Astronomy Image of the Day
Airglow Ripples over Tibet
01 September 2014
Jeff Dai

NASA Astronomy Image of the Day for 01 September 2014
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. Now Available: APOD 2015 Wall Calendars
Explore Random Posts
Image and explanation courtesy of NASA Astronomy Picture of the Day