             APOD: 2017 November 1 - Thors Helmet Emission Nebula

                         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.

                                2017 November 1
                                      [2]
                        Thor's Helmet Emission Nebula
 Image Credit & Copyright [3] : Adam Block [4] , Mt. Lemmon SkyCenter [5] , U.
                                  Arizona [6]

Explanation: This helmet-shaped cosmic cloud with wing-like appendages is
popularly called Thor [7] 's Helmet. Heroically sized even for a Norse god [8]
, Thor's Helmet spans about 30 light-years across. In fact, the helmet is more
like an interstellar bubble [9] , blown as a fast wind -- from the bright star
near the center [10]  of the bubble's blue-hued region -- sweeps through a
surrounding molecular cloud. This star, a Wolf-Rayet star [11] , is a massive
and extremely hot giant star [12]  thought to be in a brief, pre-supernova
[13]  stage of evolution. Cataloged as NGC 2359 [14] , the emission nebula
[15] is located [16]  about 12,000 light-years [17]  away toward the
constellation of the Big Dog (Canis Major [18] ). The sharp image [19] , made
using broadband and narrowband filters, captures striking details of the
nebula's [20] filamentary gas and dust structures. The blue color originates
from strong emission from oxygen [21]  atoms in the nebula.

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                Tomorrow's picture: Thor's day (Thursday) [26]

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Site notes:
  [1] archivepix.html
  [2] image/1711/ThorsHelmet_Block_1400.jpg
  [3] lib/about_apod.html#srapply
  [4] http://adamblockphotos.com
  [5] http://skycenter.arizona.edu/
  [6] http://www.as.arizona.edu/
  [7] https://en.wikipedia.org/wiki/Thor
  [8] http://www.pantheon.org/articles/t/thor.html
  [9] ap160422.html
  [10] http://adsabs.harvard.edu/abs/2014MNRAS.443...12Z
  [11] ap140701.html
  [12] ap110408.html
  [13] ap050910.html
  [14] https://en.wikipedia.org/wiki/NGC_2359
  [15] https://en.wikipedia.org/wiki/Emission_nebula
  [16] ap100319.html
  [17]
https://www.grc.nasa.gov/www/k-12/Numbers/Math/Mathematical_Thinking/
how_long_is_a_light_year.htm
  [18] http://www.internal.org/view_poem.phtml?poemID=115
  [19] http://skycenter.arizona.edu/gallery/Nebulae/NGC2359
  [20] http://iopscience.iop.org/1538-3881/118/2/948
  [21] http://fusedweb.llnl.gov/CPEP/Chart_Pages/5.Plasmas/Nebula/
Forbidden.html
  [22] https://www.facebook.com/AstronomyPictureOfTheDay
  [23] https://plus.google.com/u/1/+AstronomyPictureOfTheDay
  [24] https://www.instagram.com/astronomypicturesdaily/
  [25] http://twitter.com/apod/
  [26] ap171102.html
  [27] ap171031.html
  [28] archivepix.html
  [29] lib/apsubmit2015.html
  [30] lib/aptree.html
  [31] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [32] calendar/allyears.html
  [33] /apod.rss
  [34] lib/edlinks.html
  [35] lib/about_apod.html
  [36] http://asterisk.apod.com/discuss_apod.php?date=171101
  [37] ap171102.html
  [38] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [39] http://www.phy.mtu.edu/
  [40] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [41] http://www.astro.umd.edu/
  [42] lib/about_apod.html#srapply
  [43] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [44] https://astrophysics.gsfc.nasa.gov/
  [45] https://www.nasa.gov/
  [46] https://www.nasa.gov/centers/goddard/
  [47] http://www.mtu.edu/
