APOD: A Sun Halo Over Cambodia (2010 Feb 08)
Posted: Mon Feb 08, 2010 4:54 am
A Sun Halo Over CambodiaExplanation: Have you ever seen a halo around the Sun? This fairly common sight occurs when high thin clouds containing millions of tiny ice crystals cover much of the sky. Each ice crystal acts like a miniature lens. Because most of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees, which corresponds to the radius of the Sun halo. A similar Moon halo may be visible during the night. Pictured above, a nearly complete sun halo was photographed high above the ancient Bayon temple in Angkor, Cambodia. Exactly how ice-crystals form in clouds remains under investigation.
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