orbit:    5,913,520,000 km (39.5 AU) from the Sun        diameter: 2274 km

 Pluto is the only planet that has not been visited by a spacecraft. Even the  Hubble Space Telescope can show only the largest features on its surface.

 Pluto has only one satellite, Charon.

 Pluto's orbit is very different. At times it is closer to the Sun than Neptune (as it was from January 1979 thru February 11 1999). Pluto also rotates in the opposite direction from most of the other planets.