Science & Nature - Bishop's Ring: the volcanic halo around the Sun

A Bishop's Ring is a diffuse halo observed around the Sun following massive volcanic eruptions. First recorded by Reverend Sereno Edwards Bishop after the 1883 Krakatoa eruption, the phenomenon is caused by light diffracting through fine sulfate aerosols suspended in the stratosphere. The ring features a whitish or bluish-white inner rim with a reddish, brownish, or purple outer edge. Because diffraction places red on the outside, its width depends on particle size, occasionally spanning up to thirty degrees across the sky.

Source: Wikipedia