For 20 years (or 8%) of its 248-year orbit around the Sun, the dwarf planet Pluto is slightly closer to the Sun than Neptune. But even here at its perihelion, light from the Sun still takes 4 hours, 6 minutes to reach Pluto. At the scale of this solar system diagram, the diameter of Pluto is about the same as two grains of salt. Its largest moon, Charon, is about the size of a single grain of salt, at a distance of only about 3 millimeters from Pluto. But technically, Charon does not orbit Pluto. Rather, Pluto and Charon orbit each other around a common barycenter (or center of mass) which lies between the two objects. For this reason, some astronomers classify Pluto and Charon as a binary system. The only close-up images of Pluto and its moons were taken by the New Horizons spacecraft, during its 2015 flyby.
You can view these links to learn more about the Pluto-Charon system:
The Pluto-Charon image on this page is a montage of photos taken in 2015 by the New Horizons probe, and is courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
