Address

From SGCommand

Addresses are the symbols needed to establish a wormhole with the Stargate. Stargate addresses within a galaxy are composed of seven symbols: six constellations representing a point in space, while the seventh represents the point of origin. (Stargate)

Addresses can not contain point of origins.

Because of stellar drift, Dial Home Devices contain automatic update transceivers which allow for new locations to be fixed. This correlative update system will dial at unknown intervals to relink with the rest of the Network. However, as the DHD and Stargate were discovered separately, the Tau'ri had no way to account for the 10,000 year old addresses the Goa'uld had cataloged when they left. Abydos and Heliopolis were the only two still close enough to establish a wormhole to. Stargate Command was able to over come this with a supercomputer that located the new addresses, turning out two or three every month. However, even with all six symbols, there are still 720 possible permutations available. (SG1: "Children of the Gods", "Watergate", "Avenger 2.0") (ATL: "Rising") The planet designations given by the Tau'ri are based on a binary code used by the computer for extrapolation. (SG1: "The Broca Divide")

It is possible to establish extragalactic wormholes, but this requires a seventh additional constellation, bringing the total number of symbols to eight. (SG1: "The Fifth Race") (ATL: "Rising")

A ninth symbol has not yet been seen to be used, but is known to connect to specific Stargates, instead of specific locations, such as the one aboard the Ancient ship Destiny. (Stargate Universe)

The Ancients have pronunciation for the symbols allowing them to speak any gate address. Sometimes they would name the planet after it's address. (SG1: "Lost City, Part 2")