                        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.

                                2023 July 17
   A star surrounded by orange shells and arcs sit in the center of a dark
    starfield. Galaxies from the distant universe can be seen around the
      edges. Please see the explanation for more detailed information.

                    Shells and Arcs around Star CW Leonis
     Image Credit: ESA, NASA, Hubble, T. Ueta (U. Denver), H. Kim (KASI)

   Explanation: What's happening around this star? No one is sure. CW
   Leonis is the closest carbon star, a star that appears orange because
   of atmospheric carbon dispersed from interior nuclear fusion. But CW
   Leonis also appears engulfed in a gaseous carbon-rich nebula. What
   causes the nebula's complexity is unknown, but its geometry of shells
   and arcs are surely intriguing. The featured image by the Hubble Space
   Telescope details this complexity. The low surface gravity of carbon
   stars enhances their ability to expel carbon and carbon compounds into
   space. Some of this carbon ends up forming dark dust that is commonly
   seen in the nebulas of young star-forming regions and the disks of
   galaxies. Humans and all Earth-based life are carbon-based, and at
   least some of our carbon was likely once circulating in the atmospheres
   of near-death stars like carbon stars.

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