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 May 15
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                          Galaxy Wars: M81 and M82
     Image Credit & [3]Copyright: [4]Dietmar Hager, [5]Torsten Grossmann

   Explanation: These two galaxies are far far away, 12 million
   light-years distant toward the northern constellation of the Great
   Bear. On the left, with grand spiral arms and bright yellow core is
   spiral galaxy [6]M81, some 100,000 light-years across. On the right
   marked by red gas and dust clouds, is irregular galaxy [7]M82. The pair
   have been locked in gravitational combat for a billion years.
   [8]Gravity from each galaxy has profoundly affected the other during a
   series of cosmic close encounters. Their last go-round lasted about 100
   million years and likely raised density waves rippling around M81,
   resulting in the richness of [9]M81's spiral arms. [10]M82 was left
   with violent star forming regions and colliding gas clouds so energetic
   the galaxy glows in X-rays. In the next few billion years, their
   continuing gravitational encounters will result in a merger, and a
   [11]single galaxy will remain.

                      Tomorrow's picture: light-weekend
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    Authors & editors: [23]Robert Nemiroff ([24]MTU) & [25]Jerry Bonnell
                                 ([26]UMCP)
          NASA Official: Phillip Newman [27]Specific rights apply.
              [28]NASA Web Privacy Policy and Important Notices
                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/2005/M81-82.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. http://www.stargazer-observatory.com/
   5. http://astrogrossi.de/
   6. https://apod.nasa.gov/apod/ap190417.html
   7. https://apod.nasa.gov/apod/ap190723.html
   8. https://phys.org/news/2019-11-astronomers-stellar-halo.html
   9. http://www.youtube.com/watch?v=0seVq5ydqzk
  10. https://hubblesite.org/contents/news-releases/2001/news-2001-08.html
  11. https://science.nasa.gov/science-news/science-at-nasa/2012/31may_andromeda/
  12. https://apod.nasa.gov/apod/ap200514.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=200515
  22. https://apod.nasa.gov/apod/ap200516.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/