Core Worlds
From FEInfobase
The Core Worlds are actually a collection of star systems close to the heart of the Federation - namely, Earth and the surrounding area. Early human colonies and founding Federation member worlds, these are the planets which were left strongest at the end of the Borg War. For political strength, population numbers, and resources to offer, they are the most valuable planets to the reforging of the Federation. As such, not only do they enjoy the greatest luxuries - a comparable term when discussing the state of the Quadrant following the damage wreaked by the Borg - available in the Federation, but they also have the highest population counts, the most powerful industries, and, perhaps most importantly, the greatest defence from Starfleet.
History
Following the War, the Federation spent many years with its focus solely on Sol, and primarily just on Earth, but as the borders of Sol have remained safe from threats for some time now, it was hard to argue against the outcry to remove the so-called 'blinkers' from the higher echelons of government and Starfleet Command, and look back to the greater galaxy. Thus there is talk of expansion of administrative hubs within Starfleet and the Federation, of not centralising everything on Earth as much as has been done over the last six years.
Defences
The First Fleet has been assigned and expanded to meet this new structure of the Federation; no longer solely focused on the Sol System, they are the defenders and border patrollers of the Core Worlds. Starfleet bases of operations are being built, rebuilt, and towed to important strategic points, usually locations where such bases had been in place for centuries.
The Systems
The five star systems of the Core Worlds are as follows: