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.

2007 April 9
See Explanation.  Clicking on the picture will download
 the highest resolution version available.

Aurora Over Alaska
Credit: Joshua Strang, USAF, Wikipedia

Explanation: Higher than the highest mountain, higher than the highest airplane, lies the realm of the aurora. Aurora rarely reach below 60 kilometers, and can range up to 1000 kilometers. Aurora light results from solar shockwave causing energetic electrons and protons to striking molecules in the Earth's atmosphere. Frequently, when viewed from space, a complete aurora will appear as a circle around one of the Earth's magnetic poles. The above digitally enhanced photograph was taken in 2005 January shows a spectacular aurora borealis above the frozen landscape of Bear Lake, Alaska, USA. The above image was voted Wikipedia Commons Picture of the Year for 2006.

Tomorrow's picture: saturn swoop

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