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Pluto and Charon

Pluto-dwarf planet

Pluto used to be identified as a planet but was demoted to dwarf planet in a controversial decision by the IAU (International Astronomical Union)

Pluto has 5 known moons: Charon, Styx, Nix, Kerberos, and Hydra.

Pluto and Charon are often referred to as a binary system since Charon is very massive (about half the size of Pluto) and tidally locked with it.

Pluto is named after the Roman god of the underworld. Pluto was named by an eleven-year old girl named Venetia Burney, who was given 5 pounds as a reward.

For 20 years in its 248 year orbit, Pluto is closer to the Sun than Neptune. This is due to its eccentric orbit; the last time this occurred was between 1979 and 1999.

Compared to the rest of the solar system, very little is known about Pluto and its origins. Astronomers think that Pluto was the result of a massive collision. Some propose that Pluto is an escaped moon of Neptune. While no spacecraft have visited Pluto yet, NASA's New Horizons is scheduled to reach Pluto in July, 2015. Astronomers hope that it will provide more information about Pluto's physical and chemical characteristics, as well as a better understanding of Pluto's moons.