Theory:Doctor Who television discontinuity and plot holes/The Sun Makers


 * How will the liberated humans prevent the artificial suns from burning-out now that the Usurian controlling them has been dispatched?
 * The Doctor could have shown them how before leaving. It's also possible the Usurian was lying, to make the people believe they needed him.
 * Unlikely as he talked about it to the doctor, describing them as ineficent.
 * At the end the doctor tells them to leave pluto and return to earth, as its stated that the suns will last for a few years before buring out, its likely this is why he told them to leave.