Cepheus was the primary of a planetary system. Located near the gas cloud of the nova Arachna, this star was orbited by one planet, Terra 10. The nearest starbase was Starbase 23.

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")

According to, Cepheus and Arachna were in the same sector.