Ninth system
The Spiridon system was the star system in which the planet Spiridon was located.
When the Sixth Doctor initially thought he and Charlotte Pollard landed on Spiridon, he stated it was in the "ninth system" of "a far away galaxy", later called the "ninth galaxy" and later the "galaxy of Antares". (AUDIO: Brotherhood of the Daleks [+]Loading...["Brotherhood of the Daleks (audio story)"])
During the Last Great Time War, the Time Lords believed that the Dalek army from the Spiridon campaign was still frozen on the planet. Recognising the threat of the Daleks excavating this army for use against Gallifrey, it was recommended that reconnaissance TARDISes make regular sweeps of the Spiridon system, and that any increase in Dalek activity on the planet be reported to the War Council immediately so that appropriate action ccould be taken. (PROSE: Dalek Combat Training Manual [+]Loading...["Dalek Combat Training Manual (reference book)"])