The Core Systems, also known as the Core Worlds and The Bubble, are a sphere approximately 150 light-years in radius around Sol in the Inner Orion Spur that contains the bulk of human civilization in the Milky Way galaxy. It is where the Federation, Empire, Alliance, and other powers compete for influence, resources, territory, and control. The Core Systems occupy a volume of approximately 13.8 million cubic light-years, and encompass over 20,000 inhabited systems with over 66,000 Starports, Outposts, Asteroid Bases, and Surface Ports.
Human settlements are considerably rarer outside the bounds of the Core Systems. A few dozen isolated Asteroid Bases have been built in various nebulae. The Pleiades Nebula, California Nebula, Colonia Region, and Witch Head Nebula have become major hubs of expansion since the start of the 34th century. The Core Systems are economically linked to the Colonia Region by the Colonia Connection Highway, a string of various stations and planetary outposts established along the main travel route between the two areas.