In Greek mythology, Pluto was the god of the underworld. The planet recieved this name probably because it is so far from the sun that is dark almost constantly. Or perhaps because the first two letters-"PR"-are the initials of Percival Lowell, the person who discovered the planet.
This planet is sometimes know as a double planet because Pluto and its moon, Charon, are both similar in size.
Pluto's orbit is highly eccentric. At times, it is closer to the sun than Neptune. Right now, it is and will continue to be until 1999. Although the orbits of Pluto and Neptune cross each other, they will never collide. Pluto rotates opposite direction of all the other planets.
Pluto is composed of 70% rock and 30%water ice. It's surface temperature is probably between 35 and 45 Kelvins (-228 to -238 Celcius). The atmosphere probably consists of mainly nitrogen with some methane and carbon dioxide.
The similarities between Triton and Pluto suggest some historcal conection.
