I know what a sun dog is, but how did it get its name?

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Dear Tom,
I know what a sun dog is, but how did it get its name?
— Becky Hull, Valparaiso, Ind.
Dear Becky,
Sun dogs are the result of a circular halo around the sun. They are produced by refraction of sunlight as it passes through a thin veil of ice crystal clouds. The term “sun dog” (or mock sun) originates from Greek mythology. It was believed the god Zeus walked his dogs across the sky and that the bright “false suns” in the sky on either side of the sun’s disk were the dogs.
Sun dogs are atmospheric optical phenomena consisting of bright spots to the left and right of the sun. They appear at the same altitude above the horizon as the sun and often flank the sun within a 22-degree halo. Sun dogs are red-colored on the side nearest the sun, shifting through orange to blue at the outside.