada</a>, offering high-performance computing resources; <a href="https://www.canarie.ca/">CANARIE</a>, operating the high-speed research network for data transfer; and the University of Victoria’s <a href="https://www.uvic.ca/systems/researchcomputing/about-us/arbutus/index.php">Arbutus cloud platform</a>, supplying the scalable infrastructure.
The project leverages expertise concentrated within the <a href="https://www.uvic.ca/research/centres/arc/index.php">University of Victoria’s Astronomy Research Centre</a>, which brings together researchers from the University of Victoria, the National Research Council Herzberg Astronomy and Astrophysics Research Centre and TRIUMF, Canada’s national particle accelerator centre.
Importantly, CanSRC ensures that researchers have access to SKA data. The capabilities developed through CanSRC will strengthen Canada’s digital ecosystem for the future.
<h2>Digital discovery</h2>
CanSRC will serve as a gateway for developing and expanding the use of advanced data methods and algorithms, helping scientists from research and industry sectors harness massive datasets.
Applications of these techniques extend far beyond astronomy, with potential uses in <a href="https://public.nrao.edu/news/invisible-realms-revealed/">medical imaging</a>, remote sensing and artificial intelligence.<img src="https://counter.theconversation.com/content/255268/count.gif" alt="The Conversation" width="1" height="1" />
Falk Herwig receives funding from the National Research Council of Canada and the Natural Science and Engineering Research Council of Canada. JJ Kavelaars receives funding from the National Research Council of Canada and the Natural Science and Engineering Research Council of Canada. Sébastien Fabbro receives funding from the National Research Council of Canada and the Natural Science and Engineering Research Council of Canada.Simon Blouin does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</content>
<summary>The world’s largest space telescope, comprising thousands of antennae in the southern hemisphere, will generate massive amounts of data — some of which will be processed in Canada.</summary>
<author>
<name>Simon Blouin, Postdoctoral Fellow, Astronomy, University of Victoria</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/simon-blouin-1515474"/>
</author>
<author>
<name>Falk Herwig, Professor, Physics and Astronomy, University of Victoria</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/falk-herwig-2478128"/>
</author>
<author>
<name>JJ Kavelaars, Senior Research Officer in Astronomy, National Research Council Canada, University of Victoria</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/jj-kavelaars-420460"/>
</author>
<author>
<name>Sébastien Fabbro, Adjunct Professor, Physics and Astronomy, University of Victoria</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/sebastien-fabbro-2478129"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/264554</id>
<published>2025-09-10T16:06:57Z</published>
<updated>2025-09-10T16:06:57Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/the-discovery-of-a-gravitational-wave-10-years-ago-shook-astrophysics-these-ripples-in-spacetime-continue-to-reveal-dark-objects-in-the-cosmos-264554"/>
<title>The discovery of a gravitational wave 10 years ago shook astrophysics – these ripples in spacetime continue to reveal dark objects in the cosmos</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/689006/original/file-20250903-56-fx2iqy.jpg?ixlib=rb-4.1.0&amp;rect=0%2C0%2C7000%2C3937&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>When two massive objects – like black holes or neutron stars – merge, they warp space and time. <a class="source" href="https://www.gettyimages.com/detail/illustration/gravitational-waves-illustration-royalty-free-illustration/685026451?phrase=gravitational+waves&amp;adppopup=true">Mark Garlick/Science Photo Library</a></figcaption></figure>Scientists first detected ripples in space known as <a href="https://www.ligo.caltech.edu/page/what-are-gw">gravitational waves</a> from the <a href="https://www.ligo.caltech.edu/news/ligo20160211">merger of two black holes</a> in September 2015. This discovery marked the culmination of a 100-year quest to prove one of Einstein’s predictions.
<a href="https://theconversation.com/what-happens-when-ligo-texts-you-to-say-its-detected-one-of-einsteins-predicted-gravitational-waves-53259">Two years after this watershed moment in physics</a> came a second late-summer breakthrough in August 2017: <a href="https://www.ligo.caltech.edu/news/ligo20171016">the first detection</a> of gravitational waves accompanied by electromagnetic waves from the <a href="https://theconversation.com/ligo-announcement-vaults-astronomy-out-of-its-silent-movie-era-into-the-talkies-85727">merger of two neutron stars</a>.
Gravitational waves are exciting to scientists because they provide a completely new view of the universe. Conventional astronomy relies on electromagnetic waves – like light – but gravitational waves are an independent messenger that can emanate from objects that don’t emit light. Gravitational wave detection has unlocked the universe’s dark side, giving scientists access to phenomena never observed before. 
As a <a href="https://scholar.google.com/citations?user=33fO9GoAAAAJ&amp;hl=en">gravitational wave physicist</a> with over 20 years of research experience in the LIGO Scientific Collaboration, I have seen firsthand how these discoveries have transformed scientists’ knowledge of the universe. 
This summer, in 2025, scientists with the <a href="https://www.ligo.caltech.edu/">LIGO</a>, <a href="https://www.virgo-gw.eu/">Virgo</a> and <a href="https://gwcenter.icrr.u-tokyo.ac.jp/en/">KAGRA</a> collaboration also marked a new milestone. After a <a href="https://theconversation.com/gravitational-wave-detector-ligo-is-back-online-after-3-years-of-upgrades-how-the-worlds-most-sensitive-yardstick-reveals-secrets-of-the-universe-204339">long hiatus</a> to upgrade its equipment, this collaboration just <a href="https://www.ligo.caltech.edu/news/ligo20250826">released an updated list</a> of gravitational wave discoveries. The discoveries on this list provide researchers with an unprecedented view of the universe featuring, among other things, the <a href="https://science.psu.edu/news/LIGO_9-2025">clearest gravitational wave detection yet</a>.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/689931/original/file-20250909-56-fjf4u.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A map showing five yellow points indicating operational gravitational wave observatories: two in the US, two in Europe and one in Japan, and one orange point in India indicating a planned observatory." src="https://images.theconversation.com/files/689931/original/file-20250909-56-fjf4u.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/689931/original/file-20250909-56-fjf4u.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/689931/original/file-20250909-56-fjf4u.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/689931/original/file-20250909-56-fjf4u.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/689931/original/file-20250909-56-fjf4u.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/689931/original/file-20250909-56-fjf4u.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/689931/original/file-20250909-56-fjf4u.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The more operational gravitational-wave observatories there are around the globe, the easier it is to pin down the locations and sources of gravitational waves coming from space.
<a class="source" href="https://www.ligo.caltech.edu/image/ligo20160211c">Caltech/MIT/LIGO Lab</a>
</figcaption>
</figure>
<h2>What are gravitational waves?</h2>
Albert Einstein first predicted the existence of gravitational waves in 1916. According to Einstein’s theory of gravity, known as <a href="https://www.space.com/17661-theory-general-relativity.html">general relativity</a>, massive, dense celestial objects bend space and time. 
When these massive objects, like <a href="https://science.nasa.gov/universe/black-holes/">black holes</a> and <a href="https://www.space.com/22180-neutron-stars.html">neutron stars</a> – the end product of <a href="https://esahubble.org/wordbank/supernova/">a supernova</a> – orbit around each other, they form a binary system. The motion from this system dynamically stretches and squeezes the space around these objects, sending gravitational waves across the universe. These waves ever so slightly change the distance between other objects in the universe as they pass.
Detecting gravitational waves requires measuring distances very carefully. The LIGO, Virgo and KAGRA collaboration operates four gravitational wave observatories: <a href="https://www.ligo.caltech.edu/page/ligo-detectors">two LIGO observatories in the U.S.</a>, the <a href="https://www.virgo-gw.eu/science/detector/">Virgo observatory</a> in Italy and the <a href="https://www.symmetrymagazine.org/article/japans-kagra-searches-the-sky-for-gravitational-waves?language_content_entity=und">KAGRA observatory</a> in Japan.
Each detector has <a href="https://www.ligo.caltech.edu/page/what-is-ligo">L-shaped arms</a> that span over two miles. Each arm contains a cavity full of reflected laser light that precisely measures the distance between two mirrors.
As a gravitational wave passes, it changes the distance between the mirrors by 10-18 meters — just 0.1% of the diameter of a proton. Astronomers can measure how the mirrors oscillate to <a href="https://www.ligo.caltech.edu/page/what-is-interferometer">track the orbit of black holes</a>. 
These tiny changes in distance encode a tremendous amount of information about their source. They can tell us the masses of each black hole or neutron star, their location and whether they are spinning on their own axis.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/527294/original/file-20230519-21-zdmud0.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="An L-shaped facility with two long arms extending out from a central building." src="https://images.theconversation.com/files/527294/original/file-20230519-21-zdmud0.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/527294/original/file-20230519-21-zdmud0.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/527294/original/file-20230519-21-zdmud0.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/527294/original/file-20230519-21-zdmud0.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/527294/original/file-20230519-21-zdmud0.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/527294/original/file-20230519-21-zdmud0.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/527294/original/file-20230519-21-zdmud0.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The LIGO detector in Hanford, Wash., uses lasers to measure the minuscule stretching of space caused by a gravitational wave.
<a class="source" href="https://www.ligo.org/multimedia/gallery/lho-images/Aerial5.jpg">LIGO Laboratory</a>
</figcaption>
</figure>
<h2>A neutron star-black hole merger</h2>
As mentioned previously, the LIGO, Virgo and KAGRA collaboration recently reported <a href="https://www.ligo.caltech.edu/news/ligo20250826">128 new binary mergers</a> from data taken between May 24, 2023, and Jan. 16, 2024 – which more than doubles the previous count. 
Among these new discoveries is a <a href="https://www.ligo.caltech.edu/news/ligo20240405">neutron star–black hole merger</a>. This merger consists of a relatively light black hole with mass between 2.5 and 4.5 times the mass of our Sun paired with a neutron star that is 1.4 times the mass of our Sun. 
In this kind of system, scientists theorize that the black hole tears the neutron star apart before swallowing it, which releases electromagnetic waves. Sadly, the collaboration didn’t manage to detect any such electromagnetic waves for this particular system. 
Detecting an electromagnetic counterpart to a black hole tearing apart a neutron star is among the holy grails of astronomy and astrophysics. These electromagnetic waves will provide the rich datasets required for understanding both the extreme conditions present in matter, and extreme gravity. Scientists hope for better fortune the next time the detectors spot such a system. 
<h2>A massive binary and clear gravitational waves</h2>
In July 2025, the LIGO, Virgo and KAGRA collaboration also announced they’d found the <a href="https://www.ligo.caltech.edu/news/ligo20250715">most massive binary black hole merger</a> ever detected. The combined mass of this system is more than 200 times the mass of our Sun. And, one of the two black holes in this system likely has a mass that scientists previously assumed could not be produced from the collapse of a single star. 
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/uYncv7z9Zyc?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption>When two astrophysical objects – like black holes – merge, they send out gravitational waves.</figcaption>
</figure>
The <a href="https://doi.org/10.1103/kw5g-d732">most recent discovery</a> announced by the LIGO, Virgo and KAGRA collaboration, in September 2025, is the clearest gravitational wave observation to date. This event is a near clone of the first gravitational wave observation from 10 years ago, but because LIGO’s detectors have improved over the last decade, it stands out above the noise three times as much as the first discovery. 
Because the observed gravitational wave signal is so clear, scientists could confirm that the final black hole that formed from the merger emitted gravitational waves exactly as it should according to general relativity.
They also showed that the surface area of the final black hole was greater than the surface area of the initial black holes combined, which implies that the merger increased the entropy, <a href="https://doi.org/10.1103/PhysRevD.7.2333">according to foundational work</a> from Stephen Hawking and Jacob Bekenstein. <a href="https://www.britannica.com/science/entropy-physics">Entropy measures how disordered</a> a system is. All physical interactions are expected to increase the disorder of the universe, according to <a href="https://en.wikipedia.org/wiki/Thermodynamics">thermodynamics</a>. This recent discovery showed that black holes <a href="https://en.wikipedia.org/wiki/Black_hole_thermodynamics">obey their own laws similar to thermodynamics</a>.
<h2>The beginning of a longer legacy</h2>
The LIGO, Virgo and KAGRA collaboration’s fourth observing run is ongoing and <a href="https://observing.docs.ligo.org/plan/">will last through November</a>. My colleagues and I anticipate more than 100 additional discoveries within the coming year. 
New observations starting in 2028 may bring the tally of binary mergers to as many as 1,000 by around 2030, if the collaboration <a href="https://www.science.org/content/article/trump-s-proposed-cut-giant-physics-experiment-could-snuff-out-new-form-astronomy">keeps its funding</a>. 
Gravitational wave observation is still in its infancy. A <a href="https://dcc.ligo.org/public/0189/G2301738/003/Asharp_LVK_2023_toyama_v3.pdf">proposed upgrade to LIGO called A#</a> may increase the gravitational wave detection rate by another factor of 10. Proposed new observatories called <a href="https://cosmicexplorer.org/">Cosmic Explorer</a> and the <a href="https://www.et-gw.eu/">Einstein Telescope</a> that may be built in 10 to 20 years would increase the rate of gravitational wave detection by 1,000, relative to the current rate, by further reducing noise in the detector.<img src="https://counter.theconversation.com/content/264554/count.gif" alt="The Conversation" width="1" height="1" />
Chad Hanna receives funding from the National Science Foundation. </content>
<summary>A decade after the first discovery, scientists have used these waves to find a unique merger, a massive binary system and a crystal-clear gravitational wave signal.</summary>
<author>
<name>Chad Hanna, Professor of Physics, Penn State</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/chad-hanna-220370"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/264715</id>
<published>2025-09-09T10:06:53Z</published>
<updated>2025-09-09T10:06:53Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/a-rocky-planet-in-its-stars-habitable-zone-could-be-the-first-known-to-have-an-atmosphere-heres-what-we-found-264715"/>
<title>A rocky planet in its star’s ‘habitable zone’ could be the first known to have an atmosphere – here’s what we found</title>
<content type="html">New research using Nasa’s powerful JWST telescope has identified a planet 41 light years away which may have an atmosphere. The planet is within the <a href="https://science.nasa.gov/exoplanets/habitable-zone/">“habitable zone”</a>, the region around a star where temperatures make it possible for liquid water to exist on the surface of a rocky world. This is important because water is a key ingredient that supports the existence of life.
If confirmed by further observations, this would be the first rocky, habitable zone planet that’s also known to host an atmosphere. The findings come from two <a href="https://iopscience.iop.org/article/10.3847/2041-8213/adf42e">new</a> <a href="https://iopscience.iop.org/article/10.3847/2041-8213/adf62e">studies</a> published in the journal Astrophysical Journal Letters.
The habitable zone is partly defined by the range of temperatures generated by heat from the star. The zone is located at a distance from its star where temperatures are neither too hot nor too cold (leading to it occasionally being nicknamed “the Goldilocks zone”). 
But exoplanets (worlds orbiting stars outside our solar system) capable of hosting liquid water often also need an atmosphere with a sufficient <a href="https://www.bgs.ac.uk/discovering-geology/climate-change/how-does-the-greenhouse-effect-work/">greenhouse effect</a>. The greenhouse effect generates additional heating due to absorption and emission from gases in the atmosphere and will help prevent evaporation of water into space. 
Together with an international team of colleagues, we trained the largest telescope in space, Nasa’s <a href="https://webbtelescope.org/home">JWST</a>, on a planet called <a href="https://science.nasa.gov/exoplanet-catalog/trappist-1-e/">Trappist-1 e</a>. We wanted to determine whether this rocky world, which lies in its star’s habitable zone, hosts an atmosphere. The planet is one of <a href="https://www.nature.com/articles/nature21360">seven rocky worlds</a> known to orbit a small, cool “red dwarf” star called Trappist-1.
Rocky exoplanets are everywhere in our galaxy. The discovery of abundant rocky planets in the 2010s by the Kepler and Tess space telescopes has profound implications for our place in the Universe.
Most of the rocky exoplanets we’ve found so far orbit <a href="https://science.nasa.gov/universe/stars/types/#red-dwarfs">red dwarf stars</a>, which are much cooler than the Sun (typically 2500°C/4,500°F, compared to the Sun’s 5,600°C/10,000°F). This isn’t because planets around Sun-like stars are rare, there are just technical reasons why it is easier to find and study planets orbiting smaller stars.
Red dwarfs also offer many advantages when we seek to measure the properties of their planets. Because the stars are cooler, their habitable zones, where temperatures are favourable to liquid water, are located much closer in comparison with our solar system, because the Sun is much hotter. As such, a year for a rocky planet with the temperature of Earth that orbits a red dwarf star can be just a few days to a week compared to Earth’s 365 days.
<h2>Transit method</h2>
One way to detect exoplanets is to measure the slight dimming of light <a href="https://lco.global/spacebook/exoplanets/transit-method/">when the planet transits</a>, or passes in front of, its star. Because planets orbiting red dwarfs take less time to complete an orbit, astronomers can observe more transits in a shorter space of time, making it easier to gather data. 
During a transit, astronomers can measure absorption from gases in the planet’s atmosphere (if it has one). Absorption refers to the process whereby certain gases absorb light at different wavelengths, preventing it from passing through. This provides scientists with a way of detecting which gases are present in an atmosphere. 
Crucially, the smaller the star, the greater the fraction of its light is blocked by a planet’s atmosphere during transit. So red dwarf stars are one of the best places for us to look for the atmospheres of rocky exoplanets.
Located at a relatively close distance of 41 light years from Earth, the Trappist-1 system has attracted significant attention since its discovery in 2016. Three of the planets, Trappist-1d, Trappist-1e, and Trappist-1f (the third, fourth, and fifth planets from the star) lie within the habitable zone. 
JWST has been conducting <a href="https://physics.aps.org/articles/v15/151">a systematic search</a> for atmospheres on the Trappist-1 planets since 2022. The results for the three innermost planets, Trappist-1b, Trappist-1c and Trappist-1d, point to these worlds most likely being bare rocks with thin atmospheres at best. But the planets further out, which are bombarded with less radiation and energetic flares from the star, could still potentially possess atmospheres.
We observed Trappist-1e, the planet in the centre of the star’s habitable zone, with JWST on four separate occasions from <a href="https://iopscience.iop.org/article/10.3847/2041-8213/adf42e">June-October 2023</a>. We immediately noticed that our data was strongly affected by what’s known as “stellar contamination” from hot and cold active regions (similar to sunspots) on Trappist-1. This required a careful analysis to deal with. In the end, it took our team over a year to sift through the data and distinguish the signal coming from the star from that of the planet.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/689705/original/file-20250908-56-9dfg7q.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="" src="https://images.theconversation.com/files/689705/original/file-20250908-56-9dfg7q.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/689705/original/file-20250908-56-9dfg7q.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/689705/original/file-20250908-56-9dfg7q.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/689705/original/file-20250908-56-9dfg7q.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/689705/original/file-20250908-56-9dfg7q.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/689705/original/file-20250908-56-9dfg7q.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/689705/original/file-20250908-56-9dfg7q.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Our star-corrected JWST transmission spectrum of Trappist-1e’s atmosphere which could either be fit by the blue wiggles, suggestive of an atmospheric signal, or the orange flat line suggestive of no atmosphere at all. The white shows how these two possibilities overlap and thus the challenge to interpret our initial TRAPPIST-1e observations.
JWST
</figcaption>
</figure>
We are seeing <a href="https://iopscience.iop.org/article/10.3847/2041-8213/adf62e">two possible explanations</a> for what’s going on at Trappist-1e. The most exciting possibility is that the planet has a so-called secondary atmosphere containing heavy molecules such as nitrogen and methane. But the four observations we obtained aren’t yet precise enough to rule out the alternative explanation of the planet being a bare rock with no atmosphere.
Should Trappist-1e indeed have an atmosphere, it will be the first time we have found an atmosphere on a rocky planet in the habitable zone of another star.
Since Trappist-1e lies firmly in the habitable zone, a thick atmosphere with a sufficient greenhouse effect could allow for liquid water on the planet’s surface. To establish whether or not Trappist-1e is habitable, we will need to measure the concentrations of greenhouse gases like carbon dioxide and methane. These initial observations are an important step in that direction, but more observations with JWST will be needed to be sure if Trappist-1e has an atmosphere and, if so, to measure the concentrations of these gases.
As we speak, an additional 15 transits of Trappist-1e are underway and should be complete by the end of 2025. Our follow-up observations use a different observing strategy where we target consecutive transits of Trappist-1b (which is a bare rock) and Trappist-1e. This will allow us to use the bare rock to better “trace out” the hot and cold active regions on the star. Any excess absorption of gases seen only during Trappist-1e’s transits will be uniquely caused by the planet’s atmosphere.
So within the next two years, we should have a much better picture of how Trappist-1e compares to the rocky planets in our solar system.<img src="https://counter.theconversation.com/content/264715/count.gif" alt="The Conversation" width="1" height="1" />
Hannah Wakeford receives funding from UK Research and Innovation (UKRI) framework under the UK government’s Horizon Europe funding guarantee for an ERC Starter Grant (grant number EP/Y006313/1). Ryan MacDonald has recieved funding from NASA through the NASA Hubble Fellowship grant HST-HF2-51513.001, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555.</content>
<summary>The largest telescope in space has been trained on a rocky exoplanet.</summary>
<author>
<name>Hannah Wakeford, Associate professor, University of Bristol</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/hannah-wakeford-1480111"/>
</author>
<author>
<name>Ryan MacDonald, Lecturer in Extrasolar Planets, University of St Andrews</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/ryan-macdonald-2474916"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/262301</id>
<published>2025-08-28T12:02:24Z</published>
<updated>2025-08-28T12:02:24Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/earth-size-stars-and-alien-oceans-an-astronomer-explains-the-case-for-life-around-white-dwarfs-262301"/>
<title>Earth-size stars and alien oceans – an astronomer explains the case for life around white dwarfs</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/687815/original/file-20250827-56-6uuvu9.png?ixlib=rb-4.1.0&amp;rect=0%2C155%2C755%2C424&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>White dwarf stars, like this one shown shrouded by a planetary nebula, are much smaller than stars like our Sun. <a class="source" href="https://science.nasa.gov/missions/hubble/cocoon-of-a-new-white-dwarf/">NASA/R. Ciardullo (PSU)/H. Bond (STScI)</a></figcaption></figure>The Sun will someday die. This will happen when it runs out of hydrogen fuel in its core and can no longer produce energy <a href="https://www.energy.gov/science/doe-explainsfusion-reactions">through nuclear fusion</a> as it does now. The death of the Sun is often thought of as the end of the solar system. But in reality, it may be the beginning of a new phase of life for all the objects living in the solar system.
When stars like the Sun die, they go through a phase of rapid expansion called the <a href="https://www.space.com/22471-red-giant-stars.html">Red Giant</a> phase: The radius of the star gets bigger, and its color gets redder. Once the gravity on the star’s surface is no longer strong enough for it to hold on to its outer layers, a large fraction – up to about half – of its mass escapes into space, leaving behind a remnant called <a href="https://esahubble.org/wordbank/white-dwarf/">a white dwarf</a>.
I am a <a href="https://scholar.google.com/citations?user=n6Bo5CUAAAAJ&amp;hl=en">professor of astronomy</a> at the University of Wisconsin-Madison. In 2020, my colleagues and I <a href="https://www.nasa.gov/news-release/nasa-missions-spy-first-possible-survivor-planet-hugging-white-dwarf-star/">discovered the first intact planet</a> orbiting around a white dwarf. Since then, I’ve been fascinated by the prospect of life on planets around these, tiny, dense white dwarfs.
Researchers search for signs of life in the universe by waiting until a planet passes between a star and their telescope’s line of sight. With light from the star illuminating the planet from behind, they can use some simple physics principles <a href="https://science.nasa.gov/mission/roman-space-telescope/transit-method/">to determine</a> the types of molecules present in the planet’s atmosphere. 
<a href="https://doi.org/10.3847/2041-8213/aba9d3">In 2020, researchers realized</a> they could use this technique for planets orbiting white dwarfs. If such a planet had molecules created by living organisms in its atmosphere, the James Webb Space Telescope would probably be able to spot them when the planet passed in front of its star.
In June 2025, I <a href="https://news.wisc.edu/watery-planets-orbiting-dead-stars-may-be-good-candidates-for-studying-life-if-they-can-survive-long-enough/">published a paper</a> answering a question that first started bothering me in 2021: Could an ocean – likely needed to sustain life – even survive on a planet orbiting close to a dead star? 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/687812/original/file-20250827-56-krpnl6.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="An illustration showing a large bright circle, with a very small white dot nearby." src="https://images.theconversation.com/files/687812/original/file-20250827-56-krpnl6.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/687812/original/file-20250827-56-krpnl6.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/687812/original/file-20250827-56-krpnl6.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/687812/original/file-20250827-56-krpnl6.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/687812/original/file-20250827-56-krpnl6.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/687812/original/file-20250827-56-krpnl6.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/687812/original/file-20250827-56-krpnl6.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Despite its relatively small size, a white dwarf – shown here as a bright dot to the right of our Sun – is quite dense.
<a class="source" href="https://www.flickr.com/photos/kevinmgill/14482884687">Kevin Gill/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
<h2>A universe full of white dwarfs</h2>
A white dwarf has about half the mass of the Sun, but that mass is compressed into a volume roughly the size of Earth, with its electrons pressed as close together as the laws of physics will allow. The Sun <a href="https://www.britannica.com/topic/How-Big-Is-the-Sun">has a radius 109 times</a> the size of Earth’s – this size difference means that an Earth-like planet orbiting a white dwarf could be about the same size as the star itself. 
White dwarfs are extremely common: An estimated <a href="https://iopscience.iop.org/article/10.1088/1742-6596/172/1/012004">10 billion of them</a> exist in our galaxy. And since every low-mass star is destined to eventually become a white dwarf, countless more have yet to form. If it turns out that life can exist on planets orbiting white dwarfs, these stellar remnants could become promising and plentiful targets in the search for life beyond Earth.
But can life even exist on a planet orbiting a white dwarf? Astronomers have <a href="https://doi.org/10.1088/2041-8205/731/2/L31">known since 2011</a> that <a href="https://science.nasa.gov/exoplanets/habitable-zone/">the habitable zone</a> is extremely close to the white dwarf. This zone is the location in a planetary system where liquid water could exist on a planet’s surface. It can’t be too close to the star that the water would boil, nor so far away that it would freeze.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/687810/original/file-20250827-56-4m0x6t.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A diagram showing a sun, with three planets at varying distances away. The closest one is labeled 'too hot' the next 'just right' and the farthest 'too cold'" src="https://images.theconversation.com/files/687810/original/file-20250827-56-4m0x6t.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/687810/original/file-20250827-56-4m0x6t.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/687810/original/file-20250827-56-4m0x6t.jpeg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/687810/original/file-20250827-56-4m0x6t.jpeg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/687810/original/file-20250827-56-4m0x6t.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=566&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/687810/original/file-20250827-56-4m0x6t.jpeg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=566&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/687810/original/file-20250827-56-4m0x6t.jpeg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=566&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Planets in the habitable zone aren’t so close that their surface water would boil, but also not so far that it would freeze.
<a class="source" href="https://science.nasa.gov/exoplanets/habitable-zone/">NASA</a>
</figcaption>
</figure>
The habitable zone around a white dwarf would be <a href="https://doi.org/10.1088/2041-8205/731/2/L31">10 to 100 times closer</a> to the white dwarf than our own habitable zone is to our Sun, since white dwarfs are so much fainter.
