halo
n.
Properly, a luminous ring encircling an astronomical body, but not infrequently confounded with "aureola," or "nimbus," a somewhat similar phenomenon worn as a head-dress by divinities and saints. The halo is a purely optical illusion, produced by moisture in the air, in the manner of a rainbow; but the aureola is conferred as a sign of superior sanctity, in the same way as a bishop's mitre, or the Pope's tiara. In the painting of the Nativity, by Szedgkin, a pious artist of Pesth, not only do the Virgin and the Child wear the nimbus, but an ass nibbling hay from the sacred manger is similarly decorated and, to his lasting honor be it said, appears to bear his unaccustomed dignity with a truly saintly grace.
A halo (also known as a nimbus or Gloriole) is a ring of light that surrounds an object. They are often used in religious works to depict holy or sacred figures. In Christian sacred art (Eastern and Western churches), holy persons (saints) are depicted with a halo in the form of a golden, yellow or white circular glow around the head.
Halos, also known as
icebows, are also optical phenomena that appear near or around the Sun or Moon, and sometimes near other strong light sources such as street lights. There are many types of optical halos, but they are mostly caused by ice crystals in cold cirrus clouds located high (5-10 km, or 3-6 miles) in the upper troposphere. The particular shape and orientation of the crystals is responsible for the type of halo observed. Light is reflected and refracted by the ice crystals and may split up into colors because of dispersion, similarly to the rainbow.