Crow's Eye Nebula
From Halopedia, the Halo wiki
As early as December of 2553, the Office of Naval Intelligence research and development plant, Argent Moon, was located within the nebula. After an outbreak of asteroidea merozoite killed everyone on the station in March of 2557, Argent Moon's "smart" A.I., Rooker, made sure to put it on a course that would keep it away from all inhabited systems. Kig-Yar scavengers found it within an asteroid field in October of 2558 and sold what they knew to Jul 'Mdama, who wasted no time sending forces to the Crow's Eye Nebula to occupy it. One week later, Spartan-II Blue Team deployed to the nebula in order to secure Argent Moon for the United Nations Space Command once more but ended up destroying it instead due to the arrival of a Covenant fleet.