so that's the fastest (macro & reachable) thing ever - good luck sticking a flag on it
- overheard on Avi Loeb's radio telescope, but fortunately mis-translated.
It is hard to believe, but it means it’s been a fiery comet for billions of years, how is that possible that it havent burned up…
https://bsky.app/profile/stim3on.bsky.social/post/3m2aqnbwlw...
It is passing between two point in our night sky. I believe from a plane view, if you look at our universe from the perspective of it laying flat, it is my understanding the spin of our universe means that everything ends up within a flat plane, so in a 3 dimensional space, we have a limited Y axis. The other planets are spaced out across the X and Y axis, this is passing between or across two points.
Am I thinking of this right? I know very little about astronomy.
I would guess that observation improves over time. The wikipedia article is fascinating, estimating 10,000 such objects passing within Neptune's orbit in our solar system each day. I think that includes dust and sand sized objects.
Pan-STARRS (discovered 1I/ʻOumuamua), Zwicky Transient Facility (2I/Borisov), and ATLAS (3I/ATLAS) are the major existing projects and the Rubin Observatory/LSST will be a huge upgrade. We’re going to detect a lot more if these objects, especially since a lot of the work of the projects are looking at historical data.
He's convinced it's an essentially a local phenomenon. I look forward to how he spins this paper.
For possibly billions of years, it has simply been an inert lump of ice passing through the universe.
You may be thinking of our galaxy (the Milky Way) or even our solar system, which both rotate and as such are both somewhat flattened (the solar system much more so than the galaxy.)
But what’s happening here has little to do with that. If you imagine the closest distance that Earth gets to Mars as a yardstick, 3I/Atlas is about half that yardstick’s distance from Mars right now - much closer than Earth ever gets. It’s practically in Mars’ back yard.
The comet was discovered on 30 August 2019 by amateur astronomer Gennadiy Borisov at his personal observatory MARGO in Nauchnij, Crimea, using a 0.65 meter telescope he designed and built himself.
It would be funny if it behaves "as expected" when in the range of our instruments, but not when it thinks we can't see it :)
That's assuming you manage to avoid death from microplastics, climate change or AI-related societal collapse, etc.
True, but if it were that would solve some problems in observations:
https://academic.oup.com/mnras/article/538/4/3038/8090496?lo...
https://abc7.com/post/government-websites-displaying-message...
Just as an indicator of the speed and possible distances.
Joke explanation: a drifting vehicle is burning tires and leaving a cloud of smoke behind, like a comet.
It's in Mars' backyard, but was it, or will it also be in Jupiter's backyard? I couldn't understand that from the original post.
It seemed to me that it was just that our telescopes/cameras near Jupiter would be pointed in that direction.
It is extraordinarily unlikely you will shuffle one particular order of cards. It is 100% likely you will result in a sequence of cards.
Space is full of trillions and trillions and trillions of these. Given the rate of detection, we’ll probably see them come through regularly.
He's also a well respected and very accomplished person who has acknowledged this is a comet.
If it happens to slow down and change trajectory after it passes behind the sun, he might change his tune but he's pretty focused on the science at this point.
I'm not sure why that warrants a flood of downvotes, especially increasing after your message called me out, but hey I guess that's HN now.
Theres a LOT of people who work for the government that want to do a good job, and faithfully keep doing what they're paid to do. Administrations dont matter. The mission does. And that mission goes year by year.
Well, until now.
It's about 0.43 AU from the comet at its nearest, whereas Earth will be pretty much on the opposite side of the Sun, making observations difficult from here.
Edit: Earth, Mars and Jupiter are in roughly 120 degrees from each other as seen from the Sun, with the Earth-Sun-Jupiter angle closing up fast and the E-S-M angle growing slightly slower. In about two months the E-S-M angle will be 180.
He got attention for writing about this for Oumuamua, and now he’s just rinsing and repeating for 3I/Atlas. It’s exactly like any youtuber chasing the most effective clickbait.
It’s like when Altman talks about AIs building a Dyson sphere. Everyone with any understanding of the issues knows it’s self-serving hype.
I'm not sure how the progress of institutional and amateur observations compare. Obviously the big guys benefit from the same technological advancement, but I don't know whether the fraction of new objects discovered by amateurs has been growing or not. I suspect the odds of the first interstellar object being found by an amateur were still pretty long.
Once more survey telescopes like Nancy Grace Roman and Xuntian come online we'll increasingly find out how many there really are and I suppose if they seem to like buzzing the proverbial tower.
We're pretty much hosed.
And the current administration calls those people “the deep state” and wants to get rid of them.
Depending on its origin/history, it’s getting run over by a runaway train, or taking a sedate walk.
But ask yourself where we'd be if noone ever asked what if.
There's a reason he called his project to observe anomalous phenomenon The Galileo Project. Ring a bell?
That's how life works on Earth. If it _can_ live somewhere, it's probably already there. We think that's related to how it can survive and adapt, so it's reasonable to assume other life would be similar in that regard.
Therefore, by this logic, if Venus is able to sustain any life, it should already be there.
I know it sounds weird. What if life never got there? Well, it had plenty of opportunity. The universe is old and lots of things happened in it already.
Maybe life is a late addition to the universe, and we're one of the first instances of it. Or maybe it's rare, and we're lucky. Both the "life is new" and "life is rare" ideas, however, paint a picture of Earth being a special case somehow. "We are a special case" is not a very satisfying answer though (from the scientific point of view).
An open mind is like a fortress with its gates unbarred and its walls unguarded.But I also think the question "what if it wasn't" is useful to consider.
I'd label anyone unwilling to discuss that topic a crank, not the other way round.
He's definitely turned into a "I'm just asking questions and keeping an open mind" kinda grifter, whatever his past qualifications and respectability
Sure, like the Patriot Act was about patriotism.
"What if it's a natural object?" - We're going to observe it.
That's it. It's all we can reasonably do for now. It changes nothing.
a side effect of questioning what is inside leads to allowing some of what is outside in.
Loeb goes quite a bit further than that.
How do you know it's not? Venus is a much more difficult place for us to analyze than say, Mars.
Loeb is, to be very clear: unintelligent and unscientific. He has no desire to actually test the theories he publishes, and because of that, most of the theories are literally untestable. He just wants to shit-publish wild ideas, which is totally fine, if we were talking about a blog or something of that similar caliber. But that would not attract the $$$ views he demands to afford his lifestyle.
Apparently Wow! came from the same area and seemingly was blue-shifted by an amount that could make sense from an approaching craft, so that doesn't sound that silly to me.
Unlikely to be the real cause, not silly.
Ellie is someone I would consider having an open mind. She dedicates her work, at great risk to her own career, finding signs of extraterrestrial life. Despite everyone telling her not to waste time and resources on it. But she does and she does it by collecting the evidence first, and when she got it, double and triple checked it before making the announcement.
Avi kind of does the opposite. He hypes his ideas up first, often taking credit for others' work, without sufficient evidence.
I was talking about your scenario of space-faring silicon-based life. If Venus can support this different life, then it should be already there.
It's hard enough to find signs of life similar to ours (something familiar, carbon, metabolism), so if there is some completely different life somewhere in the solar system, it's unlikely we would be able to recognize it at first glance. So unlikely, that is almost pointless to postulate its existence.
Therefore, our best shot is to look for life similar to ours (because we know its tells). I think that's where the idea of a habitability zone comes from. It's not excluding the possibility of life existing outside of the zone, it's just making it easier for us to look (because looking everywhere means considering things we can't possibly understand).
That idea has been slightly changed since we started to hypothesize life on moons like Europa and Enceladus though. They are outside the classical habitable zone, but they have other possible means for producing liquid water that don't rely on the heat of a close star (tidal friction and residual core heat).
I've been through the last ~10 or ~15 posts on his Medium this evening, to check. Sentence-by-sentence I don't see anything that goes beyond "what if". Can you share some of the quotes you have in mind?
I think this is an interesting phenomenon, because it seems that lots of people throw personal insults at him (not saying that's you btw) without addressing the meat of whatever they're reacting to.
And lest we forget! One of the founding essays [1] of this very website discusses it: if you're slinging ad hominem attacks or personal insults around, you're by definition losing the "argument" (not that I think this qualifies as an "argument").
What do you think the natural spectrum of the Wow signal was, for determining amount of blue shift? What resolution of spectral data do you think we have on it?
It seems more likely that it'll act like a non intelligent hunk of rock going through some random trajectory.
It's less silly to declare you'll win the lottery. That has happened many times over - but we're yet to discover that can or has existed outside of Earth. While it's nearly impossible it hasn't happened several times over, it's so far impossible that we've encountered even the crumbiest excuse for life.
I assert that it is silly. We're not indigenous American happening upon European settlers. We're indigenous Americans wandering about the continent harassing mammoths, inventing stories of how it'll go when it happens.

