Comet 3I/ATLAS will make its closest approach to Earth on December 19, 2025, and can be watched via the Virtual Telescope Project live stream, scheduled to start at 04:00 UTC on December 19 (23:00 EST on December 18).
Comet 3I/ATLAS will make its closest approach to Earth at around 06:00 UTC on December 19 (01:00 EST on December 18). At that time, it will be about 1.8 AU or 270 million km (168 million miles), nearly twice the average distance between Earth and the Sun.
3I/ATLAS was first observed by the ATLAS survey in Chile on July 1, 2025, and is the third confirmed object of its kind to enter the solar system.
The comet caught the eye of the public and scientists alike, with speculations of it being an alien spaceship after Harvard professor Avi Loeb co-authored a paper exploring the hypothesis.
It then made it back into the news when a team of Auburn University physicists using NASA’s Neil Gehrels Swift Observatory detected the ultraviolet fingerprint of water in the interstellar comet 3I/ATLAS. This was the first confirmed ultraviolet detection of water from a comet that originated beyond our solar system.
The European Space Agency’s (ESA) ExoMars Trace Gas Orbiter (TGO) and Mars Express spacecraft recorded images of interstellar comet 3I/ATLAS on October 3, 2025, from about 30 million km (18.6 million miles) away, marking the closest observation of the object from any spacecraft so far.
3I/ATLAS reached perihelion at approximately 11:47 UTC on October 29, 2025, at a heliocentric distance of about 1.356 AU (203 million km or 126 million miles).
Feature image credit: Satoru Murata