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.

2004 August 4

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Solar Arcs and Halos
Credit & Copyright: Eva Seidenfaden

Explanation: Have you ever seen a bright halo around the Sun? Unusual halos and arcs were so bright one recent afternoon in Trier, Germany that even casual people on the street noticed them. The fantastic sky display is pictured above and included a 22 degree halo arc, a complete parhelic circle, a circumhorizon arc and even an infralateral arc. A computer simulation has been run that mimics the above rare display. A cloud partially blocked the usually more intense direct glare of the Sun. Sunlight refracting through falling and fluttering hexagonal ice crystals creates such displays. Such atmospheric ice crystals also cause sundogs and Moon halos.

Tomorrow's picture: cepheus rainbow

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