3I/ATLAS … still not an alien spacecraft! The Gemini Multi-Object Spectrograph on the Gemini North telescope on Maunakea in Hawaii is one of many Earth and space instruments that have caught images of the world’s 3rd-known interstellar object, 3I/ATLAS. And the images all look basically the same. They nearly all show a coma, a cloud of gas and dust that forms around a comet’s icy nucleus in the vicinity of the sun. Image via International Gemini Observatory/ NOIRLab/ NSF/ AURA/ B. Bolin. Image processing by J. Miller & M. Rodriguez/ T.A. Rector/ M. Zamani.
The world’s 3rd known interstellar object – 3I/ATLAS – made its closest pass of the sun back on October 29, 2025. It’s now heading out of the solar system. But not before it makes its closest pass by Earth, which happens today (December 19, 2025). At its closest point, 3I/ATLAS will pass within 1.8 AU (168 million miles or 270 million km) of Earth. So it’s not really close. It’s farther than the sun, Mercury, Venus and Mars all get from Earth. But it’s the closest this object will come.
The latest news on Comet 3I/ATLAS involves its source of acceleration. The comet is ripping through our solar system at around 130,000 miles per hour (210,000 kph). That’s the highest velocity ever recorded for a solar system visitor. In a paper published in the Research Notes of the AAS on December 9, 2025, scientists discuss the comet’s non-gravitational acceleration. Its gravitational acceleration is from passing the sun. But the non-gravitational acceleration is not – as some hoped – from an alien engine. It’s from outgassing. Because, of course, this interstellar object is a comet, and comets sublimate icy material when they get near stars. The scientists used data from multiple spacecraft to measure the small accelerations.

