|There is more information available on this subject at Orion Arm on the English Wikipedia.|
The Orion Arm, also referred to as the Orion Spur, is a spiral escalation of a minor spiral arm in the Milky Way galaxy that is approximately 3,500 light-years across 10,000 light-years in length. It is located near the galactic core, between the Sagittarius Arm and the Perseus Arm. It is named after the Orion constellation, many stars of which are located within the Orion Arm. The Orion Arm is most notably home to the territories of both humanity and the Covenant.
The Orion complex, the center of the Forerunner ecumene and the location of their homeworld Ghibalb, was located in the Orion Arm. Most of the Orion Arm was under the control of the ecumene until the massive Forerunner-Flood war. The Flood absorbed numerous planetary systems in the Orion Arm. Following the activation of the Halo Array in 97,445 BCE, the surviving Forerunners left the Orion Arm as well as the Milky Way galaxy itself. The Sol system, Earth and humanity's colonial space are within the Orion Arm. During the Human-Covenant War, Insurrectionists and other independent human forces began creating settlements on planets on the Sagittarius side of the Orion Arm. These settlements were not sanctioned by the UNSC. The homeworlds and colonies of the former client species of the Covenant are also found in the Orion Arm. As the Covenant continued to grow, Covenant colonies continued to spread across the Orion Arm.
- Halo: Warfleet, p. 12-13
- Orion Arm on Wikipedia
- Halo: Cryptum, page 222
- Halo Encyclopedia, page 28
- Halo: Fractures, "Coda"
- Halo: Evolutions - Essential Tales of the Halo Universe, "The Impossible Life and the Possible Death of Preston J. Cole", page 340
- Halo Encyclopedia, page 119