Explained: Why controversial Harvard astrophysicist Avi Loeb's 3I/ATLAS 'alien theory' doesn't add up

Harvard astrophysicist Avi Loeb has revived the extraterrestrial debate, but astronomers say the numbers, not the narrative, tell the real story.

When Harvard’s Avi Loeb claimed that 3I/ATLAS — a Manhattan-sized interstellar comet — might be “manufactured” by another civilisation, it immediately drew global headlines. After all, Loeb was the same scientist who once said 2017’s ‘Oumuamua’ could be alien technology.

But the world’s top astronomers are unconvinced. The data, they say, show nothing unusual — and certainly nothing artificial. Here’s how each of Loeb’s five big claims unravels under scrutiny.

1. The “technological artefact” theory has no empirical backing

Loeb argues that 3I/ATLAS could be a “technological artefact” — a fragment of alien engineering. He points to its brightness and trajectory as possible signs of design.

NASA’s small-bodies lead scientist Tom Statler disagrees flatly: “It looks like a comet. It does comet things. It very, very strongly resembles, in just about every way, the comets that we know. The evidence is overwhelmingly pointing to this object being a natural body. It’s a comet.” In other words, there’s nothing in its observable behaviour — not reflectivity, mass loss, or trajectory — that requires a non-natural explanation.

2. The “anti-tail” and nickel claims don’t hold up under better data

Loeb says the comet’s “anti-tail” — dust seemingly pointing toward the Sun — and a strange nickel-but-no-iron spectrum make it unique.

But astronomers note that anti-tails are optical illusions caused by viewing geometry. Comets like Arend–Roland (1957) and PanSTARRS (2013) have displayed the same feature when Earth crossed their orbital plane.

As for its chemical mix, the spectral readings Loeb references are low-resolution and provisional. No peer-reviewed study has confirmed his interpretation. The observed emissions fall within known cometary variation, not a violation of physics.

3. The “black swan” framing overstates the case

Loeb calls 3I/ATLAS a potential “black swan” — an event so rare it could redefine humanity’s view of the universe. But that’s a rhetorical flourish, not a scientific argument.

Chris Lintott, astrophysicist at the University of Oxford, was blunt in his response:“Any suggestion that it’s artificial is nonsense on stilts, and is an insult to the exciting work going on to understand this object.”

To the astronomy community, 3I/ATLAS isn’t rewriting physics — it’s reinforcing how little we’ve studied interstellar debris.

4. No, NASA isn’t hiding data

Loeb has hinted that NASA and observatories may be withholding key observations. But all available data — from James Webb Space Telescope, Pan-STARRS, and ATLAS — are in open-access archives.

NASA publicly stated that “no information on 3I/ATLAS has been restricted,” and several researchers have replicated the findings using those same datasets. The charge of secrecy, they argue, distracts from real analysis.

5. The “mothership” hypothesis ignores known dynamics

Loeb notes the object’s hyperbolic trajectory — its fast, steep entry into the Solar System — as a possible sign of propulsion or control.

In reality, any interstellar object will follow a hyperbolic path due to solar gravity. The orbit of 3I/ATLAS aligns perfectly with that expectation. No acceleration beyond cometary outgassing has been recorded, and no signals or manoeuvres have been observed.

The verdict

After multiple independent analyses, nothing about 3I/ATLAS requires an alien explanation. Its composition, motion, and dust behaviour all fit within the physics of natural comets.

Avi Loeb’s willingness to challenge orthodoxy keeps astronomy in the headlines — but as of now, his hypothesis stands without evidence. The scientific consensus remains clear: 3I/ATLAS is fascinating, but not fabricated.

Sometimes, space is strange enough without needing aliens to explain it.

Who is he?


Avi Loeb remains one of Harvard’s most polarising astrophysicists — brilliant, provocative, and media-savvy in equal measure. His viral claims that interstellar objects like ʻOumuamua might be alien technology, that mysterious metallic spherules collected from the Pacific could be fragments of an extraterrestrial craft, and that his “Galileo Project” could one day detect alien artefacts have catapulted him far beyond the confines of academia. To his admirers, Loeb is a modern Galileo challenging institutional dogma; to his critics, he’s an accomplished scientist indulging in premature conclusions dressed as discovery. The truth lies somewhere in between: Loeb’s hypotheses are speculative and unproven, but they’ve forced astrophysics to confront its own discomfort with bold questions — reminding science that open-mindedness and sensationalism can sometimes look dangerously alike.