Pluto

Pluto is a dwarf planet in the Solar System that serves as an interplanetary jail in the Solar System.

Description
Pluto is the largest object found in the Kuiper Belt. It comsists of two major bodies, Pluto and Charon, which orbit a common barycenter, and four small moons on chaotic orbits, named Styx, Nix, Kerberos and Hydra in distance order. The surface of the planet is covered in frozen nitrogen.

Pluto was precovered in 1909 and identified as a Solar System object in 1930. However, its size was greatly overestimated, being thought of having an Earth-like mass. In 2006, when its small size and irregular orbit became evident, Pluto, along with some other Trans-Neptunian objects, got classified as a so called "dwarf planet", a planet-like object whose orbit is not cleared enough to count the object dominant.

In the year 2550, when the crime rate in the outer Solar System became insanely high because of aliens introducing themselves to the Solar System, the Triton democracy chose to create an interplanetary jail. It opened in they year 2569 on Pluto. It is currently located underneath its surface of the southren hemisphere.