<h2>The challenge of tidal heating</h2>
Being so close to the surface of the white dwarf would bring new challenges to emerging life that more distant planets, like Earth, do not face. One of these is tidal heating. 
<a href="https://www.esi.utexas.edu/files/078-Learning-Module-What-is-Tidal-Heating.pdf">Tidal forces</a> – the differences in gravitational forces that objects in space exert on different parts of a nearby second object – deform a planet, and the friction causes the material being deformed to heat up. An example of this can be seen on <a href="https://science.nasa.gov/jupiter/jupiter-moons/io/">Jupiter’s moon Io</a>.
The forces of gravity exerted by Jupiter’s other moons tug on Io’s orbit, deforming its interior and heating it up, resulting in hundreds of volcanoes erupting constantly across its surface. As a result, no surface water can exist on Io because its surface is too hot. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/687809/original/file-20250827-56-j5xamm.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A diagram showing Jupiter, with four Moons orbiting around it. Io is the Moon closest to Jupiter, and it has four arrows pointing to the planet and other moons, representing the forces exerted on it." src="https://images.theconversation.com/files/687809/original/file-20250827-56-j5xamm.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/687809/original/file-20250827-56-j5xamm.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=587&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/687809/original/file-20250827-56-j5xamm.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=587&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/687809/original/file-20250827-56-j5xamm.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=587&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/687809/original/file-20250827-56-j5xamm.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=738&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/687809/original/file-20250827-56-j5xamm.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=738&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/687809/original/file-20250827-56-j5xamm.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=738&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Of the four major moons of Jupiter, Io is the innermost one. Gravity from Jupiter and the other three moons pulls Io in varying directions, which heats it up.
<a class="source" href="https://en.wikipedia.org/wiki/Tidal_heating_of_Io#/media/File:Tidal_heating_on_Io.png">Lsuanli/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
In contrast, the adjacent <a href="https://science.nasa.gov/jupiter/jupiter-moons/europa/">moon Europa</a> is also subject to tidal heating, but to a lesser degree, since it’s farther from Jupiter. The heat generated from tidal forces has caused Europa’s ice shell to partially melt, resulting in a <a href="https://theconversation.com/jupiters-moons-hide-giant-subsurface-oceans-europa-clipper-is-one-of-2-missions-on-their-way-to-see-if-these-moons-could-support-life-203207">subsurface ocean</a>.
Planets in the habitable zone of a white dwarf would have orbits close enough to the star to experience tidal heating, similar to how Io and Europa are heated from their proximity to Jupiter.
This proximity itself can pose a challenge to habitability. If a system has more than one planet, tidal forces from nearby planets could cause the planet’s atmosphere to trap heat until it becomes hotter and hotter, <a href="https://doi.org/10.1089/ast.2012.0867">making the planet too hot</a> to have liquid water. 
<h2>Enduring the red giant phase</h2>
Even if there is only one planet in the system, it may not retain its water. 
In the process of becoming a white dwarf, a star will expand to 10 to 100 times its original radius during the red giant phase. During that time, anything within that expanded radius will be engulfed and destroyed. In our own solar system, Mercury, Venus and Earth will be destroyed when the Sun eventually becomes a red giant before <a href="https://doi.org/10.3847/1538-3881/abb8de">transitioning into a white dwarf</a>. 
For a planet to survive this process, it would have to start out much farther from the star — perhaps at the distance of Jupiter or even beyond.
If a planet starts out that far away, it would need to migrate inward after the white dwarf has formed in order to become habitable. <a href="https://doi.org/10.1093/mnras/stt1973">Computer simulations show</a> that <a href="https://doi.org/10.1093/mnras/stu2475">this kind of migration is possible</a>, but the process could cause <a href="https://doi.org/10.3847/2041-8213/acbe44">extreme tidal heating</a> that may boil off surface water – similar to how tidal heating causes Io’s volcanism. If the migration generates enough heat, then the planet could lose all its surface water by the time it finally reaches a habitable orbit.
However, <a href="https://doi.org/10.3847/1538-4357/ada149">if the migration occurs late enough</a> in the white dwarf’s lifetime – after it has cooled and is no longer a hot, bright, newly formed white dwarf – then surface water may not evaporate away.
Under the right conditions, planets orbiting white dwarfs could sustain liquid water and potentially support life. 
<h2>Search for life on planets orbiting white dwarfs</h2>
Astronomers haven’t yet found any Earth-like, habitable exoplanets around white dwarfs. But these planets are difficult to detect.
Traditional detection methods like the transit technique are less effective because white dwarfs are much smaller than typical planet-hosting stars. In the transit technique, astronomers watch for the dips in light that occur when a planet passes in front of its host star from our line of sight. Because white dwarfs are so small, you would have to be very lucky to see a planet passing in front of one.
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/bv2BV82J0Jk?wmode=transparent&amp;start=8" frameborder="0" allowfullscreen=""></iframe>
<figcaption>The transit technique for detecting exoplanets requires watching for the dip in brightness when a planet passes in front of its host star.</figcaption>
</figure>
Nevertheless, <a href="https://doi.org/10.1093/mnras/stac2823">researchers are exploring</a> <a href="https://doi.org/10.3847/2041-8213/ad9821">new strategies</a> to detect and characterize these elusive worlds using advanced telescopes such as the <a href="https://theconversation.com/how-the-james-webb-space-telescope-has-revealed-a-surprisingly-bright-complex-and-element-filled-early-universe-podcast-196649">Webb telescope</a>.
If habitable planets are found to exist around white dwarfs, it would significantly broaden the range of environments where life might persist, demonstrating that planetary systems may remain viable hosts for life even long after the death of their host star.<img src="https://counter.theconversation.com/content/262301/count.gif" alt="The Conversation" width="1" height="1" />
Juliette Becker does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</content>
<summary>Could tiny stars a fraction the size of our solar system’s Sun have habitable planets orbiting them? A new study says it’s possible.</summary>
<author>
<name>Juliette Becker, Assistant Professor of Astronomy, University of Wisconsin-Madison</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/juliette-becker-2445856"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/263554</id>
<published>2025-08-26T14:16:08Z</published>
<updated>2025-08-26T14:16:08Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/supernovae-a-first-of-its-kind-star-explosion-raises-new-questions-about-these-momentous-events-263554"/>
<title>Supernovae: a first-of-its-kind star explosion raises new questions about these momentous events</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/687003/original/file-20250822-56-oy1qpt.jpg?ixlib=rb-4.1.0&amp;rect=0%2C576%2C2546%2C1432&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption> Keck Observatory/Adam Makarenko</figcaption></figure>Stars often end their lives with a dazzling explosion, creating and releasing material into the universe. This will then seed new life, leading to a cosmic cycle of birth, death and rebirth.
Astronomers around the world have been studying these explosions, <a href="https://www.space.com/6638-supernova.html">called supernovae</a> (derived from the Latin “an extremely bright new star”), and have discovered tens of different types. 
In 2021, astronomers observed a bright supernova, dubbed SN2021yfj, two billion light years away. In a recent paper, <a href="https://www.nature.com/articles/s41586-025-09375-3">published in Nature</a>, astronomers observed it for more than a month and discovered that it exhibits the visible signatures of heavier elements – such as argon, silicon and sulphur – since the onset of the explosion. This was previously unobserved in any stellar explosion. 
Supernovas violently eject stellar material into the cosmos, roughly keeping the same onion structure the star had before its death. This means that lighter materials – such as hydrogen and helium – will be in the outer layers and heavier ones – such as iron, silicon and sulphur – in the inner layers. 
However, massive stars can lose part of their layers during their evolution via winds (like the Sun), great eruptions (like the star Eta Carinae), or a gravitational and energetic “tug of war” with a companion star in a binary system. When this happens, circumstellar material will form around the star and will eventually be hit by the ejected material in the explosion. 
In a galaxy, there are an enormous number of stars. If you think that there are at least two trillion observed galaxies, you can picture what a vast playground of discoveries scientists play with every day. Although not all stars end with an explosion, the proportion is large enough to allow scientists to confirm and study their shell structure and chemical composition.
The luminosity (brightness) of the new discovery in terms of timeframe and behaviour was similar to other known and well-studied stellar explosions. The chemical signatures discovered in their electromagnetic spectra (colours) and their appearance over time pointed to a thick inner stellar layer expelled by the star. 
<figure class="align-center ">
<img alt="Eta Carinae" src="https://images.theconversation.com/files/687032/original/file-20250823-56-znfnr1.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/687032/original/file-20250823-56-znfnr1.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/687032/original/file-20250823-56-znfnr1.jpeg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/687032/original/file-20250823-56-znfnr1.jpeg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/687032/original/file-20250823-56-znfnr1.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/687032/original/file-20250823-56-znfnr1.jpeg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/687032/original/file-20250823-56-znfnr1.jpeg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
Eta Carinae may become a supernova similar to the most recent explosion.
</figcaption>
</figure>
This was then struck by material left in the star and expelled during the explosion. However, some traces of light elements were also present, in direct clash with the heavy elements as they should be found in stellar layers far apart from each other.
The astronomers measured the layer velocity to be around 1,000 km/s, consistent with that of massive stars called <a href="https://astronomy.swin.edu.au/cosmos/w/wolf-rayet+star">Wolf-Rayet</a>, previously identified as progenitor stars of similar stellar explosions. They modelled both the luminosity behaviour and electromagnetic spectra composition and found the thick layer, rich in silicon and sulphur, to be more massive than that of our Sun but still less than the material ejected in the final explosion.
<h2>Heavy elements</h2>
The new discovery, the first of its kind, revealed the formation site of the heavy elements and confirmed with direct observations the complete sequence of concentric shells in massive stars. Some stars develop internal “onion-like” layers of heavier elements produced by nuclear fusion, which are called shells. The latest findings have left the astronomy community with new questions: what process can strip stars down to their inner shells? Why do we see lighter elements if the star has been stripped to the inner shells?
This new supernova type is clearly another curveball thrown by the Universe to the scientists. The energy and the layers composition cannot be explained with the current massive star evolution theory. In the framework of mass loss driven by wind (a continuous stream of particles from the star), a star stripped down to the region where heavy elements form is difficult to explain.
A possible explanation would require invoking an unusual scenario where SN2021yfi actually consists of two stars – a binary system. In this case, the stripping down of the principal star would be carried out by a strong stellar wind produced by the companion star. 
An even more exotic explanation is that SN2021yfi is an extremely massive star, up to 140 times that our Sun. Instabilities in the star would release very massive shells at different stages of its evolution. These shells would eventually collide with each other while the star collapsed into a black hole, leading to no further material released into the cosmos during the explosion. 
To improve our understanding of stellar evolution, we would need to observe more such objects. But our comprehension could be limited by their intrinsic rarity – because the possibility of finding another explosion like SN2021yfi is less than 0.00001%.<img src="https://counter.theconversation.com/content/263554/count.gif" alt="The Conversation" width="1" height="1" />
Cosimo Inserra receives funding from Foundation MERAC (Mobilising European Research in Astrophysics and Cosmology) and the Engineering and Physical Sciences Research Council (EPSRC).</content>
<summary>The bright explosion revealed its internal structure.</summary>
<author>
<name>Cosimo Inserra, Reader in Astrophysics - Associate Dean of EDI, Cardiff University</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/cosimo-inserra-2462838"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/263016</id>
<published>2025-08-22T12:27:24Z</published>
<updated>2025-08-22T12:27:24Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/the-first-stars-may-not-have-been-as-uniformly-massive-as-astronomers-thought-263016"/>
<title>The first stars may not have been as uniformly massive as astronomers thought</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/686308/original/file-20250819-56-c2tduy.jpg?ixlib=rb-4.1.0&amp;rect=0%2C210%2C1177%2C662&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>Stars form in the universe from massive clouds of gas. <a class="source" href="https://commons.wikimedia.org/wiki/File:The_star_forming_cloud_RCW_34.jpg">European Southern Observatory</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></figcaption></figure>For decades, astronomers have wondered what the very first stars in the universe were like. These stars formed new chemical elements, which enriched the universe and allowed the next generations of stars to form the first planets.
<a href="https://doi.org/10.1146/annurev-astro-071221-053453">The first stars</a> were initially composed of pure hydrogen and helium, and they were massive – hundreds to thousands of times the mass of the Sun and millions of times more luminous. Their short lives ended in <a href="https://www.space.com/6638-supernova.html">enormous explosions called supernovae</a>, so they had neither the time nor raw materials to form planets, and they should no longer exist for astronomers to observe.
At least that’s what we thought.
Two studies published in the first half of 2025 suggest that collapsing gas clouds in the early universe may have formed lower-mass stars as well. <a href="https://doi.org/10.1051/0004-6361/202555316">One study</a> uses a new astrophysical computer simulation that models turbulence within the cloud, causing fragmentation into smaller, star-forming clumps. The <a href="https://doi.org/10.3847/2041-8213/adf18d">other study</a> – an independent laboratory experiment – demonstrates how molecular hydrogen, a molecule essential for star formation, may have formed earlier and in larger abundances. The process involves a catalyst that may surprise chemistry teachers.
<a href="https://scholar.google.com/citations?hl=en&amp;user=BUAUD4YAAAAJ&amp;view_op=list_works&amp;sortby=pubdate">As an astronomer</a> who studies star and planet formation and their dependence on chemical processes, I am excited at the possibility that chemistry in the first 50 million to 100 million years after the Big Bang may have been more active than we expected.
These findings suggest that the second generation of stars – the oldest stars we can currently observe and possibly the hosts of the first planets – may have formed earlier than astronomers thought.
<h2>Primordial star formation</h2>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/L2d7joOgVLg?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption>Video illustration of the star and planet formation process. Credit: Space Telescope Science Institute.</figcaption>
</figure>
<a href="https://www.almaobservatory.org/en/about-alma/how-alma-works/capabilities/star-and-planet-formation">Stars form</a> when massive clouds of hydrogen many light years across collapse under their own gravity. The collapse continues until a luminous sphere surrounds a dense core that is hot enough to sustain nuclear fusion.
<a href="https://www.space.com/what-is-nuclear-fusion">Nuclear fusion</a> happens when two or more atoms gain enough energy to fuse together. This process creates a new element and releases an incredible amount of energy, which heats the stellar core. In the first stars, hydrogen atoms fused together to create helium.
The new star shines because its surface is hot, but the energy fueling that luminosity percolates up from its core. <a href="https://www.space.com/21640-star-luminosity-and-magnitude.html">The luminosity of a star</a> is its total energy output in the form of light. The star’s brightness is the small fraction of that luminosity that we directly observe.
This process where stars form heavier elements by nuclear fusion is called <a href="https://www.sciencedirect.com/topics/physics-and-astronomy/stellar-nucleosynthesis">stellar nucleosynthesis</a>. It continues in stars after they form <a href="https://science.nasa.gov/universe/stars">as their physical properties slowly change</a>. The more massive stars can produce heavier elements such as carbon, oxygen and nitrogen, all the way up to iron, in a sequence of fusion reactions that end in a <a href="https://www.energy.gov/science/doe-explainssupernovae">supernova explosion</a>.
Supernovae can create even heavier elements, completing the <a href="https://chandra.harvard.edu/chemistry">periodic table of elements</a>. Lower-mass stars like the Sun, with their cooler cores, can sustain fusion only up to carbon. As they exhaust the hydrogen and helium in their cores, nuclear fusion stops and the stars slowly evaporate.
<figure class="align-center ">
<img alt="Two images showing spherical illustrations. The left shows a star exploding, shooting out colorful tendrils of light and color. The right shows a cloud of gas fading away." src="https://images.theconversation.com/files/685789/original/file-20250815-86-j2zqrk.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/685789/original/file-20250815-86-j2zqrk.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/685789/original/file-20250815-86-j2zqrk.jpeg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/685789/original/file-20250815-86-j2zqrk.jpeg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/685789/original/file-20250815-86-j2zqrk.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/685789/original/file-20250815-86-j2zqrk.jpeg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/685789/original/file-20250815-86-j2zqrk.jpeg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
The remnant of a high-mass star supernova explosion imaged by the Chandra X-ray Observatory, left, and the remnant of a low-mass star evaporating in a blue bubble, right.
<a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
High-mass stars have high pressure and temperature in their cores, so they <a href="https://www.amnh.org/exhibitions/permanent/the-universe/stars/high-mass-stars">burn bright and use up their gaseous fuel quickly</a>. They last only a few million years, whereas <a href="https://www.amnh.org/exhibitions/permanent/the-universe/stars/low-mass-stars">low-mass stars</a> – those less than two times the Sun’s mass – evolve much more slowly, with lifetimes of billions or even trillions of years.
If the earliest stars were all high-mass stars, then they would have exploded long ago. But if low-mass stars also formed in the early universe, they may still <a href="https://bigthink.com/starts-with-a-bang/universe-first-stars">exist for us to observe</a>.
<h2>Chemistry that cools clouds</h2>
The first star-forming gas clouds, called protostellar clouds, were warm – <a href="https://medium.com/starts-with-a-bang/ask-ethan-how-does-the-universes-temperature-change-over-time-d756cbf74f04">roughly room temperature</a>. Warm gas has internal pressure that pushes outward against the inward force of gravity trying to collapse the cloud. A hot air balloon stays inflated by the same principle. If the flame heating the air at the base of the balloon stops, the air inside cools and the balloon begins to collapse.
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/686309/original/file-20250819-56-fthtyd.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Two bright clouds of gas condensing around a small central region" src="https://images.theconversation.com/files/686309/original/file-20250819-56-fthtyd.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=237&amp;fit=clip" srcset="https://images.theconversation.com/files/686309/original/file-20250819-56-fthtyd.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=612&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/686309/original/file-20250819-56-fthtyd.jpeg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=612&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/686309/original/file-20250819-56-fthtyd.jpeg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=612&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/686309/original/file-20250819-56-fthtyd.jpeg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=769&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/686309/original/file-20250819-56-fthtyd.jpeg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=769&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/686309/original/file-20250819-56-fthtyd.jpeg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=769&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Stars form when clouds of dust collapse inward and condense around a small, bright, dense core.
<a class="source" href="https://esawebb.org/images/weic2219a/">NASA, ESA, CSA, and STScI, J. DePasquale (STScI)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a>
</figcaption>
</figure>
Only the most massive protostellar clouds with the most gravity could overcome the thermal pressure and eventually collapse. In this scenario, the first stars were all massive.
The only way to form the lower-mass stars we see today is for the protostellar clouds to cool. Gas in space <a href="https://cosmicdawn.astro.ucla.edu/light_fills_the_universe.html">cools by radiation</a>, which transforms thermal energy into light that carries the energy out of the cloud. Hydrogen and helium atoms are not efficient radiators below several thousand degrees, but molecular hydrogen, H₂, is great at cooling gas at low temperatures.
When energized, H₂ emits infrared light, which cools the gas and lowers the internal pressure. That process would make gravitational collapse more likely in lower-mass clouds. 
For decades, astronomers have reasoned that a low abundance of H₂ early on resulted in hotter clouds whose internal pressure would be too hot to easily collapse into stars. They concluded that only clouds with enormous masses, and therefore higher gravity, would collapse – leaving more massive stars.
<h2>Helium hydride</h2>
In a <a href="https://doi.org/10.1051/0004-6361/202555316">July 2025 journal article</a>, physicist Florian Grussie and collaborators at the Max Planck Institute for Nuclear Physics demonstrated that the first molecule to form in the universe, <a href="https://www.mpg.de/13392365/first-astrophysical-detection-of-helium-hydride-ion">helium hydride</a>, HeH⁺, could have been more abundant in the early universe than previously thought. They used a computer model and conducted a laboratory experiment to verify this result.
Helium hydride? In high school science you probably learned that helium is a <a href="https://www.britannica.com/science/noble-gas">noble gas</a>, meaning it does not react with other atoms to form molecules or chemical compounds. As it turns out, it does – but only under the extremely sparse and dark <a href="https://www.acs.org/molecule-of-the-week/archive/h/helium-hydride.html">conditions of the early universe</a>, before the first stars formed.
HeH⁺ reacts with hydrogen deuteride – HD, which is one normal hydrogen atom bonded to a <a href="https://www.britannica.com/science/deuterium">heavier deuterium atom</a> – to form H₂. In the process, HeH⁺ also acts as a coolant and releases heat in the form of light. So, the high abundance of both molecular coolants earlier on may have allowed smaller clouds to cool faster and collapse to form lower-mass stars.
<h2>Gas flow also affects stellar initial masses</h2>
In another study, <a href="https://doi.org/10.3847/2041-8213/adf18d">published in July</a> 2025, astrophysicist Ke-Jung Chen led a research group at the Academia Sinica Institute of Astronomy and Astrophysics using a detailed computer simulation that modeled how gas in the early universe may have flowed. 
The team’s model demonstrated that <a href="https://www.cfa.harvard.edu/news/role-turbulence-making-massive-stars">turbulence, or irregular motion</a>, in giant collapsing gas clouds can form lower-mass cloud fragments from which lower-mass stars condense. 
The study concluded that turbulence may have allowed these early gas clouds to form stars either the same size or up to 40 times more massive than the Sun’s mass.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/686304/original/file-20250819-56-9opyt5.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A clump of small bright dots representing stars, shown near a bright spot in the center of the image." src="https://images.theconversation.com/files/686304/original/file-20250819-56-9opyt5.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/686304/original/file-20250819-56-9opyt5.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=427&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/686304/original/file-20250819-56-9opyt5.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=427&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/686304/original/file-20250819-56-9opyt5.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=427&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/686304/original/file-20250819-56-9opyt5.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=537&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/686304/original/file-20250819-56-9opyt5.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=537&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/686304/original/file-20250819-56-9opyt5.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=537&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The galaxy NGC 1140 is small and contains large amounts of primordial gas with far fewer elements heavier than hydrogen and helium than are present in our Sun. This composition makes it similar to the intensely star-forming galaxies found in the early universe. These early universe galaxies were the building blocks for large galaxies such as the Milky Way.
<a class="source" href="https://esahubble.org/images/potw1529a/">ESA/Hubble &amp; NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a>
</figcaption>
</figure>
The two new studies both predict that the first population of stars could have included low-mass stars. Now, it is up to us observational astronomers to <a href="https://www.stsci.edu/contents/news-releases/2024/news-2024-204">find them</a>. 
<a href="https://theconversation.com/astronomers-have-learned-lots-about-the-universe-but-how-do-they-study-astronomical-objects-too-distant-to-visit-214320">This is no easy task</a>. Low-mass stars have low luminosities, so they are extremely faint. Several observational studies have recently reported <a href="https://www.science.org/content/article/stars-made-only-primordial-gas-finally-spotted-astronomers-claim">possible detections</a>, but none are yet confirmed with high confidence. If they are out there, though, we will find them eventually.<img src="https://counter.theconversation.com/content/263016/count.gif" alt="The Conversation" width="1" height="1" />
Luke Keller does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</content>
<summary>Two new studies challenge scientists’ previous theories on how the very first stars in the universe formed.</summary>
<author>
<name>Luke Keller, Professor of Physics and Astronomy, Ithaca College</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/luke-keller-1470962"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/263205</id>
<published>2025-08-21T20:07:17Z</published>
<updated>2025-08-21T20:07:17Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/whats-a-black-moon-heres-why-its-worth-looking-up-at-the-sky-this-week-263205"/>
<title>What’s a ‘black moon’? Here’s why it’s worth looking up at the sky this week</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/686455/original/file-20250820-56-i3calo.jpg?ixlib=rb-4.1.0&amp;rect=492%2C403%2C2374%2C1735&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>Not a black moon. <a class="source" href="https://unsplash.com/photos/a-half-moon-is-seen-in-the-dark-sky-tPa_ypYfoCQ">Jayanth Muppaneni/Unsplash </a></figcaption></figure>There’s been a lot of <a href="https://www.space.com/stargazing/a-rare-black-moon-rises-with-the-sun-on-aug-23-2025-heres-what-to-expect">buzz online</a> about the August “black moon”, happening later this week.
While you’ve probably heard of a “blue moon” before, this might be the first time you’ve encountered its ominous-sounding counterpart.
You’re not alone. In fact, neither “blue moon” nor “black moon” are astronomical terms. They describe the moments when the lunar calendar and our calendar year fall out of alignment.
So what is a black moon? The current definition has nothing to do with the actual colour of the Moon.
<div inline-promo-placement="editor"></div>
<h2>Full moon, half moon, new moon</h2>
Let’s start by defining some key lunar terms. The Moon is “full” when its whole face or disc is illuminated by the Sun. We typically get treated to a nice, bright, full moon at night when the Sun and Moon are opposite each other with Earth in-between.
A “new” moon is when none of the Moon’s face is illuminated and the far side is illuminated instead. This happens when the Moon is up during the day, because the “far side” of the Moon is illuminated when the Moon is in-between Earth and the Sun.
<figure class="align-center ">
<img alt="A graphic showing the Sun at the top and the Earth repeated in an arc at the bottom. The Moon is at a different position next to each repeated Earth. The illumination of the Earth relative to the Sun is shown, and the corresponding Moon phase is shown at" src="https://images.theconversation.com/files/686154/original/file-20250818-56-odv6fx.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/686154/original/file-20250818-56-odv6fx.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=319&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/686154/original/file-20250818-56-odv6fx.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=319&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/686154/original/file-20250818-56-odv6fx.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=319&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/686154/original/file-20250818-56-odv6fx.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=401&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/686154/original/file-20250818-56-odv6fx.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=401&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/686154/original/file-20250818-56-odv6fx.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=401&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
Diagram showing how the phases of the Moon are caused by the position of the Moon relative to Earth and the Sun.
<a class="source" href="https://science.nasa.gov/moon/moon-phases/">NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
A lunar cycle – the time it takes for the Moon to go from new, to full, to new again – is approximately 29.5 days long. Most years there are twelve full moons and twelve new moons.
But the 29.5 day cycle doesn’t fit perfectly into a calendar year, so every now and then there are thirteen full or new moons in a calendar year. <a href="https://earthsky.org/astronomy-essentials/when-is-the-next-blue-moon/">Seven years out of every nineteen years</a> will have thirteen full or new moons instead of twelve.
<h2>Blue moon, black moon</h2>
A blue moon is when we get a thirteenth full moon in one calendar year. Conversely, a black moon is when we get a thirteenth new moon in one calendar year.
Because these terms are entirely colloquial, there are a couple of definitions used for these extra moons. One is based on seasons and the other on simple calendar months.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/686457/original/file-20250820-56-ka2mwh.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A diagram showing the Earth going around the Sun with the equinoxes and solstices marked." src="https://images.theconversation.com/files/686457/original/file-20250820-56-ka2mwh.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/686457/original/file-20250820-56-ka2mwh.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=440&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/686457/original/file-20250820-56-ka2mwh.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=440&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/686457/original/file-20250820-56-ka2mwh.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=440&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/686457/original/file-20250820-56-ka2mwh.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=553&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/686457/original/file-20250820-56-ka2mwh.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=553&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/686457/original/file-20250820-56-ka2mwh.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=553&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The four seasons of the calendar year are buffered by solstices and equinoxes.
<a class="source" href="https://media.bom.gov.au/social/blog/1762/solstices-and-equinoxes-the-reasons-for-the-seasons/">Bureau of Meteorology</a>
</figcaption>
</figure>
Seasonal moons
A calendar year has four seasons, divided by equinoxes and solstices (see above).
