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 September 25
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                             Moon over Andromeda
   Composite Image Credit & [3]Copyright: [4]Adam Block and [5]Tim Puckett

   Explanation: The Great Spiral [6]Galaxy in Andromeda (also known [7]as
   M31), a mere 2.5 million light-years [8]distant, is the closest large
   spiral to our own Milky Way. Andromeda is visible to the unaided eye as
   a small, faint, fuzzy patch, but because its surface brightness is so
   low, casual [9]skygazers can't appreciate the galaxy's impressive
   extent in [10]planet Earth's sky. This entertaining composite image
   compares the [11]angular size of the nearby galaxy to a brighter, more
   familiar celestial sight. In it, a [12]deep exposure of Andromeda,
   tracing beautiful blue star clusters in spiral arms far beyond the
   bright yellow core, is combined with a typical view of a nearly full
   Moon. Shown at the same [13]angular scale, the Moon covers about 1/2
   degree on the sky, while the galaxy is clearly several times that size.
   The deep Andromeda exposure also includes two bright satellite
   galaxies, [14]M32 and [15]M110 (below and right).

                    Tomorrow's picture: Observe the Moon
     __________________________________________________________________

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    Authors & editors: [27]Robert Nemiroff ([28]MTU) & [29]Jerry Bonnell
                                 ([30]UMCP)
          NASA Official: Phillip Newman [31]Specific rights apply.
              [32]NASA Web Privacy Policy and Important Notices
                A service of: [33]ASD at [34]NASA / [35]GSFC
                           & [36]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2009/m31abtpmoon.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. http://www.caelumobservatory.com/
   5. http://www.cometwatch.com/
   6. https://apod.nasa.gov/apod/ap200430.html
   7. https://www.nasa.gov/feature/goddard/2017/messier-31-the-andromeda-galaxy
   8. http://arxiv.org/abs/astro-ph/0511045
   9. http://www.physics.ucla.edu/~huffman/m31.html
  10. https://apod.nasa.gov/apod/ap090411.html
  11. https://www.astronomy.swin.edu.au/cosmos/A/Angular+Diameter
  12. http://www.caelumobservatory.com/gallery/m31abtp.shtml
  13. https://apod.nasa.gov/apod/ap080801.html
  14. https://apod.nasa.gov/apod/ap991103.html
  15. https://apod.nasa.gov/apod/ap080909.html
  16. https://apod.nasa.gov/apod/ap200924.html
  17. https://apod.nasa.gov/apod/archivepix.html
  18. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  19. https://apod.nasa.gov/apod/lib/aptree.html
  20. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  21. https://apod.nasa.gov/apod/calendar/allyears.html
  22. https://apod.nasa.gov/apod.rss
  23. https://apod.nasa.gov/apod/lib/edlinks.html
  24. https://apod.nasa.gov/apod/lib/about_apod.html
  25. http://asterisk.apod.com/discuss_apod.php?date=200925
  26. https://apod.nasa.gov/apod/ap200926.html
  27. http://www.phy.mtu.edu/faculty/Nemiroff.html
  28. http://www.phy.mtu.edu/
  29. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  30. http://www.astro.umd.edu/
  31. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  32. https://www.nasa.gov/about/highlights/HP_Privacy.html
  33. https://astrophysics.gsfc.nasa.gov/
  34. https://www.nasa.gov/
  35. https://www.nasa.gov/centers/goddard/
  36. http://www.mtu.edu/