Astronomy Picture of the Day

Lunar Halo over Snowy Trees
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Lunar Halo over Snowy Trees
Credit & Copyright: Göran Strand
Explanation: Have you ever seen a halo around the Moon? 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 Moon Halo. A similar Sun Halo may be visible during the day. Exactly how ice-crystals form in clouds remains a topic of research. In the featured image taken last week from östersund, Sweden, a complete lunar halo was captured over snowy trees and rabbit tracks.

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