What causes the halo or ring around the sun that looks like a rainbow?
Halos (larger circles) around the Sun can be caused by the refraction (bending) and reflection of light in ice crystals in the clouds. Sometimes these halos will show color like a rainbow. You might also see two “mock suns” (also called “parhelia” or “sundogs”), one on each side of the Sun. If you see a smaller rainbow circle around the Sun, this might be a corona (not the same as the corona we think of in the Sun’s outer atmosphere), caused by the diffraction of light through water (and sometimes ice) droplets.