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 September 28
See Explanation. Clicking on the picture will download the highest resolution version available.

Aurora Over a Communications Tower
Credit & Copyright: Frank Andreassen (nettfoto.no)

Explanation: Higher than highest communications tower, higher than highest mountain, higher than highest airplane, lies the realm of the aurora. Aurorae rarely reach below 60 kilometres, and can range up to 1000 kilometres. Aurora light results from energetic electrons and protons 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. Pictured above is a particularly rare purple auroral corona that occurred on August 30, high above Harstad, Norway.

Tomorrow's picture: galaxy bash

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