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 August 6
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                              Messier 20 and 21
              Image Credit & [3]Copyright: [4]Emanuele Petrilli

   Explanation: [5]The beautiful Trifid Nebula, also known as Messier 20,
   is easy [6]to find with a small telescope in the nebula rich
   constellation Sagittarius. About 5,000 light-years away, the colorful
   study in [7]cosmic contrasts shares this well-composed, nearly 1 degree
   wide field with open star cluster [8]Messier 21 (right). 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 [9]youngest star forming
   regions in our sky, with newborn and embryonic stars embedded in its
   [10]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 years old.

                      Tomorrow's picture: dark markings
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    Authors & editors: [22]Robert Nemiroff ([23]MTU) & [24]Jerry Bonnell
                                 ([25]UMCP)
          NASA Official: Phillip Newman [26]Specific rights apply.
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                A service of: [28]ASD at [29]NASA / [30]GSFC
                           & [31]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2008/trifidnebulaM20M21_2048.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. https://www.instagram.com/_petrilli/
   5. https://apod.nasa.gov/apod/ap171020.html
   6. http://freestarcharts.com/index.php/messier-catalogue/20-guides/messier/259-messier-20-m20-trifid-nebula-emission-and-reflection-nebula
   7. http://www.cosmotography.com/images/cosmic_nurseries.html
   8. http://www.universetoday.com/31935/messier-21/
   9. http://arxiv.org/abs/astro-ph/0107111
  10. http://www.spitzer.caltech.edu/news/184-ssc2005-02-Spitzer-Finds-Stellar-Incubators-with-Massive-Star-Embryos
  11. https://apod.nasa.gov/apod/ap200805.html
  12. https://apod.nasa.gov/apod/archivepix.html
  13. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  14. https://apod.nasa.gov/apod/lib/aptree.html
  15. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  16. https://apod.nasa.gov/apod/calendar/allyears.html
  17. https://apod.nasa.gov/apod.rss
  18. https://apod.nasa.gov/apod/lib/edlinks.html
  19. https://apod.nasa.gov/apod/lib/about_apod.html
  20. http://asterisk.apod.com/discuss_apod.php?date=200806
  21. https://apod.nasa.gov/apod/ap200807.html
  22. http://www.phy.mtu.edu/faculty/Nemiroff.html
  23. http://www.phy.mtu.edu/
  24. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  25. http://www.astro.umd.edu/
  26. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  27. https://www.nasa.gov/about/highlights/HP_Privacy.html
  28. https://astrophysics.gsfc.nasa.gov/
  29. https://www.nasa.gov/
  30. https://www.nasa.gov/centers/goddard/
  31. http://www.mtu.edu/