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.

                              2019 November 20

                   Arp 273: Battling Galaxies from Hubble
     Image Credit: NASA, ESA, Hubble; Processing & Copyright: Rudy Pohl

   Explanation: What's happening to these spiral galaxies? Although
   details remain uncertain, there sure seems to be a titanic battle going
   on. The upper galaxy is labelled UGC 1810 by itself, but together with
   its collisional partners is known as Arp 273. The overall shape of the
   UGC 1810 -- in particular its blue outer ring -- is likely a result of
   wild and violent gravitational interactions. The blue color of the
   outer ring at the top is caused by massive stars that are blue hot and
   have formed only in the past few million years. The inner part of the
   upper galaxy -- itself an older spiral galaxy -- appears redder and
   threaded with cool filamentary dust. A few bright stars appear well in
   the foreground, unrelated to colliding galaxies, while several
   far-distant galaxies are visible in the background. Arp 273 lies about
   300 million light years away toward the constellation of Andromeda.
   Quite likely, UGC 1810 will devour its galactic sidekicks over the next
   billion years and settle into a classic spiral form.

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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

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