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Dwarf planet, Pluto

Average distance from the Sun     5,913,520,000 km / 39.5 AU
Diameter     2,372 km
Mass     1.31e22 kg
Orbital period around the Sun     247.94 Earth years / 90,570 Earth days
Number of moons     5 known moons, Charon, Styx, Nix, Kerberos, and Hydra
Pluto was the ninth planet until August 2006, when the International Astronomical Union reclassified it as a dwarf planet. It’s composition and atmosphere are unknown but it is likely composed of rock, ice, and frozen gases. Pluto’s orbit is more elliptical and more inclined than the orbits of the eight solar system planets. The icy dwarf planet is not massive enough to clear debris from its orbit, a key reason why it is not a planet. Pluto’s largest moon, Charon, was discovered in 1978. In 2005, two smaller moons were discovered and later named Nix and Hydra. On 14 July 2015, the New Horizons spacecraft became the first spacecraft to fly by Pluto. During its brief flyby, New Horizons made detailed measurements and observations of Pluto and its moons.

Our Solar System

Our solar system is located on the edge of a spiral arm called Orion’s Arm, and is one-half to two-thirds of the way (28,000 light-years) from the center of our Milky Way galaxy.

The Sun, Sol

The Inner Planets
    The Moon

The Asteroid Belt
  Dwarf planet, Ceres
  Asteroid, Ida
  Asteroid, Vesta
  Asteroid, Eros

The Outer Planets

The Kuiper Belt
  Dwarf planet, Pluto
  Dwarf planet, Eris

The Oort Cloud
  Dwarf planet, Sedna
  Comet Halley
  Comet Hale-Bopp

  Glossary of Terms
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