In the pre-universe, stars were doughnut-shaped. (PROSE: Millennial Rites) When the universe was rationalized 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)
Stars gave off a wide range of radiation, including ultraviolet light, visible light and more dangerous radiation. (PROSE: The Sons of the Crab) Stars of sufficiently large size would destroy themselves in a supernova.
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) and 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 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)