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Distance from sun 5,913.52 million km, 39.5294 a.u.
Diameter 2,300 km, 0.18 times earth's diameter
Mass 0.0022 times earth's mass
Density 2.03
Gravity 0.041 times earth's gravity, escape velocity 1.1 km/s
Rotation 6.3872 hours
Orbit Eccentricity 0.2484
Orbit Inclination 17.148 degrees
Axis Tilt 122.46 degrees
Sidereal Period 284.54 Earth years
Synodic Period 366.73 Earth days

History: Pluto was discovered in 1930 by Clyde Tombaugh, as a result of a search of a planet disrupting the orbit of Neptune. It was named after the Roman god of the underworld, known to the Greeks as Hades. Charon, Pluto's only satellite, was found in 1978 and named after the ferryman who brought the dead across the river Styx.

Description: Pluto is the smallest of the planets, the farthest from the sun, and the least dense of the terrestrial planets. Because it is so atypical of the usual outer satellite, it has been speculated that it is not a planet at all, but rather an escaped satellite of Neptune, or a very large comet. It rotates very slowly, and backwards, from east to west. No detail of Pluto's surface have ever been collected, except what information is gathered from the measure of the reflected light. This data suggests that it has a surface of frozen methane, a thin atmosphere, and a temperature of only about -223 degrees celcius, only 50 degrees above absolute zero.

Observation: Pluto can only be observed with moderate to large telescopes, never reaching magnitude greater than 14. Even then it only appears as a tiny point of light, with no detail visible. Charon is not visible, except by the best photographs taken by very large telescopes. Because of the eccentricity of its orbit, Pluto passes Neptune and becomes only the eighth planet from the sun for about twenty years every Plutonian orbit.

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