What Is A Sundog?

A photographic example of the phenomenon of a sundog.
A photographic example of the phenomenon of a sundog.

Sundogs are patches of light that are colorful and appear to be bright on either or both sides of the sun. They are approximately 22 degrees on either or both sides of the sun. Sundogs cover the same distance as the sun above the horizon. Sometimes they are seen as part of a ring surrounding the sun. Scientifically, the name used to refer to sundogs is “parhelion.” It is a Greek word which means “beside the sun.” Phantom or mock suns are other common names used to refer to sundogs.

Formation And Characteristics Of Sun Dogs

The formation of sundogs is by refraction and the scattering of light from hexagonal ice crystals suspended in cold cirrus clouds. Sometimes when the weather is too cold, ice crystals float in the air forming the sun dogs. Despite the fact that sundogs mostly form during cold weather, the presence of cirrus clouds leads to the formation of sundogs at any time. The air has ice crystals which take the place of a prism thus refracting sun rays making the sundogs appear. The sun rays bend in such a way that the side that is closest to the sun appears red while the side that is farthest appears blue. There is a whitetail that stretches horizontal at 22 degrees away from the sun. These colors are neither saturated nor pure since they overlap each other. The red and blue colors end up merging; showcasing a white parhelic circle.

The sundogs may also form in the night when there is a very bright full moon. Paraselenae are sundogs that occur at night. Another common name for it is moon dogs. However, moon dogs rarely appear. The moon dogs are rare because they can only appear when the moon is full or is very close to being full. Sundogs are conspicuously visible when the horizon is very near to the sun. The two halos of the sundogs tend to co-occur with each other forming a circumzenithal arc that is very colorful. When the sun rises higher, the rays passing through the ice crystals prisms get more skewed. Subsequently, there is an increase in the angle of deviation, and the sundogs end up moving further than the standard 22◦. There are beliefs that besides Earth, sundogs also form in other planets such as Neptune, Uranus, Jupiter, and Saturn.

Fascinating Facts About Sun Dogs

Most of the times, the sundogs appear either at sunrise or sunset. They appear as bright patches of white light. Light is the primary factor which influences the formation of a sundog. The shape of ice crystals determines the form of a sundog and acts as prisms to refract the light rays. The distances of the sundog from the sun affects the color of the sun dogs. The angles at which the sun rays are refracted also influences the color of the sundogs. Other planets like Uranus and Jupiter affect the position of the sundogs.


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