![\"Composite](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/09\/1758732373_375_3i-atlas-vlt.jpg\")
Credit: ESO\/O. Hainaut<\/p>\nComet 3I\/ATLAS is a visitor to our Solar System from deep space, having formed elsewhere in the Galaxy and only temporarily passing through our cosmic neighbourhood.<\/p>\n
While astronomers regularly discover and observe many comets in our night sky, the vast majority of those spotted originated within our Solar System.<\/p>\n
Credit: ESO\/O. Hainaut<\/p>\n
Interstellar comets like 3I\/ATLAS<\/a> are much more rare.<\/p>\n In fact, it’s one of only three such interstellar visitors ever discovered, the other two being 1I\/\u02bbOumuamua (2017) and 2I\/Borisov (2019).<\/p>\n Why are these objects so rare, why have we only ever seen three, and how can we discover more?<\/p>\n Dr Matthew Hopkins is a researcher at the University of Oxford in the UK, who primarily looks at interstellar objects and galactic evolution.<\/p>\n His study of 3\/ATLAS revealed it could be the oldest comet we’ve ever seen<\/a>.<\/p>\n We spoke to Matthew to find out more.<\/p>\n 3I\/ATLAS is an interstellar object that was discovered passing through our Solar System by the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey in July 2025.<\/p>\n During the survey, we built a model: the \u014ctautahi-Oxford interstellar object population model.<\/p>\n This model can, among other things, tell us about the age of a transiting body like 3I\/ATLAS.<\/p>\n I noticed that 3I\/ATLAS was bobbing up and down on its orbit around the Milky Way.<\/p>\n That was a light-bulb moment for me, because I knew that older stars also follow a similar pattern in their orbits.<\/p>\n When we did all the statistics and looked at the correlations, we found that 3I\/ATLAS was probably over seven billion years old.<\/p>\n That’s about twice the age of our Solar System.<\/p>\n Firstly, they need to be close enough that they are reflecting enough sunlight for us to be able to see them.<\/p>\n These objects don\u2019t tend to reflect a lot of light, and tend to be very dark in colour.<\/p>\n Additionally, we need to determine that the object is a moving point of light and not just something that appears in one image and is never seen again.<\/p>\n All this means asteroids<\/a> and comets<\/a> are generally difficult to find. Ones like 3I\/ATLAS, which come from outside the Solar System, are even harder.<\/p>\n There are a lot of them, though. Around 50 are predicted to be within the orbit of Jupiter at any time.<\/p>\n But there are also around five million asteroids in that volume of space, so when it comes to finding interstellar objects, the odds are stacked against us.<\/p>\n When we see the object moving, we can then work out what path it\u2019s taking as it makes its way through the Solar System.<\/p>\n If something is bound to the Sun, its path will look like a circle or an ellipse.<\/p>\n Interstellar objects have orbits that take a different form, which we call hyperbolic.<\/p>\n This means they come in on a straight line, bend around the Sun, and then leave again on a straight line.\u00a0<\/p>\n Are we likely to detect more interstellar objects?<\/p>\n The upcoming Vera C Rubin Observatory is going to make a big difference.<\/p>\n Rubin is a very sensitive telescope looking at huge areas of the sky.<\/p>\n It\u2019s going to conduct what\u2019s called the Legacy Survey of Space and Time (LSST), which is a 10-year survey of the southern sky.<\/p>\n The timescale is months. We discovered it in July 2025, when it was in the orbit of Jupiter, and it was only just visible then. <\/p>\n Right now, it\u2019s going behind the Sun and is near its closest approach. In roughly a year, it will be fading from the visibility of most of our telescopes.<\/p>\n What else can we learn from 3I\/ATLAS?<\/p>\n It\u2019s a really interesting object.<\/p>\n Firstly, its existence implies that there were planetesimals (or tiny planets) in the Galaxy a very long time ago.<\/p>\n And what we know about the composition of 3I\/ATLAS also tells us these planetesimals contained heavier elements than hydrogen and helium.