Justicia was a solar system which was used as a huge prison.
Astronomical Data
Justicia was located near the edge of the Mutter's Spiral, far away from Earth. There were auto-beacons warning all ships which came within two light-years and a deflection barrier which extended ten billion miles. It had three suns and six planets with nearly circular orbits; Justice Alpha, Justice Beta, Justice Gamma, Justice Delta, Justice Epsilon and Justice Prime. (NSA: The Monsters Inside)
History
Justicia was originally used to hold alien criminals, but due to overcrowding amongst the EarthGov colonies, human criminals were also sent to Justicia.
In the late 25th century, the Blathereen discovered another use for Justicia. The position of its planets made it suitable for warp-holes, which they could use to move the entire system and use the suns as means to destroy planets, giving them a supply of spaceship fuel. They slowly replaced people of power and led the research section of Justice Gamma to work out the necessary math. In 2501, the Ninth Doctor and Rose arrived on Justice Alpha and were arrested. The Doctor's skills meant the project could be pushed forward, but the meddling of the Doctor, Rose and three Slitheen lead to the eventual failure of the project and the destruction of the Blathereen criminal empire. (NSA: The Monsters Inside)