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 April 23
      [2]Two airplane contrails, crossing in an X, are shown across the
       middle of the image. They are bright white against a dark blue
      background. A high cloud deck is seen above the crossing, sunlit,
   contrails. A low Sun creates a dark shadow X on the high while clouds.
   A row of buildings runs across the lower part of the image. Please see
               the explanation for more detailed information.

                              Contrail Shadow X
                  Image Credit & Copyright: [3]Fatih Ekmen

   Explanation: What created this giant X in the clouds? It was the shadow
   of [4]contrails illuminated from below. When airplanes fly, humid
   [5]engine exhaust may form water droplets that might freeze in Earth's
   [6]cold upper atmosphere. These persistent [7]streams of water and ice
   scatter light from the [8]Sun above and so appear [9]bright from below.
   On rare occasions, though, when the Sun is near the horizon,
   [10]contrails can be lit from below. These contrails cast long shadows
   upwards, shadows that usually go unseen unless there is a high cloud
   deck. But that was just the case over [11]Istanbul, [12]Türkiye,
   earlier this month. Contrails occur [13]all over planet Earth and,
   generally, [14]warm the Earth when the trap [15]infrared light but cool
   the Earth when they efficiently reflect [16]sunlight. The image was
   taken by a surprised photographer in the morning [17]on the way to
   work.

                      Tomorrow's picture: a star's art
     __________________________________________________________________

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    Authors & editors: [29]Robert Nemiroff ([30]MTU) & [31]Jerry Bonnell
                                 ([32]UMCP)
          NASA Official: Amber Straughn [33]Specific rights apply.
            [34]NASA Web Privacy, [35]Accessibility, [36]Notices;
                A service of: [37]ASD at [38]NASA / [39]GSFC,
                         [40]NASA Science Activation
                           & [41]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2404/ContrailX_Ekmen_2268.jpg
   3. https://apod.nasa.gov/apod/ekmenfatihh at gmail dot com
   4. https://en.wikipedia.org/wiki/Contrail
   5. https://www.grc.nasa.gov/www/k-12/UEET/StudentSite/engines.html
   6. https://cloud1.arc.nasa.gov/solveII/outreach/middleschool-atmos.htm
   7. https://apod.nasa.gov/apod/ap231204.html
   8. https://science.nasa.gov/sun/
   9. https://apod.nasa.gov/apod/ap050513.html
  10. https://www.nasa.gov/wp-content/uploads/2023/06/contrails-k-12.pdf?emrc=9d8066
  11. https://youtu.be/eV6lTEY95yY
  12. https://en.wikipedia.org/wiki/Turkey
  13. https://apod.nasa.gov/apod/ap080429.html
  14. https://baltimorefishbowl.com/wp-content/uploads/2014/03/catsburritoscoldkittenswrapburrito-03bc734d15d3f1eed350fa0b20e309ed_h.jpg
  15. https://science.nasa.gov/ems/07_infraredwaves/
  16. https://apod.nasa.gov/apod/ap230611.html
  17. https://apod.nasa.gov/apod/ap200224.html
  18. https://apod.nasa.gov/apod/ap240422.html
  19. https://apod.nasa.gov/apod/archivepix.html
  20. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  21. https://apod.nasa.gov/apod/lib/aptree.html
  22. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  23. https://apod.nasa.gov/apod/calendar/allyears.html
  24. https://apod.com/feed.rss
  25. https://apod.nasa.gov/apod/lib/edlinks.html
  26. https://apod.nasa.gov/apod/lib/about_apod.html
  27. https://asterisk.apod.com/discuss_apod.php?date=240423
  28. https://apod.nasa.gov/apod/ap240424.html
  29. http://www.phy.mtu.edu/faculty/Nemiroff.html
  30. http://www.phy.mtu.edu/
  31. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  32. http://www.astro.umd.edu/
  33. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  34. https://www.nasa.gov/about/highlights/HP_Privacy.html
  35. https://www.nasa.gov/general/accessibility/
  36. https://www.nasa.gov/privacy/
  37. https://astrophysics.gsfc.nasa.gov/
  38. https://www.nasa.gov/
  39. https://www.nasa.gov/centers/goddard/
  40. https://science.nasa.gov/learners
  41. http://www.mtu.edu/