Mutter's Spiral

Mutter's Spiral is the Time Lord designation for the galaxy in which the Sol system is located. Humans know Mutter's Spiral as the Milky Way or as Adric referred to it, Galaxia Kuklos. By the time of Sabalom Glitz it also went by the name of the Stellian Galaxy.

Mutter's Spiral is approximately 100,000 light-years in diameter. Together with Andromeda and many other galaxies, Mutter's Spiral comprises the Local Group. Most of the planets visited by the Doctor in his travels have been, or appear to be, in this galaxy.

Planets and other locales located within Mutter's Spiral
In addition to Earth and the other planetary bodies of the Sol system, the following planets and star systems have either been visited by the Doctor and/or his companions, or have been mentioned in the various Doctor Who stories. They are either definitely located within Mutter's Spiral, or may be reasonably inferred to be:

Problematic Continuity

 * Some early BBC publicity placed Skaro within Earth's galaxy, but the majority of fans and authors agree that the Daleks' homeworld is located in another galaxy altogether.
 * 1960's and 1970's Doctor Who television writers, in particular, would frequently misuse astronomical terms, such as constellation and galaxy. These confusions have gotten integrated into established continuity.
 * Dialogue in Terror of the Autons implies that Gallifrey may lie within this galaxy, but the designation of Mutter's Spiral first given in The Deadly Assassin, and a location of "250 million light-years away" given in the 1996 television movie both indicate that Gallifrey is also located elsewhere in the Universe.
 * The fact that Serenity is a Trakenite colony would indicate that Traken was located in Mutter's Spiral, but this seems to contradict "Logopolis," in which Adric notes that, "Earth's galaxy still has a few hours left," just before Nyssa sees the entropy field consume her homeworld, thus indicating that the Traken Union was located in another, nearby galaxy. Possibly the Trakenites had advanced far enough to venture outside the confines of their own galaxy before their civilization was destroyed.

Resources

 * Encyclopedia of the Worlds of Doctor Who A-D, by David Saunders, Knight, 1988. ISBN 0-340-42842-2
 * Encyclopedia of the Worlds of Doctor Who E-K, by David Saunders, Knight, 1989. ISBN 0-340-51106-0
 * Encyclopedia of the Worlds of Doctor Who L-R, by David Saunders, Picadilly, 1990. ISBN 1-85340-081-5
 * The Doctor Who Programme Guide, by Jean-Marc and Randy Lofficier. iUniverse, 2003. ISBN 0-595-27618-0 Original edition often cited as inaccurate.
 * I, Who: The Unauthorized Guide to Doctor Who Novels, by Lars Pearson. Sidewinder Press, 1999. ISBN 0-9673746-0-X