logo
7 Big Mysteries about Interstellar Object 3I/ATLAS

7 Big Mysteries about Interstellar Object 3I/ATLAS

Earlier this month astronomers were thrilled to discover only the third known interstellar object ever seen in our solar system. Now dubbed 3I/ATLAS, the suspected comet has just zoomed past the orbit of Jupiter, traveling so fast that it's bound to slip through our sun's gravitational grip. The high speed and hyperbolic trajectory of 3I/ATLAS means it must have come from another star and was cast adrift in the Milky Way by some unknown process before it eventually, by chance, briefly swooped by our sun. It will reach about the orbit of Mars before it boomerangs back toward interstellar space, never to be seen again, at the end of this year.
That's why astronomers have been racing to study 3I/ATLAS since July 1, when Larry Denneau of the University of Hawaii first spied it using a telescope in Chile that's part of the globe-spanning Asteroid Terrestrial-Impact Last Alert System (ATLAS). Soon more powerful observatories, including the James Webb Space Telescope (JWST) and Hubble Space Telescope, will scrutinize the object—which, thanks to its alien, interstellar provenance may be the oldest comet anyone has ever seen.
'I didn't get any sleep for like 35 hours,' says Bryce Bolin of Eureka Scientific in California, who rushed to release a preprint paper and arrange additional observations following 3I/ATLAS's discovery. 'It ruined my weekend.'
On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
Stefanie Milam of NASA's Goddard Space Flight Center is part of a group that had reserved time on JWST to observe an interstellar object—if the researchers were fortunate enough for one to be discovered. But the group's luck was tested when it couldn't reach the lead of its program—Martin Cordiner, also at Goddard—to kick the observations into action. 'He was hiking in Maine when the object was discovered, and we could not reach him—he was completely off the grid,' Milam says. 'When he finally got back, his phone just blew up. I said, 'You're never allowed to go on vacation again!''
So why exactly are astronomers so eager to observe this object, and what do they hope to learn?
Where did 3I/ATLAS come from?
The first major question to answer about 3I/ATLAS is its origin. Tracing it back to an individual star is likely impossible, given the mixing of myriad stars in their orbits around our galaxy across billions of years. But we might be able to work out roughly the region it came from.
One team of astronomers has already begun doing just that, using the high velocity of the object with respect to our sun—60 kilometers (37 miles) a second—to argue that it might have come from the vicinity of our galaxy's thick disk. This is a puffy torus of older stars moving at high velocities above and below the main flat plane of the Milky Way—which is where our sun serenely orbits.
A thick-disk origin might mean that 3I/ATLAS is extremely ancient, more than eight billion years old. 'It's from a star that's potentially not even there anymore,' says Michele Bannister of the University of Canterbury in New Zealand, a co-author on the work.
Aster Taylor of the University of Michigan performed a different age analysis based on the trajectory of 3I/ATLAS and suggests the object is 11 billion to three billion years old. 'We get similar answers,' Taylor says. Such estimates might soon be revised if subsequent observations can show just how much space weathering the object has endured during its interstellar sojourn.
How big is it?
Currently, 3I/ATLAS is inside the orbit of Jupiter and approaching the orbit of Mars, which it will cross in October, passing about 0.2 astronomical unit (one fifth the Earth-sun distance) from the Red Planet.
Although early observations have led astronomers to categorize 3I/ATLAS as a comet, at the moment, it's not behaving exactly like one. The object doesn't display a large tail or enveloping coma of cast-off gas, only a hint of dust—but that is expected to change soon. As it traverses the asteroid belt between Mars and Jupiter and basks in the sun's radiance, its surface should warm enough to sublimate ice, venting sufficient material to form a large coma and perhaps a prominent tail.
A substantial coma would be like a curtain drawn over astronomers' eyes, obscuring their view of the object and complicating efforts to gauge its dimensions. Before that happens, a team led by David Jewitt at the University of California, Los Angeles, is hoping to pin down its size with Hubble in August. (Other telescopes might be able to determine the size of 3I/ATLAS, too.)
