                        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 17
         A deep image of M31, the Andromeda galaxy, shows unexpected
    oxygen-glowing arcs to its left. Please see the explanation for more
                            detailed information.

                Unexpected Clouds Toward the Andromeda Galaxy
          Image Credit & Copyright: Yann Sainty & Marcel Drechsler

   Explanation: Why are there oxygen-emitting arcs near the direction of
   the Andromeda galaxy? No one is sure. The gas arcs, shown in blue, were
   discovered and first confirmed by amateur astronomers just last year.
   The two main origin hypotheses for the arcs are that they really are
   close to Andromeda (M31), or that they are just coincidentally placed
   gas filaments in our Milky Way galaxy. Adding to the mystery is that
   arcs were not seen in previous deep images of M31 taken primarily in
   light emitted by hydrogen, and that other, more distant galaxies have
   not been generally noted as showing similar oxygen-emitting structures.
   Dedicated amateurs using commercial telescopes made this discovery
   because, in part, professional telescopes usually investigate angularly
   small patches of the night sky, whereas these arcs span several times
   the angular size of the full moon. Future observations -- both in light
   emitted by oxygen and by other elements -- are sure to follow.

                      Tomorrow's picture: JWST lensing
     __________________________________________________________________

       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
                NASA Web Privacy Policy and Important Notices
                      A service of: ASD at NASA / GSFC,
                           NASA Science Activation
                             & Michigan Tech. U.

