Solar halos and silhouetted figure. Solar halos are formed when light from the Sun is refracted by tiny hexagonal ice crystals high in the atmosphere. The most common halo is 22 arc-degrees in diameter. Here, several halos of different diameters are seen at the same time. The exact cause of this unusual halo formation is unknown, but similar observations have been made. This example was photographed in Eura, Finland on 5 June 2008.