Initial estimates suggested 3I/ATLAS might be up 20 kilometers (12 miles) across—very big for a comet—but most astronomers now think it is much smaller. 'It's probably somewhere in the range of one or two kilometers,' says John Noonan at Auburn University in Alabama. That would be somewhat comparable in size to our first two interstellar visitors: 1I/ʻOumuamua, which was discovered in 2017 and was up to about 400 meters (0.25 mile) long, and 2I/Borisov, which was found in 2019 and was about one kilometer (0.6 mile) wide.
If 3I/ATLAS turns out to be much bigger, 10 kilometers (six miles) or more, this would pose problems for preexisting estimates of many big interstellar objects reside in the galaxy. 'It's statistically extremely unlikely we should ever see something that size,' Noonan says. 'Theorists don't like that. But as an observer, I would love to see a really weird, big object.'
How fast is it spinning?
As well as its size, one of the key properties astronomers want to know about 3I/ATLAS is its rotation rate—something they might discern by watching the object's changing brightness as it spins. The spin of 3I/ATLAS could carry clues as to how the object was ejected from its home star in the first place.
'Certain ways of kicking these objects out tend to make them spin up,' Taylor says. A close pass of a gas giant planet, for instance, could easily set the object twirling while hurling it away from its home star. Conversely, a slow rotation period would suggest the object experienced a more gentle ejection.
'You could do this when stars die,' Taylor says. 'They lose a lot of mass, and so the gravitational force on objects at the outer edge of their system goes away. Those objects become unbound and just flow out into the galaxy.'
The rotation period can also tell us more about the shape of 3I/ATLAS—a steady rotation suggests a fairly spherical form, whereas a fluctuating rotation speed might suggest a 'wonky shape,' Taylor says, like that of 'Oumuamua, which was estimated to be cigar- or pancake-shaped.
What is 3I/ATLAS made of?
If 3I/ATLAS really is an ancient cometary castaway that has been drifting through the galaxy for eons, it might be full of ice that has never been heated by a star. If so, then as it gets closer, the object might suddenly erupt into activity. While that could be bad news for measuring its size, it would aid efforts to determine 3I/ATLAS's chemical composition.
JWST and Hubble would be best suited for the task of picking apart the different species of molecules that might erupt from 3I/ATLAS. Unfortunately, however, in October, when the object will be at its warmest, closest point to our star (called perihelion), Earth will be on the other side of the sun. This will make observations from our planet almost impossible.
In November, post-perihelion, Noonan will use Hubble to study 3I/ATLAS and its emissions, looking for signs of substances such as hydroxide and hydrogen that can help clarify its composition.
If the object is several billion years old, as predicted, then it might be rich in water because of the suspected formation environment around older stars. 'You would expect a lot of hydrogen coming from these water-rich irradiated objects, if this is really as old as [thought],' Noonan says.
Milam and her colleagues, meanwhile, will use JWST in August and December to observe 3I/ATLAS before and after perihelion. Thanks to its keen infrared vision, JWST is better suited for teasing out the presence of molecules such as water, carbon monoxide, carbon dioxide and ammonia.
'We can really home in and see what this thing looks like,' she says. 'Borisov had a pretty boring chemistry, but it wasn't like any object in our solar system—there was hardly any water at all but a lot of carbon monoxide and hydrogen cyanide. With JWST, we're hoping to see a lot of carbon dioxide [on 3I/ATLAS], maybe even water, if it's as pristine as people are projecting.'
Although the overall view from Earth degrades as the object approaches perihelion, some telescopes will be less visually impaired. Those operated by the Lowell Observatory in Arizona, for instance, are primed to observe 3I/ATLAS at dawn and dusk, when the sun is below the horizon. This will allow for studies even when the object will be close to our star from our planet-bound perspective. 'The Lowell Discovery Telescope is really well suited to observations close to the horizon,' says Nick Moskowitz, an astronomer at Lowell Observatory. 'We will be able to track it closer in to perihelion than other facilities.'
