The Science Behind A Sundog

GREENSBORO, NC -- You have probably seen a sundog and didn't realize exactly what you were looking at. Sundogs, which are also known as mock suns, but are technically referred to as parhelia, are brightly colored spots off to the side of the sun.

In order for a sundog to form the sun typically needs to be low on the horizon when you have high, cirrus clouds in the sky. The cirrus clouds are important as they are comprised of tiny ice crystals. In order for the sundogs to form the ice crystals need to be in the shape of a hexagonal-plate, larger than 30 micrometers and laying in the horizontal plane.

As the light from the sun passes through the ice crystals the light is refracted (or bent) at 22° before reaching your eyes. The refracting light is what causes your eye to see the additional spots of light on either side of the sun...AKA the sundog.


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