Astronomy Picture of the Day

Explanation: How can an aurora appear so near the ground? Pictured above are not aurora but nearby light pillars, a local phenomenon that can appear as a distant one. In most places on Earth, a lucky viewer can see a Sun-pillar, a column of light appearing to extend up from the Sun caused by flat fluttering ice-crystals reflecting sunlight from the upper atmosphere. Usually these ice crystals evaporate before reaching the ground. During freezing temperatures, however, flat fluttering ice crystals may form near the ground in a form of light snow, sometimes known as a crystal fog. These ice crystals may then reflect ground lights in columns not unlike a Sun-pillar. In the above picture, the colourful lights causing the light pillars surround a ice-skating rink in Fairbanks, Alaska.