                        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 January 9

                     Ice Halos by Moonlight and Sunlight
                 Image Credit & Copyright: Antonella Cicala

   Explanation: Both Moon and Sun create beautiful ice halos in planet
   Earth's sky. In fact, the two brightest celestial beacons are each
   surrounded by a complex of ice halos in these photos of the sky above
   Chamonix-Mont-Blanc in France. The panels were recorded one night
   (left) and the following day at the end of December 2025. Similar ice
   halos appear in moonlight and sunlight because they are all formed
   through the geometry of flat, hexagonal ice crystals. The ice crystals
   reflect and refract light as they flutter in the cold atmosphere above
   the mountain resort. In the pictures both Moon and Sun are surrounded
   by a more commonly seen 22 degree circular halo. Bright and sometimes
   colorful patches at the intersections of the 22 degree circular halos
   with the indicated parselenic and parhelic arcs are also known as Moon
   dogs and Sun dogs.

                    Tomorrow's picture: opposite the Sun
     __________________________________________________________________

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

