3I/ATLAS
Only the third object ever confirmed to have come from beyond the solar system.
- When
- Known to
- ± 12 hours
- Era
- Contemporary, Holocene
Discovered on 1 July 2025, 3I/ATLAS follows 1I/'Oumuamua in 2017 and 2I/Borisov in 2019. It is far larger and brighter than either, and its hyperbolic orbit and composition suggest an origin in the Milky Way's thick disc, making it plausibly older than the Sun. Telescopes across the world and several spacecraft at Mars observed it as it passed.