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.

                              2019 December 15

                        Mammatus Clouds over Nebraska
              Image Credit & Copyright: Jorn Olsen Photography

   Explanation: When do cloud bottoms appear like bubbles? Normally, cloud
   bottoms are flat. This is because moist warm air that rises and cools
   will condense into water droplets at a specific temperature, which
   usually corresponds to a very specific height. As water droplets grow,
   an opaque cloud forms. Under some conditions, however, cloud pockets
   can develop that contain large droplets of water or ice that fall into
   clear air as they evaporate. Such pockets may occur in turbulent air
   near a thunderstorm. Resulting mammatus clouds can appear especially
   dramatic if sunlit from the side. The mammatus clouds pictured here
   were photographed over Hastings, Nebraska during 2004 June.

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