The Lucy mission captured interstellar object Comet 3I/ATLAS on September 16, 2025. Lucy is on a mission to the Trojan asteroids near Jupiter. It saw the comet from about 240 million miles (390 million km) away. Image via NASA.
NASA held a press conference on November 19, 2025, to share the images that various space missions have collected of Comet 3I/ATLAS. Associate Administrator Amit Kshatriya started the conference by reassuring the public that this interstellar object is indeed a comet, and nothing related to extraterrestrial life, which has been widely speculated on social media.
You can rewatch the press conference in the player below. Read on for the newest images.
Rewatch the press conference from November 19, 2025, in this player. NASA revealed new images of interstellar object Comet 3I/ATLAS.
NASA turned many of its spacecraft and space telescopes at Comet 3I/ATLAS, only the 3rd-known visitor to our solar system. The closest to get a look at the comet was the Mars Reconnaissance Orbiter. Comet 3I/ATLAS was 19 million miles (31 million km) away when it took the image below on October 2, 2025.

The Mars Reconnaissance Orbiter (MRO) was the closest spacecraft to Comet 3I/ATLAS as it sped through the inner solar system. The HiRISE instrument on board MRO took this image on October 2, 2025, from about 19 million miles (31 million km) away. Image via NASA.

Another Mars spacecraft, MAVEN, captured the spectra of Comet 3I/ATLAS (along with the spectra of Mars). Looking at the wavelengths of light from an object helps astronomers better understand what it’s made of and how it compares to comets from our own solar system. Image via NASA.

Comet 3I/ATLAS from the solar-observing SOHO space telescope. SOHO took the image of Comet 3I/ATLAS from October 15-16, 2025, when it was otherwise too close to the sun for other instruments to see. Image via Lowell Observatory/ Qicheng Zhang/ NASA.

