                        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.

                              2020 February 19

                UGC 12591: The Fastest Rotating Galaxy Known
     Image Credit: NASA, ESA, Hubble; Processing & Copyright: Leo Shatz

   Explanation: Why does this galaxy spin so fast? To start, even
   identifying which type of galaxy UGC 12591 is difficult -- featured on
   the lower left, it has dark dust lanes like a spiral galaxy but a large
   diffuse bulge of stars like a lenticular. Surprisingly observations
   show that UGC 12591 spins at about 480 km/sec, almost twice as fast as
   our Milky Way, and the fastest rotation rate yet measured. The mass
   needed to hold together a galaxy spinning this fast is several times
   the mass of our Milky Way Galaxy. Progenitor scenarios for UGC 12591
   include slow growth by accreting ambient matter, or rapid growth
   through a recent galaxy collision or collisions -- future observations
   may tell. The light we see today from UGC 12591 left about 400 million
   years ago, when trees were first developing on Earth.

                       Tomorrow's picture: open space
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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