Sontar

Sontar, sometimes called Sontara, was the home planet of the Sontarans.

Astronomical data
Sontar originally orbited its star like any other planet, but by 1609 it had been modified so that the star orbited Sontar, as a more "logical" pattern. (PROSE: The Empire of Glass) Sontar had gravity six times greater than Earth. This was said to be why the Sontarans developed such strong physiques and muscles.

Sontar had large octagonical structures on its surface. (WC: Captain Jack's Monster Files: Sontarans, COMIC: Pureblood) According to one account, Sontar appeared red when seen from space. (WC: Captain Jack's Monster Files: Sontarans) Another account showed it green, with vast metal structures covering whole continents. (COMIC: The Betrothal of Sontar)

Somewhere on the planet was the Hall of the Fallen and the Brave. (TV: The Last Sontaran) There were also desert areas, inhabited by Sontar Sand Shrews. (PROSE: The Sontaran Games)

History
The name Sontar was included in the Sontaran battle chant, "Sontar, ha." (TV: The Sontaran Stratagem)

By the 17th century, the Sontarans had moved their star system so that their star orbited Sontar. (PROSE: The Empire of Glass)

Circa 2009, the Sontarans chanted the name of their world to work up a battle-frenzy. (TV: The Poison Sky)

Circa the 25th or 26th century, the Sontarans' enemies, the Rutans, destroyed Sontara with photonic bombs, leading to the dispersal of Sontaran troops across their home galaxy of Mutter's Spiral. (COMIC: Pureblood)

Donna's world
In the parallel world where Donna Noble never met the Tenth Doctor, Captain Jack Harkness and Torchwood Three stopped the Sontaran fleet. The Torchwood team were killed and Jack Harkness was transported to Sontar. (TV: Turn Left)