This animation shows PUNCH’s observations of Comet 3I/ATLAS from September 28 to October 10, 2025. At this time, the comet was between 231 to 235 million miles (372 to 378 million km) from Earth. Stars create streaks of light in the background as the comet moves across the sky. The bright object that appears near the comet in a couple of frames is the planet Mars. Image via NASA/ Southwest Research Institute.
See more images at NASA’s gallery.
The amazing astrophotographers Michael Jäger, Gerald Rhemann and Enrico Prosperi shared early images of 3I/ATLAS as it emerged from its closest passage near our star. Its closest approach to our sun was October 29, 2025. Now the object is in view – for telescope users – in the eastern predawn sky.
The trio posted images on the page ICQ Comet Observations on Facebook. There are a couple of other images there too, in addition to the one below. Wonderful work! Thank you for this image, which shows that the object – a comet from another star system – has been affected, as comets often are, by its close passage near our sun.
And now, the object displays multiple jets, streaming out in all directions.

M. Jäger, G. Rhemann, and E. Prosperi caught the interstellar object in a photo and wrote on November 8, 2025, at the Facebook page ICQ Comet Observations: “3I/ATLAS showed a complex tail structure early this morning. We observed it at 29 degrees elongation from the sun … At the time of exposure, the comet was 7-10 degrees above the [eastern predawn] horizon. At the end, twilight interfered with the observation, which took place under bright moonlight. We observed from a mountain location.” Image via M. Jäger, G. Rhemann, E. Prosperi.

Here’s 3I/ATLAS – the world’s 3rd-known interstellar object to pass through our solar system – around the time it passed nearest the sun. NOAA’s CCOR-1 coronagraph aboard the GOES-19 satellite caught this image. And citizen scientist Worachate Boonplod spotted the comet in this image. Way to go, Worachate! Image via Space Weather Prediction Center/ NOAA/ Worachate Boonplod.

Here’s a finder chart for 3I/ATLAS. This object passed behind the sun as seen from Earth in late October 2025. Now it has emerged in the morning sky. Use this chart to aim your telescope … and look for the “star” that appears fuzzy! Image via Bob King, aka AstroBob.
3I/ATLAS – the world’s 3rd-known object to enter our solar system from interstellar space – made its closest pass by our sun at 11:47 UTC (6:47 a.m. CDT) on October 29, 2025. At that time, the object – which is thought to be a comet from another solar system – was about 1.36 AU (1.36 Earth-sun distances, about 126 million miles or 203 million km) from our star.
The object is now headed out of our solar system again. But 3I/ATLAS hasn’t yet made its closest pass by Earth. That will come later, around December 19, 2025, when it will be about 1.8 AU (168 million miles or 270 million km) from Earth. However, 3I/ATLAS will never be visible with the eye alone from Earth. Telescope party, anyone?

Interstellar object 3I/ATLAS sped toward our sun, presumably for billions of years. On October 29, 2025, it made its closest pass by the sun. As of now, its journey toward our sun has ended, and it’s leaving our solar system. But the chance still exists for you to see it with a telescope! Animation via Tony Dunn.
So 3I/ATLAS is not visible with the unaided eye from Earth. You’ll need at least an 8-inch (20 cm) telescope, or a larger scope. And the best time for seeing it will probably be late November, when the object is still in the morning sky.
If you spot it then, you’ll be in good company. Between November 2 and 25, ESA’s Jupiter Icy Moons Explorer (JUICE) is observing the comet with various instruments. As JUICE looks toward 3I/ATLAS so soon after its closest approach to the sun, it is likely to have the best view of the comet in a very active state, with a bright halo around its nucleus and a long comet tail stretching out behind it.
JUICE’s team doesn’t expect to receive data from its observations until February 2026. Find out why here.
In addition, there are 2 other comets visible (or nearly visible) in our night sky now:
Comet Lemmon might be the best comet of 2025

