                        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.

                              2026 September 18

                      Messier 33: The Triangulum Galaxy
               Image Credit & Copyright: George Chatzifrantzis

   Explanation: The small, northern constellation Triangulum harbors this
   magnificent face-on spiral galaxy, Messier 33. 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 the Milky Way, this sharp telescopic
   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 5 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.

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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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