                        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.

                               2026 January 2

                                 NanoSail-D2
                  Image Credit & Copyright: Ralf Vandebergh

   Explanation: In 2011, on January 20, NASA's NanoSail-D2 unfurled a very
   thin and very reflective 10 square meter sail becoming the first solar
   sail spacecraft in low Earth orbit. Often considered the stuff of
   science fiction, sailing through space was suggested 400 years ago by
   astronomer Johannes Kepler, who had observed comet tails blown by the
   solar wind. But modern solar sail spacecraft designs, like NanoSail-D2,
   Japan's interplanetary spacecraft IKAROS, or the Planetary Society's
   Lightsail A, rely on the small but continuous pressure from sunlight
   itself for thrust. Glinting in the sunlight as it circled planet Earth,
   NanoSail-D2's solar sail was periodically bright and visible to the
   eye. These remarkably detailed images were captured by manually
   tracking the orbiting solar sail spacecraft with a small telescope.

                      Tomorrow's picture: moon lighting
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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.

