Sun dog

A sun dog is a natural but uncommon optical phenomenon observable in the atmosphere, typically when a low sun shines through loose cirrus clouds, e.g. in a milky-white winter afternoon sky. The sunlight is reflected and refracted by ice crystals and splits up into colors because of dispersion, similarly to the rainbow. The orientation of the ice crystals involved in this process is important. The crystals are hexagonal cylinders, and they have to be oriented vertically.

In contrast to a rainbow, sun dogs appear as near-horizontal colored spots or bars on both sides of the sun, around an angle of 22 degrees.

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The Sun Dog is a short story by Stephen King.