The Sheliak homeworld was an inhabited planet in the Shelia system. This was the homeworld of the non-humanoid warp-capable Sheliak and the capital world of the Sheliak Corporate. It was quite distant from Tau Cygna V.
In the 2255 Treaty of Armens, one of the provisions stated that if a Corporate spacecraft was located five thousand light years from its home world, the captain could request assistance from a third party. (TNG: "The Ensigns of Command", okudagram)