<\/p>\n Seven billion years ago, the Galaxy would have looked very different to how it does today, and 3I\/ATLAS is like seeing a piece of that earlier Universe in our lifetimes.<\/p>\n We have to wait for 3I\/ATLAS to emerge from behind the Sun. After that, we will start to try to understand how it evolves.<\/p>\n Our team will be studying its chemical composition, because that will tell us about its parent bodies.<\/p>\n On a bigger scale, we will be anticipating the LSST survey by the Vera C Rubin Observatory, as this will help us to spot many more of these interstellar objects.<\/p>\n Can we see 3I\/ATLAS from our back garden?<\/p>\n 3I\/ATLAS is going to remain pretty faint throughout its passage through the Solar System, so will probably be out of reach of all but the biggest amateur telescopes.<\/p>\n However, comets can be unpredictable and can undergo sudden increases in brightness due to bursts of activity, so we might get lucky.<\/p>\n","protected":false},"excerpt":{"rendered":"Comet 3I\/ATLAS is a visitor to our Solar System from deep space, having formed elsewhere in the Galaxy…\n","protected":false},"author":2,"featured_media":157844,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[90,416,56,54,55],"class_list":{"0":"post-157843","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-space","8":"tag-science","9":"tag-space","10":"tag-uk","11":"tag-united-kingdom","12":"tag-unitedkingdom"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/157843","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/comments?post=157843"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/posts\/157843\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media\/157844"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/media?parent=157843"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/categories?post=157843"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/uk\/wp-json\/wp\/v2\/tags?post=157843"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"Comet](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/09\/1758732374_152_3i-atlas-gemini-south.jpg\")
Comet 3I\/ATLAS captured by the Gemini Multi-Object Spectrograph (GMOS) on Gemini South at Cerro Pach\u00f3n in Chile, 27 August 2025. Image composed of exposures taken through red, green, blue and ultraviolet filters. Credit: International Gemini Observatory\/NOIRLab\/NSF\/AURA\/Shadow the Scientist. Image Processing: J. Miller & M. Rodriguez (International Gemini Observatory\/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage\/NSF NOIRLab), M. Zamani (NSF NOIRLab)<\/p>\n![\"matthew](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/09\/matthew-hopkins-oxford-university.jpg\")
\nWhat is 3I\/ATLAS and what makes it so interesting?<\/p>\n![\"A](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/09\/comet-3i-atlas-discovery-frame.jpg\")
A single frame showing the location of comet 3I\/ATLAS when it was discovered on 1 July 2025. Credit: ATLAS\/University of Hawaii\/NASA
\nWhy have we only ever found three interstellar visitors?<\/p>\n![\"Illustration](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/09\/3i-atlas-vs-sun.jpg\")
Illustration showing the top view of our Milky Way and the estimated orbits of both our Sun (yellow) and the 3I\/ATLAS comet (red). Credit: M. Hopkins\/\u014ctautahi-Oxford team. Base map: ESA\/Gaia\/DPAC, Stefan Payne-Wardenaar, CC-BY-SA 4.0.
\nHow do you distinguish an interstellar object from a Solar System asteroid?<\/p>\n![\"The](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/09\/rubin-telescope-twilight.jpg\")
The Rubin Observatory is located in the Chilean Andes to give it optimal conditions for observing the sky. Could it discover many more objects like 3I\/ATLAS? Credit: Rubin Observatory\/NSF\/AURA
\nHow long will 3I\/ATLAS be around for?<\/p>\n![\"Image](\"https:\/\/www.newsbeep.com\/uk\/wp-content\/uploads\/2025\/09\/1758732376_653_3i-atlas-hubble.jpg\")
Image of interstellar comet 3I\/ATLAS captured by the Hubble Space Telescope\u2019s Wide Field Camera on 21 July 2025. Credit: NASA, ESA, D. Jewitt (UCLA); Image Processing: J. DePasquale (STScI)
\nWhat\u2019s next for researchers?<\/p>\n