1. Ice Crystals: High-altitude clouds, typically cirrus clouds, contain tiny hexagonal ice crystals.
2. Light Refraction: As moonlight passes through these ice crystals, it gets refracted (bent) at different angles due to the shape of the crystals.
3. Specific Angle: The refraction occurs at a specific angle, typically 22 degrees, due to the hexagonal shape of the ice crystals. This angle is responsible for the circular shape of the halo.
4. Color Dispersion: The light is also slightly dispersed, meaning different colors are bent at slightly different angles. This can sometimes create a faint rainbow-like effect within the halo, with red appearing on the inner edge and blue on the outer edge.
Key Points:
* Halo Formation: Halos form when there are high-altitude clouds containing ice crystals and the moon is shining through them.
* Circular Shape: The 22-degree angle of refraction from the ice crystals creates the distinctive circular shape.
* Color Dispersion: The halo can sometimes display a faint rainbow effect due to the slight dispersion of light.
Interesting Fact:
While halos are commonly associated with the moon, they can also occur around the sun, known as solar halos. The principle behind their formation is the same.
