Sun dog

By Matt Young

Photograph by Nicky Turner.

Sun dog
Sun dog. The photographer writes, "The picture was taken on the terrace here at our house, Villa Santa Lucia, about 15 km south of Livorno on the Etruscan coast of Italy," October, 2021.

The sun dog is formed from refraction by hexagonal ice crystals held with their axes vertical by hydrodynamic forces (drop a small scrap of paper, and you will see how it remains mostly horizontal). If the air is not still and the crystals are not oriented, you may see the full 22° halo.