Interstellar comet 3I/ATLAS makes closest approach to Sun
The rare interstellar comet 3I/ATLAS just made its closest approach to the Sun on October 29, 2025, lighting up with a coma and tail distinctly bluer than the Sun.
Even though it disappeared from view in September, NASA's SOHO and STEREO-A spacecraft kept an eye on it—pretty impressive since this is only the third interstellar comet ever spotted.
Comet's unique features, brightening
Unlike most comets we know, 3I/ATLAS has a high carbon dioxide-to-water ratio and some unique features scientists think it picked up from another star system or during its journey through space.
Its rapid brightening and unusual colors are giving researchers fresh clues about what comets from beyond our solar system are really like.
When will it be visible again?
If you're into stargazing, mark your calendar: the comet will pop back into Earth's night sky in late November or early December.
It'll be closest to us on December 19—but you'll need a small telescope to spot it.
NASA's Psyche and Lucy missions might also get a look, offering us more clues to its origins and makeup.