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 December 20
                                      [2]
                     Red Nebula, Green Comet, Blue Stars
Image Credit & Copyright [3] : Tom Masterson [4] (Grand Mesa Observatory [5] )

Explanation: This festively colored skyscape [6]  was captured in the early
morning hours of December 17, following Comet Wirtanen's [7] closest approach
[8]  to planet Earth [9] . The comet was just visible to the eye. The lovely
green color of its fluorescing cometary atmosphere or coma is brought out here
only by adding digital exposures registered on the comet's position below the
Pleiades star cluster. The exposures also bring out blue starlight reflected
by the dust clouds surrounding the young Pleiades stars. Gaze (toward the
left) across dusty dark nebulae along the edge of the Perseus molecular cloud
and you'll travel to emission nebula [10] NGC 1499, also known as the
California nebula. Too faint [11] for the eye, the cosmic cloud's pronounced
reddish glow is from electrons recombining with ionized hydrogen atoms. Around
December 23rd, Comet Wirtanen should be easy to find with binoculars [12] when
it sweeps close to bright star Capella in the northern winter constellation
Auriga, the Charioteer.

                   Tomorrow's picture: solstice celebrating

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    Authors & editors: Robert Nemiroff [24] (MTU [25] ) & Jerry Bonnell [26]
                                  (UMCP [27] )
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Site notes:
  [1] archivepix.html
  [2] image/1812/M45-CaliNeb-46P-TomMasterson-GrandMesaObservatory.jpg
  [3] lib/about_apod.html#srapply
  [4] https://www.flickr.com/people/112501172@N04/
  [5] https://grandmesaobservatory.com/
  [6] https://www.flickr.com/photos/transientastro/...
  [7] ap181115.html
  [8] https://www.nasa.gov/feature/jpl/ see-a-passing-comet-this-sunday
  [9] ap181216.html
  [10] ap131122.html
  [11] ap090411.html
  [12] https://earthsky.org/space/
46p-wirtanen-possibly-visible-to-eye-dec-2018
  [13] ap181219.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] ap181221.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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