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. 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. These contrails cast long shadows. That was just the case over Istanbul, Türkiye, 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

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