Each season is roughly three months long and typically has three full moons. Some cultures give each of those seasonal full moons a <a href="https://www.timeanddate.com/astronomy/moon/full-moon-names.html">special name</a> – you’ve likely heard of “wolf moon”, “strawberry moon”, “harvest moon” and <a href="https://en.wikipedia.org/wiki/Full_moon#Full_moon_names">others from American folklore</a>, for example. 
Every two or three years, however, we get an extra full moon in a season. When that happens, the first, second and fourth full moons keep their usual names while the third one becomes a “<a href="https://skyandtelescope.org/observing/celestial-objects-to-watch/once-in-a-blue-moon/">blue moon</a>”.
You’d think the idiom “once in a blue moon” comes from this name, but the folklore name is <a href="https://skyandtelescope.org/observing/what-is-a-blue-moon/">actually relatively recent</a>. In the 16th century, saying the “<a href="https://iso.mit.edu/idioms/once-in-a-blue-moon/">moon is blue</a>” was more likely a way to refer to something being false or absurd.
Meanwhile, the third new moon in a season with four new moons is a “black moon” – a term than can only be traced to <a href="https://en.wikipedia.org/wiki/Black_moon">around 2016</a>.
Calendar moons
The other definition for blue and black moons is related to calendar months.
A blue moon is the second of two full moons in one calendar month, while a black moon is the second new moon in a calendar month.
<figure class="align-center ">
<img alt="The Moon showing its craters and texture, but very dark, and a slight sliver of light runs along the lower right side of the Moon." src="https://images.theconversation.com/files/686151/original/file-20250818-56-iajk8r.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/686151/original/file-20250818-56-iajk8r.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/686151/original/file-20250818-56-iajk8r.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/686151/original/file-20250818-56-iajk8r.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/686151/original/file-20250818-56-iajk8r.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/686151/original/file-20250818-56-iajk8r.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/686151/original/file-20250818-56-iajk8r.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
A typical new moon is in shadow because the far side of the Moon is illuminated by the Sun.
<a class="source" href="https://science.nasa.gov/image-detail/amf-gsfc_20171208_archive_e000872/">Goddard Space Flight Centre</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
The black moon this month is a seasonal black moon and it’s happening on <a href="https://www.timeanddate.com/astronomy/moon/black-moon.html#:%7E:text=The%20next%20Black%20Moon%20is,in%20most%20of%20the%20world.">August 23</a>. The next calendar-month black moon will happen on <a href="https://www.space.com/34162-black-moon-guide.html">August 31 2027</a>.
The next seasonal blue moon will be on <a href="https://earthsky.org/astronomy-essentials/when-is-the-next-blue-moon/">May 20 2027</a> and the next calendar-month blue moon will be on <a href="https://earthsky.org/astronomy-essentials/when-is-the-next-blue-moon/">May 31 2026</a>.
<h2>You can’t see a black moon, but look at the sky anyway</h2>
We can’t actually see the black moon. The Moon will be up during the day and the far side of it will be illuminated.
But new moons in general bode well for keen stargazers. The <a href="https://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html">full moon</a> outshines a lot of the night sky, because it’s about <a href="https://en.wikipedia.org/wiki/Apparent_magnitude#Example:_Sun_and_Moon">33,000 times brighter</a> than the brightest star in the sky, <a href="https://www.skyatnightmagazine.com/advice/brightest-star-in-night-sky">Sirius</a>. When there’s a new moon, the night sky is nice and dark, giving you more opportunities to see stars and constellations.
During the black moon on August 23 this weekend, <a href="https://www.theguardian.com/commentisfree/2018/may/21/aboriginal-astronomy-can-teach-us-about-the-link-between-sky-and-land">the celestial emu</a> or <a href="https://theconversation.com/new-coins-celebrate-indigenous-astronomy-the-stars-and-the-dark-spaces-between-them-145923">Gugurmin</a> will be beautifully positioned overhead soon after dusk in the southern hemisphere.
If you’re in the southern hemisphere somewhere very dark and free from light pollution, you’ll be able to spot <a href="https://www.eso.org/public/images/b01/">the Magellanic Clouds</a>, two small galaxies that are interacting with our Milky Way galaxy. Saturn will be visible all night, and Venus and Jupiter will be low on the northeastern horizon just before dawn.
Even though the black moon isn’t a significant astronomical event, it gives us the chance to take in the night sky on a dark, Moon-free night.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/686454/original/file-20250820-56-sepaex.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Image of the night sky with the milky way and a trace of an emu in blue colour." src="https://images.theconversation.com/files/686454/original/file-20250820-56-sepaex.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/686454/original/file-20250820-56-sepaex.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=900&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/686454/original/file-20250820-56-sepaex.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=900&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/686454/original/file-20250820-56-sepaex.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=900&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/686454/original/file-20250820-56-sepaex.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=1131&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/686454/original/file-20250820-56-sepaex.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=1131&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/686454/original/file-20250820-56-sepaex.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=1131&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Gugurmin stretches across the vast southern sky, visible within the dark parts of the Milky Way.
<a class="source" href="https://en.wikipedia.org/wiki/Australian_Aboriginal_astronomy#/media/File:Emu_in_the_Sky_with_a_tracing_of_the_Rock_Engraving_superimposed.tif">Barnaby Norris and Ray Norris/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
<hr>



Read more:
<a href="https://theconversation.com/supermoons-are-boring-here-are-5-things-in-the-sky-worth-your-time-236416">Supermoons are boring – here are 5 things in the sky worth your time</a>



<hr>
<img src="https://counter.theconversation.com/content/263205/count.gif" alt="The Conversation" width="1" height="1" />
Laura Nicole Driessen is an ambassador for the Orbit Centre of Imagination at the Rise and Shine Kindergarten, in Sydney&#39;s Inner West.</content>
<summary>The Moon will indeed be black, kind of. But that’s not why you should look up this weekend.</summary>
<author>
<name>Laura Nicole Driessen, Postdoctoral Researcher in Radio Astronomy, University of Sydney</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/laura-nicole-driessen-892965"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/263339</id>
<published>2025-08-20T20:14:44Z</published>
<updated>2025-08-20T20:14:44Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/astronomers-have-glimpsed-the-core-of-a-dying-star-confirming-theories-of-how-atoms-are-made-263339"/>
<title>Astronomers have glimpsed the core of a dying star – confirming theories of how atoms are made</title>
<content type="html">Astronomers have glimpsed the inner structure of a dying star in a rare kind of cosmic explosion called an “extremely stripped supernova”.
In a paper <a href="https://doi.org/10.1038/s41586-025-09375-3">published today in Nature</a>, Steve Schulze of Northwestern University in the United States and colleagues describe the supernova 2021yfj and a thick shell of gas surrounding it.
Their findings support our existing theories of what happens inside massive stars at the end of their lives – and how they have shaped the building blocks of the universe we see today.
<div inline-promo-placement="editor"></div>
<h2>How stars make the elements</h2>
Stars are powered by nuclear fusion – a process in which lighter atoms are squished together into heavier ones, releasing energy. 
Fusion <a href="https://iopscience.iop.org/article/10.1086/341728">happens in stages</a> over the star’s life. In a series of cycles, first hydrogen (the lightest element) is fused into helium, followed by the formation of heavier elements such as carbon. The most massive stars continue on to neon, oxygen, silicon and finally iron.
Each burning cycle is faster than the previous one. The hydrogen cycle can last for millions of years, while the silicon cycle is over in a matter of days.
As the core of a massive star keeps burning, the gas outside the core acquires a layered structure, where successive layers record the composition of the progression of burning cycles.
While all this is playing out in the star’s core, the star is also shedding gas from its surface, carried out into space by the stellar wind. Each fusion cycle creates an expanding shell of gas containing a different mix of elements.
<h2>Core collapse</h2>
What happens to a massive star <a href="https://www.google.com.au/books/edition/Progress_in_Understanding_Iron_Peak_Elem/6fHGwQEACAAJ?hl=en">when its core is full of iron</a>? The great pressure and temperature will make the iron fuse, but unlike the fusion of lighter elements, this process absorbs energy instead of releasing it.
The release of energy from fusion is what has been holding the star up against the force of gravity – so now the iron core will collapse. Depending on how big it is to start with, the collapsed core will become a neutron star or a black hole.
The process of collapse creates a “bounce”, which sends energy and matter flying outwards. This is called a core-collapse supernova explosion.
The explosion lights up the layers of gas shed from the star earlier, allowing us to see what they are made of. In all known supernovae until now, this material was either the hydrogen, the helium or the carbon layer, produced in the first two nuclear burning cycles.
The inner layers (the neon, oxygen and silicon layers) are all produced in a mere few hundred years before the star explodes, which means they don’t have time to travel out far from the star.
<h2>An explosive mystery</h2>
But that’s what makes the new supernova SN2021yfj so interesting. Schulze and colleagues found the material outside the star came from the silicon layer, the last layer just above the iron core, which forms on a timescale of a few months. 
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/wdAQAfePT84?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
The stellar wind must have expelled all the layers right down to the silicon one before the explosion occurred. Astronomers don’t understand how a stellar wind could be powerful enough to do this.
The most plausible scenario is a second star was involved. If another star were orbiting the one that exploded, its gravity might have rapidly pulled out the deep silicon layer. 
<h2>Exploding stars made the universe what it is today</h2>
Whatever the explanation, this view deep inside the star has confirmed our theories of the cycles of nuclear fusion inside massive stars.
Why is this important? Because stars are where all the elements come from.
Carbon and nitrogen are manufactured primarily by lower mass stars, similar to our own Sun. Some <a href="https://theconversation.com/cosmic-alchemy-colliding-neutron-stars-show-us-how-the-universe-creates-gold-86104">heavy elements such as gold</a> are manufactured in the exotic environments of colliding and merging neutron stars. 
However, oxygen and other elements such as neon, magnesium and sulfur mainly come from core-collapse supernovae.
We are what we are because of the inner workings of stars. The constant production of elements in stars causes the universe to change continuously. Stars and planets formed later are very different from those formed in earlier times. 
When the universe was younger it had much less in the way of “interesting” elements. Everything worked somewhat differently: stars burned hotter and faster and planets may have formed less, differently, or not at all.
How much supernovae explode and just what they eject into interstellar space is a critical question in figuring out why our Universe and our world are the way they are.<img src="https://counter.theconversation.com/content/263339/count.gif" alt="The Conversation" width="1" height="1" />
Orsola De Marco received funding from the Australian Research Council. She is affiliated (non-executive director of the Board) with Astronomy Australia Ltd. a not-for-profit company serving Australian astronomy.</content>
<summary>An ‘extremely stripped supernova’ confirms the existence of a key feature of physicists’ models of how stars produce the elements that make up the Universe.</summary>
<author>
<name>Orsola De Marco, Professor of Astrophysics, Macquarie University</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/orsola-de-marco-821522"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/262509</id>
<published>2025-08-07T18:15:00Z</published>
<updated>2025-08-07T18:15:00Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/move-over-mercury-chiron-is-in-retrograde-what-even-is-chiron-262509"/>
<title>Move over Mercury – Chiron is in retrograde. What even is Chiron?</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/684385/original/file-20250806-56-ned5kg.png?ixlib=rb-4.1.0&amp;rect=0%2C816%2C7200%2C4050&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>An artist&#39;s impression of Chiron and its coma of gas. <a class="source" href="https://www.ucf.edu/news/uncovering-a-centaurs-tracks-ucf-scientists-examine-unique-asteroid-comet-hybrid/">William Gonzalez Sierra / UCF</a></figcaption></figure>You might have seen an interesting phrase popping up in your social media feeds lately: “Chiron is in retrograde.” If you’re anything like me, you’ve never heard of Chiron before – and I’m a professional astronomer.
So what is Chiron, and what does it mean to be in retrograde? The short answer is that Chiron is an asteroid-slash-comet orbiting somewhere past Jupiter and Saturn. And until January 2026, it’s going to look like it’s going backwards in the sky. If you can spot it.
But there’s a bit more to the story.
<h2>What is Chiron?</h2>
Chiron’s official name is <a href="https://ui.adsabs.harvard.edu/abs/1979IAUS...81..245K">(2060) Chiron</a>. First things first: it’s pronounced “kai-ruhn”, with a hard K sound. 
It was <a href="https://nssdc.gsfc.nasa.gov/planetary/factsheet/chironfact.html">discovered</a> by astronomer <a href="https://en.wikipedia.org/wiki/Charles_T._Kowal">Charles Kowal</a> in 1977. This was long after the system of <a href="https://www.worldhistory.org/Western_Astrology/">Western astrology</a> was developed, which probably explains why people who check their daily horoscopes are also blissfully unaware of its existence. 
It was <a href="https://www.britannica.com/topic/Chiron-astronomy">initially classified as an asteroid</a>, or a rock in space. <a href="https://ui.adsabs.harvard.edu/abs/1989BAAS...21..933M/abstract">In 1989 astronomers discovered</a> Chiron sometimes has a tail or “coma”, which tells us that it’s actually a comet or a “dirty snowball”. Since then, Chiron has been classified as both an asteroid and a comet.
<figure class="align-center ">
<img alt="A black background with a fuzzy, white blob in the centre." src="https://images.theconversation.com/files/683932/original/file-20250805-62-bwgz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/683932/original/file-20250805-62-bwgz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/683932/original/file-20250805-62-bwgz.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/683932/original/file-20250805-62-bwgz.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/683932/original/file-20250805-62-bwgz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/683932/original/file-20250805-62-bwgz.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/683932/original/file-20250805-62-bwgz.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
Hubble Space Telescope image of Chiron showing its fuzzy coma.
<a class="source" href="https://commons.wikimedia.org/wiki/File:2060_Chiron.jpg">Hubble Space Telescope/Karen Meech</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
In 2023, more than 45 years after it was first discovered, astronomers confirmed Chiron has rings. This makes it <a href="https://www.aanda.org/articles/aa/full_html/2023/08/aa47025-23/aa47025-23.html#S8">the fourth non-planet</a> in the Solar System to have rings. (The planets <a href="https://www.eso.org/public/news/eso1410/">Jupiter, Saturn, Uranus and Neptune have rings</a>, as do the asteroid Chariklo and the dwarf planets Haumea and Quaoar.) 
<figure class="align-center ">
<img alt="A rocky asteroid is in the foreground and a bright fuzzy dot representing the Sun is in the background. The asteroid has two narrow rings around it. The background is black and full of stars." src="https://images.theconversation.com/files/683933/original/file-20250805-62-4im9ub.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/683933/original/file-20250805-62-4im9ub.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=359&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/683933/original/file-20250805-62-4im9ub.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=359&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/683933/original/file-20250805-62-4im9ub.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=359&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/683933/original/file-20250805-62-4im9ub.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=452&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/683933/original/file-20250805-62-4im9ub.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=452&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/683933/original/file-20250805-62-4im9ub.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=452&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
Artist’s impression of the Centaur asteroid 10199 Chariklo. Chariklo was the first asteroid and fifth object in our Solar System, after Saturn, Jupiter, Uranus and Neptune, found to have a ring around it.
<a class="source" href="https://webbtelescope.org/contents/media/images/01GQJ8WWVBWDQV4P05Y74FVZRH">NASA, ESA, CSA, Leah Hustak (STScI)</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
Chiron orbits the Sun in an oval-shaped orbit. The closest it gets to the Sun is about 1.3 billion kilometres (about eight times the distance between Earth and the Sun) and the furthest it gets from the Sun is a whopping 2.7 billion km (about 19 times the distance between Earth and the Sun). 
This puts it between the orbits of Jupiter and Uranus, cutting through the orbit of Saturn.
<h2>Centaurs in space</h2>
Chiron is a member of the Centaurs. This is a group of small Solar System bodies that orbit the Sun <a href="https://astronomy.swin.edu.au/cosmos/*/Centaurs">between Jupiter and Neptune</a>. Their orbits are highly unstable: they change over time because of gravitational interactions with the giant planets. 
In Greek mythology, centaurs were creatures with the lower body and legs of a horse and the torso and arms of a human. <a href="https://www.theoi.com/Georgikos/KentaurosKheiron.html">Chiron was the oldest centaur</a>, the son of the Titan Kronos. He was considered the wisest centaur. 
Fans of <a href="https://rickriordan.com/series/percy-jackson-and-the-olympians/">Percy Jackson and the Olympians</a> may also recognise Chiron as the director of Camp Halfblood.
<figure class="align-center ">
<img alt="A black background with multiple colourful circles and ovals demonstrating the orbits of planets and small solar system bodies in orbits outside Jupiter’s orbit. The many overlapping circles demonstrate how many objects there are out there in a bunch of d" src="https://images.theconversation.com/files/683935/original/file-20250805-62-w0gniz.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/683935/original/file-20250805-62-w0gniz.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=560&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/683935/original/file-20250805-62-w0gniz.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=560&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/683935/original/file-20250805-62-w0gniz.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=560&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/683935/original/file-20250805-62-w0gniz.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=704&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/683935/original/file-20250805-62-w0gniz.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=704&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/683935/original/file-20250805-62-w0gniz.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=704&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
The orbits of various centaurs, including Chiron. We can see the orbits of Jupiter, Saturn, Uranus and Neptune as well of the orbits of various Small Solar System bodies and dwarf planets.
<a class="source" href="https://centaurs.space/2021/03/16/centaur-asbolus-burning-clarity/">Nick Anthony Fiorenza</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
<h2>Chiron in retrograde</h2>
In astronomy, retrograde motion is when something is going backwards compared with everything else. 
<a href="https://theconversation.com/people-are-complaining-about-mercury-in-retrograde-but-what-does-it-actually-mean-205032">Apparent retrograde motion</a> is where an object in the sky, such as a planet, appears to be going backwards when we look at it from Earth. The object hasn’t actually changed direction; it just looks like it from our perspective. 
All the planets (and Chiron) orbit the Sun in the same direction. This means the planets typically look like they are moving in a west-to-east direction across the sky. But when Earth “catches” up to a planet (or a planet catches up to Earth) and overtakes it, the planet temporarily appears to move in a west-to-east direction in the sky.
This temporary illusion is apparent retrograde motion. It’s just like when you’re driving in a car and overtake a slower car, that slower car looks like it’s going backwards as you overtake it.
<figure class="align-center ">
<img alt="Black and white animation demonstrating retrograde motion. On the left are two concentric circles with the Sun as a dot in the centre. The Earth orbits the Sun by orbiting on the inner circle. A planet orbits the Sun by orbiting on the outer circle. A lin" src="https://images.theconversation.com/files/683937/original/file-20250805-72-91c2ws.gif?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/683937/original/file-20250805-72-91c2ws.gif?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=404&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/683937/original/file-20250805-72-91c2ws.gif?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=404&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/683937/original/file-20250805-72-91c2ws.gif?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=404&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/683937/original/file-20250805-72-91c2ws.gif?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=507&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/683937/original/file-20250805-72-91c2ws.gif?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=507&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/683937/original/file-20250805-72-91c2ws.gif?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=507&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
Animation demonstrating apparent retrograde motion. We can see the Earth and an outer planet orbiting the Sun in a circular motion on the left. On the right, we can see the direction the planet appears to be moving from Earth’s perspective.
<a class="source" href="https://in-the-sky.org/article.php?term=retrograde_motion">Dominic Ford</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
Chiron went into retrograde (that is, apparent retrograde motion) on July 30 2025 and will go back to normal on January 2 2026. But unless you have a telescope or do some long-exposure photography, you’d never know which way Chiron is travelling. Chiron is very faint, so you can’t see it with your eyes.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/684393/original/file-20250807-56-scif2o.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Painting of a centaur teaching a boy to play the lyre." src="https://images.theconversation.com/files/684393/original/file-20250807-56-scif2o.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/684393/original/file-20250807-56-scif2o.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=596&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/684393/original/file-20250807-56-scif2o.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=596&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/684393/original/file-20250807-56-scif2o.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=596&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/684393/original/file-20250807-56-scif2o.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=749&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/684393/original/file-20250807-56-scif2o.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=749&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/684393/original/file-20250807-56-scif2o.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=749&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
An ancient Roman fresco showing the centaur Chyron teaching Achilles to play the lyre.
<a class="source" href="https://commons.wikimedia.org/wiki/File:Achilleus_Lyra.jpg">National Archaeological Museum of Naples / Muesse / Wikimedia</a>
</figcaption>
</figure>
The ancient astrologers didn’t know about Chiron, but I like to think they’d appreciate a centaur in space with a ring on it.<img src="https://counter.theconversation.com/content/262509/count.gif" alt="The Conversation" width="1" height="1" />
Laura Nicole Driessen is an ambassador for the Orbit Centre of Imagination at the Rise and Shine Kindergarten, in Sydney&#39;s Inner West.</content>
<summary>If you’re like most people, you’ve never heard of it. Meet the ringed asteroid-comet hybrid prowling the outer reaches of the Solar System.</summary>
<author>
<name>Laura Nicole Driessen, Postdoctoral Researcher in Radio Astronomy, University of Sydney</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/laura-nicole-driessen-892965"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/259362</id>
<published>2025-08-04T12:41:26Z</published>
<updated>2025-08-04T12:41:26Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/2-spacecraft-flew-exactly-in-line-to-imitate-a-solar-eclipse-capture-a-stunning-image-and-test-new-tech-259362"/>
<title>2 spacecraft flew exactly in line to imitate a solar eclipse, capture a stunning image and test new tech</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/681866/original/file-20250723-56-tfxo3a.png?ixlib=rb-4.1.0&amp;rect=0%2C448%2C2048%2C1152&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>The solar corona, as viewed by Proba-3&#39;s ASPIICS coronagraph. <a class="source" href="https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Proba-3_s_first_artificial_solar_eclipse">ESA/Proba-3/ASPIICS/WOW algorithm</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></figcaption></figure>During a solar eclipse, astronomers who study heliophysics are able to study the Sun’s corona – its outer atmosphere – in ways they are unable to do at any other time.
The brightest part of the Sun is so bright that it blocks the faint light from the corona, so it is invisible to most of the instruments astronomers use. The exception is when the <a href="https://theconversation.com/solar-eclipses-result-from-a-fantastic-celestial-coincidence-of-scale-and-distance-224113">Moon blocks the Sun, casting a shadow on the Earth</a> during an eclipse. But <a href="https://scholar.google.com/citations?user=uThRO-cAAAAJ&amp;hl=en">as an astronomer</a>, I know eclipses are rare, they last only a few minutes, and they are visible only on narrow paths across the Earth. So, researchers have to work hard to get their equipment to the right place to capture these short, infrequent events.
In their quest to learn more about the Sun, scientists at the European Space Agency have built and launched a new probe designed specifically to <a href="https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Proba_Missions/Proba-3_Mission3">create artificial eclipses</a>. 
<h2>Meet Proba-3</h2>
This probe, <a href="https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Proba-3_s_first_artificial_solar_eclipse">called Proba-3</a>, works just like a real solar eclipse. One spacecraft, which is roughly circular when viewed from the front, orbits closer to the Sun, and its job is to block the bright parts of the Sun, acting as the Moon would in a real eclipse. It casts a shadow on a second probe that has a camera capable of photographing the resulting artificial eclipse.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/681944/original/file-20250724-56-7dc45t.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="An illustration of two spacecraft, one which is spherical and moves in front of the Sun, another that is box-shaped facing the Sun." src="https://images.theconversation.com/files/681944/original/file-20250724-56-7dc45t.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/681944/original/file-20250724-56-7dc45t.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=424&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/681944/original/file-20250724-56-7dc45t.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=424&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/681944/original/file-20250724-56-7dc45t.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=424&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/681944/original/file-20250724-56-7dc45t.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=533&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/681944/original/file-20250724-56-7dc45t.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=533&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/681944/original/file-20250724-56-7dc45t.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=533&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The two spacecraft of Proba-3 fly in precise formation about 492 feet (150 meters) apart.
<a class="source" href="https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Proba-3_s_first_artificial_solar_eclipse">ESA-P. Carril</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a>
</figcaption>
</figure>
Having two separate spacecraft flying independently but in such a way that one casts a shadow on the other is a challenging task. But future missions depend on scientists figuring out how to make this precision choreography technology work, and so <a href="https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Proba-3">Proba-3 is a test</a>. 
This technology is helping to pave the way for future missions that could include satellites that dock with and deorbit dead satellites or powerful telescopes with instruments located far from their main mirrors.
The side benefit is that researchers get to practice by taking important scientific photos of the Sun’s corona, allowing them to learn more about the Sun at the same time. 
<h2>An immense challenge</h2>
The two satellites launched in 2024 and <a href="https://www.esa.int/ESA_Multimedia/Images/2024/11/Proba-3_infographic_Orbit_and_ground_control">entered orbits</a> that approach Earth as close as 372 miles (600 kilometers) – that’s about 50% farther from Earth than the International Space Station – and reach more than 37,282 miles (60,000 km) at their most distant point, about one-sixth of the way to the Moon. 
During this orbit, the satellites move at speeds between 5,400 miles per hour (8,690 kilometers per hour) and 79,200 mph (127,460 kph). At their slowest, they’re still moving fast enough to go from New York City to Philadelphia in one minute. 
While flying at that speed, they can control themselves automatically, without a human guiding them, and fly 492 feet (150 meters) apart – a separation that is longer than the length of a typical football stadium – while still keeping their locations aligned to about one millimeter. 
They needed to maintain that precise flying pattern for hours in order to take a picture of the Sun’s corona, and <a href="https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Proba-3_s_first_artificial_solar_eclipse">they did it in June 2025</a>. 
The Proba-3 mission is also studying space weather by observing high-energy particles that the Sun ejects out into space, sometimes in the direction of the Earth. <a href="https://theconversation.com/are-the-northern-lights-caused-by-particles-from-the-sun-not-exactly-174019">Space weather causes</a> the aurora, also known as the northern lights, on Earth.
While the aurora is beautiful, solar storms can also <a href="https://theconversation.com/solar-storms-can-destroy-satellites-with-ease-a-space-weather-expert-explains-the-science-177510">harm Earth-orbiting satellites</a>. The hope is that Proba-3 will help scientists continue learning about the Sun and <a href="https://theconversation.com/space-weather-forecasting-needs-an-upgrade-to-protect-future-artemis-astronauts-224921">better predict dangerous space weather events</a> in time to protect sensitive satellites.<img src="https://counter.theconversation.com/content/259362/count.gif" alt="The Conversation" width="1" height="1" />
Christopher Palma does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</content>
<summary>This solar eclipse was created by 2 satellites flying in formation, allowing astronomers to photograph the Sun’s corona.</summary>
<author>
<name>Christopher Palma, Teaching Professor of Astronomy & Astrophysics, Penn State</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/christopher-palma-314031"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/260387</id>
<published>2025-07-29T12:42:47Z</published>
<updated>2025-07-29T12:42:47Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/light-pollution-is-encroaching-on-observatories-around-the-globe-making-it-harder-for-astronomers-to-study-the-cosmos-260387"/>
<title>Light pollution is encroaching on observatories around the globe – making it harder for astronomers to study the cosmos</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/681284/original/file-20250721-56-7bam7y.jpg?ixlib=rb-4.1.0&amp;rect=0%2C331%2C6343%2C3568&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>Light pollution from human activity can threaten radio astronomy – and people&#39;s view of the night sky. <a class="source" href="https://www.gettyimages.com/detail/photo/escullos-royalty-free-image/1449527468?phrase=dark%2Bsky">Estellez/iStock via Getty Images</a></figcaption></figure>Outdoor lighting for buildings, roads and advertising can help people see in the dark of night, but many astronomers are growing increasingly concerned that these lights could be blinding us to the rest of the universe.
