Comet redux

Okay, can we all please please puhleeeeeez stop posting stuff without checking to see if it's true?

I know it's a pain in the ass, but this needs to become a habit.  For all of us.  Unless you make a practice of never reposting anything anywhere -- which eliminates most people -- it's got to become an automatic reflex when you're using social media.  Stop before you hit "forward" or "share" or whatnot and take five minutes to verify that it's accurate.

The reason this comes up is something about comet 3I-ATLAS that I've now seen posted four times.  I wrote about 3I-ATLAS here only a couple of weeks ago, and to cut to the chase: the considered opinions of the astronomers who have studied it -- i.e., the people who actually know what the hell they're talking about -- are that the object is an interstellar comet made mostly of frozen carbon dioxide.  Despite the claims of people like Avi Loeb, the alien-happy Harvard astronomer, it shows no sign of being an extraterrestrial spacecraft.

That, of course, isn't sufficient for a lot of people.  Without further ado, here's the image I've seen repeatedly posted:

There is nothing in this image that is accurate, unless you're counting "3I-ATLAS is an interstellar object" and "Japan has a space agency" as being in the "correct" column.  Japan's space agency has released no such "footage."  There are no "precise pulsating lights."  No scientist -- again, with the exception of Loeb and his pals -- are "questioning if it's artificial."

And the object in the image?  That's not 3I-ATLAS.  Jack Gilbert, of the Scripps Institute of Oceanography, has identified it as a microorganism.  "That is a paramecium," Gilbert writes.  "Freshwater I believe -- although better phase contrast, and where it was found, would be ideal for better identification."

Another image that is making the rounds is from NASA, but it's being used to claim that the 3I-ATLAS has changed direction and speed in a fashion that "indicates some kind of propulsion system."  This shift in trajectory, they say, made the telescope at NOIRLab (National Optical-Infrared Astronomy Research Laboratory) image alter its aim to keep up with it, resulting in the background stars showing rainbow-colored streaks:

This isn't correct, either.  If you go to NOIRLab's website, you find a perfectly reasonable explanation of the streaks right there, without any reference to propulsion systems and alien spacecraft.  I quote:

Comet 3I/ATLAS streaks across a dense star field in this image captured by the Gemini Multi-Object Spectrograph (GMOS) on Gemini South at Cerro Pachón in Chile, one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab.  This image is composed of exposures taken through four filters -- red, green, blue and ultraviolet.  As exposures are taken, the comet remains fixed in the center of the telescope's field of view.  However, the positions of the background stars change relative to the comet, causing them to appear as colorful streaks in the final image.

Once again, the upshot: 3I-ATLAS is a comet.  That's all.  Of great interest to planetary astronomers, but likely to be forgotten by just about everyone else after March of next year, at which point it will be zooming past Jupiter and heading back out into the depths of space, never to be seen again.  There is no credible evidence it's a spaceship.  If there was, believe me, you would not be able to get the astronomers to shut up about it.  The concept some people have of scientists keeping stuff hidden because they're just that secretive, and don't want anyone to know about their big discoveries, only indicates to me that these people know exactly zero scientists.  Trust me on this.  I know some actual scientists, and every single one of them loves nothing better than telling you at length about what they're working on, even if it's something that would interest 0.00000001% of the humans who have ever lived, such as the mating habits of trench-dwelling tube worms.  If there was strong (or, honestly, any) observation that supported this thing being the ship from Rendezvous With Rama, we'd all know about it.

And after all, if there was evidence out there, the hoaxers wouldn't have to use a photograph of a paramecium to support their bogus claims.

So for fuck's sake, please be careful about what you post.  It took me (literally) thirty seconds to find a site debunking the "Japan space agency" thing.  What I'm asking you to do is usually not in any way onerous.

I mean, really; wouldn't you rather be posting things that are cool, and also true?  There is so much real science to be fascinated and astonished by, you don't need these crazy claims.

And believe me, neither does the internet as a whole.

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The rush to judgment

A loyal reader of Skeptophilia sent me an email asking me what my opinion was about two current candidates for evidence of alien spacecraft -- the Palomar transients and the object called 3I-ATLAS.

First, some facts.

The Palomar transients are some mysterious moving objects spotted on photographic plates taken at Palomar Observatory in the 1940s and 1950s, all before the launch of Sputnik 1, the first artificial satellite, in 1957.  They included both single objects and multiple objects -- in one case, five -- arrayed in a straight line.  In-depth analysis ruled out conventional explanations like meteors and flaws in the photographic plates; and curiously, there was a forty-five percent higher likelihood of transient detection within one day of nuclear testing, which was going on pretty regularly at the time.  The transients also were a little over eight percent more likely on days when there were UAP reports from other sources -- either visual observation by pilots or on-ground observers, or unexplained blips on military radar.  The authors of the paper, which appeared in Nature last week, were up front that the phenomenon was "not easily accounted for by prosaic explanations."

