                        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.

                                 2026 May 20
    A dark and whispy cloud blocks the background light from surrounding
      gas and stars. It resembles the head, snout, and jaws of a wolf.

                            The Dark Wolf Nebula
                  Image Credit & Copyright: William Vrbasso
         Text: Keighley Rockcliffe (NASA GSFC, UMBC CSST, CRESST II)

   Explanation: A dark wolf lies in gum. No, this isn’t a riddle! Today's
   image features the Dark Wolf Nebula (Sandqvist–Lindroos 17), a spooky
   dust cloud embedded within the Gum 55 (RCW 113) Nebula in the Scorpius
   constellation. While dust is a pest to us, it serves a vital role in
   creating the necessary conditions for stars to be born. The Dark Wolf
   absorbs the intense ultraviolet and visible light emitted by young
   stars in Gum 55 and re-emits it at longer, mainly infrared,
   wavelengths. This prevents the higher energy light from heating up the
   gas in the region. When a region of gas is cool enough, gravity takes
   over and causes the gas to collapse into a star. Not only does dust act
   as an interstellar thermostat, but it is also the meet-cute for single
   hydrogen atoms forming molecular hydrogen, the building block for
   stars. The seemingly sinister Dark Wolf is actually a harbinger of
   cosmic life.

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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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