Mutter's Spiral was the Time Lord designation for the galaxy in which the solar system was located. (TV: The Deadly Assassin, et. al.) Humans knew Mutter's Spiral as the Milky Way or as Adric referred to it, Galaxia Kyklos. (TV: Four to Doomsday) By the time of Sabalom Glitz, it also went by the name of the Stellian Galaxy. (TV: The Mysterious Planet) At least one Gallifrey-based robot — K9 Mark II — recognised the galaxy both by the name "the Milky Way" and by "Mutter's Spiral". (WC: Shada)
Mutter's Spiral was approximately one hundred thousand light-years in diameter. Its nearest significant neighbouring galaxy was the Andromeda Galaxy. It was also surrounded by several nearby minor satellite galaxies, such as Galaxy Seven, (PROSE: The Eyeless) and the two dwarf galaxies the Larger Magallenic Cloud and Smaller Magallenic Cloud (AUDIO: The Last Voyage).
The Doctor frequented Earth, a planet in Mutter's Spiral. (TV: An Unearthly Child, et al.) On one occasion, Earth was moved out of the galaxy to the Medusa Cascade by the Daleks. (TV: The Stolen Earth)
Tivoli was the most conquered planet in this galaxy, leading to its inhabitants (like Gibbis) welcoming invasion and subjugation. (TV: The God Complex) Other sources claimed that Earth was the most invaded, not only in the Mutter's Spiral but in four more galaxies. (PROSE: Borrowed Time)
The Akoshemon system, and indeed its planets such as Akoshemon itself, were located right on the very edge of this galaxy, so much so that from Akoshemon's moon you could see the gap between this galaxy and its nearest one. (PROSE: Fear of the Dark)
Planets and star systems
Mutter's Spiral was divided into four quadrants. In the Third Quadrant there were at least 8,023 sectors, with Sector 8023 containing Earth. (TV: Logopolis) Another sector was the Kappa Galanga sector, which contained the Lasron solar region. (PROSE: Prisoner of the Daleks) There were several galactic arms, including the Perseus arm where Mogar was located, (TV: Terror of the Vervoids) a western arm (PROSE: Between the Wars: A Slow Night in Paradise) and a secondary and tertiary arm (PROSE: Burning Heart).
- Main article: Galactic law
There were several forms of galactic government. The Galactic Alliance was one governing body. (TV: From Raxacoricofallapatorius With Love) It was also under the dominion of the Shadow Proclamation. (TV: The Stolen Earth)