A is for the Altair system, which was recovering from the effects of a recent interstellar war at the time of Spock's pon farr incident in 2267.
B is for Beta Stromgren system. Where sentient space ships go to die.
C is for the Camus system. Where ancient life-energy transference technology was uncovered during an archaeological dig.
D is for Devidia system, wherein strange aliens with orifices where their foreheads should be can transport across time and space with help from an ophidian