                        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 18
     A nearly perfect circular ring of blue stars is seen against a dark
   field of small background galaxies. In the center of the ring is a ball
        of yellow stars. Please see the explanation for more detailed
                                information.

                 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 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: sideways sun
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn; Specific rights apply.
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                             & Michigan Tech. U.

