Coelest (Earth-5875)

The Coelest system is a distant planetary system, much farther than any human system or known former Covenant-controlled systems, in the Norma Arm of the Milky Way galaxy. The system is home to the ice giant Substance and Installation 05, which orbits it, as well as a massive asteroid field at  2.4 AU from Coelest.

History
In November 2552, the Coelest system was home to the Battle of Installation 05 between the Covenant's holy city High Charity, its Second Fleet of Homogenous Clarity, and the crew of the UNSC In Amber Clad over control of Installation 05. One day later, the xenomorphs that were stored at Installation 05 escaped from their containment and invaded High Charity, leading to the fall of the city and the death of most of its inhabitants; Installation 05 itself was later glassed by the Swords of Sanghelios' Fleet of Retribution to stop other xenomorphs from escaping.