                        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.

                              2021 December 18

                              Stephan's Quintet
               Image Credit: NASA, ESA, Hubble Legacy Archive;
                   Processing & Copyright: Bernard Miller

   Explanation: The first identified compact galaxy group, Stephan's
   Quintet is featured in this eye-catching image constructed with data
   drawn from the extensive Hubble Legacy Archive. About 300 million
   light-years away, only four of these five galaxies are actually locked
   in a cosmic dance of repeated close encounters. The odd man out is easy
   to spot, though. The interacting galaxies, NGC 7319, 7318A, 7318B, and
   7317 have an overall yellowish cast. They also tend to have distorted
   loops and tails, grown under the influence of disruptive gravitational
   tides. But the predominantly bluish galaxy, NGC 7320, is closer, just
   40 million light-years distant, and isn't part of the interacting
   group. Stephan's Quintet lies within the boundaries of the high flying
   constellation Pegasus. At the estimated distance of the quartet of
   interacting galaxies, this field of view spans about 500,000
   light-years. But moving just beyond this field, up and to the right,
   astronomers can identify another galaxy, NGC 7320C, that is also 300
   million light-years distant. Including it would bring the interacting
   quartet back up to quintet status.

                      Tomorrow's picture: five in a row
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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.

