Liberty's Halo

Statue of Liberty with the 22 degrees halo in the sky over New York City in March 30, 2011.... more

by Edwin Verin

Title

Liberty's Halo

Artist

Edwin Verin

Medium

Photograph

Description

Statue of Liberty with the 22 degrees halo in the sky over New York City in March 30, 2011.

A 22� halo is a halo, one type of optical phenomenon, forming a circle 22� around the sun, or occasionally the moon (also called a moon ring or winter halo). It forms as sunlight is refracted in millions of randomly oriented hexagonal ice crystals suspended in the atmosphere. The halo is large; the radius is roughly the size of an outstretched hand at arms length.

As light passes through the 60� apex angle of the hexagonal ice prisms it is deflected twice resulting in deviation angles ranging from 22� to 50�. The angle of minimum deviation is almost 22� (or more specifically 21.84� on average; 21.54� for red light and 22.37� for blue light). This wavelength-dependent variation in refraction causes the inner edge of the circle to be reddish while the outer edge is bluish. As no light is refracted at angles smaller than 22� the sky is darker inside the halo. A 22� halo may be visible on as many as 100 days per year.

Uploaded

July 13th, 2014