Mutter's Spiral

Mutter's Spiral is the Time Lord designation for the galaxy in which the Sol system is located. (NA: Human Nature, EDA: Alien Bodies) Humans know Mutter's Spiral as the Milky Way or as Adric referred to it, Galaxia Kyklos. By the time of Sabalom Glitz it also went by the name of the Stellian Galaxy. (DW: The Mysterious Planet)

Mutter's Spiral is approximately 100,000 light-years in diameter. Its nearest significant neighboring galaxy is the Andromeda Galaxy, however it is also surrounded by several nearby minor satellite galaxies, such as the Sculptor Dwarf Galaxy (AKA Galaxy Seven).

Planets and Star Systems
The following planets and star systems 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 (and some of the 1960s books and annuals actually within the Sol system) but many fans and authors agree that the Daleks' homeworld is located in another galaxy altogether.
 * Doctor Who television writers, particularly in the 1960s and 1970s, frequently misused astronomical terms such as constellation and galaxy. These confusions were later integrated into established continuity.
 * 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