Coelest system

Coelest system
Stellar overview
Orbiting planets:	At least 4
Asteroids:	1 asteroid belt
Societal overview
Notable events:	Battle of Installation 05 Great Schism;
Affiliation:	Forerunner ecumene (formerly); Unified Earth Government/Swords of Sanghelios;

The Coelest system is a planetary system located far distant from human- or Covenant-controlled space in the Norma Arm of the Milky Way galaxy.^[1] 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.^[2] There is an asteroid field in the system, at 2.4 AU from Coelest, located close to Substance.^[3]

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, and a small group of UNSC forces on the UNSC In Amber Clad 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.^[4] In the aftermath of the battle and the subsequent end of the Human-Covenant War, the UNSC eventually established a permanent presence in the system with the construction of Lisbon Station, which serves to monitor and guard the now inactive Installation 05.