An <a href="https://theconversation.com/night-skies-are-getting-9-6-brighter-every-year-as-light-pollution-erases-stars-for-everyone-199383">estimate from 2023</a> showed that the rate of human-produced light is increasing in the night sky by <a href="https://doi.org/10.1126/science.abq7781">as much as 10% per year</a>. 
<a href="https://astro.arizona.edu/person/richard-green">I’m an astronomer</a> who has chaired a <a href="https://iau.org/CommissionB7/CommissionB7/Home.aspx">standing commission on astronomical site protection</a> for the International Astronomical Union-sponsored <a href="https://zenodo.org/records/5874725">working groups</a> studying <a href="https://iau.org/CommissionB7/CommissionB7/Home.aspx">ground-based light pollution</a>.
My work with these groups has centered around the idea that lights from human activities are now affecting astronomical observatories on what used to be <a href="https://doi.org/10.1007/s00159-021-00138-3">distant mountaintops</a>.
<figure class="align-center ">
<img alt="A map of North America showing light pollution, with almost all the eastern part of the U.S. covered from Maine to North Dakota, and hot spots on the West Coast." src="https://images.theconversation.com/files/126207/original/image-20160610-29238-1xv0gpe.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/126207/original/image-20160610-29238-1xv0gpe.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=599&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/126207/original/image-20160610-29238-1xv0gpe.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=599&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/126207/original/image-20160610-29238-1xv0gpe.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=599&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/126207/original/image-20160610-29238-1xv0gpe.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=753&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/126207/original/image-20160610-29238-1xv0gpe.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=753&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/126207/original/image-20160610-29238-1xv0gpe.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=753&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
Map of North America’s artificial sky brightness, as a ratio to the natural sky brightness.
<a class="source" href="http://advances.sciencemag.org/content/2/6/e1600377.figures-only">Falchi et al., Science Advances (2016)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a>
</figcaption>
</figure>
<h2>Hot science in the cold, dark night</h2>
While orbiting telescopes like the <a href="https://theconversation.com/how-the-hubble-space-telescope-opened-our-eyes-to-the-first-galaxies-of-the-universe-133877">Hubble Space Telescope</a> or the <a href="https://theconversation.com/how-the-james-webb-space-telescope-has-revealed-a-surprisingly-bright-complex-and-element-filled-early-universe-podcast-196649">James Webb Space Telescope</a> give researchers a unique view of the cosmos – particularly because they can see light blocked by the Earth’s atmosphere – ground-based telescopes also continue to drive cutting-edge discovery.
Telescopes on the ground capture light with gigantic and precise focusing mirrors that can be 20 to 35 feet (6 to 10 meters) wide. Moving all astronomical observations to space to escape light pollution would not be possible, because space missions have a much greater cost and so many large ground-based telescopes are already in operation or under construction.
Around the world, there are <a href="https://viveikjha.medium.com/eyes-on-the-sky-current-and-upcoming-telescopes-of-this-decade-464b84515936">17 ground-based telescopes</a> with primary mirrors as big or bigger than Webb’s 20-foot (6-meter) mirror, and three more under construction with mirrors planned to span 80 to 130 feet (24 to 40 meters).
The newest telescope starting its scientific mission right now, the <a href="https://rubinobservatory.org/">Vera Rubin Observatory</a> in Chile, has a mirror with a 28-foot diameter and a 3-gigapixel camera. One of its missions is to map the <a href="https://theconversation.com/the-vera-c-rubin-observatory-will-help-astronomers-investigate-dark-matter-continuing-the-legacy-of-its-pioneering-namesake-259233">distribution of dark matter</a> in the universe.
To do that, it will collect a sample of 2.6 billion galaxies. The typical galaxy in that sample is 100 times fainter than the natural glow in the nighttime air in the Earth’s atmosphere, so this Rubin Observatory program depends on near-total natural darkness. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/510413/original/file-20230215-28-33uihp.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Two pictures of the constellation Orion, with one showing many times more stars." src="https://images.theconversation.com/files/510413/original/file-20230215-28-33uihp.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/510413/original/file-20230215-28-33uihp.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=440&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/510413/original/file-20230215-28-33uihp.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=440&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/510413/original/file-20230215-28-33uihp.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=440&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/510413/original/file-20230215-28-33uihp.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=553&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/510413/original/file-20230215-28-33uihp.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=553&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/510413/original/file-20230215-28-33uihp.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=553&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The more light pollution there is, the fewer stars a person can see when looking at the same part of the night sky. The image on the left depicts the constellation Orion in a dark sky, while the image on the right is taken near the city of Orem, Utah, a city of about 100,000 people.
<a class="source" href="https://www.flickr.com/photos/79297308@N00/3180280752">jpstanley/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
Any light scattered at night – road lighting, building illumination, billboards – would add glare and noise to the scene, greatly reducing the number of galaxies Rubin can reliably measure in the same time, or greatly increasing the total exposure time required to get the same result.
<h2>The LED revolution</h2>
Astronomers care specifically about artificial light in the blue-green range of the <a href="https://www.britannica.com/science/electromagnetic-spectrum">electromagnetic spectrum</a>, as that used to be the darkest part of the night sky. A decade ago, the most common outdoor lighting was from <a href="https://streets.mn/2015/06/14/the-street-lights-of-the-freeways/">sodium vapor discharge lamps</a>. They produced an orange-pink glow, which meant that they put out very little blue and green light.
Even observatories relatively close to growing urban areas had skies that were naturally dark in the blue and green part of the spectrum, enabling all kinds of new observations.
Then came the solid-state LED lighting revolution. Those lights put out a broad rainbow of color with very high efficiency – meaning they produce lots of light per watt of electricity. The earliest versions of LEDs put out a large fraction of their energy in the blue and green, but advancing technology now gets the same efficiency with “warmer” lights that have <a href="https://doi.org/10.1007/s00159-021-00138-3">much less blue and green</a>.
Nevertheless, the formerly pristine darkness of the night sky now has much more light, particularly in the blue and green, from LEDs in cities and towns, lighting roads, public spaces and advertising.
The broad output of color from LEDs affects the whole spectrum, from ultraviolet through deep red.
The U.S. Department of Energy commissioned a study in 2019 which predicted that the higher energy efficiency of LEDs would mean that the amount of power used for lights at night <a href="https://www.energy.gov/sites/prod/files/2019/12/f69/2019_ssl-energy-savings-forecast.pdf">would go down</a>, with the amount of light emitted staying roughly the same. 
But satellites looking down at the Earth reveal that just isn’t the case. The amount of light is <a href="https://www.energy.gov/sites/prod/files/2019/12/f69/2019_ssl-energy-savings-forecast.pdf">going steadily up</a>, meaning that cities and businesses were willing to keep their electricity bills about the same as energy efficiency improved, and just get more light.
<h2>Natural darkness in retreat</h2>
As human activity spreads out over time, many of the remote areas that host observatories are becoming less remote. Light domes from large urban areas slightly brighten the dark sky at mountaintop observatories up to 200 miles (320 kilometers) away. When these urban areas are adjacent to an observatory, the addition to the skyglow is much stronger, making detection of the faintest galaxies and stars that much harder. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/681277/original/file-20250721-93-slsw16.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A white-domed building on a hilltop among trees." src="https://images.theconversation.com/files/681277/original/file-20250721-93-slsw16.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/681277/original/file-20250721-93-slsw16.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/681277/original/file-20250721-93-slsw16.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/681277/original/file-20250721-93-slsw16.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/681277/original/file-20250721-93-slsw16.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=566&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/681277/original/file-20250721-93-slsw16.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=566&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/681277/original/file-20250721-93-slsw16.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=566&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The Mt. Wilson Observatory in the Angeles National Forest may look remote, but urban sprawl from Los Angeles means that it is much closer to dense human activity today than it was when it was established in 1904.
<a class="source" href="https://www.flickr.com/photos/usdagov/15294182948">USDA/USFS</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
When the <a href="https://www.mtwilson.edu/history/">Mt. Wilson Observatory</a> was constructed in the Angeles National Forest near Pasadena, California, in the early 1900s, it was a very dark site, considerably far from the 500,000 people living in Greater Los Angeles. Today, 18.6 million people live in the LA area, and urban sprawl has brought civilization much closer to Mt. Wilson. 
When <a href="https://kpno.noirlab.edu/about/">Kitt Peak National Observatory</a> was first under construction in the late 1950s, it was far from metro Tucson, Arizona, with its population of 230,000. Today, that area houses 1 million people, and Kitt Peak faces much more light pollution.
Even telescopes in darker, more secluded regions – like northern Chile or western Texas – experience light pollution from industrial activities like open-pit mining or oil and gas facilities.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/681278/original/file-20250721-79-18xc8d.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A set of buildings atop a mountain in the desert." src="https://images.theconversation.com/files/681278/original/file-20250721-79-18xc8d.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/681278/original/file-20250721-79-18xc8d.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=399&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/681278/original/file-20250721-79-18xc8d.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=399&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/681278/original/file-20250721-79-18xc8d.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=399&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/681278/original/file-20250721-79-18xc8d.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=501&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/681278/original/file-20250721-79-18xc8d.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=501&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/681278/original/file-20250721-79-18xc8d.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=501&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
European Southern Observatory’s Very Large Telescope at the Paranal site in the sparsely populated Atacama Desert in northern Chile.
<a class="source" href="https://www.eso.org/public/images/eso-paranal-51/">J.L. Dauvergne &amp; G. Hüdepohl/ESO</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a>
</figcaption>
</figure>
<h2>The case of the European Southern Observatory</h2>
An interesting modern challenge is facing the <a href="https://www.eso.org/public/">European Southern Observatory</a>, which operates <a href="https://www.eso.org/public/teles-instr/">four of the world’s largest optical telescopes</a>. Their site in northern Chile is very remote, and it is nominally covered by strict national regulations protecting the dark sky. 
AES Chile, an energy provider with strong U.S. investor backing, <a href="https://www.eso.org/public/news/eso2506/">announced a plan in December 2024</a> for the development of a large industrial plant and transport hub close to the observatory. The plant would produce <a href="https://www.aesandes.com/en/press-release/aes-andes-submits-environmental-impact-assessment-project-inna">liquid hydrogen and ammonia for green energy</a>.
Even though formally compliant with the national lighting norm, the fully built operation could scatter enough artificial light into the night sky to turn the current observatory’s pristine darkness into a state similar to some of the legacy observatories now near large urban areas. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/681281/original/file-20250721-56-1hrxqa.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A map showing two industrial sites, one large, marked on a map of Chile. Just a few miles to the north are three telescope sites." src="https://images.theconversation.com/files/681281/original/file-20250721-56-1hrxqa.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/681281/original/file-20250721-56-1hrxqa.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=358&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/681281/original/file-20250721-56-1hrxqa.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=358&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/681281/original/file-20250721-56-1hrxqa.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=358&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/681281/original/file-20250721-56-1hrxqa.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=450&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/681281/original/file-20250721-56-1hrxqa.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=450&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/681281/original/file-20250721-56-1hrxqa.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=450&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The location of AES Chile’s planned project in relation to the European Southern Observatory’s telescope sites.
<a class="source" href="https://www.eso.org/public/images/INNA-map-EN/">European Southern Observatory</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a>
</figcaption>
</figure>
This light pollution could mean the facility won’t have the same ability to detect and measure the faintest galaxies and stars. 
Light pollution doesn’t only affect observatories. Today, <a href="https://doi.org/10.1126/sciadv.1600377">around 80% of the world’s population</a> cannot see the Milky Way at night. Some Asian cities are so bright that the eyes of people walking outdoors cannot become visually dark-adapted. 
In 2009, <a href="https://www.starlight2007.net/iauresolutionb5.html">the International Astronomical Union declared</a> that there is a universal right to starlight. The dark night sky belongs to all people – its awe-inspiring beauty is something that you don’t have to be an astronomer to appreciate.<img src="https://counter.theconversation.com/content/260387/count.gif" alt="The Conversation" width="1" height="1" />
Richard Green is affiliated with the International Astronomical Union and the American Astronomical Society, as well as DarkSky International. </content>
<summary>Some observatories that used to be dark and remote are now adjacent to bright urban centers. And sending all telescopes into space isn’t a viable solution.</summary>
<author>
<name>Richard Green, Astronomer Emeritus, Steward Observatory, University of Arizona</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/richard-green-2351627"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/261784</id>
<published>2025-07-29T11:57:49Z</published>
<updated>2025-07-29T11:57:49Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/the-hunt-for-planet-nine-why-there-could-still-be-something-massive-at-the-edge-of-the-solar-system-261784"/>
<title>The hunt for ‘planet nine’: why there could still be something massive at the edge of the Solar System</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/682137/original/file-20250724-56-c9ifyl.jpg?ixlib=rb-4.1.0&amp;rect=0%2C174%2C2291%2C1683&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>The Sun&#39;s gravitational pull extends more than 160 times further into space than Neptune. <a class="source" href="https://www.shutterstock.com/image-photo/solar-corona-during-total-eclipse-on-628148945">Vadim Petrakov</a></figcaption></figure>Is there a massive undiscovered planet on the outer reaches of the Solar System? The idea has been around since before the discovery of Pluto in the 1930s. Labelled as planet X, prominent astronomers had put it forward as an explanation for Uranus’s orbit, which drifts from the path of orbital motion that physics would expect it to follow. The gravitational pull of an undiscovered planet, several times larger than Earth, was seen as a possible reason for the discrepancy.
That mystery was ultimately explained by a recalculation of Neptune’s mass in the 1990s, but then a <a href="https://science.nasa.gov/solar-system/planet-x/">new theory</a> of a potential planet nine was put forward in 2016 by astronomers Konstantin Batygin and Mike Brown at Caltech (the California Institute of Technology). 
Their theory relates to the Kuiper Belt, a giant belt of dwarf planets, asteroids and other matter that lies beyond Neptune (and includes Pluto). Many Kuiper Belt objects – also referred to as trans-Neptunian objects – <a href="https://www.space.com/16144-kuiper-belt-objects.html">have been discovered</a> orbiting the Sun, but like Uranus they don’t do so in a <a href="https://www.space.com/astronomy/solar-system/evidence-of-controversial-planet-9-uncovered-in-sky-surveys-taken-23-years-apart">continuous expected direction</a>. Batygin and Brown argued that something with a large gravitational pull must be affecting their orbit, and proposed planet nine as a potential explanation.
This would be comparable to what happens with our own Moon. It orbits the Sun every 365.25 days, in line with what you would expect in view of their distance apart. However, the Earth’s gravitational pull is such that the Moon also orbits the planet every 27 days. From the point of view of an outside observer, the Moon moves in a spiralling motion as a result. Similarly, many objects in the Kuiper Belt show signs of their orbits being affected by more than just the Sun’s gravity.
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ZVnDoaT35dY?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
While astronomers and space scientists were initially sceptical about the planet nine theory, there has been <a href="https://earthsky.org/space/review-paper-physics-reports-planet-9-feb-2019/">mounting evidence</a> thanks to increasingly powerful observations that the orbits of trans-Neptunian objects are indeed erratic. As Brown <a href="https://www.newsweek.com/planet-nine-solar-system-evidence-scientists-1894718">said in 2024</a>:
<blockquote>
I think it is very unlikely that P9 does not exist. There are currently no other explanations for the effects that we see, nor for the myriad other P9-induced effects we see on the Solar System.
</blockquote>
In 2018, for example, it was announced that there was a new candidate for a dwarf planet orbiting the Sun, known as <a href="https://arxiv.org/abs/2505.15806">2017 OF201</a>. This object measures around 700km across (Earth is roughly 18x bigger) and has a highly elliptical orbit. This lack of a <a href="https://theskylive.com/2017of201-info">roughly circular orbit</a> around the Sun suggested either an impact early in its lifetime that put it on this path, or gravitational influence from planet nine.
<h2>Problems with the theory</h2>
On the other hand, if planet nine exists, why hasn’t anyone found it yet? Some astronomers question whether there’s <a href="https://www.universetoday.com/articles/maybe-the-elusive-planet-9-doesnt-exist-after-all">enough orbital data</a> from Kuiper objects to justify any conclusions about its existence, while alternative explanations get put forward for their motion, such as the effect of a <a href="https://gizmodo.com/is-the-elusive-planet-nine-actually-a-massive-ring-of-d-1831961723">ring of debris</a> or the more fantastical idea of a <a href="https://phys.org/news/2019-09-planet-primodial-black-hole.html">small black hole</a>.
The biggest issue, however, is that the outer Solar System just hasn’t been observed for long enough. For example, object 2017 OF201 has an orbital period of about 24,000 years. While an object’s orbital path around the Sun can be found in a short number of years, any gravitational effects probably need four to five orbits to notice any subtle changes.
New discoveries of objects in the Kuiper Belt have also presented challenges for the planet nine theory. <a href="https://www.nature.com/articles/s41550-025-02595-7">The latest</a> is known as <a href="https://www.skyatnightmagazine.com/news/ammonite-2023-kq14">2023 KQ14</a>, an object discovered by the <a href="https://subarutelescope.org/en/">Subaru telescope</a> in Hawaii.
It is known as a “sednoid”, meaning it spends most of its time far away from the Sun, though within the vast area in which the Sun has a gravitational pull (this area lies some 5,000AU or astronomical units away, where 1AU is the distance from the Earth to the Sun). The object’s classification as a sednoid also means the gravitational influence of Neptune has little to no effect on it.
2023 KQ14’s closest approach to the Sun is around 71AU away, while its furthest point is about 433AU. By comparison, Neptune is about 30AU away from the Sun. This new object is another with a very elliptical orbit, but it is stabler than 2017 OF201, which suggests that no large planet, including a hypothetical planet nine, is significantly affecting its path. If planet nine exists, it would therefore perhaps have to be farther than 500AU away from the Sun.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/682141/original/file-20250724-66-2asulw.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Solar System representation showing the Kuiper Belt" src="https://images.theconversation.com/files/682141/original/file-20250724-66-2asulw.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/682141/original/file-20250724-66-2asulw.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=594&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/682141/original/file-20250724-66-2asulw.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=594&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/682141/original/file-20250724-66-2asulw.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=594&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/682141/original/file-20250724-66-2asulw.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=747&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/682141/original/file-20250724-66-2asulw.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=747&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/682141/original/file-20250724-66-2asulw.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=747&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The band of green objects beyond Neptune is the Kuiper Belt.
<a class="source" href="https://en.wikipedia.org/wiki/Kuiper_belt#/media/File:Outersolarsystem_objectpositions_labels_comp.png">Wikimedia</a>
</figcaption>
</figure>
To make matters worse for the planet nine theory, this is the fourth sednoid to be discovered. The <a href="https://en.wikipedia.org/wiki/541132_Lele%C4%81k%C5%ABhonua">other three</a> also <a href="https://en.wikipedia.org/wiki/2012_VP113">exhibit</a> stable <a href="https://en.wikipedia.org/wiki/Sedna_(dwarf_planet)">orbits</a>, similarly suggesting that any planet nine would have to be very far away indeed. 
Nonetheless, the possibility remains there could still be a massive planet affecting the orbits of bodies within the Kuiper Belt. But astronomers’ ability to find any such planet remains somewhat limited by the restrictions of even unmanned space travel. It would take 118 years for a spacecraft to travel far enough away to find it, based on estimates from the speed of <a href="https://science.nasa.gov/mission/new-horizons/">Nasa’s New Horizons</a> explorer. 
This means we’ll have to continue to rely on ground- and space-based telescopes to detect anything. New asteroids and distant objects are being discovered all the time as our observing capabilities become more detailed, which should gradually shed more light on what might be out there. So watch this (very big) space, and let’s see what emerges in the coming years. 
<hr>
Get your news from actual experts, straight to your inbox. <a href="https://tcnv.link/tcukdaily">Sign up to our daily newsletter</a> to receive all The Conversation UK’s latest coverage of news and research, from politics and business to the arts and sciences.<img src="https://counter.theconversation.com/content/261784/count.gif" alt="The Conversation" width="1" height="1" />
Ian Whittaker does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</content>
<summary>The debate about an undiscovered planet X or planet 9 has been going on for more than 100 years.</summary>
<author>
<name>Ian Whittaker, Senior Lecturer in Physics, Nottingham Trent University</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/ian-whittaker-425597"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/259171</id>
<published>2025-07-24T12:46:14Z</published>
<updated>2025-07-24T12:46:14Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/an-ultra-black-coating-for-satellites-could-stop-them-spoiling-astronomy-pictures-259171"/>
<title>An ultra-black coating for satellites could stop them spoiling astronomy pictures</title>
<content type="html">Every night, as telescopes around the world open their domes to study the cosmos, astronomers are forced to contend with an unexpected form of pollution: <a href="https://skyandtelescope.org/astronomy-news/satellite-trails-mar-hubble-images/">bright white streaks</a> slicing across their images. 
These luminous trails are caused by satellites. Specifically, the growing number of “megaconstellations” launched into low Earth orbit (LEO). These mega-constellations consist of many, sometimes hundreds, of satellites. They are intended to work as a system, providing services such as global internet access. Commercial companies that operate mega-constellations include SpaceX, Amazon and OneWeb.
The streaks in astronomy images aren’t just cosmetic. They can corrupt sensitive astronomy data, generate false signals, and even trigger alerts for events that never happened.
There may now be a partial solution to the luminous trails vexing astronomers. An ultra-black coating could be applied to the satellites themselves, dimming the trails that they leave in images. This material, called <a href="https://www.surrey.ac.uk/news/surrey-nanosystems-and-university-surrey-partner-combat-satellite-reflectivity-and-protect-astronomy">Vantablack 310</a>, absorbs more than 99.99% of visible light.
Modern astronomical observations rely on long exposure imaging, collecting faint light from distant galaxies, exoplanets, or supernovae over several minutes or hours. When a satellite crosses the field of view during that time, it reflects sunlight into the telescope, creating a saturated streak across the image.
The impact is already substantial. Researchers at the <a href="https://rubinobservatory.org/">Vera C Rubin Observatory</a> in Chile – a flagship survey telescope set to revolutionise our understanding of the Universe – estimate that over 30% of the telescope’s twilight images already contain at least one satellite trail. And it’s not only visible light astronomy that’s at risk. 
Radio telescopes, infrared detectors, and even gravitational wave observatories are reporting increasing interference from satellites – including reflected light, unwanted radio emissions, and other forms of contamination. The ultra-black coating won’t alleviate these issues, of course. Other solutions will need to be found for these other forms of interference.
<hr>



Read more:
<a href="https://theconversation.com/could-the-first-images-from-the-vera-rubin-telescope-change-how-we-view-space-for-good-259857">Could the first images from the Vera Rubin telescope change how we view space for good?</a>



<hr>
<h2>A crowded sky</h2>
With more than <a href="https://www.weforum.org/stories/2017/09/why-the-new-space-race-should-focus-on-sustainability/">16,000 active satellites</a> already in orbit and tens of thousands more planned, the skies are becoming increasingly congested. While these constellations offer enormous benefits, including global internet access, disaster response, agricultural monitoring, and climate surveillance, they also threaten the clarity of astronomical observations. 
Satellites in low Earth orbit (typically 500km-600km altitude) are often visible to the naked eye shortly after sunset or before sunrise. For sensitive telescopes, they can be ten to 100 times brighter than the recommended limits set by the International Astronomical Union.
I am one of a team of researchers at the University of Surrey that is exploring Vantablack 310 as a next generation coating to reduce satellite brightness. The trials are being carried out by UK scientists in partnership with the Surrey Space Centre, and materials innovators Surrey NanoSystems.
Originally developed for high-contrast optical systems – such as instruments that need to spot faint signals next to very bright ones – the coating absorbs more than 99.99% of visible light.
<figure class="align-center ">
<img alt="Very black car surrounded by spotlights" src="https://images.theconversation.com/files/682056/original/file-20250724-56-qjhwum.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/682056/original/file-20250724-56-qjhwum.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/682056/original/file-20250724-56-qjhwum.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/682056/original/file-20250724-56-qjhwum.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/682056/original/file-20250724-56-qjhwum.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/682056/original/file-20250724-56-qjhwum.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/682056/original/file-20250724-56-qjhwum.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
Vantablack has been demonstrated on on a BMW concept car.
<a class="source" href="https://www.shutterstock.com/image-photo/frankfurt-germany-sep-10-2019-new-1502425991">Vanderwolf Images/Shutterstock</a>
</figcaption>
</figure>
In 2026, Vantablack 310 will be tested in orbit for the first time aboard <a href="https://www.surrey.ac.uk/news/universities-launch-pioneering-space-programme-boost-uk-skills-and-graduate-opportunities">Jovian 1</a>, a CubeSat – a small satellite about the size of a cereal box. It was developed at the University of Surrey and launched as part of the UK’s Jupiter programme, a university-led initiative that trains students in real-world satellite design, testing and operations, while supporting cutting-edge space research.
The mission will assess how the coating performs under the harsh conditions in space, such as temperature swings, ultraviolet radiation, and micro-meteoroid impacts. If successful, it could significantly reduce how bright satellites appear to telescopes – making the streaks they leave behind much fainter and easier to remove from astronomical images. 
Ultra-black coatings will not make satellites invisible. Even the darkest object in orbit will reflect some light. But the goal is not invisibility – it is compatibility. Reducing satellite brightness below key thresholds ensures that scientific observations remain viable.
What’s at stake is more than just clean astronomical data. The night sky is one of humanity’s oldest shared resources – a source of scientific insight, cultural heritage, and spiritual meaning across time and geography. From the star lore of indigenous people to ancient navigation systems, the night sky has always helped us understand our place in the universe.
Publicly funded observatories in lower income countries – where many of the world’s darkest skies still exist – are also disproportionately affected, despite those countries having little say in the decisions that affect their skies.
Framing the issue solely as a technical inconvenience for elite institutions misses the point. This is also about equity, access, and environmental justice. Who gets to access the sky, and who decides how it is altered, are global questions that demand inclusive solutions.
<hr>
Get your news from actual experts, straight to your inbox. <a href="https://tcnv.link/tcukdaily">Sign up to our daily newsletter</a> to receive all The Conversation UK’s latest coverage of news and research, from politics and business to the arts and sciences.<img src="https://counter.theconversation.com/content/259171/count.gif" alt="The Conversation" width="1" height="1" />
This project was funded with six months of support from the Research England Development Fund (UKRI), focusing on mitigating satellite light pollution, including the in-orbit testing of ultra-black coatings.
</content>
<summary>Streaks from satellites are disrupting observations by professional and amateur astronomers.</summary>
<author>
<name>Noelia Noël, Senior Lecturer, School of Mathematics and Physics, University of Surrey</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/noelia-noel-2408204"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/258314</id>
<published>2025-07-24T00:46:12Z</published>
<updated>2025-07-24T00:46:12Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/swirling-nebula-of-two-dying-stars-revealed-in-spectacular-detail-in-new-webb-telescope-image-258314"/>
<title>Swirling nebula of two dying stars revealed in spectacular detail in new Webb telescope image</title>
<content type="html">The day before my thesis examination, my friend and radio astronomer <a href="https://www.astron.nl/%7Ecallingham/">Joe Callingham</a> showed me <a href="https://www.eso.org/public/news/eso1838/">an image</a> we’d been awaiting for five long years – an infrared photo of two dying stars we’d requested from the <a href="https://en.wikipedia.org/wiki/Very_Large_Telescope">Very Large Telescope</a> in Chile.
