Halo

Halo, in meteorology, luminous ring sometimes observed around the sun or the moon, caused by refraction and reflection of light by ice crystals in the atmosphere of the earth. Such crystals are frequently contained in high clouds. The French philosopher and scientist René Descartes was the first to offer the correct explanation of the formation of a halo. In art, the circle of light often depicted around the head of a saint is also called a halo.

See also: Meteorology.