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 August 11

                    Arp 87: Merging Galaxies from Hubble
         Image Credit: NASA, ESA, Hubble Heritage Team (STScI, AURA)

   Explanation: This dance is to the death. Along the way, as these two
   large galaxies duel, a cosmic bridge of stars, gas, and dust currently
   stretches over 75,000 light-years and joins them. The bridge itself is
   strong evidence that these two immense star systems have passed close
   to each other and experienced violent tides induced by mutual gravity.
   As further evidence, the face-on spiral galaxy on the right, also known
   as NGC 3808A, exhibits many young blue star clusters produced in a
   burst of star formation. The twisted edge-on spiral on the left (NGC
   3808B) seems to be wrapped in the material bridging the galaxies and
   surrounded by a curious polar ring. Together, the system is known as
   Arp 87 and morphologically classified, technically, as peculiar. While
   such interactions are drawn out over billions of years, repeated close
   passages should ultimately result in the death of one galaxy in the
   sense that only one galaxy will eventually result. Although this
   scenario does look peculiar, galactic mergers are thought to be common,
   with Arp 87 representing a stage in this inevitable process. The Arp 87
   pair are about 300 million light-years distant toward the constellation
   Leo. The prominent edge-on spiral galaxy at the far left appears to be
   a more distant background galaxy and not involved in the on-going
   merger.

                     Tomorrow's picture: perseid meteors
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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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