                        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 January 19
   A colorful starfield surrounds a giant nearly-spherical nebula that has
    texture and stripes like watermelon. The lower right of the nebula is
       open making it appear like a medulla oblongata -- the stem that
      connects to a brain. Please see the explanation for more detailed
                                information.

                          CTB 1: The Medulla Nebula
                       Image Credit: Pierre Konzelmann

   Explanation: What powers this unusual nebula? CTB 1 is the expanding
   gas shell that was left when a massive star toward the constellation of
   Cassiopeia exploded about 10,000 years ago. The star likely detonated
   when it ran out of elements, near its core, that could create
   stabilizing pressure with nuclear fusion. The resulting supernova
   remnant, nicknamed the Medulla Nebula for its brain-like shape, still
   glows in visible light because of the heat generated by its collision
   with confining interstellar gas. Why the nebula also glows in X-ray
   light, though, remains a topic of research. One hypothesis holds that
   an energetic pulsar was created and powers the nebula with a fast
   outwardly moving wind. Following this lead, a pulsar was found in radio
   waves that appears to have been expelled by the supernova explosion at
   over 1000 kilometers per second. Although the Medulla Nebula appears as
   large as a full moon, it is so faint that it took 84-hours of exposure
   with a small telescope in Texas, USA, to create the featured image.

                      Tomorrow's picture: volcano world
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