A
22° halo is a
halo, one type of
optical phenomenon, forming a circle with a radius of approximately 22° around the
Sun, or occasionally the
Moon (also called a moon ring or winter halo). It forms as the sun- or moonlight is
refracted in millions of randomly oriented
hexagonal ice crystals suspended in the atmosphere. The halo is large; the radius is roughly the size of an outstretched hand at arm's length. A 22° halo may be visible on as many as 100 days per year—much more frequently than rainbows.