Fire rainbow

Today a friend sent this photo of a fire rainbow. A fire rainbow is actually, in meterological circles, known as a circumhorizontal arc. (How's that for specific terminology?)

The arc isn't a rainbow in the traditional sense—it is caused by light passing through wispy, high-altitude cirrus clouds. The sight occurs only when the sun is very high in the sky (more than 58° above the horizon). What's more, the hexagonal ice crystals that make up cirrus clouds must be shaped like thick plates with their faces parallel to the ground. This is a very rare phenomenom!