MSGID: 1:153/757.0 716be21f   
   TZUTC: -0700   
   CHRS: LATIN-1 2   
                           Astronomy Picture of the Day   
      
       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   
       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: Fatih Ekmen   
      
      Explanation: What created this giant X in the clouds? It was the shadow   
      of contrails illuminated from below. When airplanes fly, humid engine   
      exhaust may form water droplets that might freeze in Earth's cold upper   
      atmosphere. These persistent streams of water and ice scatter light   
      from the Sun above and so appear bright from below. On rare occasions,   
      though, when the Sun is near the horizon, 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 Istanbul, T+'rkiye, earlier this month. Contrails occur all over   
      planet Earth and, generally, warm the Earth when the trap infrared   
      light but cool the Earth when they efficiently reflect sunlight. The   
      image was taken by a surprised photographer in the morning on the way   
      to work.   
      
                         Tomorrow's picture: a star's art   
        __________________________________________________________________   
      
          Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)   
               NASA Official: Amber Straughn Specific rights apply.   
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                         A service of: ASD at NASA / GSFC,   
                              NASA Science Activation   
                                & Michigan Tech. U.   
      
   --- BBBS/Li6 v4.10 Toy-6   
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