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.

2005 August 31
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Crepuscular Rays Over Utah
Credit & Copyright: Jean Nesheim

Explanation: What could cause such rays of dark? Dark sky rays were caught in spectacular fashion earlier this month above Utah, USA. The cause is something surprisingly familiar: shadows. Clouds near the horizon can block sunlight from reflecting off air, making columns outward from the Sun appear unusually dark. Cloud shadows can be thought of as the complement of the more commonly highlighted crepuscular rays, also visible above, where sunlight pours though cloud holes. Sometimes, on the opposite side of the sky, anticrepuscular rays can also be seen.

Tomorrow's picture: solo spira mirabilis

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