A Halo is a luminous spot, ring or an arc that surrounds the sun or the moon. The halo is produced by the reflection or refraction of sunlight or moonlight by the ice crystals in the atmosphere. A halo is not a weather illusion but an optical phenomenon. In fact the formation of halos depends on these ice crystals that are found in the upper layers of the cirrus clouds within the atmosphere. The varied forms and quality of the ice crystals, the inclination or course of the ice crystals, the reflective property of the ice crystals, the angle of the source of light and the law of aeromechanics greatly determine the size and color of the halos. Different forms of halo are visible depending on these factors. Interestingly about 60 forms of halo have been identified till date.

A halo can be either colorful or white. Actually most halos are visible as while annular bands. However in some cases the scattering of sunlight or moonlight on the ice crystals in the upper strata of cirrus clouds cause the halo to have some tints of color.

The sun looks stunning with the luminous halos that are spread in the huge blue expanse.

Halos occur more frequently than rainbows and can be sometimes viewed twice a week.

The most common of all forms of halos are the 22degree halo and the sun dog.

The 22 degree halo is formed by reflection of sunlight by hexagon-shaped ice crystals. This slightly reddish halo surrounds the sun. The sun dog is visible above the setting sun.