An unlikely additional capability will be at Mars, where spacecraft such as NASA's Mars Atmosphere and Volatile Evolution (MAVEN) orbiter may be able to see 3I/ATLAS as it passes about 30 million kilometers (19 million miles) from the planet. 'It'll be pretty large and apparent in the sky,' Noonan says, providing the object kicks into activity as hoped. 'They'll be able to see the coma,' giving us an insight into 3I/ATLAS's activity near the sun that would otherwise be impossible to see from Earth.
Will it survive?
A big unknown about 3I/ATLAS is whether it will actually survive its close encounter with our sun. While 'Oumuamua did so, Comet Borisov was not so fortunate, with the object appearing to split and break apart on its way out of our solar system.
The same fate could befall 3I/ATLAS. 'Borisov fragmented, which is pretty usual for comets,' Bannister says. All eyes will be on our latest visitor to see if the same thing happens again.
An additional quirk of 3I/ATLAS's survivability is the impact of solar wind, which may snip away any cometary tail as it is ejected. By chance, the object is entering our solar system at quite a shallow angle, much flatter than that of most comets, which means it will experience stronger solar headwinds.
Sarah Watson of the University of Reading in England and her colleagues are using this quirk to study how the solar wind traverses into the outer solar system. 'We can potentially calculate the speed of the solar wind,' she says, by noticing the impact of the solar wind on the purported comet's tail, if one materializes.
Could we reach it?
No spacecraft will be able to reach 3I/ATLAS. It is moving too fast and is too far from Earth for us to consider launching something in time.
Yet an upcoming European Space Agency (ESA) mission called Comet Interceptor, set to launch in 2029, might attempt to visit another interstellar object, if we find one within its reach. The spacecraft will be positioned past the moon's orbit away from the sun and, if a suitable target is found, will be commanded to fire its engines and try and intercept the incoming alien object.
If no suitable interstellar object is found, Comet Interceptor will instead be sent to one of several intriguing comets of our solar system. 'It is possible we could get an interstellar object, but we have to be really lucky,' says Colin Snodgrass, an astronomer at the University of Edinburgh, who is deputy lead on the mission.
How many are there?
One of our biggest outstanding questions about interstellar objects concerns their unknown abundance. The object 3I/ATLAS is our third interstellar visitor in eight years—a real but weak hint of how many are out there, waiting to be found.
Predictions estimate there are trillions upon trillions of interstellar objects drifting around our galaxy, and perhaps one in our solar system at any given time—but they're typically just so faint that they're unlikely to be found by most telescopes. This is expected to change when a new telescope called the Vera C. Rubin Observatory begins a 10-year survey of the sky later this year.
Rubin is expected to see somewhere between six and 51 interstellar objects in its 10-year survey. Seeing such a population will tell us 'how unique, or varied, planetesimal formation is across different parts of the galaxy,' Bannister says, referring to kilometer-scale objects thought to coalesce around newborn stars that become the feedstock for planets—and, when kicked to a system's hinterlands, become a reservoir of comets.
One puzzling question is why we haven't seen much smaller interstellar objects, Moskowitz says. If smaller objects are more plentiful than larger objects, as scientists expect, then we should have seen some small interstellar objects entering our atmosphere, appearing as meteors streaking across Earth's skies at speeds and trajectories that clearly convey their interstellar origins.
Detections of such objects have been claimed, but the evidence behind them has failed to convince most experts. The apparent absence of small interstellar interlopers 'is telling us something, but we don't know what that is yet,' Moskowitz says. 'I think that's going to be one of the major questions: Why are we seeing these big cometlike things coming through the solar system, but we're not seeing things that are smaller? It may have to do with the survivability of stuff out there in the galaxy, but we need more data.'
Orange background

