                        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 February 28
     A rocky shoreline is shown with land on the right and water on the
       left. Above is a sky that shows unusually pixelated and colored
        vertical bands. Please see the explanation for more detailed
                                information.

                               Shades of Night
                 Image Credit & Copyright: Dario Giannobile

   Explanation: How does the sky turn dark at night? In stages, and with
   different characteristic colors rising from the horizon. The featured
   image shows, left to right, increasingly late twilight times after
   sunset in 20 different vertical bands. The picture was taken last month
   in Syracuse, Sicily, Italy, in the direction opposite the Sun. On the
   far left is the pre-sunset upper sky. Toward the right, prominent bands
   include the Belt of Venus, the Blue Band, the Horizon Band, and the Red
   Band. As the dark shadow of the Earth rises, the colors in these bands
   are caused by direct sunlight reflecting from air and aerosols in the
   Earth's atmosphere, multiple reflections sometimes involving a reddened
   sunset, and refraction. In practice, these bands can be diffuse and
   hard to discern, and their colors can depend on colors near the setting
   Sun. Finally, the Sun completely sets and the sky becomes dark. Don't
   despair -- the whole thing will happen in reverse when the Sun rises
   again in the morning.

                     Tomorrow's picture: extra February
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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.

