                        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.

                               2022 November 9
    The featured image shows a complex nebula that is more dense and more
    blue on one side than the other. Please see the explanation for more
                            detailed information.

            The Asymmetric Nebula Surrounding Wolf-Rayet Star 18
                   Image Credit & Copyright: Alex Woronow

   Explanation: Why does the nebula around the star WR-18 shine brighter
   on one side? Also known as NGC 3199, this active star and its
   surrounding nebula lie about 12,000 light-years away toward the
   nautical southern constellation of Carina. The featured deep image has
   been highly processed to bring out filamentary details of the glowing
   gas in the bubble-shaped nebula. The nebula is about 75 light-years
   across. Near the nebula's center is a Wolf-Rayet star, WR-18, which is
   a massive, hot, short-lived star that generates an intense and complex
   stellar wind. In fact, Wolf-Rayet stars are known to create nebulas
   with interesting shapes as their powerful winds sweep up surrounding
   interstellar material. In this case, the bright right edge was
   initially thought to indicate that a bow shock was being produced as
   the star plowed through a uniform medium, like a boat through water.
   Recent measurements and analyses, however, have shown the star is not
   moving quickly toward the bright edge. A more likely explanation has
   emerged that the material surrounding the star is not uniform, but
   clumped and denser near the bright edge.

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