NASA's SPHEREx mission observes interstellar comet 3I/ATLAS
NASA's SPHEREx mission recently watched comet 3I/ATLAS—only the third known visitor from another star system—when it brightened in December 2025, about two months after perihelion, while already heading back out of the inner solar system.
Discovered in 2025, the comet put on a show by erupting with water vapor, carbon dioxide, and organic molecules, plus a dramatic dust tail.
Comet is still visible through small telescopes
After swinging closest to the Sun in late October, 3I/ATLAS started releasing material that had not been exposed to space for billions of years.
In December, SPHEREx saw water vapor as water ice quickly sublimated into gas.
Want to catch a glimpse? The comet is visible through small telescopes during pre-dawn hours as it moves across the sky—check tools such as NASA's Eyes on the Solar System to track its path.