Orion Arm



The Orion Arm 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 and is part of the Sagittarius Arm (a major arm). It is also referred to as the Local Arm, Local Spur, or the Orion Spur. It is named "Orion" due to its proximity to the Orion constellation.

The Orion complex, the center of the Forerunner ecumene and the location of their homeworld Ghibalb, was also located in the 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 100,000 BCE, the Forerunners left the Orion Arm. The Sol system and Earth are within and amid the Orion Arm. By 2490, UNSC colonial space encompassed over 800 planets and colonies ranging from small outposts to large, important military strongholds in 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. Most of the homeworlds of the former client species of the Covenant were found in the Orion Arm. As the Covenant continued to grow, Covenant colonies continued to spread across the Orion Arm.