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.

                               2021 November 4
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                             NGC 147 and NGC 185
                Image Credit & [3]Copyright: [4]Dan Bartlett

   Explanation: Dwarf galaxies [5]NGC 147 (left) and [6]NGC 185 stand side
   by side in this sharp telescopic portrait. The two are not-often-imaged
   satellites of M31, the [7]great spiral Andromeda Galaxy, some 2.5
   million light-years away. Their separation on the sky, less than one
   degree across a pretty field of view, translates to only about 35
   thousand light-years at Andromeda's distance, but Andromeda itself is
   found well outside this frame. Brighter and more famous satellite
   galaxies of Andromeda, [8]M32 and M110, are seen closer to the great
   spiral. [9]NGC 147 and NGC 185 have been identified as binary galaxies,
   forming a gravitationally stable binary system. But recently discovered
   faint [10]dwarf galaxy Cassiopeia II also seems to be part of their
   system, forming a gravitationally bound group within Andromeda's
   intriguing population of small [11]satellite galaxies.

                     Tomorrow's picture: pixels in space
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    Authors & editors: [23]Robert Nemiroff ([24]MTU) & [25]Jerry Bonnell
                                 ([26]UMCP)
          NASA Official: Phillip Newman [27]Specific rights apply.
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                A service of: [29]ASD at [30]NASA / [31]GSFC
                           & [32]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2111/NGC147NGC185satellites.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. mailto:%20h2ologg%20[at]%20gmail
   5. https://www.nasa.gov/feature/goddard/caldwell-17
   6. https://www.nasa.gov/feature/goddard/caldwell-18
   7. https://apod.nasa.gov/apod/ap181217.html
   8. https://apod.nasa.gov/apod/ap200925.html
   9. https://ui.adsabs.harvard.edu/abs/1998AJ....116.1688V/abstract
  10. https://arxiv.org/abs/1511.08289
  11. https://astrobites.org/2013/01/26/the-curious-case-of-andromedas-satellites/
  12. https://apod.nasa.gov/apod/ap211103.html
  13. https://apod.nasa.gov/apod/archivepix.html
  14. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  15. https://apod.nasa.gov/apod/lib/aptree.html
  16. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  17. https://apod.nasa.gov/apod/calendar/allyears.html
  18. https://apod.nasa.gov/apod.rss
  19. https://apod.nasa.gov/apod/lib/edlinks.html
  20. https://apod.nasa.gov/apod/lib/about_apod.html
  21. http://asterisk.apod.com/discuss_apod.php?date=211104
  22. https://apod.nasa.gov/apod/ap211105.html
  23. http://www.phy.mtu.edu/faculty/Nemiroff.html
  24. http://www.phy.mtu.edu/
  25. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  26. http://www.astro.umd.edu/
  27. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  28. https://www.nasa.gov/about/highlights/HP_Privacy.html
  29. https://astrophysics.gsfc.nasa.gov/
  30. https://www.nasa.gov/
  31. https://www.nasa.gov/centers/goddard/
  32. http://www.mtu.edu/