Sun halo

The rainbow that encircles the sun here, a sun halo, is above Lake Antermoia in the Dolomite Mountains of northern Italy. Sun halos form when sunlight shines through ice crystals suspended in the upper atmosphere. When the light of the sun hits the crystals they serve as a prism, separating the light into individual colours of the spectrum, the same way rainbows occur after a rain shower. The halo can be white, rainbow colours or even just a partial ring, and can form around the moon as well. A full circle halo like in today’s image is called a 22° halo.
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