The
Aurora Australis as seen from the
Space ShuttleDiscovery on
STS-39. The payload bay and tail of Discovery 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.
The NASA website hosts a large number of images from the
Soviet/
Russian space agency, and other non-American space agencies. These are not necessarily in the public domain.
The
SOHO (ESA & NASA) joint project implies that all materials created by its probe are copyrighted and require permission for commercial non-educational use.
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