Comet 3I/ATLAS may be alien probe as it is larger than expected, says Harvard scientists

The solar system has a rare visitor once again. Scientists are closely studying an interstellar object that defies expectations and raises unusual possibilities.

What is 3I/ATLAS and why is it unusual?
The object, named 3I/ATLAS, was first spotted by NASA on 1 July 2025. It is only the third confirmed interstellar visitor after ‘Oumuamua in 2017 and 2I/Borisov in 2019. Classified as a comet, 3I/ATLAS has unusual motion that has drawn global scientific attention. Harvard astrophysicist Avi Loeb and his team now suggest it may be larger than initial estimates indicated, with a solid nucleus possibly over 3.1 miles in diameter.

How did scientists determine the object’s size and mass?
Loeb’s team calculated the object’s “non-gravitational acceleration” at less than 49 feet per day squared. They compared this with the gas and dust the object has been shedding. Their results indicate a mass exceeding 33 billion tons, far larger than first measurements based on Hubble observations. Loeb described 3I/ATLAS as exceptional, noting the scarcity of interstellar objects detected compared to expectations from the distribution of heavy elements in space.

Could 3I/ATLAS be alien technology?
Loeb and co-authors have put forward an unorthodox hypothesis that 3I/ATLAS could be an active intelligence technological artefact. Its unorthodox path brings it close to Venus, Mars, and Jupiter, perhaps to harvest astrometric data on planetary orbits and masses. The path and incline of the object may indicate intentional design to facilitate an intelligent being to maximise its approach within the solar system.