Try Our AI Features

Explore what Daily8 AI can do for you:

Comments

No comments yet...

Related Articles

Building a greener, smarter future
Building a greener, smarter future

Business Journals

timean hour ago

  • Business Journals

Building a greener, smarter future

San Leandro's Gate510 campus has quickly become a hub for companies shaping the future of multiple industries. Air Protein, Coreshell and Lyten are among the innovators leveraging the infrastructure and support for makers in San Leandro. Read on to discover how they're redefining what's possible. AIR PROTEIN NASA-inspired research drives sustainable food production A food production facility that once made such American breakfast innovations as Eggo Waffles and Pop-Tarts is aiming to change the way we eat once again, this time with a sustainable twist. Air Protein opened its first Air Protein Farm on San Leandro's Gate510 campus in 2023, where it does just what its name suggests: make high-quality protein out of particles in the air. Co-founders Lisa Dyson and John Reed were inspired by research from the early days of NASA, which explored ways astronauts could produce food on long space journeys. They built on that work, creating a method for growing protein in cultures, similar to the production of yogurt, cheese, and wine. The result is a neutral-tasting protein flour that can be turned into or used in any food. 'We and our investors believe we've cracked the code on making functional ingredients that have a great cost profile,' Dyson said. 'Many companies are also looking for ingredients that are resource-efficient, and that's what we do. We help CPG [Consumer Packaged Goods] companies make great products for consumers.' In choosing San Leandro, Air Protein put the company's headquarters in a location with a history of food manufacturing. Dyson said the Air Protein project team and the landlord worked closely with the City throughout the process to obtain the necessary permits for building out the facility. 'With this particular site and location, there is fermentation happening with other companies around us,' Dyson said. These include 21st Amendment Brewery and Drake's Brewing. 'That made this more appealing than some other options.' The San Leandro Air Protein Farm produces samples of its protein in large enough quantities for food product companies to use in their product development. Next up will be a larger commercial facility to support full-scale use of Air Protein in food for grocery shelves. 'That's the most exciting thing about 2025,' Dyson said. 'We're turning the science innovation that NASA started in the 1960s and 1970s, completing the mission and making it a reality.' LYTEN San Leandro lands new battery cell production facility Every once in a while, an opportunity comes along that is just too good to pass up. That's what happened to Lyten, a San Jose-based company specializing in supermaterial applications, which focuses on commercializing lithium-sulfur batteries as a high-performance, low-cost alternative to lithium-ion technology. The company was in the process of planning a gigafactory in Nevada and thinking about its next major production facility outside California when the perfect location popped up in San Leandro, said Chief Battery Technology Officer Celina Mikolajczak. A lithium-metal battery maker had closed, leaving behind a manufacturing space and equipment that was immediately of interest. Lyten snapped up the equipment and 119,000-square-foot lease at Gate510 that November. Mikolajczak expects to have a 100-megawatt-hour production line in San Leandro up and running in 2026. 'We were planning and tooling for a big factory, and then the opportunity to take over the lease in San Leandro occurred,' she said. 'We said, 'Wow, that's a big enough space. There's enough dry room capability there. There's enough power. We could get one high-volume production line running there and learn a hell of a lot and get a jump on being ready for a bigger factory.' Lyten's San Leandro site will deliver lithium-sulfur battery cells for multiple types of energy storage customers, including defense and drone applications. In doing so, the company will help U.S. manufacturers keep more of their supply chain close to home. 'With lithium-sulfur, we can develop the technology and commercialize it in the U.S. and be part of creating the next wave of manufacturing in this country,' Mikolajczak said. CORESHELL New battery anodes boost domestic supply chain Batteries have quickly become a crucial component in efforts to transition from fossil fuels to sustainable forms of energy. But the batteries most widely used in electric vehicles and other key applications today come with limitations. San Leandro-based Coreshell is one of the innovators working to change this. The company has developed a battery anode that uses 100% domestically sourced metallurgical silicon instead of graphite, allowing it to store significantly more energy without relying on a risky supply chain. 'We're replacing something that is produced only in China with silicon that is produced widely here in the United States and in Europe,' said Co-founder and CEO Jonathan Tan. 'It can be even more cost-effective.' Founded in 2017, Coreshell relocated its development work to the Gate510 campus in 2020 and opted to remain in the city when it was time to expand into the first stages of production in 2024. It moved across the street to another building on the Gate510 campus, where a team of approximately 50 people has a four megawatt-hour pilot production facility that produces its first battery cells ready for commercialization in electric vehicles. 'We're proposing a foundational change in battery chemistry by replacing graphite — one of the largest single materials in a battery — with silicon,' Tan said. 'It is imperative that we show the market how that will help people power their daily lives.' San Leandro was ideal because it offered a combination of the necessary infrastructure — including access to the heavy power Coreshell needs for manufacturing — and efficient permitting and other City support, Tan said. A San Leandro headquarters also gives Coreshell access to a strong talent pipeline from throughout the Bay Area's growing battery expertise. San Leandro Mayor Juan Gonzalez, and members of the City staff visited with Coreshell this spring. It was an opportunity for Tan and his team to share more about their work and talk about how the City can support the company's future growth. 'To have a receptive audience with the Mayor, the City Manager's office and others in San Leandro, it shows that they are invested in helping companies like Coreshell grow and be successful,' Tan said. 'We value that partnership and how they are actively working to find ways to support the success and growth of companies like ours.'

