K37 Gem 5

K37J5 is the designation of a black hole seen in The Impossible Planet, and The Satan Pit. Against all laws of Physics, a planet orbited it. The Doctor and Rose Tyler arrived in the TARDIS on a ship drilling through the planet looking for what is keeping it away from being sucked in. A Beast was trapped inside a 'pit' by an ancient race. The Doctor eventually killed the beast, causing the planet to be sucked in.