Pluto

Pluto and Charon, catch without realist
brightness taken since SpaceEngine.

Pluto is a dwarf planet discovered in 1930 by american astronomer Clyde William Tombaugh, it is a TNO (Trans-Neptunian object), that is, it is beyond the orbit of Neptun, also is the object biggest of the Kuiper Belt.

Pluto has a mass of 0,002185 M⊕ (1.25×10²² kg) and a diameter of  0.18579 D⊕ (23995 Km), therefore, its density is 1.88 g/cm³.

Its orbital period is 248 years, however as it has a very eccentric orbit, Pluto is closer the Sun than Neptune for 20 years (at perihelion), during the rest of the time Pluton is farther from the sun than Neptune.

Pluto has 5 Satellites, these are: Charon, Styx, Nix, Kerberos, and Hydra. The largest satellite pluto is Charon and both form a binary system. 

(if you want to know more about the binary system of Pluto and Charon press here).