Comet or UFO? This scientist shares 9 reasons why the 3I/ATLAS is a spacecraft and not a comet

In July 2025 a curious visitor entered our Solar System: the interstellar object dubbed 3I/ATLAS. Unlike typical space rocks that circle the Sun and behave like known comets or asteroids, this one has thrown up a series of oddities that have caught the attention of some astronomers, most notably Avi Loeb of Harvard University.

Israeli physicist Abraham ‘Avi’ Loeb is known for causing controversy when it comes to interstellar visitors. The Harvard scientist put his name in the headlines when he outrageously claimed that Oumuamua, the first ever confirmed interstellar object detected passing through the Solar System, might have been a spacecraft. There’s nothing like screaming wildly to get people’s attention.

Now, he has set his sights on 3I/ATLAS’s curious, but not inexplicable, behaviour and trajectory, arguing that while the simplest explanation (and that of the vast majority of the scientific community) remains that it is a comet, these quirks force us to at least consider more exotic possibilities.

Anyway, despite the controversy regarding Loeb’s stoking of the fire, let’s take a look at what he says:

1. Aligned like a local. 3I/ATLAS’s path sits within just five degrees of Earth’s orbital plane, something Loeb says has only a 0.2 percent chance of happening by coincidence.

2. Cosmic sightseeing. Its trajectory has taken it close to Mars and Jupiter, two planets central to humanity’s own search for life. ESA probes have already caught glimpses of it near Mars, and Loeb notes that it’ll pass within about 33 million miles of Jupiter in early 2026.

3. A strange “anti-tail.” Unlike typical comets, whose tails point away from the Sun, 3I/ATLAS has sprouted a second tail that points toward it.

4. Massive proportions. By his math, the object could be more than three miles across and weigh roughly 33 billion tons, far heavier than other known interstellar visitors like 1I/‘Oumuamua or 2I/Borisov. Statistically, that makes it an outlier among expected interstellar debris.

5. Weird metal mix. Its gas plume shows extreme nickel-to-iron ratios, puzzling scientists who say temperatures are too low for those metals to vaporise. Loeb provocatively suggests the metals might be “industrially produced.”

6. Mostly carbon dioxide. Observations indicate it’s about four percent water by mass, with a carbon-dioxide-rich coma, unusual but not unheard-of. Other astronomers counter that this composition could easily result from its birthplace around another star.

7. Unusual polarisation. 3I/ATLAS reflects light in a way never seen in other comets, showing “extreme negative polarisation.” Some scientists say it resembles objects from the far reaches beyond Neptune.

8. Linked to the “Wow! Signal.” Loeb even speculates that its incoming direction aligns within nine degrees of the mysterious 1977 radio burst known as the Wow! Signal — a long-standing SETI mystery.

9. A bluer glow. As it nears the Sun, its brightness has increased and its light turned bluer than expected, leading Loeb to wonder if it has an unknown, possibly artificial, heat source.

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