                         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 1
                                      [2]
                      The Iris Nebula in a Field of Dust
      Image Credit & Copyright: Franco Sgueglia & Francesco Sferlazza [3]

Explanation: What blue flower grows in this field of dark interstellar dust?
The Iris Nebula [4] . The striking blue color of the Iris Nebula [5]  is
created by light from the bright star SAO 19158 [6] reflecting off of a dense
patch of normally dark dust [7] . Not only is the star itself mostly blue, but
blue light from the star is preferentially reflected [8] by the dust -- the
same affect that makes Earth's sky blue [9] . The brown tint of the pervasive
dust comes partly from photoluminescence [10]  -- dust converting ultraviolet
radiation [11]  to red [12]  light. Cataloged as NGC [13]  7023, the Iris
Nebula is studied [14]  frequently because of the unusual prevalence there of
Polycyclic Aromatic Hydrocarbons [15]  (PAHs), complex molecules that are also
released on Earth during the incomplete combustion of wood fires. The bright
blue portion of the Iris Nebula [16]  spans about six light years. The Iris
[17]  Nebula, pictured here, lies about 1300 light years distant and can be
found [18] with a small telescope toward the constellation of Cepheus [19] .

        APOD Event: APOD Editor to speak at Fermilab on August 8 [20]
                  Tomorrow's picture: lunar eclipse for poets

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    Authors & editors: Robert Nemiroff [32] (MTU [33] ) & Jerry Bonnell [34]
                                  (UMCP [35] )
          NASA Official:  Phillip Newman Specific rights apply [36] .
              NASA Web Privacy Policy and Important Notices [37]
              A service of: ASD [38]  at NASA [39]  / GSFC [40]
                           & Michigan Tech. U. [41]
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Site notes:
  [1] archivepix.html
  [2] image/1808/IrisNebula_Sgueglia_2729.jpg
  [3] mailto: sferlazza @at@ gmail .dot. com
  [4] http://en.wikipedia.org/wiki/Iris_Nebula
  [5] ap101112.html
  [6] http://www.starrywonders.com/irisst8300.html
  [7] http://ned.ipac.caltech.edu/level5/Mathis/Mathis1.html
  [8] http://en.wikipedia.org/wiki/Reflection_nebula
  [9] http://spaceplace.nasa.gov/blue-sky/en/
  [10] http://en.wikipedia.org/wiki/Photoluminescence
  [11] https://science.nasa.gov/ems/10_ultravioletwaves
  [12] http://upload.wikimedia.org/wikipedia/commons/2/25/Red.svg
  [13] http://en.wikipedia.org/wiki/List_of_NGC_objects
  [14] http://adsabs.harvard.edu/abs/2005A%26A...429..193R
  [15] http://www.chem.ucl.ac.uk/cosmicdust/pah.htm#what
  [16] ap051229.html
  [17] http://en.wikipedia.org/wiki/Iris_(plant)
  [18] https://www.youtube.com/watch?v=kV3L6tMkTCs
  [19] http://hawastsoc.org/deepsky/cep/index.html
  [20] https://www.facebook.com/events/224564531505324/
  [21] ap180731.html
  [22] archivepix.html
  [23] lib/apsubmit2015.html
  [24] lib/aptree.html
  [25] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [26] calendar/allyears.html
  [27] /apod.rss
  [28] lib/edlinks.html
  [29] lib/about_apod.html
  [30] http://asterisk.apod.com/discuss_apod.php?date=180801
  [31] ap180802.html
  [32] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [33] http://www.phy.mtu.edu/
  [34] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [35] http://www.astro.umd.edu/
  [36] lib/about_apod.html#srapply
  [37] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [38] https://astrophysics.gsfc.nasa.gov/
  [39] https://www.nasa.gov/
  [40] https://www.nasa.gov/centers/goddard/
  [41] http://www.mtu.edu/
