Alnitak (Zeta Orionis) was a planetary system. This was a trinary star system. There was an inhabited planet in this system. This unnamed planet was the homeworld for a civilization that was known to the Federation in the mid-23rd century. Alnitak was the far left star in Orion's Belt, an asterism of the constellation Orion. In 1930, Captain James Kirk pointed this star out to Edith Keeler. (TOS: "The City on the Edge of Forever")
A triple star located in the constellation Orion, this system's name was not explicitly mentioned, since Kirk simply pointed to the system and noted its location in the constellation. While we know which star he must have meant, it wasn't clear which nomenclature might be more commonly used, the older usage Alnitak or the constellation catalog name, Zeta Orionis.