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Credit & Copyright: Alfred Lee   
 
Explanation:
What's that in the sky?   
   
Earlier this month, in the sky high above    
Hong Kong,    
China, not just one unusual type   
of cloud appeared -- but two.    
   
In the foreground was a long    
lenticular   
cloud,    
a cloud that forms near mountains from uprising air and might appear to some as an    
alien spaceship.   
   
Higher in the sky, and further in the background, was a colorful    
iridescent cloud.   
   
Iridescent    
clouds    
are composed of    
water droplets of similar size that    
diffract different   
colors of sunlight by different amounts.    
   
Furthest in the background is the Sun, blocked from direct view by the opaque    
lenticular, but providing the light for the colors of   
the    
iridescent.   
   
Either type of cloud is unusual to see in    
Hong Kong,    
and unfortunately, after only a few minutes, both were gone.    
   
   
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Based on Astronomy Picture
Of the Day
  