Capella IV

Capella IV was the inhabited fourth planet orbiting the primary Capella. The planet was located close to the Klingon-Federation border. It was the homeworld of the Capellans, a pre-warp humanoid species, as well as the Capellan flower and the Capellan power-cat.

In the mid-23rd century, Capella IV was valued by both the Federation and the Klingons for its rich deposits of topaline. 

Leonard McCoy was briefly stationed on Capella IV in the mid-2260s. 

In 2267, the planet served as a pawn in the Federation-Klingon Cold War, during a trade dispute between the Klingons and the Federation over topaline mining rights. The crew of the USS Enterprise (NCC-1701) was able to secure the rights for the Federation. 

In 2293, the location of Capella in the Milky Way Galaxy was labeled in a star chart that was in James T. Kirk's quarters aboard the USS Enterprise (NCC-1701-A). (, okudagram)

Background information
In the first draft of the script (dated ), Capella IV was called "Ceres VII", and the Capellans were called the "Cereans". The script described the planet as "a small planet that is predominantly greenish-blue, with red seas."

Capella IV is one of only two planets in The Original Series whose surface was depicted both on location (at Vasquez Rocks) and on Desilu Stage 10. 

Capella IV was given a "face lift" for the remastered version of "Friday's Child", with a digital planet replacing the stock footage from the classic episode.

Both and the  classified Capella IV as a class M world. According to The Worlds of the Federation, the Capellans refer to their world as "Kohath".

According to Star Trek: Star Charts (pp. 33, 37 & 47) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the Capella IV (Alpha Aurigae IV) system was located in the Alpha Quadrant. Capella IV was ruled by the Ten Tribes of Capella, and was established as a protectorate of the Federation in 2267. The dominant species were the humanoid Capellans. In 2378, there were an estimated 160,000 Capellans living on the planet. A major attraction of the planet was the tomb of Leonard James Akaar.