                        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.

                               2023 October 24
     Three large galaxies are shown, the rightmost two in collision. The
   galaxy on the far right is a large spiral galaxy with one arm connected
    to an unusual polar galaxy on the left. The smaller galaxy on the far
   left is thought to be far in the background. Please see the explanation
                       for more detailed information.

                    Arp 87: Merging Galaxies from Hubble
      Image Credit: NASA, ESA, Hubble; Processing: Harshwardhan Pathak

   Explanation: This dance is to the death. 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. While such interactions are drawn out over billions of years,
   repeated close passages will ultimately create one merged galaxy.
   Although this scenario does look unusual, galactic mergers are thought
   to be common, with Arp 87 representing a stage in this inevitable
   process. The Arp 87 dancing pair are about 300 million light-years
   distant toward the constellation of the Lion (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: 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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