Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                               2019 August 29

                              M27: Not a Comet
                    Image Credit & Copyright: Bob Franke

   Explanation: While hunting for comets in the skies above 18th century
   France, astronomer Charles Messier diligently kept a list of the things
   he encountered that were definitely not comets. This is number 27 on
   his now famous not-a-comet list. In fact, 21st century astronomers
   would identify it as a planetary nebula, but it's not a planet either,
   even though it may appear round and planet-like in a small telescope.
   Messier 27 (M27) is an excellent example of a gaseous emission nebula
   created as a sun-like star runs out of nuclear fuel in its core. The
   nebula forms as the star's outer layers are expelled into space, with a
   visible glow generated by atoms excited by the dying star's intense but
   invisible ultraviolet light. Known by the popular name of the Dumbbell
   Nebula, the beautifully symmetric interstellar gas cloud is over 2.5
   light-years across and about 1,200 light-years away in the
   constellation Vulpecula. This impressive color composite highlights
   details within the well-studied central region and fainter, seldom
   imaged features in the nebula's outer halo. It incorporates broad and
   narrowband images recorded using filters sensitive to emission from
   hydrogen and oxygen atoms.

                     Tomorrow's picture: pixels in space
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

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