                        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.

                                 2022 May 8

                   Spiral Galaxy NGC 1512: The Inner Rings
               Image Credit: NASA, ESA, Hubble Space Telescope

   Explanation: Most galaxies don't have any rings -- why does this galaxy
   have two? To begin, the bright band near NGC 1512's center is a nuclear
   ring, a ring that surrounds the galaxy center and glows brightly with
   recently formed stars. Most stars and accompanying gas and dust,
   however, orbit the galactic center in a ring much further out -- here
   seen near the image edge. This ring is called, counter-intuitively, the
   inner ring. If you look closely, you will see this the inner ring
   connects ends of a diffuse central bar that runs horizontally across
   the galaxy. These ring structures are thought to be caused by NGC
   1512's own asymmetries in a drawn-out process called secular evolution.
   The gravity of these galaxy asymmetries, including the bar of stars,
   cause gas and dust to fall from the inner ring to the nuclear ring,
   enhancing this ring's rate of star formation. Some spiral galaxies also
   have a third ring -- an outer ring that circles the galaxy even further
   out.

                     Tomorrow's picture: martian eclipse
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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.

