Astronomy Picture of the Day

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.

2021 February 1
See Explanation.  Clicking on the picture will download
the highest resolution version available.

Lunar Halo over Snowy Trees
Image 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.

APOD is available via Instagram: in English, Indonesian, Persian, and Portuguese
Tomorrow's picture: meteor streak and drift


< | Archive | Submissions | Index | Search | Calendar | RSS | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.