The spiral arm or, more accurately, spur of our galaxy in which is found the Inner Sphere, Middle Regions and much of the Outer Volumes of the Terragen Sphere. Also called the Orion Spur or Local Arm. A fairly minor arm.
Local Arm - Text by M. Alan Kazlev The arm of the Milky Way Galaxy where most of Terragen civilization is still located, and which includes the Sol System. It is also called the Orion Arm.
Local Bubble - Text by M. Alan Kazlev "Low density" plasma region of space left by former supernova some tens of millions of year ago. Approximately equivalent to the Inner Sphere.