I gasped – the stars were wreathed in a huge spiral of dust, like a snake eating its own tail.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/681656/original/file-20250723-56-pvart2.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="An orange swirl on a black background with a blue dot in the middle." src="https://images.theconversation.com/files/681656/original/file-20250723-56-pvart2.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/681656/original/file-20250723-56-pvart2.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/681656/original/file-20250723-56-pvart2.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/681656/original/file-20250723-56-pvart2.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/681656/original/file-20250723-56-pvart2.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/681656/original/file-20250723-56-pvart2.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/681656/original/file-20250723-56-pvart2.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The coils of Apep as captured by the European Space Observatory’s Very Large Telescope.
<a class="source" href="https://www.eso.org/public/images/eso1838a/">ESO/Callingham et al.</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
We named it <a href="https://en.wikipedia.org/wiki/Apophis">Apep</a>, for the Egyptian serpent god of destruction. Now, our team has finally been lucky to use NASA’s James Webb Space Telescope (JWST) to look at Apep.
If anything could top the first shock of seeing its beautiful spiral nebula, it’s this breathtaking new image, with the JWST data now analysed in <a href="https://arxiv.org/abs/2507.14498">two</a> <a href="https://arxiv.org/abs/2507.14610">papers</a> on arXiv. 
<h2>Violent star deaths</h2>
Right before they die as supernovae, the universe’s most massive stars violently shed their outer hydrogen layers, leaving their heavy cores exposed.
These are called <a href="https://www.annualreviews.org/content/journals/10.1146/annurev.astro.45.051806.110615">Wolf-Rayet stars</a> after their discoverers, who noticed powerful streams of gas blasting out from these objects, much stronger than the stellar wind from our Sun. The Wolf-Rayet stage lasts only millennia – a blink of the eye in cosmic time scales – before they violently explode.
Unlike our Sun, <a href="https://science.nasa.gov/universe/stars/multiple-star-systems/">many stars in the universe</a> exist in pairs known as binaries. This is especially true of the most massive stars, such as Wolf-Rayets.
When the fierce gales from a Wolf-Rayet star clash with their weaker companion’s wind, they compress each other. In the eye of this storm forms a dense, cool environment in which the carbon-rich winds can condense into dust. The earliest carbon dust in the cosmos – the first of the material making up our own bodies – was made this way. 
The dust from the Wolf-Rayet is blown out in almost a straight line, and the orbital motion of the stars wraps it into a <a href="https://en.wikipedia.org/wiki/Wolf%E2%80%93Rayet_nebula">spiral-shaped nebula</a>, appearing exactly like water from a sprinkler when viewed from above.
We expected Apep to look like one of these elegant pinwheel nebulas, <a href="https://ui.adsabs.harvard.edu/abs/1999Natur.398..487T/abstract">discovered</a> by our colleague and co-author <a href="https://www.physics.usyd.edu.au/%7Egekko/wr104.html">Peter Tuthill</a>. To our surprise, it did not.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/681684/original/file-20250723-56-uot9wj.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A black backfground with a swirling red spiral in the centre that brightens to an orange globe." src="https://images.theconversation.com/files/681684/original/file-20250723-56-uot9wj.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/681684/original/file-20250723-56-uot9wj.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=369&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/681684/original/file-20250723-56-uot9wj.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=369&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/681684/original/file-20250723-56-uot9wj.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=369&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/681684/original/file-20250723-56-uot9wj.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=463&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/681684/original/file-20250723-56-uot9wj.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=463&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/681684/original/file-20250723-56-uot9wj.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=463&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The ‘pinwheel’ nebula of the triple Wolf-Rayet star system WR104.
<a class="source" href="https://www.physics.usyd.edu.au/~gekko/pinwheel.html">Peter Tuthill</a>
</figcaption>
</figure>
<h2>Equal rivals</h2>
The new image was taken using <a href="https://jwst-docs.stsci.edu/jwst-mid-infrared-instrument">JWST’s infrared camera</a>, like the <a href="https://en.wikipedia.org/wiki/Thermography">thermal cameras</a> used by hunters or the military. It represents hot material as blue, and colder material in green through to red. 
It turns out Apep isn’t just one powerful star blasting a weaker companion, but two Wolf-Rayet stars. The rivals have near-equal strength winds, and the dust is spread out in a very wide <a href="https://en.wikipedia.org/wiki/Mach_wave">cone</a> and wrapped into a wind-sock shape.
When we <a href="https://www.nature.com/articles/s41550-018-0617-7">originally described Apep in 2018</a>, we noted a third, more distant star, speculating whether it was also part of the system or a chance interloper along the line of sight.
The dust appeared to be moving much slower than the winds, which was hard to explain. We suggested the dust might be carried on a slow, thick wind from the equator of a fast-spinning star, rare today but common in the early universe.
The new, much more detailed data from JWST reveals three more dust shells zooming farther out, each cooler and fainter than the last and spaced perfectly evenly, against a background of swirling dust. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/681945/original/file-20250724-56-6ownej.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Three shells of dust, looking like coiled snakes, the middle one yellow and the outer ones red against a background of blue stars." src="https://images.theconversation.com/files/681945/original/file-20250724-56-6ownej.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/681945/original/file-20250724-56-6ownej.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=472&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/681945/original/file-20250724-56-6ownej.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=472&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/681945/original/file-20250724-56-6ownej.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=472&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/681945/original/file-20250724-56-6ownej.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=593&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/681945/original/file-20250724-56-6ownej.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=593&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/681945/original/file-20250724-56-6ownej.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=593&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The Apep nebula in false colour, displaying infrared data from JWST’s MIRI camera.
Han et al./White et al./Dholakia; NASA/ESA
</figcaption>
</figure>
<h2>New data, new knowledge</h2>
The JWST data are now published and interpreted in a pair of papers, one <a href="https://arxiv.org/abs/2507.14498">led by Caltech astronomer Yinuo Han</a>, and the other by <a href="https://arxiv.org/abs/2507.14610">Macquarie University Masters student Ryan White</a>.
<a href="https://arxiv.org/abs/2507.14498">Han’s paper</a> reveals how the nebula’s dust cools, links the background dust to the foreground stars, and suggests the stars are farther away from Earth than we thought. This implies they are extraordinarily bright, but weakens our original claim about the slow winds and rapid rotation. 
In <a href="https://arxiv.org/abs/2507.14610">White’s paper</a>, he develops a fast computer model for the shape of the nebula, and uses this to decode the orbit of the inner stars very precisely.
He also noticed there’s a “bite” taken out out of the dust shells, exactly where the wind of the third star would be chewing into them. This proves the Apep family isn’t just a pair of twins – they have a third sibling.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/681696/original/file-20250723-66-tm6man.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="" src="https://images.theconversation.com/files/681696/original/file-20250723-66-tm6man.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/681696/original/file-20250723-66-tm6man.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=596&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/681696/original/file-20250723-66-tm6man.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=596&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/681696/original/file-20250723-66-tm6man.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=596&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/681696/original/file-20250723-66-tm6man.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=750&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/681696/original/file-20250723-66-tm6man.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=750&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/681696/original/file-20250723-66-tm6man.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=750&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
An illustration of the cavity carved by the third star companion in the Apep system.
<a class="source" href="https://arxiv.org/abs/2507.14610">White et al. (2025)</a>
</figcaption>
</figure>
Understanding systems like Apep tells us more about star deaths and the origins of carbon dust, but <a href="https://iopscience.iop.org/article/10.3847/1538-4357/addf30">these systems</a> also have a fascinating beauty that emerges from their seemingly simple geometry.
The violence of stellar death carves puzzles that would make sense to Newton and Archimedes, and it is a scientific joy to solve them and share them.<img src="https://counter.theconversation.com/content/258314/count.gif" alt="The Conversation" width="1" height="1" />
Benjamin Pope receives funding from the Australian Research Council and the Big Questions Institute. </content>
<summary>The stars are wreathed in a huge spiral of dust, like a snake eating its own tail.</summary>
<author>
<name>Benjamin Pope, Associate Professor, School of Mathematical and Physical Sciences, Macquarie University</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/benjamin-pope-60746"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/253387</id>
<published>2025-07-23T12:38:11Z</published>
<updated>2025-07-23T12:38:11Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/binary-star-systems-are-complex-astronomical-objects-a-new-ai-approach-could-pin-down-their-properties-quickly-253387"/>
<title>Binary star systems are complex astronomical objects − a new AI approach could pin down their properties quickly</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/674595/original/file-20250616-56-6o363w.jpg?ixlib=rb-4.1.0&amp;rect=0%2C40%2C1280%2C720&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>In a binary star system, two stars orbit around each other. <a class="source" href="https://www.eso.org/public/images/eso1311a/">ESO/L. Calçada</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></figcaption></figure>Stars are the fundamental building blocks of our universe. Most stars host planets, like our Sun hosts our solar system, and if you look more broadly, groups of stars make up <a href="https://www.britannica.com/science/globular-cluster">huge structures such as clusters</a> and <a href="https://science.nasa.gov/universe/galaxies/">galaxies</a>. So before astrophysicists can attempt to understand these large-scale structures, we first need to understand basic properties of stars, such as their mass, radius and temperature.
But measuring these basic properties has proved exceedingly difficult. This is because stars are quite literally at astronomical distances. If our Sun were a basketball on the East Coast of the U.S., then <a href="https://earthsky.org/astronomy-essentials/proxima-centauri-our-suns-nearest-neighbor/">the closest star, Proxima</a>, would be an orange in Hawaii. Even the world’s largest telescopes cannot resolve an orange in Hawaii. Measuring radii and masses of stars appears to be out of scientists’ reach.
Enter <a href="https://www.space.com/22509-binary-stars.html">binary stars</a>. Binaries are systems of two stars revolving around a mutual center of mass. Their motion is governed by <a href="https://science.nasa.gov/resource/orbits-and-keplers-laws/">Kepler’s harmonic law</a>, which connects three important quantities: the sizes of each orbit, the time it takes for them to orbit, called the orbital period, and the total mass of the system. 
<a href="https://scholar.google.com/citations?user=ugp0OAcAAAAJ&amp;hl=en">I’m an astronomer</a>, and my research team has been working on advancing our theoretical understanding and modeling approaches to binary stars and multiple stellar systems. For the past two decades we’ve also been pioneering the use of artificial intelligence in interpreting observations of these cornerstone celestial objects.
<h2>Measuring stellar masses</h2>
Astronomers can measure orbital size and period of a binary system easily enough from observations, so with those two pieces they can calculate the total mass of the system. Kepler’s harmonic law acts as a scale to weigh celestial bodies. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/676902/original/file-20250626-56-6vpvjs.gif?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="An animation of a large star, which appears stationary, with a smaller, brighter star orbiting around it and eclipsing it when it passes in front." src="https://images.theconversation.com/files/676902/original/file-20250626-56-6vpvjs.gif?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/676902/original/file-20250626-56-6vpvjs.gif?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=343&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/676902/original/file-20250626-56-6vpvjs.gif?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=343&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/676902/original/file-20250626-56-6vpvjs.gif?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=343&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/676902/original/file-20250626-56-6vpvjs.gif?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=431&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/676902/original/file-20250626-56-6vpvjs.gif?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=431&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/676902/original/file-20250626-56-6vpvjs.gif?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=431&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Binary stars orbit around each other, and in eclipsing binary stars, one passes in front of the other, relative to the telescope lens.
<a class="source" href="https://commons.wikimedia.org/wiki/File:Algol-type_variable_binary_star_animation_6.gif">Merikanto/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
Think of a playground seesaw. If the two kids weigh about the same, they’ll have to sit at about the same distance from the midpoint. If, however, one child is bigger, he or she will have to sit closer, and the smaller kid farther from the midpoint. 
It’s the same with stars: The more massive the star in a binary pair, the closer to the center it is and the slower it revolves about the center. When astronomers measure the speeds at which the stars move, they can also tell how large the stars’ orbits are, and as a result, what they must weigh.
<h2>Measuring stellar radii</h2>
Kepler’s harmonic law, unfortunately, tells astronomers nothing about the radii of stars. For those, astronomers rely on another serendipitous feature of Mother Nature.
Binary star orbits are oriented randomly. Sometimes, it happens that a telescope’s line of sight aligns with the plane a binary star system orbits on. This fortuitous alignment means the stars eclipse one another as they revolve about the center. The shapes of these eclipses allow astronomers to find out the stars’ radii using straightforward geometry. These systems are called <a href="https://www.britannica.com/science/eclipse/Eclipsing-binary-stars">eclipsing binary stars</a>.
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/gmzmNDzUHEk?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption>By taking measurements from an eclipsing binary star system, astronomers can measure the radii of the stars.</figcaption>
</figure>
More than half of all Sun-like stars are found in binaries, and eclipsing binaries account for about 1% to 2% of all stars. That may sound low, but the universe is vast, so there are lots and lots of eclipsing systems out there – <a href="https://doi.org/10.3847/1538-4365/acda31">hundreds of millions</a> in our galaxy alone.
By observing eclipsing binaries, astronomers can measure not only the masses and radii of stars but also how hot and how bright they are.
<h2>Complex problems require complex computing</h2>
Even with eclipsing binaries, measuring the properties of stars is no easy task. Stars are deformed as they rotate and pull on each other in a binary system. They interact, they irradiate one another, they can have spots and magnetic fields, and they can be tilted this way or that. 
To study them, astronomers use <a href="https://phoebe-project.org">complex models</a> that have many knobs and switches. As an input, the models take parameters – for example, a star’s shape and size, its orbital properties, or how much light it emits – <a href="https://doi.org/10.31577/caosp.2025.55.3.313">to predict</a> how an observer would see such an eclipsing binary system.
Computer models take time. Computing model predictions typically takes a few minutes. To be sure that we can trust them, we need to try lots of parameter combinations – typically tens of millions. 
This many combinations requires hundreds of millions of minutes of compute time, just to determine basic properties of stars. That amounts to over 200 years of computer time. 
Computers linked in a cluster can compute faster, but even using a computer cluster, it takes three or more weeks to “solve,” or determine all the parameters for, a single binary. This challenge explains why there are only about 300 stars for which astronomers have accurate measurements of their fundamental parameters.
The models used to solve these systems have already been heavily optimized and can’t go much faster than they already do. So, researchers need an entirely new approach to reducing computing time.
<h2>Using deep learning</h2>
One solution <a href="https://doi.org/10.3847/1538-4365/ada4ae">my research team has explored</a> involves <a href="https://www.ibm.com/think/topics/deep-learning">deep-learning</a> <a href="https://news.mit.edu/2017/explained-neural-networks-deep-learning-0414">neural networks</a>. The basic idea is simple: We wanted to replace a computationally expensive physical model with a much faster AI-based model.
First, we computed a huge database of predictions about a hypothetical binary star – using the features that astronomers can readily observe – where we varied the hypothetical binary star’s properties. We are talking hundreds of millions of parameter combinations. Then, we compared these results to the actual observations to see which ones best match up. AI and neural networks are ideally suited for this task.
In a nutshell, <a href="http://neuralnetworksanddeeplearning.com/">neural networks are mappings</a>. They map a certain known input to a given output. In our case, they map the properties of eclipsing binaries to the expected predictions. Neural networks emulate the model of a binary but without having to account for all the complexity of the physical model.
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/bfmFfD2RIcg?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption>Neural networks detect patterns and use their training to predict an output, based on an input.</figcaption>
</figure>
We train the neural network by showing it each prediction from our database, along with the set of properties used to generate it. Once fully trained, the neural network will be able to accurately predict what astronomers should observe from the given properties of a binary system. 
Compared to a few minutes of runtime for the physical model, a neural network uses artificial intelligence to get the same result within a tiny fraction of a second.
<h2>Reaping the benefits</h2>
A tiny fraction of a second works out to about a millionfold runtime reduction. This brings the time down from weeks on a supercomputer to mere minutes on a single laptop. It also means that we can analyze hundreds of thousands of binary systems in a couple of weeks on a computer cluster.
This reduction means we can obtain <a href="https://theconversation.com/astronomers-have-learned-lots-about-the-universe-but-how-do-they-study-astronomical-objects-too-distant-to-visit-214320">fundamental properties</a> – stellar masses, radii, temperatures and luminosities – for every eclipsing binary star ever observed within a month or two. The big challenge remaining is to show that AI results really give the same results as the physical model.
This task is the crux of my team’s <a href="https://doi.org/10.3847/1538-4365/ada4ae">new paper</a>. In it we’ve shown that, indeed, the AI-driven model yields the same results as the physical model across over 99% of parameter combinations. This result means the AI’s <a href="https://www.sciencedirect.com/topics/computer-science/robust-optimization">performance is robust</a>. Our next step? Deploy the AI on all observed eclipsing binaries.
Best of all? While we applied this methodology to binaries, the basic principle applies to any complex physical model out there. Similar AI models are already speeding up many real-world applications, from <a href="https://www.nytimes.com/2025/05/21/climate/ai-weather-models-aurora-microsoft.html">weather forecasting</a> to <a href="https://builtin.com/artificial-intelligence/ai-trading-stock-market-tech">stock market analysis</a>.<img src="https://counter.theconversation.com/content/253387/count.gif" alt="The Conversation" width="1" height="1" />
Andrej Prša receives funding from the National Aeronautics and Space Administration.</content>
<summary>It takes a supercomputer weeks to output the properties of one stellar binary. A new study shows AI can do it in a fraction of the time.</summary>
<author>
<name>Andrej Prša, Professor of Astrophysics and Planetary Science, Villanova University</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/andrej-prsa-2357700"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/261656</id>
<published>2025-07-22T20:09:34Z</published>
<updated>2025-07-22T20:09:34Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/could-the-latest-interstellar-comet-be-an-alien-probe-why-spotting-cosmic-visitors-is-harder-than-you-think-261656"/>
<title>Could the latest ‘interstellar comet’ be an alien probe? Why spotting cosmic visitors is harder than you think</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/681398/original/file-20250722-64-jcue21.jpg?ixlib=rb-4.1.0&amp;rect=0%2C457%2C1357%2C851&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>Comet 3I/ATLAS <a class="source" href="https://noirlab.edu/public/images/noirlab2522b/">International Gemini Observatory/NOIRLab/NSF/AURA/K. Meech/Jen Miller/Mahdi Zamani</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></figcaption></figure>On July 1, astronomers spotted an unusual high-speed object zooming towards the Sun. Dubbed <a href="https://science.nasa.gov/solar-system/comets/3i-atlas/">3I/ATLAS</a>, the surprising space traveller had one very special quality: its orbit showed it had come from outside our Solar System.
For only the third time ever, we had discovered a true interstellar visitor. And it was weird.
<h2>3I/ATLAS breaking records</h2>
3I/ATLAS appeared to be <a href="https://www.livescience.com/space/comets/nasa-confirms-that-mysterious-object-shooting-through-the-solar-system-is-an-interstellar-visitor-and-it-has-a-new-name">travelling</a> at 245,000 kilometres per hour, making it the fastest object ever detected in our Solar System.
It was also huge. Early estimates suggest the object <a href="https://www.scientificamerican.com/article/new-interstellar-object-3i-atlass-biggest-mysteries-explained">could be up to 20km in size</a>. Finally, scientists believe it may even be <a href="https://arxiv.org/pdf/2507.05318">older than our Sun</a>.
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-vzafaw0t08?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption>Davide Farnocchia, navigation engineer at NASA’s JPL, explains the discovery of 3I/ATLAS.</figcaption>
</figure>
<h2>Could it be alien?</h2>
Our first assumption when we see something in space is that it’s a lump of rock or ice. But the strange properties of 3I/ATLAS have suggested to some that it may be something else entirely.
Harvard astrophysics professor Avi Loeb and colleagues last week uploaded a paper titled <a href="https://arxiv.org/abs/2507.12213">Is the Interstellar Object 3I/ATLAS Alien Technology?</a> to the arXiv preprint server. (The paper has not yet been peer reviewed.)
Loeb is a <a href="https://www.npr.org/2025/03/21/g-s1-54967/one-scientists-search-for-alien-life-and-the-controversy-it-has-sparked">controversial figure</a> among astronomers and astrophysicists. He has previously <a href="https://www.scientificamerican.com/article/astronomer-avi-loeb-says-aliens-have-visited-and-hes-not-kidding1/">suggested</a> that the first known interstellar object, 1I/ʻOumuamua, discovered in 2017, may also have been an alien craft.
Among other oddities Loeb suggests may be signs of deliberate alien origin, he notes the orbit of 3I/ATLAS takes it improbably close to Venus, Mars and Jupiter.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/681399/original/file-20250722-64-t5gwpe.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="" src="https://images.theconversation.com/files/681399/original/file-20250722-64-t5gwpe.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/681399/original/file-20250722-64-t5gwpe.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=391&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/681399/original/file-20250722-64-t5gwpe.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=391&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/681399/original/file-20250722-64-t5gwpe.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=391&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/681399/original/file-20250722-64-t5gwpe.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=492&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/681399/original/file-20250722-64-t5gwpe.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=492&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/681399/original/file-20250722-64-t5gwpe.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=492&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The trajectory of comet 3I/ATLAS as it passes through the Solar System, with its closest approach to the Sun in October.
<a class="source" href="https://science.nasa.gov/solar-system/comets/3i-atlas/">NASA/JPL-Caltech</a>
</figcaption>
</figure>
<h2>We’ve sent out our own alien probes</h2>
The idea of alien probes wandering the cosmos may sound strange, but <a href="https://theconversation.com/after-45-years-the-5-billion-year-legacy-of-the-voyager-2-interstellar-probe-is-just-beginning-188077">humans sent out a few ourselves</a> in the 1970s. Both Voyager 1 and 2 have officially left our Solar System, and Pioneer 10 and 11 are not far behind.
So it’s not a stretch to think that alien civilisations – if they exist – would have launched their own galactic explorers.
However, this brings us to a crucial question: short of little green men popping out to say hello, how would we actually know if 3I/ATLAS, or any other interstellar object, was an alien probe? 
<h2>Detecting alien probes 101</h2>
The first step to determining whether something is a natural object or an alien probe is of course to spot it. 
Most things we see in our Solar System don’t emit light of their own. Instead, we only see them by the light they reflect from the Sun.
Larger objects generally reflect more sunlight, so they are easier for us to see. So what we see tends to be larger comets and asteroid, especially farther from Earth.
It can be very difficult to spot smaller objects. At present, we can track objects down to a size of ten or 20 metres out as far from the Sun as Jupiter.
Our own Voyager probes are about ten metres in size (if we include their radio antennas). If an alien probe was similar, we probably wouldn’t spot it until it was somewhere in the asteroid belt between Jupiter and Mars.
If we did spot something suspicious, to figure out if it really were a probe or not we would look for a few telltales.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/681406/original/file-20250722-56-gsiabb.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A streak of coloured light against a background of stars." src="https://images.theconversation.com/files/681406/original/file-20250722-56-gsiabb.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/681406/original/file-20250722-56-gsiabb.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/681406/original/file-20250722-56-gsiabb.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/681406/original/file-20250722-56-gsiabb.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/681406/original/file-20250722-56-gsiabb.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/681406/original/file-20250722-56-gsiabb.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/681406/original/file-20250722-56-gsiabb.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Viewing 3I/ATLAS through coloured filters reveals the colours that make up its tail.
<a class="source" href="https://noirlab.edu/public/images/noirlab2522c/">International Gemini Observatory/NOIRLab/NSF/AURA/K. Meech (IfA/U. Hawaii) / Jen Miller &amp; Mahdi Zamani (NSF NOIRLab)</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
First off, because a natural origin is most likely, we would look for evidence that no aliens were involved. One clue in this direction might be if the object were emitting a “tail” of gas in the way that comets do.
However, we might also want to look for hints of alien origin. One very strong piece of evidence would be any kind of radio waves coming from the probe as a form of communication. This is assuming the probe was still in working order, and not completely defunct. 
We might also look for signs of <a href="https://theconversation.com/a-strange-bright-burst-in-space-baffled-astronomers-for-more-than-a-year-now-theyve-solved-the-mystery-259893">electrostatic discharge</a> caused by sunlight hitting the probe.
Another dead giveaway would be signs of manoeuvring or propulsion. An active probe might try to correct its course or reposition its antennas to send and receive signals to and from its origin.
And a genuine smoking gun would be an approach to Earth in a stable orbit. Not to brag, but Earth is genuinely the most interesting place in the Solar System – we have water, a healthy atmosphere, a strong magnetic field and life. A probe with any decision-making capacity would likely want to investigate and collect data about our interesting little planet. 
<h2>We may never know</h2>
Without clear signs one way or the other, however, it may be impossible to know if some interstellar objects are natural or alien-made.
Objects like 3I/ATLAS remind us that space is vast, strange, and full of surprises. Most of them have natural explanations. But the strangest objects are worth a second look.
For now, 3I/ATLAS is likely just an unusually fast, old and icy visitor from a distant system. But it also serves as a test case: a chance to refine the way we search, observe and ask questions about the universe.<img src="https://counter.theconversation.com/content/261656/count.gif" alt="The Conversation" width="1" height="1" />
Sara Webb does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</content>
<summary>If aliens did a flyby through the Solar System, would we even realise?</summary>
<author>
<name>Sara Webb, Lecturer, Centre for Astrophysics and Supercomputing, Swinburne University of Technology</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/sara-webb-984920"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/259754</id>
<published>2025-07-15T12:31:23Z</published>
<updated>2025-07-15T12:31:23Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/sculptor-galaxy-image-provides-brilliant-details-that-will-help-astronomers-study-how-stars-form-259754"/>
<title>Sculptor galaxy image provides brilliant details that will help astronomers study how stars form</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/679174/original/file-20250709-56-9n41lk.png?ixlib=rb-4.1.0&amp;rect=297%2C0%2C604%2C339&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>This image of the Sculptor galaxy will give astronomers detailed information on a variety of stars, nebulae and galactic regions. <a class="source" href="https://www.eso.org/public/news/eso2510/">European Southern Observatory</a></figcaption></figure>If you happen to find yourself in the Southern Hemisphere with binoculars and a good view of the night sky on a dark and clear summer night, you might just be able to spot the <a href="https://www.constellation-guide.com/sculptor-galaxy-ngc-253/">Sculptor galaxy</a>. And if your eyes were prisms that could separate light into the thousands of colors making it up, then congratulations: After hours of staring, you could have recreated the <a href="https://www.eso.org/public/news/eso2510/">newest image</a> of one of the nearest neighbors to our Milky Way galaxy.
This is not just another stunningly gorgeous picture of a nearby galaxy. Because it reveals the type of light coming from each location in the galaxy, this image of the Sculptor galaxy is a treasure trove of information that astronomers around the world cannot wait to pick apart. 
As an <a href="https://ccapp.osu.edu/people/mcclain.378">astronomy Ph.D. student</a> at Ohio State University, I (Rebecca) am one of the lucky people who gets to stare at this image for hours every day, alongside <a href="https://astronomy.osu.edu/people/leroy.42">my adviser (Adam)</a>, discovering meaning behind the beauty everyone can appreciate.
<h2>Creating the image</h2>
The Sculptor galaxy lies <a href="https://arxiv.org/abs/2506.14921">11 million light-years</a> from the Milky Way. This may sound unfathomably far, but it actually makes Sculptor one of the closest galaxies to Earth. 