One of the Palomar transients, from July 1952 [Image courtesy of Stephen Bruel and Beatriz Villarroel, Nature, 20 October 2025]

3I-ATLAS is an interstellar object -- that's what the "I" stands for.  (The ATLAS part is because it was discovered by the Asteroid Terrestrial-impact Last Alert System; but fear not, the closest it will get to Earth is 1.8 astronomical units, so it poses no impact threat.)  We know it's an unbound interstellar object because of its speed and trajectory.  It's on a hyperbolic path, having come from somewhere in deep space, falling into the gravity well of the Sun, where it will ultimately slingshot its way back out of the Solar System and into deep space once again.  From analyses of the object itself, as well as the gas and dust it is currently ejecting, it appears to be an icy comet something on the order of three kilometers across, and mostly composed of frozen carbon dioxide, with small amounts of water ice, carbon monoxide, and carbonyl sulfide.

Comet 3I-ATLAS [Image licensed under the Creative Commons International Gemini Observatory/NOIRLab/NSF/AURA/Shadow the Scientist, 3I-ATLAS noirlab2525b crop, CC BY 4.0]

3I-ATLAS was immediately grabbed by (now rather notorious) astronomer Avi Loeb, whose unfortunate habit of shouting "IT'S ALIENS!" every time something unexplained happens has brought up repeated comparisons to The Boy Who Cried Wolf.  Not long after 3I-ATLAS was confirmed to be an interstellar object, Loeb and a couple of collaborators published a paper on arXiv in which they said its "anomalous characteristics" indicate it's an extraterrestrial spacecraft, and might in fact be hostile.  The claim was equally quickly shot down by a large number of exasperated astrophysicists who are sick unto death of Loeb's antics.  One, Samantha Lawler, said, "while it is important to remain open-minded about any 'testable prediction', the new paper [by Loeb et al.] pushes this sentiment to the limit...  [E]xtraordinary claims require extraordinary evidence, but unfortunately, the evidence presented is absolutely not extraordinary."

What strikes me here -- especially with regards to the (many) folks who have weighed in on the possibility that these are evidence of extraterrestrial intelligence -- is the need for a rush to judgment.  (Nota bene: this is in no way meant as a criticism of the reader who contacted me with the question; she was just interested in my take both on the facts of the case, and people's reactions to them.)  In the case of 3I-ATLAS, I think the evidence very strongly suggests that what we have here is simply a large comet of interstellar origin, so something of great interest to astronomers and astrophysicists, but unlikely otherwise to be earthshattering in any sense including the literal one.  As far as the Palomar transients go -- well, we don't know.  The most recent of them occurred seventy-odd years ago, and all we have is some old photographic plates to go by.  They're certainly curious, and I'm glad they're being looked at, but... that's about all we can say for the time being.

"Well, what about the Menzel Gap?" I've seen asked multiple times.  Isn't that suggestive?  The "Menzel Gap" refers to the fifteen-year block of missing plates attributable to actions by Harvard Observatory astronomer Donald Howard Menzel, a prominent scoffer about aliens and UFOs, who became notorious for ordering the destruction of hundreds, possibly thousands, of astronomical photographic plates stored there.  Menzel cited considerations of storage space, claiming we'd already learned as much from them as we could, but UFO aficionados hint at something darker.  Menzel had top secret security clearance, they say; he led a "clandestine life as an elite member of the U. S. intelligence community" and was systematically covering up evidence of aliens visiting the Earth in the fashion of Cigarette-Smoking Man on The X Files.

Why he and others would go to all that trouble to stop the public from finding out about aliens is never really explained.  "They were just that evil" is about the clearest it gets, often along with vague claims that it was to prevent panic amongst the populace.

As if what the government was openly doing at the time, and that made headlines worldwide, wasn't equally bad.

In any case, back to the original question: what do I think about all this?

Well, the truth is, I don't think anything.  I simply don't know.  It seems likely that whatever the Palomar transients were, they were not all due to the same cause; it could be that some were debris from nuclear testing, but that clearly doesn't account for all of them.  Menzel might have been a misguided bureaucrat, or might have been destroying the plates to prevent their being co-opted by the UFOs-and-aliens crowd, or may have had some other motives entirely.  In any case, it's okay to say "we don't know," and then just leave it there.  Perhaps researchers will find more evidence, perhaps not; in either case, the best thing is to hold the question in abeyance, indefinitely if need be.

So that's where we have to leave it.  I know that's disappointing; believe me, I've been waiting since I was a six-year-old breathlessly watching Lost in Space for unequivocal evidence of aliens.  At the moment, what we've got simply doesn't amount to much.  But if you're as intrigued by the possibilities as I am, I have two suggestions.

First, learn some actual astronomy and astrophysics.  You're less likely to fall for specious claims if you have a good command of the facts and current scientific models.

Second, keep looking up.  As has been commented many times, "It's never aliens... until it is."  I still think it's likely that life is common in the universe, and although the distances and scale (and the Einsteinian Cosmic Speed Limit) make it unlikely they've come here, it's not impossible.  Maybe there have been extraterrestrial spacecraft passing by, or even landing on, our planet.

Wouldn't it be fun if you were the first to know?  Make sure and take lots of pictures, okay?

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