Cluster Compound
Cluster Compound is an arena in CQC Championship. It features an arena in a vast and dense asteroid field, making it a deadly battleground. It was the the third confirmed arena. [1][2]
This arena is located in the Eta Cephei system, specifically within the A Ring of the first planet. Being an exploited system of Zachary Hudson, it is only 47 light years away from Sol. It has a population of 256,477, aligned with the Federation, Democratic, has a refinery and colony economy, and it is a real star (HIP 102422/HD 198149).
It likely can't be visited in-game because no marker shows up for it, although just because there is no marker doesn't mean it can't be visited. It could still be in there, and there is no consensus on this since no one has tried to comb the whole ring system.