Halo (optical phenomenon)
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A halo is an optical phenomenon produced by light interacting with ice crystals suspended in the atmosphere. Halos can have many forms, ranging from colored or white rings to arcs and spots in the sky. Many of these appear near the Sun or Moon, but others occur elsewhere or even in the opposite part of the sky. Among the best known halo types are the circular halo, light pillars, and sun dogs, but many others occur; some are fairly common while others are extremely rare.
A 22° halo around the Sun, observed over Bretton Woods, New Hampshire, USA on February 13, 2021
A 22° halo and circumscribed halo around the Moon, observed near Kitt Peak National Observatory
From top to bottom: A circumzenithal arc, supralateral arc, Parry arc, upper tangent arc, and 22° halo
A halo display observed over the South Pole
Optical phenomenon
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Optical phenomena are any observable events that result from the interaction of light and matter.
A 22° halo around the Moon in Atherton, California
A solar halo as seen from 41° south latitude
A circumzenithal arc over Grand Forks, North Dakota
The Belt of Venus over Paranal Observatory atop Cerro Paranal in the Atacama Desert, northern Chile