Subj : Daily APOD Report
To   : All
From : Alan Ianson
Date : Wed Feb 17 2021 00:17:19

                        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.

                              2021 February 17

                      Sun Pillar with Upper Tangent Arc
                    Image Credit & Copyright: Mike Cohea

   Explanation: This was not a typical sun pillar. Just after sunrise two
   weeks ago in Providence, Rhode Island, USA, a photographer, looking out
   his window, was suddenly awestruck. The astonishment was caused by a
   sun pillar that fanned out at the top. Sun pillars, singular columns of
   light going up from the Sun, are themselves rare to see, and are known
   to be caused by sunlight reflecting from wobbling, hexagon-shaped
   ice-disks falling through Earth's atmosphere. Separately, upper tangent
   arcs are known to be caused by sunlight refracting through falling
   hexagon-shaped ice-tubes. Finding a sun pillar connected to an upper
   tangent arc is extraordinary, and, initially, took some analysis to
   figure out what was going on. A leading theory is that this sun pillar
   was also created, in a complex and unusual way, by falling ice tubes.
   Few might believe that such a rare phenomenon was seen again if it
   wasn't for the quick thinking of the photographer -- and the camera on
   his nearby smartphone.

                 News from Mars: NASA Perseverance Coverage
                       Tomorrow's picture: open space
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