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.

                              2019 December 30
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                              Messier 20 and 21
    Image Credit & [3]Copyright: [4]Stanislav Volskiy, [5]Chilescope Team

   Explanation: [6]The beautiful Trifid Nebula, also known as Messier 20,
   is easy [7]to find with a small telescope in the nebula rich
   constellation Sagittarius. About 5,000 light-years away, the colorful
   study in [8]cosmic contrasts shares [9]this well-composed, nearly 1
   degree wide field with open star cluster [10]Messier 21 (top left).
   Trisected by dust lanes the Trifid itself is about 40 light-years
   across and a mere 300,000 years old. That makes it one of the
   [11]youngest star forming regions in our sky, with newborn and
   embryonic stars embedded in its [12]natal dust and gas clouds.
   Estimates of the distance to open star cluster M21 are similar to
   M20's, but though they share this gorgeous telescopic skyscape there is
   no apparent connection between the two. In fact, M21's stars are much
   older, about 8 million [13]years old.

                   Tomorrow's picture: M31's little sister
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    Authors & editors: [25]Robert Nemiroff ([26]MTU) & [27]Jerry Bonnell
                                 ([28]UMCP)
          NASA Official: Phillip Newman [29]Specific rights apply.
              [30]NASA Web Privacy Policy and Important Notices
                A service of: [31]ASD at [32]NASA / [33]GSFC
                           & [34]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/1912/M20_volskiy.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. https://volskiy.smugmug.com/
   5. http://www.chilescope.com/
   6. https://apod.nasa.gov/apod/ap171020.html
   7. http://freestarcharts.com/index.php/messier-catalogue/20-guides/messier/259-messier-20-m20-trifid-nebula-emission-and-reflection-nebula
   8. http://www.cosmotography.com/images/cosmic_nurseries.html
   9. https://volskiy.smugmug.com/Nebulas/i-kzZ6f3P
  10. http://www.universetoday.com/31935/messier-21/
  11. http://arxiv.org/abs/astro-ph/0107111
  12. http://www.spitzer.caltech.edu/news/184-ssc2005-02-Spitzer-Finds-Stellar-Incubators-with-Massive-Star-Embryos
  13. http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1996AJ....112.1073F&db_key=AST&nosetcookie=1
  14. https://apod.nasa.gov/apod/ap191229.html
  15. https://apod.nasa.gov/apod/archivepix.html
  16. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  17. https://apod.nasa.gov/apod/lib/aptree.html
  18. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  19. https://apod.nasa.gov/apod/calendar/allyears.html
  20. https://apod.nasa.gov/apod.rss
  21. https://apod.nasa.gov/apod/lib/edlinks.html
  22. https://apod.nasa.gov/apod/lib/about_apod.html
  23. http://asterisk.apod.com/discuss_apod.php?date=191230
  24. https://apod.nasa.gov/apod/ap191231.html
  25. http://www.phy.mtu.edu/faculty/Nemiroff.html
  26. http://www.phy.mtu.edu/
  27. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  28. http://www.astro.umd.edu/
  29. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  30. https://www.nasa.gov/about/highlights/HP_Privacy.html
  31. https://astrophysics.gsfc.nasa.gov/
  32. https://www.nasa.gov/
  33. https://www.nasa.gov/centers/goddard/
  34. http://www.mtu.edu/