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.

2012 November 4
See Explanation.  Clicking on the picture will download 
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Lenticular Clouds Over Washington
Credit & Copyright: Tim Thompson

Explanation: Are those UFOs near that mountain? No -- they are multilayered lenticular clouds. Moist air forced to flow upward around mountain tops can create lenticular clouds. Water droplets condense from moist air cooled below the dew point, and clouds are opaque groups of water droplets. Waves in the air that would normally be seen horizontally can then be seen vertically, by the different levels where clouds form. On some days the city of Seattle, Washington, USA, is treated to an unusual sky show when lenticular clouds form near Mt. Rainier, a large mountain that looms just under 100 kilometres southeast of the city. This image of a spectacular cluster of lenticular clouds was taken in 2008 December.

Tomorrow's picture: distant moon


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