                        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.

                              2022 December 21

                    Sun Halo at Sixty-three Degrees North
                   Image Credit & Copyright: Goran Strand

   Explanation: Happy Solstice! Today is the December solstice, marking an
   astronomical beginning of summer in the southern hemisphere and winter
   in the north. On its yearly trek through planet Earth's skies, at this
   solstice the Sun reaches its southern most declination, 23.5 degrees
   south, at 21:48 UTC. About 4 days ago the Sun was near this seasonal
   southern limit and so only just above the horizon at local noon over
   Ostersund in central Sweden. This view looking over the far northern
   lakeside city finds the midday Sun with a beautiful solar ice halo.
   Naturally occurring atmospheric ice crystals can produce the
   tantalizing halo displays, refracting and reflecting the sunlight
   through their hexagonal geometry. Still, with the Sun low and near the
   horizon in the clear sky, likely sources of the ice crystals producing
   this intense halo are snow cannons. Operating at a local ski area, the
   snowmaking machines create a visible plume at the top of the nearby
   island Froson toward the right side of the panorama.

                     Tomorrow's picture: northern spiral
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