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.

                               2020 January 15
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

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

   Explanation: Why would 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]clouds, 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 last year over [20]Ostersund, [21]Sweden.

   Follow APOD in English on: [22]Instagram, [23]Facebook, [24]Reddit, or
                                 [25]Twitter
                    Tomorrow's picture: a stellar galaxy
     __________________________________________________________________

      [26]< | [27]Archive | [28]Submissions | [29]Index | [30]Search |
   [31]Calendar | [32]RSS | [33]Education | [34]About APOD | [35]Discuss |
                                    [36]>
     __________________________________________________________________

    Authors & editors: [37]Robert Nemiroff ([38]MTU) & [39]Jerry Bonnell
                                 ([40]UMCP)
          NASA Official: Phillip Newman [41]Specific rights apply.
              [42]NASA Web Privacy Policy and Important Notices
                A service of: [43]ASD at [44]NASA / [45]GSFC
                           & [46]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2001/IridescentClouds_Strand_1500.jpg
   3. http://www.astrofotografen.se/
   4. https://www.atoptics.co.uk/droplets/irid1.htm
   5. https://www.nasa.gov/directorates/heo/scan/spectrum/overview/index.html
   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://apod.nasa.gov/apod/sun.html
  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://en.wikipedia.org/wiki/Cloud_iridescence
  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://www.instagram.com/astronomypicturesdaily/
  23. https://www.facebook.com/AstronomyPictureOfTheDay
  24. https://www.reddit.com/r/apod
  25. https://twitter.com/apod/
  26. https://apod.nasa.gov/apod/ap200114.html
  27. https://apod.nasa.gov/apod/archivepix.html
  28. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  29. https://apod.nasa.gov/apod/lib/aptree.html
  30. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  31. https://apod.nasa.gov/apod/calendar/allyears.html
  32. https://apod.nasa.gov/apod.rss
  33. https://apod.nasa.gov/apod/lib/edlinks.html
  34. https://apod.nasa.gov/apod/lib/about_apod.html
  35. http://asterisk.apod.com/discuss_apod.php?date=200115
  36. https://apod.nasa.gov/apod/ap200116.html
  37. http://www.phy.mtu.edu/faculty/Nemiroff.html
  38. http://www.phy.mtu.edu/
  39. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  40. http://www.astro.umd.edu/
  41. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  42. https://www.nasa.gov/about/highlights/HP_Privacy.html
  43. https://astrophysics.gsfc.nasa.gov/
  44. https://www.nasa.gov/
  45. https://www.nasa.gov/centers/goddard/
  46. http://www.mtu.edu/