© Nick Rober
What is it?
The ring is referred to as a '22-degree halo' and appears as a light circle around the sun or moon. Why the name? The circle has a radius of ~22°.
What causes it?
Thin, high clouds called 'cirrus clouds' are made up of millions of tiny ice crystals thousands of feet in the atmosphere. Light reflecting off the moon or shining from the sun is refracted, which then creates a visible ring surrounding the sun/moon.
In-Depth: Refraction of light is defined as the bending or splitting of light through a medium. In this case, the light is being bent by the ice crystals in the air that make up the cloud.
What does it mean?
There is no major function of a 22° ring other than that it indicates high cirrus clouds within the sky. It's simply just a cool atmospheric phenomenon!
Are all halos the same?
What's interesting about halos is each one is unique to the person observing it. Similar to rainbows, a person looking at a group of ice crystals (that form the halo) are different ice crystals than what someone else would see standing in a different position.
