Betelgeuse, the left most star in Orion's Belt.
Alnitak (or Zeta Orionis) is a trinary star system that makes up the third star in Orion's Belt, and is the location of at least one planet.
In circa 2030, a planet in this system was home to a writer who wrote a classic theme to the words, "Let me help." He recommended those words even over "I love you." (TOS: "The City on the Edge of Forever")
Background
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.