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Pluto (astronomy)
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Pluto (astronomy)
Dwarf planet. Until its reclassification in 2006 it was considered to be the smallest and, usually, outermost planet of the Solar System. The existence of Pluto was predicted by calculation by US astronomer Percival Lowell and located by US astronomer Clyde Tombaugh in 1930. Its highly elliptical orbit occasionally takes it within the orbit of Neptune, as in 1979–99. Pluto has a mass about 0.002 of that of Earth.
Mean distance from the Sun
5.8 billion km/3.6 billion mi
Equatorial diameter
2,300 km/1,438 mi
Rotation period
6.39 Earth days
Year
248.5 Earth years
Atmosphere
thin atmosphere with small amounts of methane gas
Surface
low density, composed of rock and ice, primarily frozen methane; there is an ice cap at Pluto's north pole
Satellites
one moon, Charon
© Research Machines plc 2008. All rights reserved. Helicon Publishing is a division of Research Machines plc.
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