A Class M planet with two large landmasses, used for the first trial of Dr Richard Daystrom's M-5 multitronic computer in The Ultimate Computer.
Alpha Carinae II appears in the Original Series episode The Ultimate Computer. With most of the Enterprise crew sent ashore and the M-5 computer installed to run the ship, the first exercise in the test programme is an approach to the planet and a routine survey.
The M-5 puts the ship into orbit, analyses the planet and makes landing party recommendations faster than the officers can. Its choices differ from Kirk's. It prefers a junior geologist with experience of similar worlds, and it leaves out both the captain and Dr McCoy as non-essential personnel.
Kirk is stung by the judgement, and the smooth performance seems to bear out Daystrom's claims. The later stages of the trial go badly wrong when the machine destroys an ore freighter and attacks the starships sent for war games.