                         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.

                               2019 February 21
                                      [2]
                            Reflections on vdB 9
            Image Credit & Copyright [3] : Guenter Kerschhuber [4]

Explanation: Centered in a well-composed celestial still life, pretty, blue
vdB 9 is the 9th object [5]  in Sidney van den Bergh's 1966 catalog [6] of
reflection nebulae. It shares this telescopic field of view, about twice the
size of a full moon on the sky, with stars and dark, obscuring dust clouds in
the northerly constellation Cassiopeia. Cosmic dust is preferentially
reflecting blue starlight from embedded, hot star SU Cassiopeiae [7] , giving
vdB 9 the characteristic bluish tint associated with a classical reflection
nebula. SU Cas is a Cepheid variable star, though even at its brightest it is
just too faint to be seen with the unaided eye. Still Cepheids play an
important role in determining distances in our galaxy and beyond [8] . At the
star's well-known distance of 1,540 light-years, this cosmic canvas [9]  would
be about 24 light-years across.

                      Tomorrow's picture: pixels in space

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Site notes:
  [1] archivepix.html
  [2] image/1902/20181013VDB9kerschhuber.jpg
  [3] lib/about_apod.html#srapply
  [4] http://kerschhuber.astronomie.at/index.html
  [5] ap121026.html
  [6] http://adsabs.harvard.edu/abs/1966AJ.....71..990V
  [7] http://simbad.harvard.edu/simbad/
sim-basic?Ident=vdb+9&submit=SIMBAD+search
  [8] http://heritage.stsci.edu/2011/15/caption.html
  [9] http://kerschhuber.astronomie.at/Nebula/slides/VDB9.html
  [10] ap190220.html
  [11] archivepix.html
  [12] lib/apsubmit2015.html
  [13] lib/aptree.html
  [14] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [15] calendar/allyears.html
  [16] /apod.rss
  [17] lib/edlinks.html
  [18] lib/about_apod.html
  [19] http://asterisk.apod.com/discuss_apod.php?date=190221
  [20] ap190222.html
  [21] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [22] http://www.phy.mtu.edu/
  [23] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [24] http://www.astro.umd.edu/
  [25] lib/about_apod.html#srapply
  [26] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [27] https://astrophysics.gsfc.nasa.gov/
  [28] https://www.nasa.gov/
  [29] https://www.nasa.gov/centers/goddard/
  [30] http://www.mtu.edu/
