An interstellar comet known as 3I/ATLAS, which swept past the Sun in 2024, could be a 12‑billion‑year‑old relic from deep space and has even been described by a Harvard physicist as a possible alien probe, according to new research and long-running controversy over its origins. The object, only the third confirmed interstellar visitor ever seen in our solar system, was tracked as it brightened dramatically before heading back out towards the dark between the stars.
3I/ATLAS first appeared in telescopes in July 2024, immediately drawing attention because its orbit made clear it did not originate in our own planetary system. Its steep, hyperbolic trajectory marked it out as a true interstellar interloper, following in the footsteps of 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019. Those earlier objects were too faint and fleeting to yield much detail. This time, astronomers had a rare opportunity: a comparatively bright comet, passing close enough to the Sun for the world's most powerful observatories to pick it apart.
