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 September 7

                               In Wolf's Cave
     Image Credit & Copyright: Charlie Bracken, Mladen Dugec, Max Whitby

   Explanation: The mysterious blue reflection nebula found in catalogs as
   VdB 152 or Ced 201 really is very faint. It lies at the tip of the long
   dark nebula Barnard 175 in a dusty complex that has also been called
   Wolf's Cave. At the center of this deep and widefield telescopic view,
   the cosmic apparitions are nearly 1,400 light-years away along the
   northern Milky Way in the royal constellation Cepheus. Near the edge of
   a large molecular cloud, pockets of interstellar dust in the region
   block light from background stars or scatter light from the embedded
   bright star giving the the nebula its characteristic blue color.
   Ultraviolet light from the star is also thought to cause a dim reddish
   luminescence in the nebular dust. Though stars do form in molecular
   clouds, this star seems to have only accidentally wandered into the
   area, as its measured velocity through space is very different from the
   cloud's velocity. Another dense, obscuring dark nebula, LDN 1221, is
   easy to spot at the upper right in the frame, while the more colorful
   planetary nebula Dengel-Hartl 5 is just below center. Faint reddish
   emission from an ancient supernova remnant can also be traced (lower
   right to upper left) against the dust-rich complex in Cepheus.

                       Tomorrow's picture: perijove 11
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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