JT227 was a source of the rare element Promethium 62, which proved to be the Second Great and Bountiful Human Empire's salvation in the Third Dalek War.
History
Spindroids were used to mine the planet as it was radioactive, constantly guarding it from space in satelites that ringed the planet. Humanity's discovery of Promethium 62 meant that the Daleks were at last retreating from Human space, as it helped to break Dalek forcefields, forcing the Daleks out of star system out of system. However, the Daleks found the source of the element, JT227. The Daleks arrived and appeared from hyperspace in the parts of every one of the 200 satelites orbiting JT227. Causing the Spindroids to go on full alert and fight the Daleks faster and harder the Humans ever could. The Daleks only managed to breach a few of the satelites, although the Promethium hardened casings of the Spindroids couldn't withstand Dalek firepower well, they were soon able to destroy the Daleks armed with blasters of their own and deadly blades. The disasterous defeat caused the Daleks to vanish from the Human front. (DWBIT: #55)