NASA: Senegal is 56th country to sign Artemis Accords
NASA: Senegal is 56th country to sign Artemis Accords

UPI

time4 hours ago

  • UPI

NASA: Senegal is 56th country to sign Artemis Accords

From left, Ambassador of Senegal to the United States Abdoul Wahab Haidara, Director General of the Senegalese space agency Maram Kairé, NASA Chief of Staff Brian Hughes and Department of State Bureau of African Affairs Senior Bureau Official Jonathan Pratt pose for a photo during an Artemis Accords signing ceremony Thursday at the Mary W. Jackson NASA Headquarters building in Washington. Photo by Keegan Barber/NASA July 25 (UPI) -- Senegal has become the 56th country to sign the Artemis Accords for peaceful space exploration, NASA announced Friday. Signing the Artemis Accords means to explore peaceably and transparently, to render aid to those in need, to ensure unrestricted access to scientific data that all of humanity can learn from, to ensure activities do not interfere with those of others, to preserve historically significant sites and artifacts, and to develop best practices for how to conduct space exploration activities for the benefit of all, a NASA press release said. "Today, NASA built upon the strong relations between our two nations as the Senegalese Agency for Space Studies signed the Artemis Accords," acting NASA Administrator Sean Duffy said. Director General of the Senegalese space agency Maram Kairé signed the accords on behalf of Senegal. Jonathan Pratt, senior bureau official for African Affairs at the U.S. State Department, and Abdoul Wahab Haidara, ambassador of Senegal to the United States, also participated in the event. "Senegal's adherence to the Artemis Accords reflects our commitment to a multilateral, responsible, and transparent approach to space," Kairé said. "This signature marks a meaningful step in our space diplomacy and in our ambition to contribute to the peaceful exploration of outer space." Astronomers from Senegal have supported NASA missions by participating in multiple observations when asteroids or planets pass in front of stars, casting shadows on Earth. In 2021, NASA also collaborated with Kairé and a group of astronomers for a ground observation campaign in Senegal. As the asteroid Orus passed in front of a star, they positioned telescopes along the path of the asteroid's shadow to estimate its shape and size. NASA's Lucy spacecraft will approach Orus in 2028, as part of its mission to explore Jupiter's Trojan asteroids. More countries are expected to sign the Artemis Accords in the months and years ahead, as NASA continues its work to establish a safe, peaceful and prosperous future in space, the release said.

‘Possibly hostile' alien threat detected in unknown interstellar object, a shocking new study claims
‘Possibly hostile' alien threat detected in unknown interstellar object, a shocking new study claims

New York Post

time5 hours ago

  • New York Post

‘Possibly hostile' alien threat detected in unknown interstellar object, a shocking new study claims

