In the pre-universe, stars were doughnut-shaped. (PROSE: Millennial Rites) When the universe was rationalised they became spherical. (TV: The End of the World, 42, Amy's Choice, The Rings of Akhaten)[additional sources needed] In the after-universe, the stars were spherical, but usually green. (COMIC: The Stockbridge Child)
In general, only more advanced species were capable of manipulating or using stars.
The Time Lords were capable of controlling stars to their own ends. They used stellar manipulators like the Hand of Omega to control stars. (TV: Remembrance of the Daleks) The Tenth Doctor said they invented black holes. (TV: The Satan Pit) They used the black holes to power their time travel. (TV: The Three Doctors, The Deadly Assassin)
The Great Old Ones could be returned to their bodies by the positions of the stars. Unfortunately for them, the constant expansion of the universe meant the stars would never return to their proper positions. (PROSE: White Darkness)
Other references Edit
The reality bomb caused the destruction of all reality, making the stars seem to "go out". (TV: Turn Left, Journey's End) The total event collapse, the destruction of the universe, caused every star to supernova. (TV: The Pandorica Opens) The stars went out when the Great Intelligence invaded the Doctor's time stream to turn all of his victories into defeats; this was witnessed by Madame Vastra on Trenzalore. (TV: The Name of the Doctor)