Astronomy Image of the Day
A Sun Pillar
30 December 2002
Dave Liquorice

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NASA Astronomy Image of the Day for 30 December 2002
Have you ever seen a sun pillar? When the air is cold and the Sun is rising or setting, falling ice crystals can reflect sunlight and create an unusual column of light. Ice sometimes forms flat, stop-sign shaped crystals as it falls from high-level clouds. Air resistance causes these crystals to lie nearly flat much of the time as they flutter to the ground. Sunlight reflects off crystals that are properly aligned, creating the sun-pillar effect. In the above picture, a sun-pillar reflects light from a setting Sun.
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Image and explanation courtesy of NASA Astronomy Picture of the Day