                        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.

                              2024 February 23

                   The Pencil Nebula Supernova Shock Wave
                   Image Credit & Copyright: Helge Buesing

   Explanation: This supernova shock wave plows through interstellar space
   at over 500,000 kilometers per hour. Centered and moving upward in the
   sharply detailed color composite its thin, bright, braided filaments
   are actually long ripples in a cosmic sheet of glowing gas seen almost
   edge-on. Discovered in the 1840s by Sir John Herschel, the
   narrow-looking nebula is sometimes known as Herschel's Ray. Cataloged
   as NGC 2736, its pointed appearance suggests its modern popular name,
   the Pencil Nebula. The Pencil Nebula is about 800 light-years away.
   Nearly 5 light-years long it represents only a small part of the Vela
   supernova remnant though. The enormous Vela remnant itself is around
   100 light-years in diameter, the expanding debris cloud of a star that
   was seen to explode about 11,000 years ago. Initially, the section of
   the shock wave seen as the Pencil nebula was moving at millions of
   kilometers per hour but has slowed considerably, sweeping up
   surrounding interstellar material.

                      Tomorrow's picture: light-weekend
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