P3A-707 was a planet in the Milky Way galaxy, which Dr. Daniel Jackson suggested SG-1 travel to after escaping Hadante, but he ruled it out and choose P2A-509 instead. (SG1: "Prisoners")
Daniel's comment "P3A-707 might work, but there's no telling how long we'd be there before -" seems to imply that it is an isolated world or there were no missions scheduled to visit it in the near future.