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Credit & Copyright: Jeff Dai
Explanation:
Why would the sky look like a giant target?
Airglow.
Following a giant thunderstorm over
Bangladesh
in late April, giant circular ripples of glowing air appeared over
Tibet,
China, as
pictured above.
The unusual
pattern
is created by atmospheric
gravity waves, waves of alternating air pressure that can grow with height as
the air thins, in this case about 90 kilometers up.
Unlike auroras powered by collisions with energetic charged
particles and seen at high latitudes, airglow is due to
chemiluminescence,
the production of light in a chemical reaction.
More typically seen near the horizon,
airglow keeps the night sky from
ever being completely dark.
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A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day