Article
Article
Sun dog
Article By:
Greenler, Robert Department of Physics, University of Wisconsin, Madison, Wisconsin.
Last reviewed:December 2019
DOI:https://doi.org/10.1036/1097-8542.667350
A bright spot of light that sometimes appears on either side of the Sun, the same distance above the horizon as the Sun and separated from it by an angle of about 22° (see illustration). For higher Sun elevations, the angle increases slightly. These spots are known by many common names: sun dogs, mock suns, false suns, or the 22° parhelia. They usually show a red edge on the side closest to the Sun. On some occasions the entire spectrum of colors can be spread out in the sun-dog spot but, commonly, the red edge is followed by an orange or yellow band that merges into a diffuse white region. The effects result from the refraction by sunlight through small, flat, hexagonal-shaped ice crystals falling through the air such that their flat faces are oriented nearly horizontally. See also: Halo; Meteorological optics
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