                        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 March 11
    Several images of a full moon setting are superposed. The moon images
   are nearly white near the top, but turn orange and then are covered by
   low clouds near the horizon. Unusually, the setting moon images line up
   almost vertically. In the foreground is a beach with waves illuminated
   by blue-glowing plankton. Please see the explanation for more detailed
                                information.

                            A Full Plankton Moon
      Credit & Copyright: Petr Horálek / Institute of Physics in Opava

   Explanation: What glows in the night? This night featured a combination
   of usual and unusual glows. Perhaps the most usual glow was from the
   Moon, a potentially familiar object. The full Moon's nearly vertical
   descent results from the observer being near Earth's equator. As the
   Moon sets, air and aerosols in Earth's atmosphere preferentially
   scatter out blue light, making the Sun-reflecting satellite appear
   reddish when near the horizon. Perhaps the most unusual glow was from
   the bioluminescent plankton, likely less familiar objects. These
   microscopic creatures glow blue, it is thought, primarily to surprise
   and deter predators. In this case, the glow was caused primarily by
   plankton-containing waves crashing onto the beach. The image was taken
   on Soneva Fushi Island, Maldives just over one year ago.

     Your Sky Surprise: What picture did APOD feature on your birthday?
                                 (post 1995)
                     Tomorrow's picture: horizon spiral
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn; Specific rights apply.
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                           NASA Science Activation
                             & Michigan Tech. U.

