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.

                                 2024 July 7
    [2]A landscape shows the sky above, shallow water in front, and hills
    to the right. The sunset sky is filled with beautifully multicolored
   clouds. These clouds are clearly reflected by the calm water in front.
          Please see the explanation for more detailed information.

                        Iridescent Clouds over Sweden
                        Image Credit: [3]Goran Strand

   Explanation: Why are these clouds multi-colored? A relatively rare
   phenomenon in clouds known as [4]iridescence can bring up unusual
   colors vividly -- or even a whole [5]spectrum of colors simultaneously.
   These [6]polar stratospheric clouds [7]also, known as [8]nacreous and
   mother-of-pearl clouds, are formed of small [9]water droplets of nearly
   uniform size. When the [10]Sun is in the right position and, typically,
   hidden from direct view, [11]these thin clouds can be seen
   significantly [12]diffracting sunlight in a nearly coherent manner,
   with [13]different colors being deflected by different amounts.
   Therefore, [14]different colors will come to the observer from slightly
   [15]different directions. Many [16]clouds start with uniform regions
   that could show [17]iridescence but quickly become too thick, too
   mixed, or too angularly far from the [18]Sun to exhibit striking
   colors. The featured image and an [19]accompanying video were taken
   late in 2019 over [20]Ostersund, [21]Sweden.

                 Tomorrow's picture: red planet, blue planet
     __________________________________________________________________

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    Authors & editors: [33]Robert Nemiroff ([34]MTU) & [35]Jerry Bonnell
                                 ([36]UMCP)
          NASA Official: Amber Straughn [37]Specific rights apply.
            [38]NASA Web Privacy, [39]Accessibility, [40]Notices;
                A service of: [41]ASD at [42]NASA / [43]GSFC,
                         [44]NASA Science Activation
                           & [45]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2407/IridescentClouds_Strand_1500.jpg
   3. http://www.astrofotografen.se/
   4. https://en.wikipedia.org/wiki/Cloud_iridescence
   5. https://science.nasa.gov/ems/01_intro/
   6. https://en.wikipedia.org/wiki/Polar_stratospheric_cloud
   7. https://en.wikipedia.org/wiki/Cloud_iridescence
   8. https://apod.nasa.gov/apod/ap200110.html
   9. https://www.atoptics.co.uk/droplets/clouds.htm
  10. https://science.nasa.gov/sun/
  11. http://cimss.ssec.wisc.edu/wxwise/class/iredsnce.html
  12. http://www.exploratorium.edu/snacks/diffraction/index.html
  13. https://youtu.be/VljrlBkJUl0
  14. https://en.wikipedia.org/wiki/Iridescence
  15. http://www.kaushik.net/avinash/wp-content/uploads/2010/02/many_different_directions.jpg
  16. https://scijinks.gov/rainbow-clouds/
  17. https://apod.nasa.gov/apod/ap140708.html
  18. https://solarsystem.nasa.gov/solar-system/sun/in-depth/
  19. https://youtu.be/VljrlBkJUl0
  20. https://www.youtube.com/watch?v=E0z1BqhtyLA
  21. https://en.wikipedia.org/wiki/Sweden
  22. https://apod.nasa.gov/apod/ap240706.html
  23. https://apod.nasa.gov/apod/archivepix.html
  24. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  25. https://apod.nasa.gov/apod/lib/aptree.html
  26. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  27. https://apod.nasa.gov/apod/calendar/allyears.html
  28. https://apod.com/feed.rss
  29. https://apod.nasa.gov/apod/lib/edlinks.html
  30. https://apod.nasa.gov/apod/lib/about_apod.html
  31. https://asterisk.apod.com/discuss_apod.php?date=240707
  32. https://apod.nasa.gov/apod/ap240708.html
  33. http://www.phy.mtu.edu/faculty/Nemiroff.html
  34. http://www.phy.mtu.edu/
  35. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  36. http://www.astro.umd.edu/
  37. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  38. https://www.nasa.gov/about/highlights/HP_Privacy.html
  39. https://www.nasa.gov/general/accessibility/
  40. https://www.nasa.gov/privacy/
  41. https://astrophysics.gsfc.nasa.gov/
  42. https://www.nasa.gov/
  43. https://www.nasa.gov/centers/goddard/
  44. https://science.nasa.gov/learners
  45. http://www.mtu.edu/