Image Credit & Copyright: Yuri
Beletsky (Las Campanas Observatory, Carnegie Institution)
Explanation:
As far as the eye could see, it was a dark night at Las Campanas Observatory in
the southern Atacama desert of Chile. But near local midnight on April 11, this
mosaic of 3 minute long exposures revealed a green, unusually intense,
atmospheric airglow stretching over thin clouds. Unlike aurorae powered by
collisions with energetic charged particles and seen at high latitudes, the
airglow is due to chemiluminescence, the production of light in a chemical
reaction, and found around the globe. The chemical energy is provided by the
Sun's extreme ultraviolet radiation. Like aurorae, the greenish hue of this
airglow does originate at altitudes of 100 kilometers or so dominated by
emission from excited oxygen atoms. The gegenschein, sunlight reflected by dust
along the solar system's ecliptic plane was still visible on that night, a
faint bluish cloud just right of picture center. At the far right, the Milky
Way seems to rise from the mountain top perch of the Magellan telescopes. Left
are the OGLE project and du Pont telescope domes.
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