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.

                               2021 January 19

                   A Lunar Corona with Jupiter and Saturn
                  Image Credit & Copyright: Alessandra Masi

   Explanation: Why does a cloudy moon sometimes appear colorful? The
   effect, called a lunar corona, is created by the quantum mechanical
   diffraction of light around individual, similarly-sized water droplets
   in an intervening but mostly-transparent cloud. Since light of
   different colors has different wavelengths, each color diffracts
   differently. Lunar Coronae are one of the few quantum mechanical color
   effects that can be easily seen with the unaided eye. Solar coronae are
   also sometimes evident. The featured composite image was captured a few
   days before the close Great Conjunction between Saturn and Jupiter last
   month. In the foreground, the Italian village of Pieve di Cadore is
   visible in front of the Sfornioi Mountains.

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                     Tomorrow's picture: magnetic spiral
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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