Doctor Who: The Sun Makers

The TARDIS, along with the Doctor, Leela and K-9, arrives on Pluto in the distant future. The time travelers discover the planet has a breathable atmosphere and enjoys heat from six small suns, but the humans who live there are taxed and exploited heavily for the privilege. When Leela is captured and sentenced to death, the Doctor must save his companion, as well as stopping the ruthless Company, before it is too late.