                        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 June 15

                      M15: Dense Globular Star Cluster
      Image Credit: NASA, ESA, Hubble Legacy Archive; Processing: Ehsan
                                 Ebrahimian

   Explanation: Messier 15 is an immense swarm of over 100,000 stars. A 13
   billion year old relic of the early formative years of our galaxy it's
   one of about 170 globular star clusters that still roam the halo of the
   Milky Way. Centered in this sharp reprocessed Hubble image, M15 lies
   some 35,000 light-years away toward the constellation Pegasus. Its
   diameter is about 200 light-years, but more than half its stars are
   packed into the central 10 light-years or so, making one of the densest
   concentrations of stars known. Hubble-based measurements of the
   increasing velocities of M15's central stars are evidence that a
   massive black hole resides at the center of the dense cluster. M15 is
   also known to harbour a planetary nebula. Called Pease 1 (aka PN Ps 1),
   it can be seen in this image as a small blue blob below and just right
   of center.

                    Tomorrow's picture: when time lapses
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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