Today's Astronomy Picture of the Day, brought to you by NASA and photographer Jeff Dai, is simply breathtaking: vivid, majestic, otherworldly.
This photo shows the Southeastern Asian night sky as I've never seen it before. Staring at it I feel like it could be a space-time gate from an unknown dimension to our home planet. Nevertheless, the scientific explanation of the phenomenon you're looking at is just as fantastic and interesting:-
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.
Image credit: Jeff Dai via APOD
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