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.

                                2020 April 17

                      The Windmill and the Star Trails
                 Image Credit & Copyright: Antonio Gonzalez

   Explanation: Stars can't turn these old wooden arms, but it does look
   like they might in this scene from a rotating planet. The well-composed
   night skyscape was recorded from Garafia, a municipality on the island
   of La Palma, Canary Islands, planet Earth. The center of the once
   working windmill, retired since 1953, is lined-up with the north
   celestial pole, the planet's rotation axis projected on to the northern
   sky. From a camera fixed to a tripod, the star trails are a reflection
   of the planet's rotation traced in a digital composite of 39 sequential
   exposures each 25 seconds long. Brought out by highlighting the final
   exposure in the sequence, the stars themselves appear at the ends of
   their short concentric arcs. A faint band of winter's Milky Way and
   even a diffuse glow from our neighboring Andromeda Galaxy also shine in
   the night.

                      Tomorrow's picture: light-weekend
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                      A service of: ASD at NASA / GSFC
                             & Michigan Tech. U.

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