This system consisted of a primary and nine planets. Primary was named Sigma Draconis. Three planets, Sigma Draconis III, Sigma Draconis IV, and Sigma Draconis VI, were populated by native species. These three planets were classified as M class. The other planets in the system - Sigma Draconis I, Sigma Draconis II, Sigma Draconis V, Sigma Draconis VII, Sigma Draconis VIII, and Sigma Draconis IX - were not M-class. There were surveys and long-range scans of this system. Information on the system was stored in the library computers of Federation starships. In 2268, the USS Enterprise entered the system to search for Commander Spock's brain. (TOS: "Spock's Brain")
Presumably, Sigma Draconis system was located in the Alpha Quadrant.
According to the Star Trek: Star Charts (pgs. 19, 44), the Sigma Draconis system was located in Sector 004 (Sigma Draconis sector).
The Enterprise returned to the Sigma Draconis system and discovered a planet composed entirely of liquid in the Ninth UK Story Arc. It continued exploring the system in the Tenth UK Story Arc, discovering it to be a theater of warfare in the conflict between the Eldorians and the Norusians.