Astronomy Picture of the Day

   [1]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
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                      M15: Dense Globular Star Cluster
    Image Credit: [3]NASA, [4]ESA, [5]Hubble Legacy Archive; Processing:
                             [6]Ehsan Ebrahimian

   Explanation: [7]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 [8]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. [9]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 [10]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: [22]Robert Nemiroff ([23]MTU) & [24]Jerry Bonnell
                                 ([25]UMCP)
          NASA Official: Phillip Newman [26]Specific rights apply.
              [27]NASA Web Privacy Policy and Important Notices
                A service of: [28]ASD at [29]NASA / [30]GSFC
                           & [31]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2306/M15-3.jpg
   3. https://www.nasa.gov/
   4. https://www.esa.int/
   5. https://hla.stsci.edu/
   6. https://www.instagram.com/anugrafy/
   7. https://www.nasa.gov/feature/goddard/2017/messier-15
   8. https://www.instagram.com/p/CtL-6FgNc5l/
   9. https://arxiv.org/abs/astro-ph/0209314
  10. https://ui.adsabs.harvard.edu/abs/2020AJ....159..276B/abstract
  11. https://apod.nasa.gov/apod/ap230614.html
  12. https://apod.nasa.gov/apod/archivepix.html
  13. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  14. https://apod.nasa.gov/apod/lib/aptree.html
  15. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  16. https://apod.nasa.gov/apod/calendar/allyears.html
  17. https://apod.nasa.gov/apod.rss
  18. https://apod.nasa.gov/apod/lib/edlinks.html
  19. https://apod.nasa.gov/apod/lib/about_apod.html
  20. http://asterisk.apod.com/discuss_apod.php?date=230615
  21. https://apod.nasa.gov/apod/ap230616.html
  22. http://www.phy.mtu.edu/faculty/Nemiroff.html
  23. http://www.phy.mtu.edu/
  24. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  25. http://www.astro.umd.edu/
  26. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  27. https://www.nasa.gov/about/highlights/HP_Privacy.html
  28. https://astrophysics.gsfc.nasa.gov/
  29. https://www.nasa.gov/
  30. https://www.nasa.gov/centers/goddard/
  31. http://www.mtu.edu/