What is the Sun halo?

About Sun halo:

• What is it? It is an optical phenomenon that occurs due to sunlight refracting millions of hexagonal ice crystals suspended in the atmosphere.
• How it is formed?
  • When white light passes through unique hexagonal ice crystals found in upper-level cirrus clouds, causing the halo to have colours.
  • The clouds contain millions of tiny ice crystals, which refract, split and even reflect the light to give an impression of a circular rainbow ring.
  • The crystals have to be oriented and positioned just so with respect to your eye, for the halo to appear.
  • Light undergoes two refractions as it passes through the ice crystals and the bending that occurs depends on the ice crystal's diameter.
  • The two refractions bend the light by 22 degrees from its original point, producing a ring of light around the Sun or the Moon.
• The lunar halos are mostly colourless as moonlight is not very bright.
• In the case of the Sun, these colours are more noticeable and appear as bright as a rainbow.