Coelest system

The Coelest system is a planetary system previously located outside human- or Covenant-controlled space. It is home to the ice giant Substance, which serves as the gravity anchor for Installation 05. Substance is the fourth planet in the system, and is located in its outer reaches. There is an asteroid field in the system, at 2.4 AU from Coelest, located close to Substance.

In early November 2552, the system became the site of the enormous Battle of Installation 05 as the Covenant holy city of High Charity, its defensive fleet, a small group of UNSC forces on the arrived at Installation 05. Over the course of the battle, the Flood on the installation escaped containment, and the ring was sterilized by the combined High Charity defensive fleets as a result.

Locations

 * Substance
 * Installation 05
 * Opusculus

List of appearances

 * Halo 2
 * Halo: Ghosts of Onyx
 * Halo 2 Anniversary