View larger. | Infographic showing the path of comet 3I/ATLAS, the 3rd interstellar object known to enter our solar system. It displays the orbits of Earth, Mars and ESA’s Juice spacecraft around the sun, along with key dates and events as comet 3I/ATLAS travels through the inner solar system in 2025. Colored and numbered dots mark important observation points by telescopes and spacecraft. Image via ESA.
EarthSky’s Deborah Byrd and veteran skywatcher Bob King, aka AstroBob, talked about seeing 3 comets in the sky in late October and early November. They are comets Lemmon, SWAN and the interstellar wonder 3I/ATLAS.
If you’re interested in tracking the object, NASA’s Eyes on the Solar System tool offers interactive simulations of its path. Also, NASA recently launched a new page devoted to 3I/ATLAS.
There was a lot of excitement when this object passed Mars on October 3, 2025. The hope was that some Mars spacecraft might be turned to see the object. Keep reading to learn what happened.
The world’s 3rd known interstellar object – 3I/ATLAS – made its closest approach to Mars at 4 UTC on October 3, 2025 (11 p.m. CDT on October 2). At that time, the comet was approximately 18 million miles (29 million kilometers) from Mars. It was the object’s closest approach to any planet during its one-time journey through our solar system.
According to the European Space Agency (ESA), both the ExoMars Trace Gas Orbiter (TGO) and Mars Express turned their cameras toward 3I/ATLAS as it passed near Mars between October 1-7, 2025.
TGO’s CaSSIS instrument captured a series of images on October 3, 2025, when the comet was approximately 20 million miles (32 million km) away from the spacecraft. The images showed the comet as “a slightly fuzzy white dot” amidst streaked stars. See an animated gif – made from these images – below.
The images were challenging because the spacecraft’s imaging system is designed for the bright surface of Mars (just hundreds to thousands km away), yet this target was orders of magnitude farther and much fainter. Read more about the flyby and the TGO images here.
So, ESA’s ExoMars Trace Gas Orbiter did capture an image, but it did not show much. So far, we have not seen an image from the Mars Express of 3I/ATLAS specifically.

Here are the images from ESA’s ExoMars Trace Gas Orbiter (TGO) as it turned its eyes toward interstellar object Comet 3I/ATLAS on October 3, 2025. Comet 3I/ATLAS is the slightly fuzzy white dot moving downward near the middle of the image. Despite not being designed to capture something so far away, ExoMars TGO revealed the coma of gas and dust surrounding the icy-rocky nucleus. Image via ESA/ TGO/ CaSSIS.
Where did 3I/ATLAS come from? We know it came from the Sagittarius direction in our sky; that is, it came from the direction of the center of our Milky Way galaxy. But there are billions of stars in that direction. Which one is the home system of this object?
There have been many studies and ideas. One team of scientists, led by Xabier Pérez-Couto of the University of A Coruña in Spain, traced the path of interstellar object 3I/ATLAS back 10 million years. The astronomers were seeking its origin star, or any stars that might have perturbed its path as it traveled from its point of origin to our solar system.
The researchers examined 3I/ATLAS’s trajectory with the help of the Gaia space observatory’s data on stars. For 12 years, Gaia collected data on billions of stars in our Milky Way galaxy, precisely noting their positions again and again and thereby determining their motions. These astronomers’ calculations took them more than 100 million astronomical units (AU, or Earth-sun units) from our solar system. With these data in hand, researchers said they identified 93 nominal “encounters” for 3I/ATLAS, 62 of which were “significant.” Yet, they found that none of those encounters produced any meaningful perturbation of ATLAS’s orbit.
So, in other words, all of those 93 (or 62) encounters happened too fast, with the stars too far from 3I/ATLAS to meaningfully impact its trajectory. In the end, they didn’t find a star along 3I/ATLAS’s path that might have been responsible for bringing this 3rd-known interstellar object to us.

Here’s an image of interstellar object Comet 3I/ATLAS from the Gemini Multi-Object Spectrograph (GMOS) on the Gemini South telescope at Cerro Pachón in Chile. NOIRLab released this image on September 4, 2025. The colors of the background stars are due to 4 filters. The comet was fixed in the center of the telescope’s field of view, while the positions of the background stars changed, showing streaks. Image via 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).
And, as you might imagine, tracing 3I/ATLAS’ path backward through the galaxy is a daunting task. That’s in part because small uncertainties in orbits and stellar motions grow rapidly over time. But based on the researchers’ analyses of the interstellar object’s vertical motion in the galaxy (its path is known to weave up and down in the galactic disk), they concluded that it likely originated from the Milky Way’s thin disk, not its thick disk as was mentioned some months ago. The thin disk contains somewhat younger objects than the thick disk. But the researchers’ paper said:
[3I/ATLAS] may nonetheless be an old object, consistent with ejection from a long-lived primordial planetesimal disk in an early-formed system.
The scientists published their not-yet peer-reviewed paper on arXiv on September 10, 2025.

