Solar halo. This atmospheric optical phenomenon is seen here around the Sun, and is caused by prismatic refraction of sunlight through randomly-oriented hexagonal ice crystals in the atmosphere. This is the common 22-degree halo, so called as its diameter extends across 22 arc-degrees of the sky. The beginnings of a sundog (twinned patches of brighter areas either side of the Sun) are also visible. Photographed in Brittany, France.