Star Trek: 10 Worlds You Will NEVER Visit
5. Ceti Alpha IV, V, & VI
Captain Kirk, whose body sources tell us is being stored on Daystrom Station for Sha Ka Ree only knows what purpose, once left history's maddest madman Khan Noonien Singh behind on Ceti Alpha V and never went back to check up on him. When Ceti Alpha VI blew up, the previously M-class (ish) Ceti Alpha V shifted in its orbit and became more inhospitable than your Vulcan in-laws.
In 2285, Khan and co. made their escape by commandeering the USS Reliant after two seemingly incompetent, yet highly experienced Starfleet officers beamed down to Ceti Alpha V believing it was VI. Are you still thinking of sending your kids to the Academy? Technically speaking, you can still go to Ceti Alpha V, but when GTN sent Blass, he mentioned an "eel-like creature" before his transmission cut off. He hasn't been his usual energetic, chatty self since.
The rest of this sorry star system isn't much better. In the 2380s, GTN interviewed Malvus, a Mizarian merchant on Starbase 25. After he stopped trying to hawk us some dodgy Data (Lore?) bubble bath, Malvus opened up about the time he was stranded by Starfleet officer Beckett Mariner on Ceti Alpha IV, which was "much worse than Ceti Alpha V".