Only the third known object to enter our Solar System from another star. In late October 2026 the James Webb telescope read the ice of comet 3I/ATLAS and found it resembles the frozen worlds beyond Neptune.
The October 28, 2026 study: Webb's spectrograph read the comet's water ice three times and found grains that mirror the icy bodies past Neptune — a time capsule from another star system.
NASA's own page on the visitor — when it was spotted, how close it came, and why the agency says every sign points to an ordinary (if alien-born) comet.
Discovered July 1, 2025 on a hyperbolic orbit no Sun-bound comet could have. The full dossier on its path, chemistry and the race to study it before it leaves forever.
Anton Petrov walks through how 3I/ATLAS was found and what its glowing coma is actually made of.
A short explainer on the flyby — and why a rock from another star is the closest thing to sampling an alien solar system.
The cigar-shaped object that started it all — and accelerated as it left, with no visible tail, sparking a decade of argument about what it really was.
Found by an amateur astronomer, this one looked unmistakably like a comet — the proof that interstellar objects pass through more often than we thought.
Harvard's Avi Loeb keeps asking whether these visitors are natural. Here's the case for and against — and why almost every astronomer says: comet.