Comet 3I/ATLAS Larger Than Expected, Could Be Alien Probe: Astrophysicist

A massive interstellar object hurtling through the solar system may be considerably larger than initial observations suggested, according to a new analysis. It could even have alien technology, according to Harvard astrophysicist Avi Loeb and his research team.

The object, known as 3I/ATLAS, was first spotted by NASA on July 1, 2025, and has since captured the attention of scientists worldwide for its unusual trajectory and cosmic origins. Classified as a comet, 3I/ATLAS is only the third confirmed interstellar visitor to the solar system, following ‘Oumuamua in 2017 and 2I/Borisov in 2019, reported The New York Post.

Recent calculations from Loeb's team suggest that the object's mass may exceed 33 billion tons, far surpassing earlier estimates. By studying its path, Loeb and his team determined that the object's “non-gravitational acceleration” was “smaller than 49 feet per day, squared,” according to a recent blog post. The scientists then compared this with the amount of gas and dust the object has been shedding to determine its size.

Further estimates indicate that the solid-density nucleus of 3I/ATLAS could be larger than 3.1 miles in diameter, a significant increase over previous projections based on Hubble Space Telescope observations.

Loeb emphasised the object's exceptional nature, as it is akin to finding a needle in an intergalactic haystack. “Given the limited reservoir of heavy elements, we should have discovered on the order of a hundred thousand interstellar objects on the 0.1-kilometer scale of 1I/'Oumuamua before finding 3I/ATLAS, yet we only detected two interstellar objects previously,” he said.

Despite its rapid approach towards the inner solar system, 3I/ATLAS is not a threat to Earth. Its path, however, will bring it unusually close to Jupiter, Venus and Mars, passing within 1.67 million miles of Mars' orbit over the weekend.

Loeb and his colleagues have also proposed a theory. They say the object could be “a piece of alien technology intentionally sent to us".

“The hypothesis in question is that [3I/ATLAS] is a technological artifact, and furthermore has active intelligence. If this is the case, then two possibilities follow,” Dr Loeb, Adam Drowl, and Adam Hibberd wrote in a paper published on July 17.

Several unusual characteristics reportedly support this idea. The object exhibits non-gravitational acceleration and its path takes it near Venus, Mars and Jupiter, which could be potential “key target planets.”

Loeb further speculated that the tilt and trajectory might enable any intelligent entity on board to collect “astrometric measurements, to determine the orbits and masses of the Solar System planets, allowing it to prepare an optimal approach strategy to the Solar System.”