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.

                               2020 November 7
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                      The Hercules Cluster of Galaxies
               Image Credit & [3]Copyright: [4]Howard Trottier

   Explanation: These are galaxies of the Hercules Cluster, an archipelago
   of [5]island universes a mere 500 million light-years away. Also known
   as [6]Abell 2151, this cluster is loaded with gas and dust rich,
   star-forming [7]spiral galaxies but has relatively few [8]elliptical
   galaxies, which lack gas and dust and the associated newborn stars. The
   colors in [9]this deep composite image clearly show the star forming
   galaxies with a blue tint and galaxies with older stellar populations
   with a yellowish cast. The sharp picture spans about 1/2 degree across
   the cluster center, corresponding to over 4 million light-years at the
   cluster's estimated distance. Diffraction [10]spikes around brighter
   foreground stars in our own Milky Way galaxy are produced by the
   imaging telescope's mirror support vanes. In the cosmic vista many
   galaxies seem to be [11]colliding or [12]merging while others seem
   [13]distorted - clear evidence that [14]cluster galaxies commonly
   interact. [15]In fact, the Hercules Cluster itself may be seen as the
   result of ongoing mergers of smaller galaxy clusters and is thought to
   be similar to [16]young galaxy clusters in the much more distant, early
   [17]Universe.

                       Tomorrow's picture: a dark moon
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    Authors & editors: [29]Robert Nemiroff ([30]MTU) & [31]Jerry Bonnell
                                 ([32]UMCP)
          NASA Official: Phillip Newman [33]Specific rights apply.
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                A service of: [35]ASD at [36]NASA / [37]GSFC
                           & [38]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2011/Abell2151_Howard_Trottier_2020_FFTelescope1024.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. https://www.sfu.ca/physics/people/profiles/trottier.html
   5. https://apod.nasa.gov/apod/ap051222.html
   6. http://www.atlasoftheuniverse.com/superc/her.html
   7. https://apod.nasa.gov/apod/ap070529.html
   8. https://apod.nasa.gov/apod/ap060520.html
   9. https://www.astrobin.com/6s026s/?nc=user
  10. http://en.wikipedia.org/wiki/Diffraction_spike
  11. https://apod.nasa.gov/apod/ap040612.html
  12. https://apod.nasa.gov/apod/ap090618.html
  13. https://apod.nasa.gov/apod/ap030607.html
  14. http://www.messier.seds.org/gal_clus.html
  15. http://arxiv.org/abs/astro-ph/0501406
  16. http://www.nasa.gov/jpl/spitzer/galaxy-cluster-abell2744-20140207/
  17. https://apod.nasa.gov/apod/ap060323.html
  18. https://apod.nasa.gov/apod/ap201106.html
  19. https://apod.nasa.gov/apod/archivepix.html
  20. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  21. https://apod.nasa.gov/apod/lib/aptree.html
  22. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  23. https://apod.nasa.gov/apod/calendar/allyears.html
  24. https://apod.nasa.gov/apod.rss
  25. https://apod.nasa.gov/apod/lib/edlinks.html
  26. https://apod.nasa.gov/apod/lib/about_apod.html
  27. http://asterisk.apod.com/discuss_apod.php?date=201107
  28. https://apod.nasa.gov/apod/ap201108.html
  29. http://www.phy.mtu.edu/faculty/Nemiroff.html
  30. http://www.phy.mtu.edu/
  31. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  32. http://www.astro.umd.edu/
  33. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  34. https://www.nasa.gov/about/highlights/HP_Privacy.html
  35. https://astrophysics.gsfc.nasa.gov/
  36. https://www.nasa.gov/
  37. https://www.nasa.gov/centers/goddard/
  38. http://www.mtu.edu/