"Low density" plasma region of space left by former supernova some tens of millions of year ago. Approximately equivalent to the Inner Sphere.
- Bubble (astronomy) - Text by M. Alan Kazlev
A roughly spheroidal shell of interstellar gas blown outward from a star by a stellar explosion or strong stellar wind. Large bubbles are caused by supernova explosions and contain gas that is much hotter but also much more diffuse (about one atom per cubic cm) than that of the surrunding interstellar medium. These are also called loops.
- Bubble (galactography)
- 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.
- Orion Arm, Orion Spur