Do You Remember Your Arthur C. Clarke?

Tuckerfan · Jul 3, 2025

Because an interstellar object is passing through our solar system. It appears to be 20 km in diameter, the same as Rama.

It's Official: NASA Confirms New Interstellar Object Is Zooming Through Solar System

Astronomers on Wednesday confirmed the discovery of an interstellar object racing through our Solar System – only the third ever spotted, though scientists suspect many more may slip past unnoticed.

The visitor from the stars, designated 3I/Atlas by the International Astronomical Union's Minor Planet Center, is likely the largest yet detected. It has been classified as a comet.

"The fact that we see some fuzziness suggests that it is mostly ice rather than mostly rock," Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, told AFP.

Originally known as A11pl3Z before it was confirmed to be of interstellar origin, the object poses no threat to Earth, said Richard Moissl, head of planetary defense at the European Space Agency.

"It will fly deep through the Solar System, passing just inside the orbit of Mars," but will not hit our neighbouring planet, he said.

Excited astronomers are still refining their calculations, but the object appears to be zooming more than 60 kilometres (37 miles) a second.

This would mean it is not bound by the Sun's orbit, unlike comets and asteroids, which all originate from within the Solar System.

Its trajectory also "means it's not orbiting our star, but coming from interstellar space and flying off to there again," Moissl said.

"We think that probably these little ice balls get formed associated with star systems," added McDowell. "And then as another star passes by, tugs on the ice ball, frees it out. It goes rogue, wanders through the galaxy, and now this one is just passing us."

The NASA-funded ATLAS survey in Hawaii first discovered the object on Tuesday, US astronomer David Rankin wrote on the social media platform Bluesky.

Professional and amateur astronomers across the world then searched through past telescope data, tracing its trajectory back to at least June 14.

The object is currently estimated to be roughly 10-20 kilometers wide, Moissl said, which would make it the largest interstellar interloper ever detected. But the object could be smaller if it is made out of ice, which reflects more light.

"It will get brighter and closer to the Sun until late October and then still be observable (by telescope) until next year," Moissl said.
Our third visitor

This marks only the third time humanity has detected an object entering the solar system from the stars.

The first, 'Oumuamua, was discovered in 2017. It was so strange that at least one prominent scientist became convinced it was an alien vessel – though this has since been dismissed by further research.

Our second interstellar visitor, 2I/Borisov, was spotted in 2019.

Mark Norris, an astronomer at the UK's University of Central Lancashire, told AFP that the new object appears to be "moving considerably faster than the other two extra-solar objects that we previously discovered."

The object is currently roughly around the distance from Jupiter away from Earth, Norris said.

He lamented that he would not be able to observe the object on his telescope on Wednesday night, because it is currently only visible in the Southern Hemisphere.

Norris pointed to modelling estimating that there could be as many as 10,000 interstellar objects drifting through the Solar System at any given time, though most would be smaller than the newly discovered object.

If true, this suggests that the newly online Vera C. Rubin Observatory in Chile could soon be finding these dim interstellar visitors every month, Norris said.

Moissl said it is not feasible to send a mission into space to intercept the new object.

Still, these visitors offer scientists a rare chance to study something outside of our Solar System.

For example, if we detected precursors of life such as amino acids on such an object, it would give us "a lot more confidence that the conditions for life exist in other star systems," Norris said.
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MikeH92467 · Jul 3, 2025

Rendezvous with Rama is an amazing book and with Denis Villeneuve directing it could make a really good movie. Of course, the problem is that the ending is so ambiguous.

Tuckerfan · Jul 17, 2025

Our Best View Yet of Interstellar Comet 3I/ATLAS

If it were to hit the Earth, the impact would be 100x that of the rock that took out the dinos.

Tererunererun · Jul 17, 2025

They do everything in triplicate.

Bailey · Jul 17, 2025

It's pretty wild to consider that there is a good chance this thing is significantly older than our solar system. It could well have been roaming around the galaxy before the stars that eventually went supernova to produce our solar system were even born.

Bickendan · Jul 18, 2025

Tuckerfan said: ↑

Our Best View Yet of Interstellar Comet 3I/ATLAS

If it were to hit the Earth, the impact would be 100x that of the rock that took out the dinos.
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Paging @Lanzman

Tererunererun · Jul 18, 2025

I've given up on his ability to attract an extinction event after Trump's second inauguration. Lanz's attraction beam is impotent in comparison.

Lanzman · Jul 18, 2025

Bickendan said: ↑

Tuckerfan said: ↑

Our Best View Yet of Interstellar Comet 3I/ATLAS

If it were to hit the Earth, the impact would be 100x that of the rock that took out the dinos.
Click to expand...

