A
halo (from
Greek ,
halos; also known as a
nimbus,
icebow or
gloriole) is an
optical phenomenon produced by light interacting with
ice crystals suspended in the atmosphere, resulting in a wide variety of colored or white rings, arcs and spots in the sky. Many halos are near the Sun or Moon, but others occur elsewhere or even in the opposite part of the sky. Among the most well known halo types are the
circular halo (properly called the
22° halo),
light pillars and
sun dogs, but there are many more; some of them fairly common, others (extremely) rare.