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 February 7

                Blue Straggler Stars in Globular Cluster M53
                       Image Credit: ESA/Hubble, NASA

   Explanation: If our Sun were part of this star cluster, the night sky
   would glow like a jewel box of bright stars. This cluster, known as M53
   and cataloged as NGC 5024, is one of about 250 globular clusters that
   survive in our Galaxy. Most of the stars in M53 are older and redder
   than our Sun, but some enigmatic stars appear to be bluer and younger.
   These young stars might contradict the hypothesis that all the stars in
   M53 formed at nearly the same time. These unusual stars are known as
   blue stragglers and are unusually common in M53. After much debate,
   blue stragglers are now thought to be stars rejuvenated by fresh matter
   falling in from a binary star companion. By analyzing pictures of
   globular clusters like the featured image taken by the Hubble Space
   Telescope, astronomers use the abundance of stars like blue stragglers
   to help determine the age of the globular cluster and hence a limit on
   the age of the universe. M53, visible with a binoculars towards the
   constellation of Bernice's Hair (Coma Berenices), contains over 250,000
   stars and is one of the furthest globulars from the center of our
   Galaxy.

                      Tomorrow's picture: ripple stars
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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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