Interstellar Comet 3I/ATLAS Reaches Earth Flyby

An interstellar comet from another star system made its closest approach to Earth on December 19, 2025, passing safely at a distance of 1.8 astronomical units, or about 168 million miles. The object, designated 3I/ATLAS and the third confirmed interstellar visitor to our solar system, reached this point around 0600 GMT, posing no threat to the planet as it continued its outbound journey through the inner solar system.

Discovered on July 1, 2025, by the NASA-funded Asteroid Terrestrial-impact Last Alert System telescope in Chile, 3I/ATLAS follows the paths of 1I/Oumuamua in 2017 and 2I/Borisov in 2019. Astronomers confirmed its interstellar origin through its hyperbolic trajectory and high speed of approximately 68 kilometers per second, indicating it is not bound by the sun's gravity. The comet reached perihelion, its nearest point to the sun, on October 29, 2025, at 1.36 AU, or roughly 203 million kilometers. Earlier, on October 3, it passed Mars at about 19 million miles.

Observations revealed 3I/ATLAS as an active comet with a bright coma, a gaseous envelope around its nucleus, and two tails: a straight ion tail shaped by solar winds and a curving dust tail. Spectroscopic...