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.

                               2020 October 7

                     Ou4: A Giant Squid in a Flying Bat
                   Image Credit & Copyright: Yannick Akar

   Explanation: A very faint but very large squid-like nebula is visible
   in planet Earth's sky -- but inside a still larger bat. The Giant Squid
   Nebula cataloged as Ou4, and Sh2-129 also known as the Flying Bat
   Nebula, are both caught in this cosmic scene toward the royal royal
   constellation Cepheus. Composed with 55 hours of narrowband image data,
   the telescopic field of view is 3 degrees or 6 Full Moons across.
   Discovered in 2011 by French astro-imager Nicolas Outters, the Squid
   Nebula's alluring bipolar shape is distinguished here by the telltale
   blue-green emission from doubly ionized oxygen atoms. Though apparently
   completely surrounded by the reddish hydrogen emission region Sh2-129,
   the true distance and nature of the Squid Nebula have been difficult to
   determine. Still, a more recent investigation suggests Ou4 really does
   lie within Sh2-129 some 2,300 light-years away. Consistent with that
   scenario, Ou4 would represent a spectacular outflow driven by HR8119, a
   triple system of hot, massive stars seen near the center of the nebula.
   The truly giant Squid Nebula would physically be nearly 50 light-years
   across.

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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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