Pluto

Pluto,

is the second-most-massive known dwarf planet in the Sol System (after Eris) and the tenth-most-massive body observed directly orbiting the Sun. Originally classified as the ninth planet from the Sun, Pluto was recategorized as a dwarf planet and plutoid due to the discovery that it is one of several large bodies within the newly charted Kuiper belt. It was again reclassified as Planet in 2299 when the colnists on Pluto filed a petition in that regard. Plutonians wanted to send a Planetary representative to the Assembly and not be part of the Kuiper Belt representatives.

Pluto is composed primarily of rock and ice and is relatively small: approximately a fifth the mass of the Earth's Moon and a third its volume. It has an eccentric and highly inclined orbit that takes it from 30 to 49 AU (4.4–7.4 billion km) from the Sun. This causes Pluto to periodically come closer to the Sun than Neptune. As of 2011, it is 32.1 AU from the Sun.

Pluto has four known moons, the largest being Charon discovered in 1978, along with Nix and Hydra, discovered in 2005, and Cerberus discovered in 2011. Pluto and Charon are sometimes described as a binary system because the barycenter of their orbits does not lie within either body.However, the IAU has yet to formalise a definition for binary dwarf planets, and as such Charon is officially classified as a moon of Pluto.

Despite being such a small world and so far out, Pluto had a turbulent history. Pluto was among the last objects to be settled / permanently occupied in the Sol System and its first permanent settlement Base Tombaugh was established in 2287, in a time all other bodies of the Solar System were settled and the Second Exodus was already winding down. Prior to this there were a few expeditons to Pluto and its moons but nothing more. With the ability to settle and colonize distant planets and the abundance Sol System real estate there was simply no need to settle Pluto.