A light pillar is an atmospheric optical phenomenon in the form of a vertical column of light which appears to extend above and/or below a light source. The effect, sometimes also called the crystal beam phenomenon, is created by the reflection of light from numerous tiny ice crystals suspended in the atmosphere or clouds. The light can come from the Sun (usually when it is near or even below the horizon) in which case the phenomenon is called a sun pillar or solar pillar. It can also come from the Moon or from terrestrial sources such as streetlights.
Author: Samuli Ikäheimo
SPONLI is a project about astrophotography, for amateur astronomers.