Paging @Lanzman
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Yeah yeah. Atlas is still a ways away. Meanwhile, Apophis continues toward a close approach . . .

DEI Hire · Jul 19, 2025

Not close enough.

Tuckerfan · Jul 27, 2025

https://www.ladbible.com/news/world...lien-threat-spy-3iatlas-comet-788721-20250727

Tererunererun · Jul 27, 2025

Finally.

Tuckerfan · Aug 11, 2025

Well, this is interesting.

Avi Loeb Figured Out Why Spacecraft Have Comae!

Avi Loeb has two new blog posts out about 3I/ATLAS, and they’re doozies!

Steve Desch recently posted a snarky piece entitled “This is not the quality of pseudoscience infotainment to which I have grown accustomed” fake-complaining that Avi’s work on interstellar-objects-as-alien-spacecraft with 3I/ATLAS feels phoned-in compared to his work on ‘Oumuamua and the “interstellar” meteor he went trawling for in the Pacific. These latest pieces feel like Avi has taken this to heart and is trying to rise to the occasion!

It’s standard for Avi to claim that he simply follows the evidence and doing good science. With ‘Oumuamua he was quoted saying “If someone comes to me and says, ‘For these scientific reasons, I have a scenario that makes much more sense than yours,’ then I’d rip that paper up and accept it.” But when it was shown that a comet model fit the data better than a light sail model, there was no ripping.

Indeed, the entire ATLAS saga has been an exercise in goalpost moving and motivated reasoning. First he dismissed clear evidence of a coma as just smearing due to improper tracking of the asteroid (even when the papers he was citing clearly accounted for this). At the time he dismissed evidence of a dusty coma by claiming the data were also consistent with a very large, red object that just happened to have the same spectrum as dust. He insisted that the lack of a detection of gases like water was anomalous and meant we should keep the spacecraft interpretation alive.

Later he claimed papers confirming earlier reports of an asymmetric coma somehow vindicated his earlier position (although we were left wondering whether he admitted it had a coma and why this isn’t enough to know it’s a comet).

Since then, water has been indirectly detected in the coma by the Swift satellite. Did this make Avi concede? Perhaps Steve’s snark got to him because he rolled up his sleeves and came up with some more inspired arguments.

For the Swift detection, he grabbed on to the fact that the amount of water implied by the measurement depends on the amount of reddening we see in the ultraviolet—basically, how much UV light is being blocked by the dusty coma. The reddening in the infrared was measured in another paper, and he wrote:

If we adopt the level of reddening measured in the first paper mentioned above, namely ∼10% per 1000 Angstrom, then we derive from this plot a water production rate of zero.

He backs this up with this figure:

Water production rate as a function of reddening for 3I/ATLAS. (Figure 2 from Z. Xing et al. 2025)

where, sure, if there is 10%/1000Å reddening in the UV then there’s no implied water. He then snarked:

Remarkably, the spectrum reported in the first paper implies no water production based on the second paper, yet both papers claim that water was detected around 3I/ATLAS.

But as Agata Rożek pointed out on BlueSky:

Well, for one thing, he compares reddening in UV adopted by authors of paper2 to reddening in near infrared measured in paper1 as if they were the same thing. And conveniently crops the figure from paper2 to not show the other measurements made at longer wavelengths, consistent with paper1.

Indeed, check out what he left out of his post:

You see, dust famously is more opaque at shorter wavelengths like the UV (here around 4400Å), which is why the paper looks at lots of measurements across lots of wavelengths to get a handle on it. The rest of the figure here shows reddening values (x-axis) at many different wavelengths (y-axis). Avi adopts the smaller values appropriate for infrared wavelengths (here around 8000Å) for the UV observations, and then claims this means the two papers are inconsistent with each other. By cropping the figure it sure seems like he’s trying to elide the fact that he’s using an infrared reddening value for a UV observation so he can get the answer he wants.*

But the real doozy came in this morning. Avi finally figured out why his spacecraft has a dusty coma! It’s an early warning system for collisions you see:

To protect an interstellar spacecraft of that scale, its creators might have designed it to spray a stream of particles ahead of it, as precursors that would flag any dangerous rock along the path, allowing the craft to navigate away from obstacles…

The interaction of the sprayed particles with potential obstacles would give an advance warning of a few minutes to 3I/ATLAS at its measured hyperbolic speed.

A buffer zone of large particles would show up in images of 3I/ATLAS as a glow of reflected sunlight ahead of the interstellar object. The glow will not be accompanied by any gas particles, as they would be pushed back by the Solar wind and hence be useless for the purpose of flagging dangerous rocks ahead of 3I/ATLAS.

