Pluto.
Pluto usually orbits beyond the orbit of Neptune. It is smaller than any of the "dwarf planets". Pluto is also smaller than seven of the solar system's moons (the Moon, Io, Europa, Ganymede, Callisto, Titan and Triton). _ Pluto has a satellite, Charon. There has recently been considerable controversy about the classification of Pluto. It was classified as the ninth planet shortly after its discovery and remained so for 75 years. But on 2006 the IAU decided on a new definition of "planet" which does not include Pluto. Pluto's orbit is highly eccentric. At times it is closer to the Sun than Neptune. Pluto rotates in the opposite direction from most of the other planets. The surface temperature on Pluto varies between about -235 and -210 C