What is a 22° halo?

By Patrick Looß - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=93889081

A 22° halo is an optical illusion that occurs around the sun or Moon.

The halo is approximately 22° around either sun or Moon and only occurs under very specific conditions.

These halos form when sunlight or moonlight is refracted by hexagonal ice crystals that are suspended in the atmosphere.

A halo will form when cirrus or cirrostratus clouds are present.