Light-year

A light-year was a unit of measurement used to measure interstellar distance. It was quantified as the distance that light travelled in a vacuum over the course of an Earth year. Time could be further measured as light-centuries. (DW: The Ribos Operation)

Known Distances

 * The Ao constellation and Qqaba were 9.6 light-years from Gallifrey. (NA: Lungbarrow)
 * Vega 3 was 27 light-years from Earth. (AK9: K9 and the Beasts of Vega)
 * Aldebaran II was 65 light-years from Earth. (BBCR: The Paradise of Death)
 * Sunday was 100 light-years from Earth. (NSA: Wetworld)
 * Beta Caprisis was 100 light-years from Earth. (NA: Sanctuary)
 * Ribos was 300 light-years from the Magellanic Clouds. (DW: The Ribos Operation)
 * Bellatrix was 324 light years away from Earth. (NA: Nightshade)
 * gger was 500 light-years from Earth. (DWAN: Listen - The Stars)
 * Crimson Heart was 10,000 light-years from Earth. (SJA: Death of the Doctor)
 * The Orpheus constellation was 10,000 light-years from Earth. (K9TV: Aeolian)
 * Gallifrey was 30,000 light years from Earth. (PDA: The Devil Goblins from Neptune)
 * Gorgos was 100,000,000 light-years from Earth. (SJA: Eye of the Gorgon)
 * The Second Doctor once dematerialised the TARDIS 4 quadrillion light-years from the nearest galaxy. (DWAN: When Starlight Grows Cold)

Known Measurements

 * The Mutter's Spiral galaxy was around 100,000 light-years in diameter. (NSA: The Eyeless)
 * The Morestran empire spanned 80,000,000 light-years. (PDA: Zeta Major)