Astronomy Picture of the Day

                         Astronomy Picture of the Day

    Discover the cosmos! [1] Each day a different image or photograph of our
 fascinating universe is featured, along with a brief explanation written by a
                           professional astronomer.

                                2018 August 24
                                      [2]
                              Messier 20 and 21
            Image Credit & Copyright [3] : Ignacio Diaz Bobillo [4]

Explanation: The beautiful Trifid [5]  Nebula, also known as Messier 20, is
easy to find [6]  with a small telescope in the nebula rich constellation
Sagittarius. About 5,000 light-years away, the colorful study in cosmic
contrasts [7]  shares this well-composed [8] , nearly 1 degree wide field with
open star cluster Messier 21 [9] (bottom 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 youngest [10]  star forming regions in our sky, with
newborn and embryonic stars embedded in its natal dust and gas clouds [11] .
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 [12] .

                      Tomorrow's picture: speeding spiral

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    Authors & editors: Robert Nemiroff [24] (MTU [25] ) & Jerry Bonnell [26]
                                  (UMCP [27] )
          NASA Official:  Phillip Newman Specific rights apply [28] .
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Site notes:
  [1] archivepix.html
  [2] image/1808/M20M21Bobillo.jpg
  [3] lib/about_apod.html#srapply
  [4] http://www.pampaskies.com/gallery3/index.php
  [5] 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.pampaskies.com/gallery3/Deep-Space...
  [9] http://www.universetoday.com/31935/messier-21...
  [10] http://arxiv.org/abs/astro-ph/0107111
  [11] http://www.spitzer.caltech.edu/news/
184-ssc2005-02-Spitzer-Finds-Stellar-Incubators-with-Massive-Star-Embryos
  [12] http://cdsads.u-strasbg.fr/cgi-bin/
nph-bib_query?1996AJ....112.1073F&db_key=AST&nosetcookie=1
  [13] ap180823.html
  [14] archivepix.html
  [15] lib/apsubmit2015.html
  [16] lib/aptree.html
  [17] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apo...
  [18] calendar/allyears.html
  [19] /apod.rss
  [20] lib/edlinks.html
  [21] lib/about_apod.html
  [22] http://asterisk.apod.com/discuss_apod.php?dat...
  [23] ap180825.html
  [24] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [25] http://www.phy.mtu.edu/
  [26] https://antwrp.gsfc.nasa.gov/htmltest/jbonnel...
  [27] http://www.astro.umd.edu/
  [28] lib/about_apod.html#srapply
  [29] https://www.nasa.gov/about/highlights/HP_Priv...
  [30] https://astrophysics.gsfc.nasa.gov/
  [31] https://www.nasa.gov/
  [32] https://www.nasa.gov/centers/goddard/
  [33] http://www.mtu.edu/

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