Astronomy Picture of the Day

Explanation: A new visitor tothe inner Solar System, cometC/2025 R2(SWAN)sports a long ion tail extending diagonally acrossthis almost 7 degree wide telescopic field of viewrecorded on September 21.A fainter fellow comet also making its inner Solar System debut,C/2025 K1 (ATLAS),can be spotted above and left of SWAN's greenish coma,just visible against the background sea of starsin the constellation Virgo.Both new comets were only discovered in 2025and are joined in this celestial frame by ruddy planet Mars (bottom),a more familiar wanderer in planet Earth's night skies.The cometsmay appear to be in a race, nearly neck and neckin their voyage through the inner Solar System and around the Sun.But this comet SWAN has already reached its perihelionor closest approach to the Sun on September 12and is now outbound along its orbit.This comet ATLASis still inbound though, and will make its perihelion passage on October 8.