Tau Cygna V was the inhabited H-class fifth planet in the Tau Cygna system. This system was located over 5,000 light years from the Sol Sector, within the de Laure belt. According to Section 133, Paragraph 77 of the Treaty of Armens, the planet had been ceded from the Federation to the Sheliak Corporate in 2255.
In 2274, the SS Artemis landed on the planet's surface. One third of the crew and passengers died of the hyperonic radiation. The survivors established a new colony. In 2366, the population had reached 15,253 Humans, which, however, had to be evacuated, due to the Sheliak claim on the planet. After the evacuation, the Sheliak established their colony on the planet. (TNG: "The Ensigns of Command")