This diagram shows the thin disk of the Milky Way in teal and the thick disk in yellow. A new paper says Comet 3I/ATLAS likely came from the Milky Way’s thin disk. Image via Gaba P/ Wikipedia (CC BY-SA 3.0).
3I/ATLAS is thought to have been drifting through interstellar space for many billions of years before encountering our solar system. Pérez-Couto and team said that the interstellar comet is a:
… key probe of the galactic population of icy planetesimals.
In other words, the formation of solar systems is a messy process. In a solar system’s earliest days, rocks and pockets of gas and dust bang into each other and get swept up into clumps, which eventually get big enough to begin gathering yet more rocks, gas and dust to themselves via the force of gravity. Thus, planets come to be, astronomers think. According to theories of planet formation, clearing processes are also common, and those sometimes involve material – often the outer, icy regions of debris – getting ejected from a system altogether. As the paper said:
… interstellar space should be filled with planetesimals.

In mid-September, the data at the Comet Observation database (COBS), maintained by Crni Vrh Observatory, showed that interstellar comet 3I/ATLAS was outperforming expectations. It was brightening faster than expected. Image via COBS (CC BY 4.0).
Plus, there are other ways these interstellar interlopers might have achieved their lonely paths through our Milky Way galaxy. The possibilities range from close passages of other stars to tidal fragmentation of comets. So, as the paper said:
Identifying the origin of interstellar objects is key to understanding planet formation efficiency, the distribution of volatiles and organics in the galaxy, and the dynamical pathways by which planetary systems evolve.
All that from a small chunk of icy stuff (we know it’s icy in part because 3I/ATLAS has formed a tail, as icy comets do)!
On August 7, 2025, NASA shared an updated estimate of the size of the object’s nucleus, or core. Shortly after the object was first identified on July 1, 2025, 3I/ATLAS was estimated to have a diameter of about 12 miles (20 km). Then in late July – using data from the new Vera C. Rubin Observatory in Chile – the size estimate dropped to 6 miles (10 km). The latest analysis uses data from the NASA/ESA Hubble Space Telescope. It reduces the estimated diameter of 3I/ATLAS’s nucleus still further, to 3.5 miles (5.6 km).
And, the astronomers using Hubble data said, the object could be even smaller, as small as 1,050 feet (320 meters) across!
EarthSky’s Deborah Byrd interviewed Colin Orion Chandler of the DiRAC Institute of the University of Washington about size estimates for 3I/ATLAS. Watch in the player below, or on YouTube.
By the way, the two previously known interstellar objects are 1I/ ‘Oumuamua and 2I/Borisov. ‘Oumuamua’s size is thought to be about 656 feet (200 meters) across at its widest (you’ll recall it has an elongated shape). And Borisov is thought to be less than 3,280 feet (1 km) across.

View larger. | The Hubble Space Telescope captured this image of interstellar object 3I/ATLAS on July 21, 2025. It was the sharpest image yet of the object, acquired when the object was 277 million miles (446 million km) from Earth. This object is now generally believed to be a comet by most astronomers. In this image, a comet-like, teardrop-shaped cocoon of dust can be seen coming off its solid, presumably icy nucleus. Image via NASA/ ESA/ D. Jewitt (UCLA); Image Processing: J. DePasquale (STScI).
Shortly after the discovery of 3I/ATLAS – on July 1, 2025 – astronomers said it was likely the oldest comet we’ve ever seen. That claim came from University of Oxford astronomer Matthew Hopkins, whose analysis suggested 3I/ATLAS might be more than 7 billion years old, predating our solar system by more than 3 billion years! Hear him explain in the player below, or on YouTube.
Scientists first spotted 3I/ATLAS in early July 2025. And since then, people have asked one question countless times: will we send out a spacecraft to take a closer look? EarthSky’s Will Triggs spoke to University of Edinburgh astronomer Colin Snodgrass on August 21, 2025, to find out the answer. Colin essentially said, no, we don’t have time to organize a space mission specifically for 3I/ATLAS. But he talked about a future mission, the European Space Agency’s Comet Interceptor. This upcoming spacecraft will be primed to intercept future interstellar objects. Watch Will’s interview with Colin in the player below, or on YouTube.
It’s worth noting that the behavior of 3I/ATLAS is much like the signature of previously seen sun-bound comets originating within our solar system. But 3I/ATLAS is moving fast. In fact, it’s traveling through our solar system at roughly 130,000 miles per hour (210,000 kph). That’s the highest velocity ever recorded for a solar system visitor.
The Asteroid Terrestrial-impact Last Alert System (ATLAS) – a system of survey telescopes – detected our new interstellar visitor on July 1, 2025. And the Minor Planet Center confirmed its interstellar nature the following day (July 2, 2025), naming it 3I/ATLAS (or C/2025 N1). The “3I” means it’s the 3rd interstellar visitor that we’ve found. Its trajectory and speed revealed it as an object not from our solar system, but from another star system.
The Hubble Space Telescope imaged the object on July 21, 2025. See the post from Bluesky below.
Hubble Space Telescope images of interstellar comet 3I/ATLAS are out! These were taken 5 hours ago. Plenty of cosmic rays peppering the images, but the comet's coma looks very nice and puffy. Best of luck to the researchers trying to write up papers for this… archive.stsci.edu/proposal_sea… ?
— astrafoxen (@astrafoxen.bsky.social) July 21, 2025 at 4:28 PM