This scenario is consistent with the current data on 3I/ATLAS.

Now that’s original! But wait, why not jut use a radar system to find obstacles?

The use of a radar system might have been avoided to eliminate an obvious electromagnetic signature of artificial origin.

I’m not sure why he doesn’t just go all-in at this point and declare that to hide the technological nature of their spacecraft they generate an artificial coma of dust of gases to exactly mimic a real comet and throw us off the scent?

Avi previously invoked the “Duck Test” for 3I/Atlas:

If the interstellar object looks like a comet, moves like a comet, and outgasses like a comet, then it probably is a comet.

But he’s clearly not applying this. The point of the Duck Test is that if something acts for the most part like a common object, it probably is. It is sort of a statement about how your Bayesian prior should heavily lean towards the conclusion that you’re looking at something common, not exotic; another way of saying “extraordinary claims require extraordinary evidence”. It should not take a high level of proof to convince you that a bird swimming on the pond is a duck: if it swims, quacks, and looks like a duck, it probably is a duck.

But here 3I/ATLAS has the coma of a comet, the dust of a comet, and now the water of a comet…but somehow it’s still likely to be an alien spacecraft? Avi has inverted the whole point of the Duck Test, requiring the duck to pass every test for being a duck before he concedes it’s not a cleverly disguised T-800 or something.

At this point, it almost feels like he’s trolling us (well, maybe Steve Desch in particular!). It’s tempting to just write it all off as silly except that some people are clearly taking him seriously and preparing for the worst. Given the history of cults like Heavens Gate, it’s not hard to imagine that his rhetoric might be not just irresponsible but downright dangerous.

*A more generous interpretation is that he’s confused about what the plot shows, and thinks that because the units of reddening are given as %/1000Å (i.e. a slope) it is a quantity that should be constant across the EM spectrum (which would be true if the opacity law were linear in wavelength). In that case you just have a bunch of different measurements and he’s simply cherry picking. But this is contradicted by the 3rd (right hand) panel, which clearly shows that the reddening slopes are expected to change with wavelength. There’s really no excuse.
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Tuckerfan · Aug 23, 2025

Huh. It looks like Avi Loeb was wrong again. Imagine that.

https://spherex.caltech.edu/news/3i-atlas-co2-coma

Tuckerfan · Sep 6, 2025

https://sites.psu.edu/astrowright/2...-shown-that-avi-loeb-is-wrong-about-3i-atlas/

Paladin · Sep 6, 2025

60 km/s and accelerating as it approaches. Hmmm.

While it clearly wouldn't be possible this time around, perhaps NASA should think about a mission that could intercept a future one, and plant some instruments on it.

notnick · Sep 7, 2025

Paladin said: ↑

60 km/s and accelerating as it approaches. Hmmm.

While it clearly wouldn't be possible this time around, perhaps NASA should think about a mission that could intercept a future one, and plant some instruments on it.
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that would be great but your favorite president is gutting NASA as fast as he can.

Tuckerfan · Sep 29, 2025

Tuckerfan · Oct 3, 2025

NASA goes dark hours before first look at interstellar object moving closer to Earth

Tuckerfan · Oct 4, 2025

3I/ATLAS is Captured in New Images as Mysterious Object Cruises Past Mars—What Does the Latest Data Reveal?

tafkats · Oct 4, 2025

notnick said: ↑

that would be great but your favorite president is gutting NASA as fast as he can.
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Somebody should tell him that NASA is working on a plan to put a giant billboard of his face in orbit.

Tuckerfan · Oct 8, 2025

Interstellar comet 3I/ATLAS may come from the mysterious frontier of the early Milky Way, new study hints

Tuckerfan · Oct 23, 2025

NASA’s Jupiter Probe Could Snag First-Ever Sample From an Interstellar Comet

Tuckerfan · Oct 23, 2025

Tuckerfan · Nov 4, 2025

Tuckerfan · Nov 6, 2025

'Interstellar visitor' 3I/ATLAS may have just changed color — for the third time

notnick · Nov 6, 2025

hope we don't get tangled up in blue...........sorry

Tuckerfan · Nov 10, 2025

https://archive.is/GZy5f

Tuckerfan · Nov 12, 2025

Lanzman · Nov 12, 2025

Yeah, tidal forces will do that to you.

Tuckerfan · Nov 22, 2025

'3I/ATLAS is a comet': NASA finally releases new 3I/ATLAS images and addresses alien rumors

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Do You Remember Your Arthur C. Clarke?

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