A mysterious intergalactic object could potentially be a 'hostile' alien spacecraft that's slated to attack our planet in November, according to a controversial new study by a small group of scientists. 'The consequences, should the hypothesis turn out to be correct, could potentially be dire for humanity,' the researchers wrote in the inflammatory paper, which was published July 16 to the preprint server arXiv, South West News Service reported. 3 Comet 3I/ATLAS streaks across a dense star field in this image captured by the Gemini North telescope's Gemini Multi-Object Spectrograph, July 2025. NSF NOIRLab/ Ob et al. / SWNS Advertisement Dubbed 3I/ATLAS, the interstellar entity was discovered on July 1, rocketing toward the sun at more than 130,000 mph, Live Science reported. Less than 24 hours later, it was confirmed to be an interstellar object with initial observations suggesting that it could be a comet that measures up to 15 miles in diameter — larger than Manhattan. However, in the new paper, the trio of researchers suggested that it might be a piece of extraterrestrial spy technology in disguise. One of the researchers, Avi Loeb — a prominent Harvard astrophysicist known for linking extraterrestrial objects to alien life — previously made waves after floating the theory that 2017 interstellar object ʻOumuamua could be an artificial recon probe sent by an alien civilization, based on its odd shape and acceleration. Advertisement In this study, which he collaborated on with Adam Hibberd and Adam Crowl of the Initiative for Interstellar Studies in London, Loeb postulated that 3I/ATLAS's trajectory suggests a similarly alien origin. The trio felt the object's speed — which was significantly faster than ʻOumuamua and other objects — and the fact that it entered our solar system from a different angle than its predecessors offer 'various benefits to an extraterrestrial intelligence,' Loeb wrote in a blog post. 3 'The consequences, should the hypothesis turn out to be correct, could potentially be dire for humanity,' the researchers wrote in the inflammatory paper. ESA/Hubble/NASA/ESO/ / SWNS One benefit is that 3I/ATLAS will make close approaches to Jupiter, Mars and Venus, which could allow aliens to stealthily plant spy 'gadgets' there, Loeb wrote. Advertisement When the so-called undercover UFO reaches its closest to the Sun (perihelion) in late November, it will be concealed from Earth's view. 'This could be intentional to avoid detailed observations from Earth-based telescopes when the object is brightest or when gadgets are sent to Earth from that hidden vantage point,' Loeb declared. If this anomaly is a 'technological artifact,' this could support the dark forest hypothesis, which argues we haven't found signs of extraterrestrial entities because they are remaining undercover to shield themselves from predators or prey. Loeb warns that this could suggest that an attack is likely and would 'possibly require defensive measures to be undertaken.' 3 The Deep Random Survey telescope managed to capture images of interstellar object 3I/Atlas (pictured) in July 2025. K Ly/Deep Random Survey / SWNS Advertisement The problem is that 3I/ATLAS is traveling too fast for an Earth-based spacecraft to intercept it before it exits the solar system. 'It is therefore impractical for earthlings to land on 3I/ATLAS at closest approach by boarding chemical rockets, since our best rockets reach at most a third of that speed,' Loeb wrote. However, other scientists have thrown cold water on the so-called alien origins of the object, which they believe is a comet. 'All evidence points to this being an ordinary comet that was ejected from another solar system, just as countless billions of comets have been ejected from our own solar system,' added Samantha Lawler, an astronomer at the University of Regina in Canada who studies solar system dynamics, Live Science reported. In fact, even Loeb admitted in his blog that his alien spy probe theory is a bit far-fetched: 'By far, the most likely outcome will be that 3I/ATLAS is a completely natural interstellar object, probably a comet.' The researchers also warned the public to take the paper, which has not yet been peer-reviewed, with a grain of salt. 'This paper is contingent on a remarkable but, as we shall show, testable hypothesis, to which the authors do not necessarily ascribe, yet is certainly worthy of an analysis and a report,' they wrote. 'The hypothesis is an interesting exercise in its own right, and is fun to pursue, irrespective of its likely validity.' Advertisement However, critics have called their project a mockery of the work of other scientists, who have provided plenty of evidence that 3I/ATLAS is not evidence of a pending close encounter. 'Astronomers all around the world have been thrilled at the arrival of 3I/ATLAS, collaborating to use advanced telescopes to learn about this visitor,' Chris Lintott, an astronomer at the University of Oxford who helped simulate 3I/ATLAS's galactic origins, told Live Science. 'Any suggestion that it's artificial is nonsense on stilts, and is an insult to the exciting work going on to understand this object.'

DOWNLOAD THE APP

Get Started Now: Download the App

Ready to dive into a world of global content with local flavor? Download Daily8 app today from your preferred app store and start exploring.
app-storeplay-store