Lunar Halo over Snowy Trees

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. APOD is available via Instagram: in English , Indonesian , Persian , and Portuguese