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.

2006 June 13
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Driving Toward a Sun Halo
Credit & Copyright: Lauri Turtiainen

Explanation: What's happened to the Sun? Sometimes it looks like the Sun is being viewed through a large lens. In the above case, however, there are actually millions of lenses: ice crystals. As water freezes in the upper atmosphere, small, flat, six-sided, ice crystals might be formed. As these crystals flutter to the ground, much time is spent with their faces flat, parallel to the ground. An observer may pass through the same plane as many of the falling ice crystals near sunrise or sunset. During this alignment, each crystal can act like a miniature lens, refracting sunlight into our view and creating phenomena like parhelia, the technical term for sundogs. The above image was taken during early 2006 February near Helsinki, Finland with a quickly deployed cellular camera phone. Visible in the image center is the Sun, while two bright sundogs glow prominently from both the left and the right. Also visible is the 22 degree halo also created by sunlight reflecting off of atmospheric ice crystals.

Tomorrow's picture: 2 cameras, 2 telescopes, 2 thousand miles

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