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 December 31

                         M33: The Triangulum Galaxy
                     Image Credit & Copyright: Rui Liao

   Explanation: The small, northern constellation Triangulum harbors this
   magnificent face-on spiral galaxy, M33. Its popular names include the
   Pinwheel Galaxy or just the Triangulum Galaxy. M33 is over 50,000
   light-years in diameter, third largest in the Local Group of galaxies
   after the Andromeda Galaxy (M31), and our own Milky Way. About 3
   million light-years from the Milky Way, M33 is itself thought to be a
   satellite of the Andromeda Galaxy and astronomers in these two galaxies
   would likely have spectacular views of each other's grand spiral star
   systems. As for the view from planet Earth, this sharp image shows off
   M33's blue star clusters and pinkish star forming regions along the
   galaxy's loosely wound spiral arms. In fact, the cavernous NGC 604 is
   the brightest star forming region, seen here at about the 7 o'clock
   position from the galaxy center. Like M31, M33's population of
   well-measured variable stars have helped make this nearby spiral a
   cosmic yardstick for establishing the distance scale of the Universe.

                      Tomorrow's picture: a new decade
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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