Pluto is a dwarf planet in our solar system. ... Pluto is not very big. It is only half as wide as the United States. Pluto is smaller than Earth's moon. This dwarf planet takes 248 Earth years to go around the sun. If you lived on Pluto, you ... Pluto is in an area of space called the Kuiper (KY-per) Belt. read more
For the Earth and moon, because their masses are so different, the center of mass of the system is inside of Earth's surface. It is not at the physical center of Earth, however. That the Pluto-Charon-Nix-Hydra-etc. system has a center of mass beyond Pluto's surface is NOT a reason for its demotion to dwarf planet. read more
Pluto, only a little over twice its diameter, at 2,374 km was called a planet, as was Mercury, about twice the diameter of Pluto at 4,879 km. Basically they had the choice, either to call Ceres a planet, or Pluto a non planet. read more