                        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 April 2
       A colorful oval nebula is shown star field is shown in a sparse
       starfield. Fainter red nebulosity surrounds the bright oval. A
     relatively bright star is seen in the oval's center. Please see the
                 explanation for more detailed information.

                      M57: The Ring Nebula from Hubble
      Image Credit: NASA, ESA, Hubble Legacy Archive; Processing: Judy
                                   Schmidt

   Explanation: It was noticed hundreds of years ago by stargazers who
   could not understand its unusual shape. It looked like a ring on the
   sky. Except for the rings of Saturn, the Ring Nebula (M57) may be the
   most famous celestial circle. We now know what it is, and that its
   iconic shape is due to our lucky perspective. The recent mapping of the
   expanding nebula's 3-D structure, based in part on this clear Hubble
   image,indicates that the nebula is a relatively dense, donut-like ring
   wrapped around the middle of an (American) football-shaped cloud of
   glowing gas. Our view from planet Earth looks down the long axis of the
   football, face-on to the ring. Of course, in this well-studied example
   of a planetary nebula, the glowing material does not come from planets.
   Instead, the gaseous shroud represents outer layers expelled from the
   dying, once sun-like star, now a tiny pinprick of light seen at the
   nebula's center. Intense ultraviolet light from the hot central star
   ionizes atoms in the gas. The Ring Nebula is about one light-year
   across and 2,500 light-years away.

         Tomorrow's picture: the beasts at the center of our galaxy
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

