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.

                              2019 November 27

                 Hoag's Object: A Nearly Perfect Ring Galaxy
         Image Credit: NASA, ESA, Hubble; Processing: Benoit Blanco

   Explanation: Is this one galaxy or two? This question came to light in
   1950 when astronomer Arthur Hoag chanced upon this unusual
   extragalactic object. On the outside is a ring dominated by bright blue
   stars, while near the center lies a ball of much redder stars that are
   likely much older. Between the two is a gap that appears almost
   completely dark. How Hoag's Object formed, including its nearly
   perfectly round ring of stars and gas, remains unknown. Genesis
   hypotheses include a galaxy collision billions of years ago and the
   gravitational effect of a central bar that has since vanished. The
   featured photo was taken by the Hubble Space Telescope and recently
   reprocessed using an artificially intelligent de-noising algorithm.
   Observations in radio waves indicate that Hoag's Object has not
   accreted a smaller galaxy in the past billion years. Hoag's Object
   spans about 100,000 light years and lies about 600 million light years
   away toward the constellation of the Snake (Serpens). Many galaxies far
   in the distance are visible toward the right, while coincidentally,
   visible in the gap at about seven o'clock, is another but more distant
   ring galaxy.

                       Tomorrow's picture: open space
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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.

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