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.
2014 September 1
Airglow Ripples over Tibet
Image 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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Authors & editors:
Robert Nemiroff
(
MTU) &
Jerry Bonnell (
UMCP)
NASA Official: Phillip Newman
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