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.

                                 2025 June 3
     [2]A starfield is seen over water, clouds, and the lights of a city
       below. The starfield is oddly not black, but shows a repeating
   assortment of transparent colors diagonally from the lower left to the
   upper right. Please see the explanation for more detailed information.

                       Rainbow Airglow over the Azores
        Image Credit & Copyright: [3]Miguel Claro ([4]TWAN); Rollover
                         Annotation: [5]Judy Schmidt

   Explanation: Why would the sky glow like a giant repeating rainbow?
   [6]Airglow. Now, air glows all of the time, but it is usually hard to
   see. A disturbance however -- like an approaching storm -- may cause
   noticeable rippling in the [7]Earth's atmosphere. These [8]gravity
   waves are [9]oscillations in air analogous to those created when a
   [10]rock is thrown in calm water. The long-duration exposure nearly
   along the vertical walls of [11]airglow likely made the undulating
   structure particularly visible. OK, but where do the colors originate?
   The deep red glow likely originates from [12]OH molecules about 87
   kilometers high, excited by [13]ultraviolet light from the Sun. The
   orange and green [14]airglow is likely caused by [15]sodium and
   [16]oxygen atoms slightly higher up. The [17]featured image was
   captured during a [18]climb up [19]Mount Pico in the [20]Azores of
   [21]Portugal. Ground lights originate from the island of [22]Faial in
   the [23]Atlantic Ocean. A spectacular sky is visible through this
   banded airglow, with the central band of our [24]Milky Way Galaxy
   running up the image center, and M31, the [25]Andromeda Galaxy, visible
   near the top left.

       APOD Turns 30!: [26]Free Public Lecture in Anchorage on June 11
                      Tomorrow's picture: Rubin begins
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    Authors & editors: [38]Robert Nemiroff ([39]MTU) & [40]Jerry Bonnell
                                 ([41]UMCP)
          NASA Official: Amber Straughn [42]Specific rights apply.
            [43]NASA Web Privacy, [44]Accessibility, [45]Notices;
                A service of: [46]ASD at [47]NASA / [48]GSFC,
                         [49]NASA Science Activation
                           & [50]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2506/GravityWaves_Claro_1486.jpg
   3. https://www.miguelclaro.com/wp/biography/
   4. https://twanight.org/about/
   5. https://www.planetary.org/profiles/judy-schmidt
   6. https://svs.gsfc.nasa.gov/12963
   7. https://www.nasa.gov/image-article/earths-atmospheric-layers-3/
   8. https://en.wikipedia.org/wiki/Gravity_wave
   9. http://www.atoptics.co.uk/blog/atmospheric-gravity-waves/
  10. https://www.youtube.com/watch?v=T9QwiBFN9gI
  11. https://apod.nasa.gov/apod/ap150904.html
  12. https://en.wikipedia.org/wiki/Hydroxyl
  13. https://science.nasa.gov/ems/10_ultravioletwaves
  14. http://www.pnas.org/content/112/49/E6728.abstract
  15. https://periodic.lanl.gov/11.shtml
  16. https://periodic.lanl.gov/8.shtml
  17. http://www.miguelclaro.com/wp/?portfolio=rainbow-bands-of-airglow-in-gravity-waves-above-pico-island
  18. https://www.youtube.com/watch?v=-GlioVTgjuI
  19. https://en.wikipedia.org/wiki/Mount_Pico
  20. https://en.wikipedia.org/wiki/Azores
  21. https://en.wikipedia.org/wiki/Portugal
  22. https://youtu.be/jPg7KFv2a-s
  23. https://en.wikipedia.org/wiki/Atlantic_Ocean
  24. https://science.nasa.gov/resource/the-milky-way-galaxy/
  25. https://apod.nasa.gov/apod/ap181217.html
  26. https://www.facebook.com/photo?fbid=1236113895188422&set=a.439352174864602
  27. https://apod.nasa.gov/apod/ap250602.html
  28. https://apod.nasa.gov/apod/archivepix.html
  29. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  30. https://apod.nasa.gov/apod/lib/aptree.html
  31. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  32. https://apod.nasa.gov/apod/calendar/allyears.html
  33. https://apod.com/feed.rss
  34. https://apod.nasa.gov/apod/lib/edlinks.html
  35. https://apod.nasa.gov/apod/lib/about_apod.html
  36. https://asterisk.apod.com/discuss_apod.php?date=250603
  37. https://apod.nasa.gov/apod/ap250604.html
  38. http://www.phy.mtu.edu/faculty/Nemiroff.html
  39. http://www.phy.mtu.edu/
  40. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  41. http://www.astro.umd.edu/
  42. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  43. https://www.nasa.gov/about/highlights/HP_Privacy.html
  44. https://www.nasa.gov/general/accessibility/
  45. https://www.nasa.gov/privacy/
  46. https://astrophysics.gsfc.nasa.gov/
  47. https://www.nasa.gov/
  48. https://www.nasa.gov/centers/goddard/
  49. https://science.nasa.gov/learners
  50. http://www.mtu.edu/