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, the planet Krop Tor orbited it. The Doctor and Rose Tyler arrived in the TARDIS on a base drilling through the planet looking for what is keeping it away from being dragged in. The Beast was imprisoned inside a 'pit' by an ancient race. The Doctor eventually killed the beast, causing the planet to be dragged in.