Cepheus was a star system with one planet, Terra 10. This system was located near the gas cloud of the nova Arachna. The nearest starbase was Starbase 23. This star was located less than 90 light years from the Sol system.
Prior to stardate 5577, no radio transmissions were ever produced in this system. In 2269, an intersat code message was transmitted from Terra 10. It was later determined by the USS Enterprise that an Earth expedition had established a colony on the system's only planet. The colony was later evacuated to a new planet, Verdanis. (TAS: "The Terratin Incident")