An atmospheric oddity captured the fascination of viewers in Arizona Tuesday, as conditions aligned to create a rainbow ring around the sun.
The phenomenon, known as a halo, sun halo or 22-degree halo, is one of several colorful conditions created when moisture in the atmosphere (either ice crystals or water droplets) acts as a prism, breaking up the light from the sun into the component bands of the visible spectrum.
Other types of rainbows in and around the sun created by these same conditions include sun dogs--when flares of light appear on either side of the sun--and sun pillars, which are vertical shafts that extend above and below the sun.
Several of these phenomena are also possible around the moon, though they are less common.
