                        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 w
                    ritten by a professional astronomer.

                              2021 November 15

                       Light Pillar over Volcanic Etna
                   Image Credit & Copyright: Giancarlo Tinč

   Explanation: What happening above that volcano? Something very unusual
   -- a volcanic light pillar. More typically, light pillars are caused by
   sunlight and so appear as a bright column that extends upward above a
   rising or setting Sun. Alternatively, other light pillars -- some quite
   colorful -- have been recorded above street and house lights. This
   light pillar, though, was illuminated by the red light emitted by the
   glowing magma of an erupting volcano. The volcano is Italy's Mount
   Etna, and the featured image was captured with a single shot a few
   hours after sunset in mid-June. Freezing temperatures above the
   volcano's ash cloud created ice-crystals either in cirrus clouds high
   above the volcano -- or in condensed water vapor expelled by Mount
   Etna. These ice crystals -- mostly flat toward the ground but
   fluttering -- then reflected away light from the volcano's caldera.

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