Description: A Solar halo

Explaination: A halo is a ring of light surrounding the Sun or moon. Most halos appear as bright white rings but in some instances, the dispersion of light as it passes through ice crystals can cause a halo to have some color. Halos form when light from the Sun or moon is refracted by columnar ice crystals associated with thin, high-level clouds (like cirrus or cirrostratus clouds). [More]

Photographed by: [email protected]

Date: May 2001

Location: ??, Brunei Darussalam

Remarks: Courtesy and copyrighted of  [email protected]

MESSAGE FROM THE PHOTOGRAPHER

From: <[email protected]>

Assalamualaikum,

I stumbled upon your astronomy website by accident (thru an email
forwarded to me) and I thought you might like to see a picture of the
sun I took a few days ago. It was an amazing sight, many people saw it,
people in Bandar might have missed it because of overcast sky. I dont
know the scientific explanation for the phenomenon, but most people
said it signified the death of a Wali of important person, and Allah
lessened the strength of the sun's rays by covering it with a gray disc.

Solar halo through cirrus

(E. Linacre and B. Geerts)

A halo is a ring of light surrounding the Sun or moon. Most halos appear as bright white rings but in some instances, the dispersion of light as it passes through ice crystals can cause a halo to have some color. Halos form when light from the Sun or moon is refracted by columnar ice crystals associated with thin, high-level clouds (like cirrus or cirrostratus clouds).

Fig 1. Sun ray geometry for the 22° halo. The horizontal line shown can, in reality, be in any direction.

A 22° (degrees) halo is a ring of light 22° from the Sun (or moon), i.e. a hand’s breadth at arm’s length (Fig 1). It is not the only, but the most common type of halo observed. Solar rays undergo two refractions as they pass through an ice crystal and the amount of bending that occurs depends upon the ice crystal's diameter. A 22° halo is due to columnar ice crystals with diameters less than 20 micrometres (Fig 2).

Fig 2. Columnar ice crystals refract light at 22°.

A 22° halo develops when light enters one side of a columnar ice crystal and exits through another side. The light is refracted when it enters the ice crystal and once again when it leaves the ice crystal. The two refractions bend the light by 22° from its original direction, producing a ring of light observed at 22° from the sun or moon.