For this reason, Sculptor has been the primary target for many observations. In 2022, an international team of scientists observed Sculptor with the <a href="https://www.eso.org/public/teles-instr/paranal-observatory/vlt/vlt-instr/muse/">Multi-Unit Spectroscopic Explorer</a>, MUSE, on the European Southern Observatory’s <a href="https://www.eso.org/public/teles-instr/paranal-observatory/vlt/">Very Large Telescope</a> in Chile, and <a href="https://www.eso.org/public/news/eso2510/">publicly released</a> the data this June.
Most <a href="https://theconversation.com/is-mars-really-red-a-physicist-explains-the-planets-reddish-hue-and-why-it-looks-different-to-some-telescopes-256398">astronomical observations obtain</a> either an image of a single color of light – for example, red or blue – or <a href="https://science.nasa.gov/ems/09_visiblelight/">a spectrum</a>, which splits the light coming from the whole galaxy into many different colors. 
MUSE, conveniently, does both, <a href="https://theconversation.com/is-mars-really-red-a-physicist-explains-the-planets-reddish-hue-and-why-it-looks-different-to-some-telescopes-256398">producing a spectrum</a> at every location it observes. One observation creates thousands of images in thousands of colors, each tracing the critical components that make up the galaxy: stars, dust and gas.
It may look like only one picture, but this image of Sculptor is actually over 100 individual observations and 8 million individual spectra, painstakingly stitched together to reveal millions of stars all in one cohesive galaxy.
<h2>Scientific significance</h2>
The light associated with the stars in Sculptor is colored white, and gas made up of charged particles is colored red. The largest concentration of both is found in the spiral arms. At the very center of the galaxy is a nuclear starburst: a region of extreme star formation that is <a href="https://www.nasa.gov/image-article/chandra-determines-what-makes-galaxys-wind-blow/">blowing material out of the galaxy</a>.
There is even information in the absence of light. Dust obscures light emitted from behind it, creating a shadow effect called <a href="https://theastroenthusiast.com/dust-lanes-in-the-sculptor-galaxy/">dust lanes</a>. Tracing these dust lanes reveals the cold, dense material that <a href="https://theconversation.com/what-is-space-made-of-an-astrophysics-expert-explains-all-the-components-from-radiation-to-dark-matter-found-in-the-vacuum-of-space-235402">exists between stars</a>. Scientists believe this dark material is the fuel that will form the next generation of stars.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/679446/original/file-20250710-56-mms2ey.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Clouds of gas punctuated by bright dots which represent stars." src="https://images.theconversation.com/files/679446/original/file-20250710-56-mms2ey.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/679446/original/file-20250710-56-mms2ey.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=350&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/679446/original/file-20250710-56-mms2ey.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=350&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/679446/original/file-20250710-56-mms2ey.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=350&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/679446/original/file-20250710-56-mms2ey.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=440&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/679446/original/file-20250710-56-mms2ey.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=440&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/679446/original/file-20250710-56-mms2ey.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=440&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Complex gaseous nebulae (red) surround young and massive stars (white) in this zoom-in of a cluster of star-forming regions.
European Southern Observatory/VLT/MUSE
</figcaption>
</figure>
There is a lot to look at in this image, but the subject of my work and what I find most interesting is the gas illuminated in red. In <a href="https://www.britannica.com/science/H-II-region">these star-forming regions</a>, young and massive stars excite the gas around them, which then glows with a specific color to reveal the chemical makeup and physical conditions of the gas.
This image represents one of the first times that astronomers have obtained images of thousands of star-forming regions at this impressive level of detail. A component of our team’s research uses the data from MUSE to understand how these regions are structured and how they interact with the surrounding galaxy.
By meticulously piecing all of this information together, astronomers can use this image to learn more about the formation and evolution of stars across the universe.<img src="https://counter.theconversation.com/content/259754/count.gif" alt="The Conversation" width="1" height="1" />
Rebecca McClain receives funding from the National Science Foundation. Adam Leroy receives funding from NASA/Space Telescope Science Institute that supports research related to the survey of NGC 253 discussed in this article. </content>
<summary>Researchers stitched together hundreds of images from the Very Large Telescope to form a breathtaking photo of a nearby galaxy.</summary>
<author>
<name>Rebecca McClain, Ph.D. Student in Astronomy, The Ohio State University</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/rebecca-mcclain-2420021"/>
</author>
<author>
<name>Adam Leroy, Professor of Astronomy, The Ohio State University</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/adam-leroy-2420025"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/260422</id>
<published>2025-07-04T02:16:18Z</published>
<updated>2025-07-04T02:16:18Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/astronomers-have-spied-an-interstellar-object-zooming-through-the-solar-system-260422"/>
<title>Astronomers have spied an interstellar object zooming through the Solar System</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/678264/original/file-20250704-56-ajzgow.jpg?ixlib=rb-4.1.0&amp;rect=0%2C215%2C2403%2C1351&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption> <a class="source" href="https://deeprandomsurvey.org/">K Ly / Deep Random Survey</a></figcaption></figure>This week, astronomers spotted the third known interstellar visitor to our Solar System.
First detected by the <a href="https://en.wikipedia.org/wiki/Asteroid_Terrestrial-impact_Last_Alert_System">Asteroid Terrestrial-impact Last Alert System (ATLAS)</a> on July 1, the cosmic interloper was given the temporary name A11pl3Z. Experts at NASA’s Center for Near Earth Object Studies and the International Astronomical Union (IAU) have confirmed the find, and the object now has an official designation: 3I/ATLAS. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/678167/original/file-20250703-56-69zch4.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A diagram of the Solar System out to Jupiter detailing the path of interstellar object 3I/ATLAS." src="https://images.theconversation.com/files/678167/original/file-20250703-56-69zch4.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/678167/original/file-20250703-56-69zch4.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=391&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/678167/original/file-20250703-56-69zch4.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=391&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/678167/original/file-20250703-56-69zch4.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=391&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/678167/original/file-20250703-56-69zch4.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=491&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/678167/original/file-20250703-56-69zch4.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=491&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/678167/original/file-20250703-56-69zch4.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=491&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The orbital path of 3I/ATLAS through the Solar System.
<a class="source" href="https://assets.science.nasa.gov/dynamicimage/assets/science/psd/planetary-defense/3I_interstellar%20comet%20orbit.jpg?w=1840&amp;h=1200&amp;fit=clip&amp;crop=faces%2Cfocalpoint">NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a>
</figcaption>
</figure>
There are a few strong clues that suggest 3I/ATLAS came from outside the Solar System. 
First, it’s moving really fast. <a href="https://minorplanetcenter.net/mpec/K25/K25N12.html">Current observations</a> show it speeding through space at around 245,000km per hour. That’s more than enough to escape the Sun’s gravity. 
An object near Earth’s orbit would only need to be travelling at just over 150,000km/h to break free from the Solar System.
Second, 3I/ATLAS has a wildly eccentric orbit around the Sun. Eccentricity measures how “stretched” an orbit is: 0 eccentricity is a perfect circle, and anything up to 1 is an increasingly strung-out ellipse. Above 1 is an orbit that is not bound to the Sun.
3I/ATLAS has an estimated eccentricity of 6.3, by far the highest ever recorded for any object in the Solar System.
<h2>Has anything like this happened before?</h2>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/678168/original/file-20250703-68-brg8fd.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="An artist's impression of the first confirmed interstellar object, 1I/'Oumuamua." src="https://images.theconversation.com/files/678168/original/file-20250703-68-brg8fd.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/678168/original/file-20250703-68-brg8fd.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=375&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/678168/original/file-20250703-68-brg8fd.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=375&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/678168/original/file-20250703-68-brg8fd.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=375&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/678168/original/file-20250703-68-brg8fd.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=471&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/678168/original/file-20250703-68-brg8fd.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=471&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/678168/original/file-20250703-68-brg8fd.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=471&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
An artist’s impression of the first confirmed interstellar object, 1I/‘Oumuamua.
<a class="source" href="https://www.eso.org/public/images/eso1737a/">ESO/M. Kornmesser</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
The first interstellar object spotted in our Solar System was the cigar-shaped <a href="https://en.wikipedia.org/wiki/1I/%CA%BBOumuamua">‘Oumuamua</a>, discovered in 2017 by the Pan-STARRS1 telescope in Hawaii. Scientists tracked it for 80 days before eventually confirming it came from interstellar space.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/678169/original/file-20250703-56-jdfriz.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="The interstellar comet 2I/Borisov, imaged by the Hubble Space Telescope." src="https://images.theconversation.com/files/678169/original/file-20250703-56-jdfriz.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/678169/original/file-20250703-56-jdfriz.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/678169/original/file-20250703-56-jdfriz.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/678169/original/file-20250703-56-jdfriz.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/678169/original/file-20250703-56-jdfriz.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=565&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/678169/original/file-20250703-56-jdfriz.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=565&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/678169/original/file-20250703-56-jdfriz.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=565&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The interstellar comet 2I/Borisov, imaged by the Hubble Space Telescope.
<a class="source" href="https://esahubble.org/images/heic1918a/">NASA, ESA, and D. Jewitt (UCLA)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a>
</figcaption>
</figure>
The second interstellar visitor, comet <a href="https://en.wikipedia.org/wiki/2I/Borisov#Observation">2I/Borisov</a>, was discovered two years later by amateur astronomer Gennadiy Borisov. This time it only took astronomers a few weeks to confirm it came from outside the Solar System.
This time, the interstellar origin of 3I/ATLAS has been confirmed in a matter of days.
<h2>How did it get here?</h2>
We have only ever seen three interstellar visitors (including 3I/ATLAS), so it’s hard to know exactly how they made their way here.
However, <a href="https://iopscience.iop.org/article/10.3847/PSJ/adb1e9">recent research</a> published in The Planetary Science Journal suggests these objects might be more common than we once thought. In particular, they may come from relatively nearby star systems such as Alpha Centauri (our nearest interstellar neighbour, a mere 4.4 light years away).
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/678173/original/file-20250703-56-3s74ub.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Two bright stars of the Alpha Centauri triple star system." src="https://images.theconversation.com/files/678173/original/file-20250703-56-3s74ub.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/678173/original/file-20250703-56-3s74ub.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=390&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/678173/original/file-20250703-56-3s74ub.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=390&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/678173/original/file-20250703-56-3s74ub.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=390&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/678173/original/file-20250703-56-3s74ub.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=490&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/678173/original/file-20250703-56-3s74ub.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=490&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/678173/original/file-20250703-56-3s74ub.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=490&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Alpha Centauri A and Alpha Centauri B, from the triple star system Alpha Centauri.
<a class="source" href="https://www.eso.org/public/images/eso1629v/">ESA/Hubble &amp; NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
<a href="https://en.wikipedia.org/wiki/Alpha_Centauri">Alpha Centauri</a> is slowly moving closer to us, with its closest approach expected in about 28,000 years. If it flings out material in the same way our Solar System does, scientists estimate around a million objects from Alpha Centauri larger than 100 metres in diameter could already be in the outer reaches of our Solar System. That number could increase tenfold as Alpha Centauri gets closer.
Most of this material would have been ejected at relatively low speeds, less than 2km/s, making it more likely to drift into our cosmic neighbourhood over time and not dramatically zoom in and out of the Solar System like 3I/ATLAS appears to be doing. While the chance of one of these objects coming close to the Sun is extremely small, the study suggests a few tiny meteors from Alpha Centauri, likely no bigger than grains of sand, may already hit Earth’s atmosphere every year.
<h2>Why is this interesting?</h2>
Discovering new interstellar visitors like 3I/ATLAS is thrilling, not just because they’re rare, but because each one offers a unique glimpse into the wider galaxy. Every confirmed interstellar object expands our catalogue and helps scientists better understand the nature of these visitors, how they travel through space, and where they might have come from.
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/DTuq-vBsDJE?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption>A swarm of new asteroids discovered by the NSF–DOE Vera C. Rubin Observatory.</figcaption>
</figure>
Thanks to powerful new observatories such as the <a href="https://rubinobservatory.org/">NSF–DOE Vera C. Rubin Observatory</a>, our ability to detect these elusive objects is rapidly improving. In fact, during its first 10 hours of test imaging, Rubin <a href="https://rubinobservatory.org/news/rubin-first-look/swarm-asteroids">revealed 2,104 previously unknown asteroids</a>. 
This is an astonishing preview of what’s to come. With its wide field of view and constant sky coverage, Rubin is expected to revolutionise our search for interstellar objects, potentially turning rare discoveries into routine ones.
<h2>What now?</h2>
There’s still plenty left to uncover about 3I/ATLAS. Right now, it’s officially classified as a comet by the IAU Minor Planet Center. 
But some scientists argue it <a href="https://phys.org/news/2025-07-inbound-astronomers-interstellar.html">might actually be an asteroid</a>, roughly 20km across, based on the lack of typical comet-like features such as a glowing coma or a tail. More observations will be needed to confirm its nature.
Currently, 3I/ATLAS is inbound, just inside Jupiter’s orbit. It’s expected to reach its closest point to the Sun, slightly closer than the planet Mars, on October 29. After that, it will swing back out towards deep space, making its closest approach to Earth in December. (It will pose no threat to our planet.)
Whether it’s a comet or an asteroid, 3I/ATLAS is a messenger from another star system. For now, these sightings are rare – though as next-generation observatories such as Rubin swing into operation, we may discover interstellar companions all around.<img src="https://counter.theconversation.com/content/260422/count.gif" alt="The Conversation" width="1" height="1" />
Kirsten Banks does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</content>
<summary>An object dubbed 3I/ATLAS is only the third interloper from outside the Solar System seen in all of human history.</summary>
<author>
<name>Kirsten Banks, Lecturer, School of Science, Computing and Engineering Technologies, Swinburne University of Technology</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/kirsten-banks-2278823"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/257421</id>
<published>2025-06-30T12:31:18Z</published>
<updated>2025-06-30T12:31:18Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/how-can-the-james-webb-space-telescope-see-so-far-257421"/>
<title>How can the James Webb Space Telescope see so far?</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/672026/original/file-20250603-56-52fim0.png?ixlib=rb-4.1.0&amp;rect=0%2C517%2C4159%2C2339&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>This is a James Webb Space Telescope image of NGC 604, a star-forming region about 2.7 million light-years from Earth. <a class="source" href="https://webbtelescope.org/contents/media/images/2024/110/01HQNV4GP6PR6E7ZSJXRRBQQDS?page=1&amp;filterUUID=91dfa083-c258-4f9f-bef1-8f40c26f4c97">NASA/ESA/CSA/STScI</a></figcaption></figure>
<a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>.
<hr>
<blockquote>
How does the camera on the James Webb Space Telescope work and see so far out? – Kieran G., age 12, Minnesota
</blockquote>
<hr>
Imagine a camera so powerful it can see light from galaxies that formed more than <a href="https://science.nasa.gov/mission/webb/webbs-mirrors/">13 billion years ago</a>. That’s exactly what NASA’s James Webb Space Telescope is built to do. 
Since it launched in <a href="https://science.nasa.gov/mission/webb/launch/">December 2021</a>, Webb has been orbiting more than a million miles from Earth, capturing breathtaking images of deep space. But how does it actually work? And how can it see so far? The secret lies in its powerful cameras – especially ones that don’t see light the way our eyes do.
<a href="https://scholar.google.com/citations?user=iBT78yoAAAAJ&amp;hl=en">I’m an astrophysicist</a> who studies galaxies and supermassive black holes, and the Webb telescope is an incredible tool for observing some of the earliest galaxies and black holes in the universe.
When Webb takes a picture of a distant galaxy, astronomers like me are actually seeing what that galaxy looked like billions of years ago. The light from that galaxy has been traveling across space for the billions of years it takes to reach the telescope’s mirror. It’s like having a time machine that takes snapshots of the early universe.
By using a giant mirror to collect ancient light, Webb has been discovering new secrets about the universe.
<h2>A telescope that sees heat</h2>
Unlike regular cameras or even the Hubble Space Telescope, which take images of visible light, Webb is designed to see a kind of light that’s invisible to your eyes: <a href="https://science.nasa.gov/ems/07_infraredwaves/">infrared light</a>. Infrared light has longer wavelengths than visible light, which is why our eyes can’t detect it. But with the right instruments, Webb can capture infrared light to study some of the earliest and most distant objects in the universe.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/672020/original/file-20250603-56-afzvl4.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A dog, shown normally, then through thermal imaging, with the eyes, mouth and ears brighter than the rest of the dog." src="https://images.theconversation.com/files/672020/original/file-20250603-56-afzvl4.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/672020/original/file-20250603-56-afzvl4.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=418&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/672020/original/file-20250603-56-afzvl4.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=418&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/672020/original/file-20250603-56-afzvl4.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=418&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/672020/original/file-20250603-56-afzvl4.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=525&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/672020/original/file-20250603-56-afzvl4.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=525&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/672020/original/file-20250603-56-afzvl4.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=525&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Infrared cameras, like night-vision goggles, allow you to ‘see’ the infrared waves emitting from warm objects such as humans and animals. The temperatures for the images are in degrees Fahrenheit.
NASA/JPL-Caltech
</figcaption>
</figure>
Although the human eye cannot see it, people can detect infrared light as a form of heat using specialized technology, such as infrared cameras or thermal sensors. For example, night-vision goggles use infrared light to detect warm objects in the dark. Webb uses the same idea to study stars, galaxies and planets.
Why infrared? When visible light from faraway galaxies travels across the universe, <a href="https://www.skyatnightmagazine.com/space-science/redshift">it stretches out</a>. This is because the <a href="https://theconversation.com/where-is-the-center-of-the-universe-252695">universe is expanding</a>. That stretching turns visible light into infrared light. So, the most distant galaxies in space don’t shine in visible light anymore – they glow in faint infrared. That’s the light Webb is built to detect.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A diagram of the electromagnetic spectrum, with radio, micro and infrared waves having a longer wavelength than visible light, while UV, X-ray and gamma rays have shorter wavelengths than visible light." src="https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=356&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=356&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=356&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=447&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=447&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=447&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The rainbow of visible light that you can see is only a small slice of all the kinds of light. Some telescopes can detect light with a longer wavelength, such as infrared light, or light with a shorter wavelength, such as ultraviolet light. Others can detect X-rays or radio waves.
<a class="source" href="https://en.wikipedia.org/wiki/Electromagnetic_spectrum#/media/File:EM_Spectrum_Properties_edit.svg">Inductiveload, NASA/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
<h2>A golden mirror to gather the faintest glow</h2>
Before the light reaches the cameras, it first has to be collected by the Webb telescope’s <a href="https://www.nasa.gov/image-article/james-webb-space-telescopes-golden-mirror/">enormous golden mirror</a>. This mirror is over 21 feet (6.5 meters) wide and made of 18 smaller mirror pieces that fit together like a honeycomb. It’s coated in a thin layer of real gold – not just to look fancy, but because gold reflects infrared light extremely well. 
The mirror gathers light from deep space and reflects it into the telescope’s instruments. The <a href="https://theconversation.com/how-do-you-build-a-mirror-for-one-of-the-worlds-biggest-telescopes-49927">bigger the mirror</a>, the more light it can collect – and the farther it can see. Webb’s mirror is the largest ever launched into space.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/672021/original/file-20250603-68-pimc7g.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="The JWST's mirror, which looks like a large, roughly hexagonal shiny surface made up of 18 smaller hexagons put together, sitting in a facility. The mirror is reflecting the NASA meatball logo." src="https://images.theconversation.com/files/672021/original/file-20250603-68-pimc7g.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/672021/original/file-20250603-68-pimc7g.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/672021/original/file-20250603-68-pimc7g.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/672021/original/file-20250603-68-pimc7g.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/672021/original/file-20250603-68-pimc7g.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/672021/original/file-20250603-68-pimc7g.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/672021/original/file-20250603-68-pimc7g.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Webb’s 21-foot primary mirror, made of 18 hexagonal mirrors, is coated with a plating of gold.
NASA
</figcaption>
</figure>
<h2>Inside the cameras: NIRCam and MIRI</h2>
The most important “eyes” of the telescope are two science instruments that act like cameras: NIRCam and MIRI.
NIRCam stands for near-infrared camera. It’s the primary camera on Webb and takes stunning images of galaxies and stars. It also has <a href="https://www.space.com/what-is-a-coronagraph.html">a coronagraph</a> – a device that blocks out starlight so it can photograph very faint objects near bright sources, such as planets orbiting bright stars. 
<a href="https://science.nasa.gov/mission/webb/nircam/">NIRCam works by imaging near-infrared light</a>, the type closest to what human eyes can almost see, and splitting it into different wavelengths. This helps scientists learn not just what something looks like but what it’s made of. Different materials in space absorb and emit infrared light at specific wavelengths, creating a kind of unique <a href="https://theconversation.com/accelerating-exoplanet-discovery-using-chemical-signatures-of-stars-118818">chemical fingerprint</a>. By studying these fingerprints, scientists can uncover the properties of distant stars and galaxies.
MIRI, or the mid-infrared instrument, <a href="https://science.nasa.gov/mission/webb/mid-infrared-instrument-miri/">detects longer infrared wavelengths</a>, which are especially useful for spotting cooler and dustier objects, such as stars that are still forming inside clouds of gas. MIRI can even help find clues about the types of molecules in the atmospheres of <a href="https://theconversation.com/to-search-for-alien-life-astronomers-will-look-for-clues-in-the-atmospheres-of-distant-planets-and-the-james-webb-space-telescope-just-proved-its-possible-to-do-so-184828">planets that might support life</a>.
Both cameras are far more sensitive than the standard cameras used on Earth. NIRCam and MIRI can detect the tiniest amounts of heat from billions of light-years away. If you had Webb’s NIRCam as your eyes, you could see the heat from a bumblebee on the Moon. That’s how sensitive it is. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/672022/original/file-20250603-62-caxykh.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Two photos of space, with lots of stars and galaxies shown as little dots. The right image shows more, brighter dots than the left." src="https://images.theconversation.com/files/672022/original/file-20250603-62-caxykh.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/672022/original/file-20250603-62-caxykh.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/672022/original/file-20250603-62-caxykh.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/672022/original/file-20250603-62-caxykh.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/672022/original/file-20250603-62-caxykh.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/672022/original/file-20250603-62-caxykh.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/672022/original/file-20250603-62-caxykh.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Webb’s first deep-field image: The MIRI image is on the left and the NIRCam image is on the right.
NASA
</figcaption>
</figure>
Because Webb is trying to detect faint heat from faraway objects, it needs to keep itself as cold as possible. That’s why it carries <a href="https://science.nasa.gov/mission/webb/webbs-sunshield/">a giant sun shield about the size of a tennis court</a>. This five-layer sun shield blocks heat from the Sun, Earth and even the Moon, helping Webb stay incredibly cold: around -370 degrees F (-223 degrees C). 
MIRI needs to be even colder. It has its own special refrigerator, called a cryocooler, to keep it chilled to nearly -447 degrees F (-266 degrees C). If Webb were even a little warm, its own heat would drown out the distant signals it’s trying to detect.
<h2>Turning space light into pictures</h2>
Once light reaches the Webb telescope’s cameras, it hits sensors called detectors. <a href="https://science.nasa.gov/mission/webb/infrared-detectors/">These detectors</a> don’t capture regular photos like a phone camera. Instead, they convert the incoming infrared light into digital data. That data is then sent back to Earth, where scientists process it into <a href="https://theconversation.com/james-webb-space-telescope-an-astronomer-explains-the-stunning-newly-released-first-images-186800">full-color images</a>.
The colors we see in Webb’s pictures aren’t what the camera “sees” directly. Because infrared light is invisible, scientists assign colors to different wavelengths to help us understand what’s in the image. These processed images help show the structure, age and composition of galaxies, stars and more.
By using a giant mirror to collect invisible infrared light and sending it to super-cold cameras, Webb lets us see galaxies that formed just after the universe began.
<hr>
Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.
And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.<img src="https://counter.theconversation.com/content/257421/count.gif" alt="The Conversation" width="1" height="1" />
Adi Foord does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</content>
<summary>The James Webb Space Telescope has 2 powerful instruments that see light the human eye can’t.</summary>
<author>
<name>Adi Foord, Assistant Professor of Astronomy and Astrophysics, University of Maryland, Baltimore County</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/adi-foord-1472117"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/259857</id>
<published>2025-06-27T13:10:15Z</published>
<updated>2025-06-27T13:10:15Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/could-the-first-images-from-the-vera-rubin-telescope-change-how-we-view-space-for-good-259857"/>
<title>Could the first images from the Vera Rubin telescope change how we view space for good?</title>
<content type="html">We are entering a new era of cosmic exploration. The new <a href="https://rubinobservatory.org/">Vera C Rubin Observatory</a> in Chile will transform astronomy with its extraordinary ability to map the universe in breathtaking detail. It is set to reveal secrets previously beyond our grasp. Here, we delve into the first images taken by Rubin’s telescope and what they are already showing us.
These images vividly showcase the unprecedented power that Rubin will use to
revolutionise astronomy and our understanding of the Universe. Rubin is truly transformative, thanks to its unique combination of sensitivity, vast sky area coverage and exceptional image quality. 
These pictures powerfully demonstrate those attributes. They reveal not only bright objects in exquisite detail but also faint structures, both near and far, across a large area of sky.
<h2>Cosmic nurseries – nebulae in detail</h2>
The stunning <a href="https://rubinobservatory.org/news/rubin-first-look/trifid-lagoon">pink and blue clouds</a> in this image are the Lagoon (lower left) and Trifid (upper right) nebulae. The word nebula comes from the Latin for cloud, and these giant clouds are truly enormous – so vast it takes light decades to travel across them. They are stellar nurseries, the very birth sites for the next generation of stars and planets in our Milky Way galaxy.
The intense radiation from hot, young stars energises the gas particles, causing
them to glow pink. Further from these nascent stars, colder regions consist of
microscopic dust grains. These reflect starlight (a process known in astronomy as
“scattering”), much like our atmosphere, creating the beautiful blue hues. Darker filaments within are much denser regions of dust, obscuring all but the brightest background stars.
To detect these colours, astronomers use filters over their instruments, allowing only certain wavelengths of light onto the detectors. Rubin has six such filters, spanning from short ultraviolet (UV) wavelengths through the visible spectrum to longer near-infrared light. Combining information from these different filters enables detailed measurements of the properties of stars and gas, such as their temperature and size.
Rubin’s speed – its ability to take an image with one filter and then quickly move to the next – combined with the sheer area of sky it can see at any one time, is what makes it so unique and so exciting. The level of detail, revealing the finest and faintest structures, will enable it to map the substructure and satellite galaxies of the Milky Way like never before.
<h2>Mapping galaxies across billions of light years</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/676637/original/file-20250625-56-30x25f.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/676637/original/file-20250625-56-30x25f.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=368&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/676637/original/file-20250625-56-30x25f.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=368&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/676637/original/file-20250625-56-30x25f.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=368&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/676637/original/file-20250625-56-30x25f.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=462&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/676637/original/file-20250625-56-30x25f.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=462&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/676637/original/file-20250625-56-30x25f.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=462&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
This image captures a small section of NSF–DOE Vera C. Rubin Observatory’s view of the Virgo Cluster, offering a vivid glimpse of the variety in the cosmos.
