                        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.

                               2023 January 20

                          Galaxy Wars: M81 and M82
               Image Credit & Copyright: Andreas Aufschnaiter

   Explanation: The two dominant galaxies near center are far far away, 12
   million light-years distant toward the northern constellation of the
   Great Bear. On the right, with grand spiral arms and bright yellow core
   is spiral galaxy M81. Also known as Bode's galaxy, M81 spans some
   100,000 light-years. On the left is cigar-shaped irregular galaxy M82.
   The pair have been locked in gravitational combat for a billion years.
   Gravity from each galaxy has profoundly affected the other during a
   series of cosmic close encounters. Their last go-round lasted about 100
   million years and likely raised density waves rippling around M81,
   resulting in the richness of M81's spiral arms. M82 was left with
   violent star forming regions and colliding gas clouds so energetic that
   the galaxy glows in X-rays. In the next few billion years, their
   continuing gravitational encounters will result in a merger, and a
   single galaxy will remain. This extragalactic scenario also includes
   other members of the interacting M81 galaxy group with NGC 3077 below
   and right of the large spiral, and NGC 2976 at upper right in the
   frame. Captured under dark night skies in the Austrian Alps, the
   foreground of the wide-field image is filled with integrated flux
   nebulae. Those faint, dusty interstellar clouds reflect starlight above
   the plane of our own Milky Way galaxy.

                      Tomorrow's picture: light-weekend
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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.

