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.


 * In retrospect, the reference to Pluto being a planet is an anachronism, since it was stripped of planetary status in 2006.
 * K-9, who references Pluto being a planet, is from the year 5000; presumably at some point before then the demotion was rescinded, or new criteria for determining planetary status established. The reference to a 10th planet, Cassius, might support the latter argument, as none of the formerly-planet-sized bodies found beyond Pluto in real life, such as Eris, would appear to have qualified as a 10th planet.