                        Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                              2025 September 26

                         A SWAN, an ATLAS, and Mars
                    Image Credit & Copyright: Adam Block

   Explanation: A new visitor to the inner Solar System, comet C/2025 R2
   (SWAN) sports a long ion tail extending diagonally across this almost 7
   degree wide telescopic field of view recorded 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 stars in the constellation Virgo.
   Both new comets were only discovered in 2025 and are joined in this
   celestial frame by ruddy planet Mars (bottom), a more familiar wanderer
   in planet Earth's night skies. The comets may appear to be in a race,
   nearly neck and neck in their voyage through the inner Solar System and
   around the Sun. But this comet SWAN has already reached its perihelion
   or closest approach to the Sun on September 12 and is now outbound
   along its orbit. This comet ATLAS is still inbound though, and will
   make its perihelion passage on October 8.

                      Tomorrow's picture: light-weekend
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                             & Michigan Tech. U.

