Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2010 February 8
Explanation: 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.
Authors & editors:
(MTU) & Jerry Bonnell (USRA)
NASA Official: Phillip Newman. Specific rights apply.
A service of: ASD at NASA/GSFC
& Michigan Tech. U.