Subj : Daily APOD Report
To   : All
From : Alan Ianson
Date : Wed Dec 20 2023 00:09:12

                        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 December 20
   A building is seen from a distance on white snow and with mountains in
   the background. An ice-crystal filled sky is seen above. Superposed on
    the night sky are numerous curving whisps -- halos of ice reflecting
     background moonlight. Please see the explanation for more detailed
                                information.

                           Ice Halos over Bavaria
                  Image Credit & Copyright: Bastian Werner

   Explanation: What's causing those unusual sky arcs? Ice crystals. While
   crossing a field of fresh snow near F+'ssen, Bavaria, Germany, earlier
   this month, the photographer noticed that he had entered an ice fog.
   For suspended water to freeze into an ice fog requires quite cold
   temperatures, and indeed the air temperature on this day was measured
   at well below zero. The ice fog reflected light from the Sun setting
   behind St. Coleman Church. The result was one of the greatest
   spectacles the photographer has ever seen. First, the spots in the
   featured picture are not background stars but suspended ice and snow.
   Next, two prominent ice halos are visible: the 22-degree halo and the
   46-degree halo. Multiple arcs are also visible, including, from top to
   bottom, antisolar (subsun), circumzenithal, Parry, tangent, and
   parhelic (horizontal). Finally, the balloon shaped curve connecting the
   top arc to the Sun is the rarest of all: it is the heliac arc, created
   by reflection from the sides of hexagonally shaped ice crystals
   suspended in a horizontal orientation.

                       Tomorrow's picture: open space
     __________________________________________________________________

       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.

--- BBBS/Li6 v4.10 Toy-6
 * Origin: The Rusty MailBox - Penticton, BC Canada (1:153/757)

.