T'Khut, or The Watcher, was the third planet in the Vulcan system, and shared a tidally locked co-orbit with Vulcan around a common center of gravity orbiting the star 40 Eridani A - Vulcan and T'Khut were only 149,895.3579 kilometers apart. T'Khut was a Class G, Class H or Class K planet, and had one moon, T'Rukhemai (the "Eye of the Watcher"). (TOS novel: Sarek; ST references: Star Charts, The Worlds of the Federation; Last Unicorn RPG module: The Way of Kolinahr: The Vulcans)