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.

                                2021 March 12

                                 Messier 81
                   Image Credit & Copyright: Wissam Ayoub

   Explanation: One of the brightest galaxies in planet Earth's sky is
   similar in size to our Milky Way Galaxy: big, beautiful Messier 81.
   Also known as NGC 3031 or Bode's galaxy for its 18th century
   discoverer, this grand spiral can be found toward the northern
   constellation of Ursa Major, the Great Bear. The sharp, detailed
   telescopic view reveals M81's bright yellow nucleus, blue spiral arms,
   pinkish starforming regions, and sweeping cosmic dust lanes. Some dust
   lanes actually run through the galactic disk (left of center), contrary
   to other prominent spiral features though. The errant dust lanes may be
   the lingering result of a close encounter between M81 and the nearby
   galaxy M82 lurking outside of this frame. M81's faint, dwarf irregular
   satellite galaxy, Holmberg IX, can be seen just below the large spiral.
   Scrutiny of variable stars in M81 has yielded a well-determined
   distance for an external galaxy -- 11.8 million light-years.

                    Tomorrow's picture: one hand clapping
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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