Sun Pillar Redux
December 14, 2002
Provided and copyright by: James Kaler, Astronomy Department, University of Illinois
Summary authors & editors: James Kaler
A spectacular dawn sun pillar spears upward from a bank of clouds that lies above the eastern horizon. Sun pillars are caused by the reflection of sunlight from floating ice crystals. They are collectively one of the many phenomena that involve the interplay between sunlight (or moonlight) and the Earth's atmosphere, and illustrate both optical principles and the natures of clouds and of the Earth's covering atmospheric blanket. Here, the Sun is entirely hidden below the cloud edge. The pillar starts brilliantly in seemingly clear air, and then extends higher as a result of reflection from crystals in the upper cloud bank. Moments later, the Sun rose from behind the clouds, and the pillar faded away. Such "clear air" sun pillars are rare.
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