<a class="source" href="https://rubinobservatory.org/gallery/collections/first-look-gallery/32ejonfcf955v6luvhdvbd746c">Credit: NSF–DOE Vera C. Rubin Observatory</a>
</figcaption>
</figure>
The images of galaxies powerfully demonstrate the scale at which the Rubin
observatory will map the universe beyond our own Milky Way. The large galaxies
visible here (such as the two bright spiral shaped galaxies visible in the lower right quarter of the picture) belong to the <a href="https://rubinobservatory.org/news/rubin-first-look/cosmic-treasure-chest">Virgo cluster</a>, a giant structure containing more than 1,000 galaxies, each holding billions to trillions of stars.
This image beautifully showcases the huge diversity of shapes, sizes and colours of galaxies in our universe revealed by Rubin in their full technicolour glory. Inside these galaxies, bright dots are visible – these are star-forming regions, just like the Lagoon and Trifid nebulae, but remarkably, these are millions of light years away from us. 
The still image captures just 2% of the area of a full Rubin image revealing a universe that is teeming with celestial bodies. The full image, which contains around ten million galaxies, would need several hundred ultra high-definition TV screens to display in all its detail. By the end of its ten-year survey, Rubin will catalogue the properties of some 20 billion galaxies, their colours and locations on the sky containing information about even more mysterious components of our universe such as dark matter and dark energy. Dark matter makes up most of the matter in the cosmos, but does not reflect or emit light. Dark energy seems to be responsible for the accelerating expansion of the universe.
<h2>The UK’s role</h2>
These unfathomable numbers demand data processing on a whole new scale.
Uncovering new discoveries from this data requires a giant collaborative effort, in which UK astronomy is playing a major role. The UK will process around 1.5 million Rubin images and hosts one of three international data access centres for the project, providing scientists across the globe with access to the vast Rubin data. Here at the University of Southampton, we are leading two critical software
development contributions to Rubin. 
First of these is the capability to combine the Rubin images with those at longer infrared wavelengths. This extends the colours that Rubin sees, providing key diagnostic information about the properties of stars and galaxies. Second is the software that will link Rubin observations to another new instrument <a href="https://www.4most.eu/cms/home/">called 4MOST</a>, soon to be installed at the Vista telescope in Chile.
Part of 4MOST’s job will be to snap up and classify rapidly changing “sources”, or objects, in the sky that have been discovered by Rubin. One such type of rapidly changing source is a stellar explosion known <a href="https://esahubble.org/wordbank/supernova/">as a supernova</a>. We expect to have catalogued more supernova explosions within just two years than have ever been made previously. Our contributions to the Rubin project will therefore lead to a totally new understanding of how the stars and galaxies in our universe live and die, offering an unprecedented glimpse into the grand cosmic cycle.
The Rubin observatory isn’t just a new telescope – it’s a new pair of eyes on the
universe, revealing the cosmos in unprecedented detail. A treasure trove of
discoveries await, but most interesting among them will be the hidden secrets of the universe that we are yet to contemplate. The first images from Rubin have been a spectacular demonstration of the vastness of the universe. What might we find in
this gargantuan dataset of the cosmos as the ultimate timelapse movie of our
universe unfolds?<img src="https://counter.theconversation.com/content/259857/count.gif" alt="The Conversation" width="1" height="1" />
Professor Manda Banerji receives funding from the Royal Society and the Science and Technology Facilities Council. Dr Philip Wiseman receives funding from the Science and Technology Facilities Council</content>
<summary>The new observatory can take very high resolution images of distant objects in space.</summary>
<author>
<name>Professor Manda Banerji, Professor of Astrophysics, School of Physics & Astronomy, University of Southampton</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/professor-manda-banerji-2421335"/>
</author>
<author>
<name>Dr Phil Wiseman, Research Fellow, Astronomy, University of Southampton</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/dr-phil-wiseman-1513455"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/249834</id>
<published>2025-06-25T12:44:16Z</published>
<updated>2025-06-25T12:44:16Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/how-do-scientists-calculate-the-probability-that-an-asteroid-could-hit-earth-249834"/>
<title>How do scientists calculate the probability that an asteroid could hit Earth?</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/668461/original/file-20250516-62-wffqck.jpg?ixlib=rb-4.1.0&amp;rect=0%2C56%2C950%2C534&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>NASA&#39;s Webb telescope captured a photo of the asteroid 2024 YR4 from afar. <a class="source" href="https://newsroom.ap.org/detail/NewlyDiscoveredAsteroid/eecb6be6ddc3406caaa5cdd2c4a9be8f/photo?Query=2024%20yr4&amp;mediaType=photo&amp;sortBy=&amp;dateRange=Anytime&amp;totalCount=9&amp;currentItemNo=1">European Space Agency via AP</a></figcaption></figure>I was preparing for my early morning class back in January 2025 when I received <a href="https://science.nasa.gov/blogs/planetary-defense/2025/01/29/nasa-shares-observations-of-recently-identified-near-earth-asteroid/">a notice regarding an asteroid called 2024 YR4</a>. It said the probability it could hit Earth was unusually high.
As defending Earth from unexpected intruders such as asteroids is <a href="https://scholar.google.com/citations?user=8_qb8h8AAAAJ&amp;hl=en">part of my expertise</a>, I immediately started receiving questions from my students and colleagues about what was happening. 
When scientists spot an asteroid whose trajectory might <a href="https://theconversation.com/neowise-the-nasa-mission-that-cataloged-objects-around-earth-for-over-a-decade-has-come-to-an-end-237921">take it close to Earth</a>, they monitor it frequently and calculate the probability that it might collide with our planet. As they receive more observational data, they get a better picture of what could happen. 
Just having more data points early doesn’t make scientists’ predictions better. They need to keep following the asteroid as it moves through space to better understand its trajectory.
Reflecting on the incident a few months later, I wondered whether there might have been a better way for scientists to communicate about the risk with the public. We got accurate information, but as the questions I heard indicated, it wasn’t always enough to understand what it actually means. 
<h2>Numbers change every day</h2>
The 2024 YR24 asteroid has a <a href="https://blogs.nasa.gov/webb/2025/04/02/nasas-webb-finds-asteroid-2024-yr4-is-building-sized/">diameter of about 196 feet (60 meters)</a> – equivalent to approximately a 15-story building in length.
At the time of the announcement in January, the asteroid’s impact probability was reported to <a href="https://science.nasa.gov/blogs/planetary-defense/2025/01/29/nasa-shares-observations-of-recently-identified-near-earth-asteroid/">exceed 1%</a>. The impact probability describes how likely a hazardous asteroid is to hit Earth. For example, if the impact probability is 1%, it means that in 1 of 100 cases, it hits Earth. One in 100 is kind of rare, but still too close for comfort if you’re talking about the odds of a collision that could devastate Earth.
Over time, though, further observations and analyses revealed an almost-zero chance of this asteroid colliding with Earth. 
After the initial notice in January, the impact probability continuously increased up to 3.1% on <a href="https://science.nasa.gov/blogs/planetary-defense/2025/02/19/dark-skies-bring-new-observations-of-asteroid-2024-yr4-lower-impact-probability/">Feb. 18</a>, but dropped to 1.5% on <a href="https://science.nasa.gov/blogs/planetary-defense/2025/02/19/dark-skies-bring-new-observations-of-asteroid-2024-yr4-lower-impact-probability/">Feb. 19</a>. Then, the impact probability continuously went down, until it hit 0.004% on <a href="https://science.nasa.gov/blogs/planetary-defense/2025/02/24/latest-calculations-conclude-asteroid-2024-yr4-now-poses-no-significant-threat-to-earth-in-2032-and-beyond/">Feb. 24</a>. <a href="https://cneos.jpl.nasa.gov/sentry/details.html#?des=2024%20YR4">As of June 15</a>, it now has an impact probability of less than 0.0000081%.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/668464/original/file-20250516-56-eggnpx.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A diagram showing the orbit paths of Earth, 2024 YR4 and some other planets in the solar system. 2024 YR4's orbit intersects with Earth's." src="https://images.theconversation.com/files/668464/original/file-20250516-56-eggnpx.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/668464/original/file-20250516-56-eggnpx.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=391&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/668464/original/file-20250516-56-eggnpx.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=391&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/668464/original/file-20250516-56-eggnpx.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=391&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/668464/original/file-20250516-56-eggnpx.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=492&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/668464/original/file-20250516-56-eggnpx.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=492&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/668464/original/file-20250516-56-eggnpx.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=492&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The orbit of 2024 YR4 will take it close to Earth, but scientists have found the chance of a collision to be exceedingly low.
<a class="source" href="https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2024%20YR4&amp;view=VOP">NASA/JPL</a>
</figcaption>
</figure>
But while the probability of hitting Earth went down, the probability of the asteroid hitting the Moon started increasing. It went up to 1.7% on <a href="https://science.nasa.gov/blogs/planetary-defense/2025/02/24/latest-calculations-conclude-asteroid-2024-yr4-now-poses-no-significant-threat-to-earth-in-2032-and-beyond/">Feb. 24</a>. As of April 2, it is <a href="https://science.nasa.gov/blogs/planetary-defense/2025/04/02/nasa-update-on-the-size-estimate-and-lunar-impact-probability-of-asteroid-2024-yr4/">3.8%</a>.
If it hits the Moon, some ejected materials from this collision could reach the Earth. However, these materials would burn away when they enter the Earth’s thick atmosphere. 
<h2>Impact probability</h2>
To see whether an approaching object could hit Earth, researchers find out what an asteroid’s orbit looks like using a technique called astrometry. This technique can accurately determine an object’s orbit, down to only a few kilometers of uncertainty. But astrometry needs accurate observational data taken for a long time. 
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/53Js-_vo3mo?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption>If an asteroid might get close to Earth, astronomers take observational data to better track the object’s path and eliminate uncertainty.</figcaption>
</figure>
Any uncertainty in the calculation of the object’s orbit causes variations in the predicted solution. Instead of one precise orbit, the calculation usually gives scientists a cloud of its possible orbits. The ellipse enclosing these locations is called an error ellipse. 
The <a href="https://doi.org/10.1016/j.icarus.2015.05.032">impact probability</a> describes how many orbital predictions in this ellipse hit the Earth. 
Without enough observational data, the orbital uncertainty is high, so the ellipse tends to be large. In a large ellipse, there’s a higher chance that the ellipse “accidentally” includes Earth – even if the center is off the planet. So, even if an asteroid ultimately won’t hit Earth, its error ellipse might <a href="https://doi.org/10.1016/j.icarus.2015.05.032">still include the planet</a> before scientists collect enough data to narrow down the uncertainty.
As the level of uncertainty goes down, the ellipse shrinks. So, when Earth is inside a small error ellipse, the impact probability may become higher than when it’s inside a large error ellipse. Once the error ellipse shrinks enough that it no longer includes Earth, the impact probability goes down significantly. That’s what happened to 2024 YR4.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/668495/original/file-20250516-62-591osa.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A diagram showing impact probability on the y axis and time on the x axis, with three drawings of the Earth and an error ellipse. As time goes on, the ellipse shrinks and in the third drawing it isn't overlapping with the Earth." src="https://images.theconversation.com/files/668495/original/file-20250516-62-591osa.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/668495/original/file-20250516-62-591osa.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=310&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/668495/original/file-20250516-62-591osa.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=310&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/668495/original/file-20250516-62-591osa.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=310&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/668495/original/file-20250516-62-591osa.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=390&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/668495/original/file-20250516-62-591osa.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=390&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/668495/original/file-20250516-62-591osa.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=390&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
As the error ellipse shrinks, the chance of the asteroid hitting Earth either goes down or goes way up, if it ends up overlapping with the Earth.
Toshi Hirabayashi
</figcaption>
</figure>
The impact probability is a single, practical value offering meaningful insight into an impact threat. However, just using the impact probability without any context may not provide meaningful guidelines to the public, as we saw with 2024 YR4. 
Holding on and waiting for more data to refine a collision prediction, or introducing new metrics for assessing impacts on Earth, are alternative courses of action to provide people with better guidelines for future threats before adding confusion and fear.<img src="https://counter.theconversation.com/content/249834/count.gif" alt="The Conversation" width="1" height="1" />
I have been studying planetary defense, particularly being part of past, ongoing, and future small body missions. I was part of the NASA/DART mission. I am currently part of the NASA/Lucy mission and the ESA/Hera mission. I am also on the Hayabusa2# team, led by the Japanese Aerospace Exploration Agency (JAXA), as part of an international collaboration. I have no affiliation with JAXA. </content>
<summary>Keeping Earth safe from asteroids isn’t just spotting them – it’s also helping people understand what a high-impact probability with Earth means.</summary>
<author>
<name>Toshi Hirabayashi, Associate Professor of Aerospace Engineering, Georgia Institute of Technology</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/toshi-hirabayashi-1647682"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/259233</id>
<published>2025-06-24T12:35:37Z</published>
<updated>2025-06-24T12:35:37Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/the-vera-c-rubin-observatory-will-help-astronomers-investigate-dark-matter-continuing-the-legacy-of-its-pioneering-namesake-259233"/>
<title>The Vera C. Rubin Observatory will help astronomers investigate dark matter, continuing the legacy of its pioneering namesake</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/675460/original/file-20250619-62-xds3ac.jpg?ixlib=rb-4.1.0&amp;rect=1438%2C0%2C6178%2C3472&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>The Rubin Observatory is scheduled to release its first images in 2025. <a class="source" href="https://noirlab.edu/public/images/iotw2229a/">RubinObs/NOIRLab/SLAC/NSF/DOE/AURA/B. Quint</a></figcaption></figure>Everything in space – from the Earth and Sun to black holes – accounts for just <a href="https://iopscience.iop.org/article/10.3847/1538-4357/ad3fb5">15% of all matter in the universe</a>. The rest of the cosmos seems to be made of an invisible material astronomers call <a href="https://theconversation.com/dark-matter-the-mystery-substance-physics-still-cant-identify-that-makes-up-the-majority-of-our-universe-85808">dark matter</a>.
Astronomers know dark matter exists because its gravity affects other things, such as light. But understanding what dark matter is remains an active area of research.
With the release of its <a href="https://rubinobservatory.org/news/rubin-first-look">first images</a> this month, the Vera C. Rubin Observatory has begun a 10-year mission to help unravel the mystery of dark matter. The observatory will continue the legacy of its namesake, a trailblazing astronomer who advanced our understanding of the other 85% of the universe.
As a <a href="https://airandspace.si.edu/people/staff/samantha-thompson">historian of astronomy</a>, I’ve studied how Vera Rubin’s contributions have shaped astrophysics. The observatory’s name is fitting, given that its data will soon provide scientists with a way to build on her work and shed more light on dark matter.
<h2>Wide view of the universe</h2>
From its vantage point in the Chilean Andes mountains, the Rubin Observatory will document everything visible in the southern sky. Every three nights, the observatory and its 3,200 megapixel camera will make a record of the sky. 
This camera, about the size of a small car, is the <a href="https://rubinobservatory.org/explore/how-rubin-works/technology/camera">largest digital camera ever built</a>. Images will capture an area of the sky roughly 45 times the size of the full Moon. With a big camera with a wide field of view, Rubin will produce about five petabytes of data every year. That’s <a href="https://www.npr.org/2019/04/10/711723383/watch-earth-gets-its-first-look-at-a-black-hole">roughly 5,000 years’ worth of MP3 songs</a>.
After weeks, months and years of observations, astronomers will have a time-lapse record revealing anything that explodes, flashes or moves – <a href="https://www.space.com/6638-supernova.html">such as supernovas</a>, <a href="https://www.space.com/15396-variable-stars.html">variable stars</a> or asteroids. They’ll also have the largest survey of galaxies ever made. These galactic views are key to investigating dark matter.
<h2>Galaxies are the key</h2>
Deep field images from the <a href="https://esahubble.org/images/heic0611b/">Hubble Space Telescope</a>, the <a href="https://theconversation.com/james-webb-space-telescope-an-astronomer-explains-the-stunning-newly-released-first-images-186800">James Webb Space Telescope</a> and others have visually revealed the abundance of galaxies in the universe. These images are taken with a long exposure time to collect the most light, so that even very faint objects show up.
Researchers now know that those galaxies aren’t randomly distributed. Gravity and dark matter pull and guide them into a structure that resembles a spider’s web or a tub of bubbles. The Rubin Observatory will expand upon these previous galactic surveys, increasing the precision of the data and capturing billions more galaxies. 
In addition to helping structure galaxies throughout the universe, dark matter also distorts the appearance of galaxies through an effect referred to as <a href="https://esawebb.org/wordbank/gravitational-lensing/">gravitational lensing</a>. 
Light travels through space in a straight line − unless it gets close to something massive. Gravity bends light’s path, which distorts the way we see it. This gravitational lensing effect provides clues that could help astronomers locate dark matter. The stronger the gravity, the bigger the bend in light’s path.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/675243/original/file-20250618-62-7m86qz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Many galaxies, represented as bright dots, some blurred, against a dark background." src="https://images.theconversation.com/files/675243/original/file-20250618-62-7m86qz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/675243/original/file-20250618-62-7m86qz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=612&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/675243/original/file-20250618-62-7m86qz.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=612&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/675243/original/file-20250618-62-7m86qz.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=612&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/675243/original/file-20250618-62-7m86qz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=769&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/675243/original/file-20250618-62-7m86qz.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=769&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/675243/original/file-20250618-62-7m86qz.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=769&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The white galaxies seen here are bound in a cluster. The gravity from the galaxies and the dark matter bends the light from the more distant galaxies, creating contorted and magnified images of them.
<a class="source" href="https://esawebb.org/images/weic2209a/">NASA, ESA, CSA and STScI</a>
</figcaption>
</figure>
<h2>Discovering dark matter</h2>
For centuries, astronomers tracked and measured the motion of planets in the solar system. They found that all the planets followed the path predicted by <a href="https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/newtons-laws-of-motion/">Newton’s laws of motion</a>, except for Uranus. Astronomers and mathematicians reasoned that if Newton’s laws are true, there must be some missing matter – another massive object – out there tugging on Uranus. <a href="https://www.nasa.gov/history/175-years-ago-astronomers-discover-neptune-the-eighth-planet/">From this hypothesis</a>, they discovered Neptune, confirming Newton’s laws.
With the ability to see fainter objects in the 1930s, astronomers began tracking the motions of galaxies. 
California Institute of Technology astronomer <a href="https://www.amnh.org/learn-teach/curriculum-collections/cosmic-horizons-book/fritz-zwicky">Fritz Zwicky</a> coined the term dark matter in 1933, after observing <a href="https://www.nasa.gov/image-article/coma-galaxy-cluster/">galaxies in the Coma Cluster</a>. He calculated the mass of the galaxies based on their speeds, which did not match their mass based on the number of stars he observed. 
He suspected that the cluster could contain an invisible, missing matter that kept the galaxies from flying apart. But for several decades he lacked enough observational evidence to support his theory.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/675244/original/file-20250618-56-vwa3gg.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A woman adjusting a large piece of equipment." src="https://images.theconversation.com/files/675244/original/file-20250618-56-vwa3gg.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/675244/original/file-20250618-56-vwa3gg.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=445&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/675244/original/file-20250618-56-vwa3gg.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=445&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/675244/original/file-20250618-56-vwa3gg.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=445&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/675244/original/file-20250618-56-vwa3gg.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=559&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/675244/original/file-20250618-56-vwa3gg.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=559&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/675244/original/file-20250618-56-vwa3gg.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=559&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Vera Rubin operates the Carnegie spectrograph at Kitt Peak National Observatory in Tucson.
<a class="source" href="https://noirlab.edu/public/images/noirlab2003a/">Carnegie Institution for Science</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
<h2>Enter Vera Rubin</h2>
In 1965, <a href="https://www.amnh.org/learn-teach/curriculum-collections/cosmic-horizons-book/vera-rubin-dark-matter">Vera Rubin</a> became the first women hired onto the scientific staff at the Carnegie Institution’s Department of Terrestrial Magnetism in Washington, D.C. 
She worked with Kent Ford, who had built an extremely sensitive <a href="https://www.scientificamerican.com/article/ancient-stars-how-does-spectrograph-work/">spectrograph</a> and was looking to apply it to a scientific research project. Rubin and Ford used the spectrograph to measure how fast stars orbit around the center of their galaxies. 
In the solar system, where most of the mass is within the Sun at the center, the closest planet, Mercury, moves faster than the farthest planet, Neptune.
“We had expected that as stars got farther and farther from the center of their galaxy, they would orbit slower and slower,” <a href="https://books.google.com/books?id=OVBUt6yrMtAC&amp;">Rubin said in 1992</a>. 
What they found in galaxies surprised them. Stars far from the galaxy’s center were moving <a href="https://doi.org/10.1086/150317">just as fast as stars closer in</a>. 
“And that really leads to only two possibilities,” <a href="https://books.google.com/books?id=OVBUt6yrMtAC&amp;">Rubin explained</a>. “Either Newton’s laws don’t hold, and physicists and astronomers are woefully afraid of that … (or) stars are responding to the gravitational field of matter which we don’t see.”
Data piled up as Rubin created plot after plot. Her colleagues didn’t doubt her observations, but the interpretation remained a debate. <a href="https://repository.aip.org/rubin-vera-1989-april-3">Many people were reluctant</a> to accept that dark matter was necessary to account for the findings in Rubin’s data. 
Rubin continued studying galaxies, measuring how fast stars moved within them. She wasn’t interested in investigating dark matter itself, but she carried on with documenting its effects on the motion of galaxies. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/675245/original/file-20250618-56-z4fjt6.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A quarter with a woman looking upwards engraved onto it." src="https://images.theconversation.com/files/675245/original/file-20250618-56-z4fjt6.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/675245/original/file-20250618-56-z4fjt6.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/675245/original/file-20250618-56-z4fjt6.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/675245/original/file-20250618-56-z4fjt6.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/675245/original/file-20250618-56-z4fjt6.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/675245/original/file-20250618-56-z4fjt6.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/675245/original/file-20250618-56-z4fjt6.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
A U.S quarter honors Vera Rubin’s contributions to our understanding of dark matter.
<a class="source" href="https://noirlab.edu/public/images/rubin-2025-americanwomen-quarterscoin-verarubin/">United States Mint</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
<h2>Vera Rubin’s legacy</h2>
Today, more people are aware of Rubin’s observations and contributions to our understanding of dark matter. In 2019, a congressional bill was introduced to rename the former Large Synoptic Survey Telescope to the Vera C. Rubin Observatory. In June 2025, the U.S. Mint <a href="https://womenshistory.si.edu/blog/new-quarter-honors-vera-rubin-astronomer-who-revealed-universes-hidden-mass">released a quarter</a> featuring Vera Rubin.
Rubin continued to accumulate data about the motions of galaxies throughout her career. Others picked up where she left off and have helped <a href="https://doi.org/10.1038/s41550-017-0059">advance dark matter research</a> over the past 50 years.
In the 1970s, physicist James Peebles and astronomers Jeremiah Ostriker and Amos Yahil <a href="https://doi.org/10.1086/152513">created computer simulations of individual galaxies</a>. They concluded, similarly to Zwicky, that there was not enough visible matter in galaxies to keep them from flying apart. 
They suggested that whatever dark matter is − be it cold stars, black holes or some unknown particle − there could be as much as 10 times the amount of dark matter than ordinary matter in galaxies.
Throughout its 10-year run, the Rubin Observatory should give even more researchers the opportunity to add to our understanding of dark matter.<img src="https://counter.theconversation.com/content/259233/count.gif" alt="The Conversation" width="1" height="1" />
Samantha Thompson does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</content>
<summary>Vera C. Rubin’s research into stars in galaxies led to the modern understanding of dark matter.</summary>
<author>
<name>Samantha Thompson, Astronomy Curator, National Air and Space Museum, Smithsonian Institution</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/samantha-thompson-2415968"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/258786</id>
<published>2025-06-23T12:38:03Z</published>
<updated>2025-06-23T12:38:03Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/astronomy-has-a-major-data-problem-simulating-realistic-images-of-the-sky-can-help-train-algorithms-258786"/>
<title>Astronomy has a major data problem – simulating realistic images of the sky can help train algorithms</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/674229/original/file-20250613-56-qi55ha.png?ixlib=rb-4.1.0&amp;rect=0%2C922%2C4004%2C2252&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>A simulation of a set of synthetic galaxies. Photons are sampled from these galaxies and have been simulated through the Earth&#39;s atmosphere, a telescope and a sensor using a code called PhoSim. John Peterson/Purdue</figcaption></figure>Professional astronomers don’t make discoveries by looking through an eyepiece like you might with a backyard telescope. Instead, they collect digital images in <a href="https://theconversation.com/new-powerful-telescopes-allow-direct-imaging-of-nascent-galaxies-12-billion-light-years-away-74910">massive cameras attached to large telescopes</a>.
Just as you might have an endless library of digital photos stored in your cellphone, many astronomers collect more photos than they would ever have the time to look at. Instead, <a href="https://www.physics.purdue.edu/people/faculty/peterson.php">astronomers like me</a> look at some of the images, then build algorithms and later use computers to combine and analyze the rest.
But how can we know that the algorithms we write will work, when we don’t even have time to look at all the images? We can practice on some of the images, but one new way to build the best algorithms is to simulate some fake images as accurately as possible.
With fake images, we can customize the exact properties of the objects in the image. That way, we can see if the algorithms we’re training can uncover those properties correctly. 
My research group and collaborators have found that the best way to create fake but realistic astronomical images is to painstakingly simulate light and its interaction with everything it encounters. Light is composed of <a href="https://theconversation.com/do-photons-wear-out-an-astrophysicist-explains-lights-ability-to-travel-vast-cosmic-distances-without-losing-energy-252880">particles called photons</a>, and we can simulate each photon. We wrote a publicly available code to do this called the <a href="http://www.phosim.org">photon simulator, or PhoSim</a>.
The goal of the PhoSim project is to create realistic fake images that help us understand where distortions in images from real telescopes come from. The fake images help us train programs that sort through images from real telescopes. And the results from studies using PhoSim can also help astronomers correct distortions and defects in their real telescope images.
<h2>The data deluge</h2>
But first, why is there so much astronomy data in the first place? This is primarily due to the rise of dedicated survey telescopes. A survey telescope maps out a region on the sky rather than just pointing at specific objects.
These observatories all have a large collecting area, a large field of view and a dedicated survey mode to collect as much light over a period of time as possible. Major surveys from the past two decades include the <a href="https://www.sdss.org/">SDSS</a>, <a href="https://science.nasa.gov/mission/kepler/">Kepler</a>, <a href="https://noirlab.edu/public/programs/ctio/victor-blanco-4m-telescope/decam/">Blanco-DECam</a>, <a href="https://hsc.mtk.nao.ac.jp/ssp/">Subaru HSC</a>, <a href="https://science.nasa.gov/mission/tess/">TESS</a>, <a href="https://www.ztf.caltech.edu/">ZTF</a> and <a href="https://www.esa.int/Science_Exploration/Space_Science/Euclid">Euclid</a>.
The <a href="http://www.rubinobservatory.org">Vera Rubin Observatory</a> in Chile has recently finished construction and will soon join those. Its survey begins soon after its official “<a href="https://doi.org/10.1038/d41586-025-01798-2">first look” event on June 23, 2025</a>. It will have a particularly strong set of survey capabilities. 
