                        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.

                                2021 July 25

                         Crescent Neptune and Triton
                        Image Credit: NASA, Voyager 2

   Explanation: Gliding silently through the outer Solar System, the
   Voyager 2 spacecraft camera captured Neptune and Triton together in
   crescent phase. The elegant picture of the gas giant planet and its
   cloudy moon was taken from behind just after closest approach in 1989.
   It could not have been taken from Earth because Neptune never shows a
   crescent phase to sunward Earth. The unusual vantage point also robs
   Neptune of its familiar blue hue, as sunlight seen from here is
   scattered forward, and so is reddened like the setting Sun. Neptune is
   smaller but more massive than Uranus, has several dark rings, and emits
   more light than it receives from the Sun.

                     Tomorrow's picture: galaxy grabber
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