Astronomy Picture of the Day

   [1]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.

                              2022 November 20
   [2]The featured image shows a dark field with a photographer lit in red
   imaging a night sky tinged with green airglow and decorated with clouds
        that appear collectively like a giant spiral. Please see the
                 explanation for more detailed information.

                         Airglow Ripples over Tibet
                    Image Credit & Copyright: [3]Jeff Dai

   Explanation: Why would the sky look like a giant target? [4]Airglow.
   Following a giant thunderstorm over [5]Bangladesh in late April, giant
   circular ripples of glowing air appeared over [6]Tibet, [7]China, as
   [8]pictured here. The unusual [9]pattern is created by atmospheric
   [10]gravity waves, waves of alternating air pressure that can grow
   [11]with height as the air thins, in this case about 90-kilometers up.
   Unlike [12]auroras powered by collisions with energetic charged
   particles and seen at high latitudes, [13]airglow is due to
   [14]chemiluminescence, the production of light in a chemical reaction.
   More typically seen near the horizon, [15]airglow keeps the night sky
   from ever being [16]completely dark.

                      Tomorrow's picture: butterfly sky
     __________________________________________________________________

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    Authors & editors: [28]Robert Nemiroff ([29]MTU) & [30]Jerry Bonnell
                                 ([31]UMCP)
          NASA Official: Phillip Newman [32]Specific rights apply.
              [33]NASA Web Privacy Policy and Important Notices
                A service of: [34]ASD at [35]NASA / [36]GSFC,
                         [37]NASA Science Activation
                           & [38]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2211/rippledsky_dai_960.jpg
   3. http://www.flickr.com/photos/jeffdai/
   4. https://earthobservatory.nasa.gov/images/147122/aurora-meet-airglow
   5. https://en.wikipedia.org/wiki/Bangladesh
   6. https://en.wikipedia.org/wiki/Tibet
   7. https://en.wikipedia.org/wiki/China
   8. https://www.flickr.com/photos/jeffdai/14845763849/
   9. http://www.theatlantic.com/technology/archive/2014/04/a-bullseye-in-the-sky-over-texas/360705/
  10. http://www.nasa.gov/multimedia/imagegallery/image_feature_484.html
  11. https://climatekids.nasa.gov/whats-in-the-atmosphere/
  12. https://apod.nasa.gov/apod/ap221009.html
  13. https://apod.nasa.gov/apod/ap220313.html
  14. https://www.atoptics.co.uk/highsky/airglow2.htm
  15. https://en.wikipedia.org/wiki/Airglow
  16. https://apod.nasa.gov/apod/ap200408.html
  17. https://apod.nasa.gov/apod/ap221119.html
  18. https://apod.nasa.gov/apod/archivepix.html
  19. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  20. https://apod.nasa.gov/apod/lib/aptree.html
  21. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  22. https://apod.nasa.gov/apod/calendar/allyears.html
  23. https://apod.nasa.gov/apod.rss
  24. https://apod.nasa.gov/apod/lib/edlinks.html
  25. https://apod.nasa.gov/apod/lib/about_apod.html
  26. http://asterisk.apod.com/discuss_apod.php?date=221120
  27. https://apod.nasa.gov/apod/ap221121.html
  28. http://www.phy.mtu.edu/faculty/Nemiroff.html
  29. http://www.phy.mtu.edu/
  30. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  31. http://www.astro.umd.edu/
  32. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  33. https://www.nasa.gov/about/highlights/HP_Privacy.html
  34. https://astrophysics.gsfc.nasa.gov/
  35. https://www.nasa.gov/
  36. https://www.nasa.gov/centers/goddard/
  37. https://science.nasa.gov/learners
  38. http://www.mtu.edu/