The Rubin observatory can look at a region of the sky all at once that is several times larger than the full Moon, and it can survey the entire southern celestial hemisphere every few nights. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/673780/original/file-20250611-56-rj3bnr.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="An observatory, which looks like a building with a dome atop it, on a mountainside, with a starry sky shown in the background." src="https://images.theconversation.com/files/673780/original/file-20250611-56-rj3bnr.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/673780/original/file-20250611-56-rj3bnr.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=324&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/673780/original/file-20250611-56-rj3bnr.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=324&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/673780/original/file-20250611-56-rj3bnr.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=324&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/673780/original/file-20250611-56-rj3bnr.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=408&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/673780/original/file-20250611-56-rj3bnr.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=408&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/673780/original/file-20250611-56-rj3bnr.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=408&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The Vera Rubin Observatory will take in lots of light to construct maps of the sky.
<a class="source" href="https://noirlab.edu/public/images/iotw2207a">Rubin Observatory/NSF/AURA/B. Quint</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
A survey can shed light on practically every topic in astronomy. 
Some of the ambitious research questions include: making measurements about <a href="https://theconversation.com/we-need-to-consider-alternatives-to-dark-matter-that-better-explain-cosmological-observations-226765">dark matter</a> and <a href="https://theconversation.com/dark-energy-may-have-once-been-springier-than-it-is-today-desi-cosmologists-explain-what-their-collaborations-new-measurement-says-about-the-universes-history-253067">dark energy</a>, mapping the Milky Way’s distribution of stars, <a href="https://theconversation.com/neowise-the-nasa-mission-that-cataloged-objects-around-earth-for-over-a-decade-has-come-to-an-end-237921">finding asteroids</a> in the solar system, building a three-dimensional map of galaxies in the universe, finding new <a href="https://theconversation.com/goodbye-kepler-hello-tess-passing-the-baton-in-the-search-for-distant-planets-93688">planets outside the solar system</a> and tracking millions of objects that change over time, <a href="https://theconversation.com/im-an-astrophysicist-mapping-the-universe-with-data-from-the-chandra-x-ray-observatory-clear-sharp-photos-help-me-study-energetic-black-holes-229668">including supernovas</a>.
All of these surveys create a massive data deluge. They generate tens of terabytes every night – that’s millions to billions of pixels collected in seconds. In the <a href="https://rubinobservatory.org/explore/how-rubin-works/technology/data">extreme case of the Rubin observatory</a>, if you spent all day long looking at images equivalent to the size of a 4K television screen for about one second each, you’d be looking at them 25 times too slow and you’d never keep up.
At this rate, no individual human could ever look at all the images. But automated programs can process the data. 
Astronomers don’t just survey an astronomical object like a planet, galaxy or supernova once, either. Often <a href="https://theconversation.com/astronomers-have-learned-lots-about-the-universe-but-how-do-they-study-astronomical-objects-too-distant-to-visit-214320">we measure</a> the same object’s size, shape, brightness and position in many different ways under many different conditions.
But more measurements do come with more complications. For example, measurements taken under certain weather conditions or on one part of the camera may disagree with others at different locations or under different conditions. Astronomers can correct these errors – called systematics – with careful calibration or algorithms, but only if we understand the reason for the inconsistency between different measurements. That’s where PhoSim comes in. Once corrected, we can use all the images and make more detailed measurements.
<h2>Simulations: One photon at a time</h2>
To understand the origin of these systematics, we built <a href="https://www.phosim.org">PhoSim</a>, which can simulate the propagation of light particles – photons – through the Earth’s atmosphere and then into the telescope and camera.
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/3pc8aPeeMBs?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption>A simulation of photons traveling from a single star to the Vera Rubin Observatory, made using PhoSim. The layers of turbulence in the atmosphere move according to wind patterns (top middle), and the mirrors deform (top right) depending on the temperature and forces exerted on them. The photons with different wavelengths (colors) are sampled from a star, refract through the atmosphere and then interact with the telescope’s mirrors, filter and lenses. Finally, the photons eject electrons in the sensor (bottom middle) that are counted in pixels to make an image (bottom right). John Peterson/Purdue</figcaption>
</figure>
PhoSim simulates the atmosphere, including air turbulence, as well as distortions from the shape of the telescope’s mirrors and the electrical properties of the sensors. The photons are propagated using a variety of physics that predict what photons do when they encounter the air and the telescope’s mirrors and lenses. 
The simulation ends by collecting electrons that have been <a href="https://en.wikipedia.org/wiki/Charge-coupled_device">ejected by photons</a> into a grid of pixels, to make an image.
Representing the light as trillions of photons is computationally efficient and an application of the <a href="https://en.wikipedia.org/wiki/Monte_Carlo_method">Monte Carlo method</a>, which uses random sampling. Researchers used PhoSim to verify some aspects of the Rubin observatory’s design and estimate how its images would look.
<figure class="align-center ">
<img alt="Rubin simulation with PhoSim, showing black dots representing stars and galaxies against a bright background" src="https://images.theconversation.com/files/674261/original/file-20250613-62-4kzf3u.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/674261/original/file-20250613-62-4kzf3u.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=318&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/674261/original/file-20250613-62-4kzf3u.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=318&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/674261/original/file-20250613-62-4kzf3u.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=318&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/674261/original/file-20250613-62-4kzf3u.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=400&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/674261/original/file-20250613-62-4kzf3u.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=400&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/674261/original/file-20250613-62-4kzf3u.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=400&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
A simulations of a series of exposures of stars, galaxies and background light through the Rubin observatory using PhoSim. Photons are sampled from the objects and then interact with the Earth’s atmosphere and Rubin’s telescope and camera.
John Peterson/Purdue
</figcaption>
</figure>
The results are complex, but so far we’ve connected the variation in temperature across telescope mirrors directly to astigmatism – angular blurring – in the images. We’ve also studied how high-altitude turbulence in the atmosphere that can disturb light on its way to the telescope shifts the positions of stars and galaxies in the image and causes blurring patterns that correlate with the wind. We’ve demonstrated how the electric fields in telescope sensors – which are intended to be vertical – can get distorted and warp the images.
Researchers can use these new results to correct their measurements and better take advantage of all the data that telescopes collect. 
Traditionally, astronomical analyses haven’t worried about this level of detail, but the meticulous measurements with the current and future surveys will have to. Astronomers can make the most out of this deluge of data by using simulations to achieve a deeper level of understanding.<img src="https://counter.theconversation.com/content/258786/count.gif" alt="The Conversation" width="1" height="1" />
John Peterson does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</content>
<summary>To make a truly realistic fake picture of a galaxy, you can model exactly how light particles travel through the atmosphere and telescope to reach its sensor.</summary>
<author>
<name>John Peterson, Assoc. Professor of Physics and Astronomy, Purdue University</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/john-peterson-2407885"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/256398</id>
<published>2025-06-16T12:39:30Z</published>
<updated>2025-06-16T12:39:30Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/is-mars-really-red-a-physicist-explains-the-planets-reddish-hue-and-why-it-looks-different-to-some-telescopes-256398"/>
<title>Is Mars really red? A physicist explains the planet’s reddish hue and why it looks different to some telescopes</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/667706/original/file-20250513-56-vwwqg9.jpg?ixlib=rb-4.1.0&amp;rect=71%2C0%2C937%2C527&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>Siccar Point, photographed by the Curiosity rover, is near Mars&#39; Gale Crater. <a class="source" href="https://apod.nasa.gov/apod/ap220831.html">NASA/JPL-Caltech/MSSS; Processing &amp; License: Kevin M. Gill</a></figcaption></figure>
<a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>.
<hr>
<blockquote>
Is Mars really as red as people say it is? – Jasmine, age 14, Everson, Washington
</blockquote>
<hr>
People from cultures across the world have been looking at Mars since ancient times. Because it appears reddish, it has often been called the red planet. 
The English name for the planet comes from the Romans, who named it after <a href="https://www.britannica.com/topic/Mars-Roman-god">their god of war</a> because its color reminded them of blood. In reality, the reddish color of Mars comes from <a href="https://science.nasa.gov/mars/facts/">iron oxide in the rocks and dust</a> covering its surface. 
Your blood is also red <a href="https://theconversation.com/blood-in-your-veins-is-not-blue-heres-why-its-always-red-97064">because of a mixture of iron and oxygen</a> in a molecule called hemoglobin. So in a way, the ancient connection between the planet Mars and blood wasn’t completely wrong. Rust, which is a common form of iron oxide found here on Earth, also often has a reddish color. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/668492/original/file-20250516-56-hk8xlj.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Rust flakes on metal." src="https://images.theconversation.com/files/668492/original/file-20250516-56-hk8xlj.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/668492/original/file-20250516-56-hk8xlj.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/668492/original/file-20250516-56-hk8xlj.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/668492/original/file-20250516-56-hk8xlj.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/668492/original/file-20250516-56-hk8xlj.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/668492/original/file-20250516-56-hk8xlj.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/668492/original/file-20250516-56-hk8xlj.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Iron oxide, found in rust on old metal machinery, is the compound that colors rocks and dust on Mars’ surface reddish brown.
<a class="source" href="https://www.flickr.com/photos/7603557@N08/7383824180">Lars Hammar/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a>
</figcaption>
</figure>
<a href="https://facultyweb.kennesaw.edu/djoffe/">In my current research</a> on exoplanets, I observe different types of signals from planets beyond Earth. Lots of interesting physics goes into how researchers perceive the colors of planets and stars through different types of telescopes.
<h2>Observing Mars with probes</h2>
If you look closely at pictures of Mars taken by rovers on its surface, you can see that most of the planet isn’t purely red, but more of a rusty brown or tan color. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/667141/original/file-20250511-56-f6zvnn.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A photo showing the front of a lander as well as dusty, rocky terrain." src="https://images.theconversation.com/files/667141/original/file-20250511-56-f6zvnn.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/667141/original/file-20250511-56-f6zvnn.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=474&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/667141/original/file-20250511-56-f6zvnn.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=474&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/667141/original/file-20250511-56-f6zvnn.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=474&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/667141/original/file-20250511-56-f6zvnn.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=595&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/667141/original/file-20250511-56-f6zvnn.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=595&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/667141/original/file-20250511-56-f6zvnn.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=595&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
You can see Mars’ rusty color in this photo taken by the Viking lander.
<a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA01522">NASA/JPL</a>
</figcaption>
</figure>
Probes sent from Earth have taken pictures showing rocks with a rusty color. A 1976 <a href="https://photojournal.jpl.nasa.gov/catalog/PIA01522">picture from the Viking lander</a>, the very first spacecraft to land on Mars, shows the Martian ground covered with a layer of rusty orange dust. 
Not all of Mars’ surface has the same color. At the poles, its ice caps appear white. These ice caps contain frozen water, like the ice we usually find on Earth, but these ice caps are also covered by a layer of <a href="https://science.nasa.gov/resource/dry-ice-on-mars/">frozen carbon dioxide</a> – dry ice. 
This layer of dry ice can evaporate very quickly when sunlight shines on it and grows back again when it becomes dark. This process causes the white ice caps to grow and shrink in size depending on the Martian seasons.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/667707/original/file-20250513-56-ox4ihy.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A photo of Mars from space. It looks reddish brown in color, with white clouds at the poles." src="https://images.theconversation.com/files/667707/original/file-20250513-56-ox4ihy.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/667707/original/file-20250513-56-ox4ihy.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/667707/original/file-20250513-56-ox4ihy.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/667707/original/file-20250513-56-ox4ihy.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/667707/original/file-20250513-56-ox4ihy.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/667707/original/file-20250513-56-ox4ihy.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/667707/original/file-20250513-56-ox4ihy.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
This picture from the Hubble Space Telescope shows the planet with the same rusty color covering large parts of its surface.
<a class="source" href="https://webbtelescope.org/contents/media/images/2018/10/4115-Image">NASA, ESA, Zolt G. Levay (STScI)</a>
</figcaption>
</figure>
<h2>Beyond visible light</h2>
Mars also gives off light in colors that you can’t see with your eyes but that scientists can measure with special cameras on telescopes. 
Light itself can be thought of not only as a wave but also as a <a href="https://www.symmetrymagazine.org/article/what-is-a-photon?language_content_entity=und">stream of particles called photons</a>. The amount of energy carried by each photon is related to its color. For example, blue and violet photons have more energy than orange and red photons. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A diagram of the electromagnetic spectrum, with radio, micro and infrared waves having a longer wavelength than visible light, while UV, X-ray and gamma rays have shorter wavelengths than visible light." src="https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=356&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=356&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=356&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=447&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=447&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/668491/original/file-20250516-62-i9y8b9.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=447&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The rainbow of visible light that you can see is only a small slice of all the kinds of light. Some telescopes can detect light with a longer wavelength, such as infrared light, or light with a shorter wavelength, such as ultraviolet light. Others can detect X-rays or radio waves.
<a class="source" href="https://en.wikipedia.org/wiki/Electromagnetic_spectrum#/media/File:EM_Spectrum_Properties_edit.svg">Inductiveload, NASA/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a>
</figcaption>
</figure>
<a href="https://science.nasa.gov/ems/10_ultravioletwaves/">Ultraviolet photons</a> have even more energy than the photons you can see with your eyes. These photons are found in direct sunlight, and because they have so much energy, they can damage the cells in your body. You <a href="https://theconversation.com/how-do-the-chemicals-in-sunscreen-protect-our-skin-from-damage-74355">can use sunscreen</a> to protect yourself from them. 
<a href="https://science.nasa.gov/ems/07_infraredwaves/">Infrared photons</a> have less energy than the photons you can see with your eyes, and you don’t need any special protection from them. This is how some types of night-vision goggles work: They can see light in the infrared spectrum as well as the visible color spectrum. Scientists can take pictures of Mars in the infrared spectrum using special cameras that work almost like night-vision goggles for telescopes.
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/667709/original/file-20250513-68-7f07ph.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Two photos of Mars from space -- one labeled 'visible true color' that looks reddish brown and one labeled 'infrared false color' that looks green and red." src="https://images.theconversation.com/files/667709/original/file-20250513-68-7f07ph.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/667709/original/file-20250513-68-7f07ph.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/667709/original/file-20250513-68-7f07ph.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/667709/original/file-20250513-68-7f07ph.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/667709/original/file-20250513-68-7f07ph.png?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/667709/original/file-20250513-68-7f07ph.png?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/667709/original/file-20250513-68-7f07ph.png?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
The Hubble Space Telescope could take pictures in both visible light and infrared light.
<a class="source" href="https://webbtelescope.org/contents/media/images/4179-Image">NASA, James Bell (Cornell University), Justin Maki (NASA-JPL), Mike J. Wolff (SSI)</a>
</figcaption>
</figure>
The colors on the infrared picture aren’t really what the infrared light looks like, because you can’t see those colors with your eyes. They are called “false colors,” and researchers add them to look at the picture more easily. 
When you compare the visible color picture and the infrared picture, you can see some of the same features – and the ice caps are visible in both sets of colors. 
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/667710/original/file-20250513-56-l20b51.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="Mars shown from space, colored gray, green and brown." src="https://images.theconversation.com/files/667710/original/file-20250513-56-l20b51.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=237&amp;fit=clip" srcset="https://images.theconversation.com/files/667710/original/file-20250513-56-l20b51.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/667710/original/file-20250513-56-l20b51.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/667710/original/file-20250513-56-l20b51.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=600&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/667710/original/file-20250513-56-l20b51.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/667710/original/file-20250513-56-l20b51.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/667710/original/file-20250513-56-l20b51.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=754&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
A UV view of Mars with the MAVEN spacecraft.
<a class="source" href="https://science.nasa.gov/resource/maven-spacecraft-stuns-with-ultraviolet-views-of-red-planet/">NASA/LASP/CU Boulder</a>
</figcaption>
</figure>
NASA’s MAVEN spacecraft, launched in 2013, has even taken <a href="https://science.nasa.gov/resource/maven-spacecraft-stuns-with-ultraviolet-views-of-red-planet/">pictures with ultraviolet light</a>, giving scientists a different view of both the surface of Mars and its atmosphere. 
Each new type of picture tells scientists more about the Martian landscape. They hope to use these details to answer questions about how Mars formed, how long it had <a href="https://marsed.asu.edu/mep/volcanoes">active volcanoes</a>, where <a href="https://theconversation.com/ancient-mars-may-have-had-a-carbon-cycle-a-new-study-suggests-the-red-planet-may-have-once-been-warmer-wetter-and-more-favorable-for-life-255207">its atmosphere came from</a> and whether it had <a href="https://theconversation.com/our-mostly-dry-planetary-neighbors-once-had-lots-of-water-what-does-that-imply-for-us-43817">liquid water on its surface</a>.
Astronomers are always looking for new ways to take telescope pictures outside of the <a href="https://theconversation.com/where-does-black-fall-on-the-color-spectrum-a-color-scientist-explains-234540">regular visible spectrum</a>. They can even make images using <a href="https://theconversation.com/less-than-1-of-the-worlds-biggest-radio-telescope-is-complete-but-its-first-image-reveals-a-sky-dotted-with-ancient-galaxies-252382">radio waves</a>, microwaves, <a href="https://theconversation.com/im-an-astrophysicist-mapping-the-universe-with-data-from-the-chandra-x-ray-observatory-clear-sharp-photos-help-me-study-energetic-black-holes-229668">X-rays</a> and gamma rays. Each part of the spectrum they can use to look at an object in space represents new information they can learn from.
Even though people have been looking at Mars since ancient times, we still have much to learn about this fascinating neighbor.
<hr>
Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.
And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.<img src="https://counter.theconversation.com/content/256398/count.gif" alt="The Conversation" width="1" height="1" />
David Joffe receives funding from the NASA Office of STEM Engagement through a grant from the Georgia Space Grant Consortium</content>
<summary>Mars isn’t a bright, fire-engine red, but the iron oxide in its rocks makes it appear redder than other planets, especially from afar.</summary>
<author>
<name>David Joffe, Associate Professor of Physics, Kennesaw State University</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/david-joffe-2390964"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
<entry>
<id>tag:theconversation.com,2011:article/252695</id>
<published>2025-06-10T12:21:15Z</published>
<updated>2025-06-10T12:21:15Z</updated>
<link rel="alternate" type="text/html" href="https://theconversation.com/where-is-the-center-of-the-universe-252695"/>
<title>Where is the center of the universe?</title>
<content type="html"><figure><img src="https://images.theconversation.com/files/665893/original/file-20250505-56-1mt7ki.jpg?ixlib=rb-4.1.0&amp;rect=0%2C64%2C1700%2C956&amp;q=45&amp;auto=format&amp;w=496&amp;fit=clip" /><figcaption>In space, there are four dimensions: length, width, height and time. <a class="source" href="https://www.gettyimages.com/detail/photo/milky-way-in-universe-abstract-night-sky-and-space-royalty-free-image/1200406584?phrase=the%2Buniverse">scaliger/iStock/NASA via Getty Images Plus</a></figcaption></figure>About a century ago, scientists were struggling to reconcile what seemed a contradiction in <a href="https://www.space.com/17661-theory-general-relativity.html">Albert Einstein’s theory of general relativity</a>.
<a href="https://asd.gsfc.nasa.gov/blueshift/index.php/2015/11/25/100-years-of-general-relativity/">Published in 1915</a>, and already widely accepted worldwide by physicists and mathematicians, the theory assumed the universe was static – unchanging, unmoving and immutable. In short, Einstein believed the size and shape of the universe today was, more or less, the same size and shape it had always been.
But when astronomers looked into the night sky at faraway galaxies with powerful telescopes, they saw hints the universe was anything but that. These new observations suggested the opposite – that it was, <a href="https://skyserver.sdss.org/dr1/en/astro/universe/universe.asp">instead, expanding</a>. 
Scientists soon realized Einstein’s theory didn’t actually say the universe had to be static; the theory could support an expanding universe as well. Indeed, by using the same mathematical tools provided by Einstein’s theory, scientists created new models that showed the universe was, in fact, <a href="https://www.pbs.org/wgbh/aso/databank/entries/dp29hu.html">dynamic and evolving</a>. 
I’ve spent decades trying to understand general relativity, including in my current job <a href="https://scholar.google.com/citations?user=GEn0OTgAAAAJ&amp;hl=en">as a physics professor</a> teaching courses <a href="https://web.uri.edu/physics/meet/robert-coyne/">on the subject</a>. I know wrapping your head around the idea of an ever-expanding universe can feel daunting – and part of the challenge is overriding your natural intuition about how things work. For instance, it’s hard to imagine something as big as the universe not having a center at all, but physics says that’s the reality.
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/BBKV2N550XE?wmode=transparent&amp;start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption>The universe gets bigger every day.</figcaption>
</figure>
<h2>The space between galaxies</h2>
First, let’s define what’s meant by “expansion.” On Earth, “expanding” means something is getting bigger. And in regard to the universe, that’s true, sort of. Expansion might also mean “everything is getting farther from us,” which is also true with regard to the universe. Point a telescope at distant galaxies and they all do appear <a href="https://science.nasa.gov/mission/hubble/science/science-highlights/discovering-a-runaway-universe/">to be moving away from us</a>.
What’s more, the farther away they are, the faster they appear to be moving. Those galaxies also seem to be moving away from each other. So it’s more accurate to say that everything in the universe is getting <a href="https://science.nasa.gov/dark-energy/#:%7E">farther away from everything else</a>, all at once.
This idea is subtle but critical. It’s easy to think about the creation of the universe like exploding fireworks: Start with <a href="https://physics.mit.edu/news/it-all-started-with-a-big-bang-the-quest-to-unravel-the-mystery-behind-the-birth-of-the-universe/">a big bang</a>, and then all the galaxies in the universe fly out in all directions from some central point. 
But that analogy isn’t correct. Not only does it falsely imply that the expansion of the universe started from a single spot, which it didn’t, but it also suggests that the galaxies are the things that are moving, which isn’t entirely accurate. 
It’s not so much the galaxies that are moving away from each other – it’s the space between galaxies, the fabric of the universe itself, that’s <a href="https://www.livescience.com/65978-what-happens-in-intergalactic-space.html">ever-expanding as time goes on</a>. In other words, it’s not really the galaxies themselves that are moving through the universe; it’s more that <a href="https://www.space.com/52-the-expanding-universe-from-the-big-bang-to-today.html">the universe itself</a> is carrying them farther away as it expands.
A common analogy is to imagine sticking some dots on the surface of a balloon. As you blow air into the balloon, it expands. Because the dots are stuck on the surface of the balloon, they get farther apart. Though they may appear to move, the dots actually stay exactly where you put them, and the distance between them gets bigger simply by virtue of the balloon’s expansion. 
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/672328/original/file-20250604-74-2xt71o.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="split screen of a green balloon with red dots and a squiggle on the surface, lightly inflated and then much more blown up" src="https://images.theconversation.com/files/672328/original/file-20250604-74-2xt71o.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" srcset="https://images.theconversation.com/files/672328/original/file-20250604-74-2xt71o.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/672328/original/file-20250604-74-2xt71o.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/672328/original/file-20250604-74-2xt71o.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=338&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/672328/original/file-20250604-74-2xt71o.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/672328/original/file-20250604-74-2xt71o.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/672328/original/file-20250604-74-2xt71o.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=424&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
It’s the space between the dots that’s growing.
<a class="source" href="https://www.jpl.nasa.gov/edu/resources/lesson-plan/model-the-expanding-universe/">NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a>
</figcaption>
</figure>
Now think of the dots as galaxies and the balloon as the fabric of the universe, and you begin to get the picture. 
Unfortunately, while this analogy is a good start, it doesn’t get the details quite right either.
<h2>The 4th dimension</h2>
Important to any analogy is an understanding of its limitations. Some flaws are obvious: A balloon is small enough to fit in your hand – not so the universe. Another flaw is more subtle. The balloon has two parts: its latex surface and its air-filled interior. 
These two parts of the balloon are described differently in the language of mathematics. The balloon’s surface is two-dimensional. If you were walking around on it, you could move forward, backward, left, or right, but you couldn’t move up or down without leaving the surface. 
Now it might sound like we’re naming four directions here – forward, backward, left and right – but those are just movements along two basic paths: side to side and front to back. That’s what makes the surface two-dimensional – length and width. 
The inside of the balloon, on the other hand, is three-dimensional, so you’d be able to move freely in any direction, including up or down – length, width and height. 
This is where the confusion lies. The thing we think of as the “center” of the balloon is a point somewhere in its interior, in the air-filled space beneath the surface. 
But in this analogy, the universe is more like the latex surface of the balloon. The balloon’s air-filled interior has no counterpart in our universe, so we can’t use that part of the analogy – only the surface matters.
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/671018/original/file-20250529-62-c5loiz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img alt="A blown-up purple balloon on a blue background." src="https://images.theconversation.com/files/671018/original/file-20250529-62-c5loiz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=237&amp;fit=clip" srcset="https://images.theconversation.com/files/671018/original/file-20250529-62-c5loiz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/671018/original/file-20250529-62-c5loiz.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/671018/original/file-20250529-62-c5loiz.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=450&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/671018/original/file-20250529-62-c5loiz.jpg?ixlib=rb-4.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=566&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/671018/original/file-20250529-62-c5loiz.jpg?ixlib=rb-4.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=566&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/671018/original/file-20250529-62-c5loiz.jpg?ixlib=rb-4.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=566&amp;fit=crop&amp;dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
Trying to figure out how the universe works? Start by contemplating a balloon.
<a class="source" href="https://www.gettyimages.com/detail/photo/single-pink-balloon-on-blue-background-royalty-free-image/671323546">Kristopher_K/iStock via Getty Images Plus</a>
</figcaption>
</figure>
So asking, “Where’s the center of the universe?” is somewhat like asking, “Where’s the center of the balloon’s surface?” There simply isn’t one. You could travel along the surface of the balloon in any direction, for as long as you like, and you’d never once reach a place you could call its center because you’d never actually leave the surface.
In the same way, you could travel in any direction in the universe and would never find its center because, much like the surface of the balloon, it <a href="https://www.astronomy.com/science/ask-astro-where-is-the-center-of-the-universe/">simply doesn’t have one</a>.
Part of the reason this can be so challenging to comprehend is because of the way the universe is described in the language of mathematics. The surface of the balloon has two dimensions, and the balloon’s interior has three, but the universe exists in four dimensions. Because it’s not just about how things move in space, but how they move in time.
Our brains are wired to think about space and time separately. But in the universe, they’re interwoven into a single fabric, called “<a href="https://phys.org/news/2023-11-four-dimensional-universe.html">space-time</a>.” That unification changes the way the universe works relative to what our intuition expects.
And this explanation doesn’t even begin to answer the question of how something <a href="https://theconversation.com/what-is-the-universe-expanding-into-if-its-already-infinite-239702">can be expanding indefinitely</a> – scientists are still trying to puzzle out what powers this expansion.
So in asking about the center of the universe, we’re confronting the limits of our intuition. The answer we find – everything, expanding everywhere, all at once – is a glimpse of just how strange and beautiful our universe is.<img src="https://counter.theconversation.com/content/252695/count.gif" alt="The Conversation" width="1" height="1" />
Rob Coyne receives funding from the National Aeronautics and Space Administration (NASA) and the US National Science Foundation (NSF).</content>
<summary>As the universe expands, it feels like it must be spreading out from some initial point. But a physicist explains why that’s not how it works. Hint: space-time is involved.</summary>
<author>
<name>Rob Coyne, Teaching Professor of Physics, University of Rhode Island</name>
<foaf:homepage rdf:resource="https://theconversation.com/profiles/rob-coyne-2350542"/>
</author>
<rights>Licensed as Creative Commons – attribution, no derivatives.</rights>
</entry>
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