                        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 September 1

                   The Great Globular Cluster in Hercules
      Image Credit & Copyright: Serge Brunier, Jean-François Bax, David
                               Vernet OCA/C2PU

   Explanation: In 1716, English astronomer Edmond Halley noted, "This is
   but a little Patch, but it shows itself to the naked Eye, when the Sky
   is serene and the Moon absent." Of course, M13 is now less modestly
   recognized as the Great Globular Cluster in Hercules, one of the
   brightest globular star clusters in the northern sky. Sharp telescopic
   views like this one reveal the spectacular cluster's hundreds of
   thousands of stars. At a distance of 25,000 light-years, the cluster
   stars crowd into a region 150 light-years in diameter. Approaching the
   cluster core, upwards of 100 stars could be contained in a cube just 3
   light-years on a side. For comparison, the closest star to the Sun is
   over 4 light-years away. The remarkable range of brightness recorded in
   this image follows stars into the dense cluster core.

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