                        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 w
                    ritten by a professional astronomer.

                              2021 November 10

                           Video of a Green Flash
                 Video Credit & Copyright: Paolo Lazzarotti

   Explanation: Many think it is just a myth. Others think it is true but
   its cause isn't known. Adventurers pride themselves on having seen it.
   It's a green flash from the Sun. The truth is the green flash does
   exist and its cause is well understood. Just as the setting Sun
   disappears completely from view, a last glimmer appears startlingly
   green. The effect is typically visible only from locations with a low,
   distant horizon, and lasts just a few seconds. A green flash is also
   visible for a rising Sun, but takes better timing to spot. A dramatic
   green flash was caught on video last month as the Sun set beyond the
   Ligurian Sea from Tuscany, Italy. The second sequence in the featured
   video shows the green flash in real time, while the first is sped up
   and the last is in slow motion. The Sun itself does not turn partly
   green -- the effect is caused by layers of the Earth's atmosphere
   acting like a prism.

   Discovery + Outreach: Graduate student research position open for APOD
                           Tomorrow's picture: 67P
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

