Context: A mesmerising phenomenan — a rainbow around the Sun know as a Sun halo, was observed recently in Bengaluru. What is it? How is it formed? The halo that appeared around the Sun is a 22-degree ring that appears due to the dispersion of light as white light passes through ice crystals found in upper-level cirrus clouds, causing the halo to have colours. 1. 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. 2. The crystals have to be oriented and positioned just so with respect to your eye, in order for the halo to appear. Similarly, what are lunar halos? Seen around the Moon, lunar halos are mostly colourless as moonlight is not very bright. Sources: the Hindu.