                APOD: 2018 February 22 - When Roses Aren t Red

                         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 February 22
                                      [2]
                            When Roses Aren't Red
        Image Credit & Copyright [3] : Eric Coles [4]  and Mel Helm [5]

Explanation: Not all roses are red of course [6] , but they can still be very
pretty. Likewise, the beautiful Rosette Nebula [7]  and other star forming
regions are often shown in astronomical images with a predominately red hue,
in part because the dominant emission in the nebula is from hydrogen atoms [8]
. Hydrogen's strongest optical emission line, known as H-alpha, is in the red
region of the spectrum, but the beauty of an emission nebula need not be
appreciated in red light alone. Other atoms [9]  in the nebula are also
excited by energetic starlight and produce narrow emission lines as well. In
this gorgeous view of the Rosette Nebula, narrowband images are combined to
show emission from sulfur atoms in red, hydrogen in blue, and oxygen in green.
In fact, the scheme of mapping [10]  these narrow atomic emission lines into
broader colors is adopted in many Hubble images [11] of stellar nurseries. The
image spans about 100 light-years in the constellation Monoceros, at the 3,000
light-year estimated [12] distance of the Rosette Nebula [13] . To make the
Rosette red, just follow this link [14]  or slide your cursor over the image.

                 Tomorrow's picture: the moon isn't blue [15]

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    Authors & editors: Robert Nemiroff [27] (MTU [28] ) & Jerry Bonnell [29]
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Site notes:
  [1] archivepix.html
  [2] image/1802/RosetteNebulaNBHColesHelm1024.jpg
  [3] lib/about_apod.html#srapply
  [4] http://www.astrobin.com/users/coles44/
  [5] http://www.pbase.com/melhelm
  [6] https://en.wikipedia.org/wiki/Roses_Are_Red
  [7] http://www.atlasoftheuniverse.com/nebulae/ngc2237.html
  [8] https://en.wikipedia.org/wiki/H-alpha
  [9] http://astro.u-strasbg.fr/~koppen/discharge/index.html
  [10] http://hubblesite.org/sci.d.tech/behind_the_pictures/
meaning_of_color/eagle.shtml
  [11] http://hubblesite.org/
  [12] http://www.atlasoftheuniverse.com/5000lys.html
  [13] http://www.messier.seds.org/xtra/ngc/n2244.html
  [14] image/1802/RosetteHRGBColesHelm1024.jpg
  [15] ap180223.html
  [16] ap180221.html
  [17] archivepix.html
  [18] lib/apsubmit2015.html
  [19] lib/aptree.html
  [20] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [21] calendar/allyears.html
  [22] /apod.rss
  [23] lib/edlinks.html
  [24] lib/about_apod.html
  [25] http://asterisk.apod.com/discuss_apod.php?date=180222
  [26] ap180223.html
  [27] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [28] http://www.phy.mtu.edu/
  [29] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [30] http://www.astro.umd.edu/
  [31] lib/about_apod.html#srapply
  [32] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [33] https://astrophysics.gsfc.nasa.gov/
  [34] https://www.nasa.gov/
  [35] https://www.nasa.gov/centers/goddard/
  [36] http://www.mtu.edu/
