Orion Arm (Earth-5875)

The Orion Arm, also referred to as the Orion–Cygnus Arm and the Orion Spur, is a minor spiral of the Milky Way galaxy. Being approximately 3,500 light-years across 10,000 light-years in length, the Orion Arm is located near the Galactic Center, between the Sagittarius Arm and the Perseus Arm. The Orion Arm is home to territories belonging to humanity, the former Covenant species, and the xenomorphs.

History
The Orion Arm, much like most of the Milky Way galaxy, was home to thousands of worlds under the governance of the forerunner Ecumene until the Forerunner-Xenomorph War, which saw the loss of most forerunner worlds for the xenomorphs and their infection. After the activation of the Halo Array in 97,445 BCE, the forerunners and all life in the galaxy was extinguished, aside from the species sheltered in the Ark and the xenomorphs left at the Halo Array.

The Orion Arm is home to humanity, Earth and its colonies, as well as that of the Covenant. Through the First Contact War, some Insurrectionist cells started to establish independent settlements on planets at the Orion/Sagittarius Arm borders.