The <a href="https://en.wikipedia.org/wiki/Aurora_Australis" class="extiw" title="en:Aurora Australis">Aurora Australis</a> as seen from the <a href="https://en.wikipedia.org/wiki/Space_Shuttle" class="extiw" title="en:Space Shuttle">Space Shuttle</a> <a href="https://en.wikipedia.org/wiki/Space_Shuttle_Discovery" class="extiw" title="en:Space Shuttle Discovery"><i>Discovery</i></a> on <a href="https://en.wikipedia.org/wiki/STS-39" class="extiw" title="en:STS-39">STS-39</a>. The payload bay and tail of <i>Discovery</i> can be seen on the left hand side of the picture. Auroras are caused when high-energy electrons pour down from the Earth’s magnetosphere and collide with atoms. Red aurora occurs from 200 km to as high as 500 km altitude and is caused by the emission of 6300 Angstrom wavelength light from oxygen atoms. Green aurora occurs from about 100 km to 250 km altitude and is caused by the emission of 5577 Angstrom wavelength light from oxygen atoms. The light is emitted when the atoms return to their original unexcited state.
NASA (Crew of STS-39)<br>(The original uploader was <a href="https://en.wikipedia.org/wiki/User:Seth_Ilys" class="extiw" title="wikipedia:User:Seth Ilys">Seth Ilys</a> at <a href="https://en.wikipedia.org/wiki/" class="extiw" title="wikipedia:">English Wikipedia</a>.)
1991-05
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