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                        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.

                              2021 February 17
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                      Sun Pillar with Upper Tangent Arc
                   Image Credit & Copyright: [3]Mike Cohea

   Explanation: This was not a typical sun pillar. Just after sunrise two
   weeks ago in [4]Providence, [5]Rhode Island, [6]USA, a photographer,
   looking out his window, was suddenly awestruck. The astonishment was
   caused by a [7]sun pillar that [8]fanned out at the top. Sun pillars,
   singular columns of light going up from [9]the Sun, are themselves rare
   to see, and are known to be caused by sunlight [10]reflecting from
   wobbling, [11]hexagon-shaped ice-disks falling through [12]Earth's
   atmosphere. Separately, upper [13]tangent arcs are known to be caused
   by sunlight refracting through falling [14]hexagon-shaped ice-tubes.
   Finding a [15]sun pillar connected to an [16]upper tangent arc is
   extraordinary, and, initially, took some analysis to figure out what
   was going on. A leading theory is that this [17]sun pillar was also
   created, in a complex and unusual way, by falling ice tubes. Few might
   believe that such a [18]rare phenomenon was seen again if it wasn't for
   the quick thinking of the photographer -- and the camera on his nearby
   [19]smartphone.

               News from Mars: [20]NASA Perseverance Coverage
                       Tomorrow's picture: open space
     __________________________________________________________________

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    Authors & editors: [32]Robert Nemiroff ([33]MTU) & [34]Jerry Bonnell
                                 ([35]UMCP)
          NASA Official: Phillip Newman [36]Specific rights apply.
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                A service of: [38]ASD at [39]NASA / [40]GSFC
                           & [41]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2102/SunPillar_Cohea_3400.jpg
   3. https://www.mikecohea.com/about
   4. https://youtu.be/zJ-g6DpBsAs
   5. https://en.wikipedia.org/wiki/Rhode_Island
   6. https://www.cia.gov/the-world-factbook/countries/united-states/
   7. https://apod.nasa.gov/apod/ap180606.html
   8. https://catsherdyou.com/wp-content/uploads/2016/05/cat_fan_working_sm.jpg
   9. https://solarsystem.nasa.gov/solar-system/sun/overview/
  10. https://apod.nasa.gov/apod/ap191227.html
  11. https://www.atoptics.co.uk/halo/platpill.htm
  12. https://spaceplace.nasa.gov/atmosphere/en/
  13. https://www.atoptics.co.uk/halo/colsolat.htm
  14. https://www.atoptics.co.uk/halo/colpill.htm
  15. https://apod.nasa.gov/apod/ap060205.html
  16. https://en.wikipedia.org/wiki/Upper_and_lower_tangent_arcs
  17. https://www.atoptics.co.uk/halo/pillar.htm
  18. https://apod.nasa.gov/apod/ap200224.html
  19. https://en.wikipedia.org/wiki/Camera_phone#/media/File:Sharp_J-SH04_CP+_2011.jpg
  20. https://mars.nasa.gov/mars2020/timeline/landing/watch-online/
  21. https://apod.nasa.gov/apod/ap210216.html
  22. https://apod.nasa.gov/apod/archivepix.html
  23. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  24. https://apod.nasa.gov/apod/lib/aptree.html
  25. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  26. https://apod.nasa.gov/apod/calendar/allyears.html
  27. https://apod.nasa.gov/apod.rss
  28. https://apod.nasa.gov/apod/lib/edlinks.html
  29. https://apod.nasa.gov/apod/lib/about_apod.html
  30. http://asterisk.apod.com/discuss_apod.php?date=210217
  31. https://apod.nasa.gov/apod/ap210218.html
  32. http://www.phy.mtu.edu/faculty/Nemiroff.html
  33. http://www.phy.mtu.edu/
  34. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  35. http://www.astro.umd.edu/
  36. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  37. https://www.nasa.gov/about/highlights/HP_Privacy.html
  38. https://astrophysics.gsfc.nasa.gov/
  39. https://www.nasa.gov/
  40. https://www.nasa.gov/centers/goddard/
  41. http://www.mtu.edu/