View larger. | A side-on view of the Milky Way, showing the estimated orbits of both our sun and Comet 3I/ATLAS. In this artist’s concept, 3I/ATLAS is the red dashed line, and the sun’s path is the yellow dotted line. The large extent of 3I’s orbit vertically into the outer thick disk is clear. Meanwhile, the sun stays nearer the plane of the galaxy. Image via Royal Astronomical Society/ M. Hopkins/ Otautahi-Oxford team. Base map: ESA/ Gaia/ DPAC, Stefan Payne-Wardenaar (CC BY 4.0).

On the left, the interstellar object Comet 3I/ATLAS streaks across a dense star field as seen by the Gemini North Telescope in Hawaii. The colors are courtesy of 3 filters: red, green and blue. On the right, an inset shows the comet’s compact coma, or cloud of gas and dust surrounding its icy nucleus. NOIRLab released this image on July 15, 2025. Image via International Gemini Observatory/ NOIRLab/ NSF/ AURA/ K. Meech (IfA/U. Hawaii). Image processing: Jen Miller & Mahdi Zamani (NSF NOIRLab).

3I/ATLAS, the white spot in the center, is approximately 126 million miles (203 million km) from the sun and made its closest approach on October 29. It poses no danger to Earth, coming no closer than 170 million miles (270 million km), which is more than 1.8 astronomical units (AU, or distance from the Earth to the sun). Image via ESA.

View at EarthSky Community Photos. | Filipp Romanov captured the interstellar object on July 2, 2025, when it was still named A11pI3Z. Filipp wrote: “I confirmed new interstellar object candidate A11pl3Z remotely using iTelescope.Net T72 (0.51-m f/6.8 reflector + CCD) in Chile.” Thank you, Filipp!
After Comet 3I/ATLAS makes its close approach to the sun, you can find it in the morning sky.

This star chart is for around 5 a.m. CST on December 12, 2025. On that date, the comet will be close to 2 stars and a dim spiral galaxy in the constellation Leo the Lion. Image via Eddie Irizarry/ Stellarium.
Bottom line: Interstellar object Comet 3I/ATLAS makes it closest pass by Earth today (December 19, 2025). How close will it come? And where will it go after this?
Via:
Even if this was a scanning beam I think we can assume it would take a lot of energy and so may be based on a simple scalable physical process. Using hydrogen to create it makes sense as it is low mass and can be replenished.
By sending out a pulse of light they could not just light up the ship-facing side of objects but also determine their precise location and velocity. Seems like something you'd want to do to not waste your thousand-year mission by accidentally colliding with a dark object.
The Wow! signal could be just such an event.
Aliens might use some type of scanning beam rather than a big flash, but I doubt we have the 1977 data to differentiate between a beam scanning our area and a solar-system-wide flash.
Perfect and brutal.
In the mid 1990s we’d only seen a handful of exoplanets. That they were basically everywhere we looked early on clued us in to their prevalence.