It is about 40 times the Earth-Sun distance from the Sun...some 3.6 billion miles, and orbits the Sun every 249 years. It is 2300 kilometers in diameter and has a density of about 2 gm/cc which means it is an icy body with little rocky material in it.
Pluto has a single satellite called Charon ( pronounced Sharon) and orbits the planet every 6.4 days (see above Hubble Space Telescope image). It faces the planet the same way our Moon does, always showing the same face to Pluto. Charon seems to be rich in water ice, but no methane or ammonia, is present. Its diameter is only 1186 miles, and its mass is insufficient to hold an atmosphere.
Pluto does have a tenuous atmosphere of methane, but Pluto is too small to retain it and it must be continuously leaking away as it is generated from the methane ices on its surface which are 'sublimating' into gas without passing through a liquid state at all, at these low pressures.
The Hubble Space Telescope recently photographed the surface of Pluto but shows only large splotches of light and dark areas. Visit the Space telescope Science Institute and follow the links to their collection of recent photographs in their photo archive. Or click here for a picture and a summary.
For an extensive summary of Pluto, visit NASA's Pluto Express Science Page
Copyright 1997 Dr. Sten Odenwald
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