Official Setting information is in darkgreen
. Extended Universe information is in steelblue
In 2013, the Unified Government began exploring the galaxy for close-range colonisable planets. Their definition of close-range is within 100 ly of the Solar system. The majority of the Unified Government colonies and the territory traditionally viewed to be within Unified Government control or jurisdiction is this 100 light-year area.
Long-range colonization fleets (specifically the new-Macross class fleets) are routinely sent beyond 100 ly to explore regions of space using Zentraadi star charts, in the hopes of finding colonisable planets. Due to the rarity of finding colonisable planets along their routes of exploration, as well as the sheer distance from Earth, any colonies in this area are generally considered to be outside of Unified Government control. However, due to the nature of their establishment, these colonies tend to be the most tightly boUnified Governmentd to Unified Government jurisdiction; with some not being able to survive without continual input and supplies from the Unified Government.
The core of the Unified Government has a diameter of 50 ly and is 50 ly 'tall.' Near the core of the Unified Government is a 50 ly thick ring extending beyond the core. It too is 50 ly 'tall.'
Sectors 3 through 10 start 100 ly distant from the Solar system, and end approximately 200 ly from Earth. The area within the first 35 to 75 ly (135 to 175 ly from Earth) has been explored the most and has the largest number of colonies. They are all 50 ly 'tall.'
Sectors 11 to 26 begin at 200 ly from Earth. Their outer borders have yet to be placed, but will most likely be 300 to 400 ly from Earth. These sectors have only the most rudimentary of explorations to date, and will most likely not be explored and colonized en mass for another 25 to 50 years. The sectors are the wild frontiers of the Unified Government, and at least one sector is Unified Governmentder the control of a non-Unified Government allied group.
Why 50 ly 'tall'? The Milky Way Galaxy is about 3,000 ly in thick, 80-100,000 ly in diameter, and about 250-300,000 thousand ly in circumference; in other words: expansive, but quite thin. The author has opted for the creative interpretation that in the Orion/Local Arm, the majority of the stars are within 75 ly from the Ecliptic (the orbit of Earth aroUnified Governmentd Sol.)*
Above the 'prime' sectors of the Unified Government are the Roman numeral layer and below are the Greek letter layer. Thus, there is Sector 1, Sector 1I, Sector 1?. The thickness of the Roman and Greek sectors is significantly greater than 50 ly, however the number of star systems drops, and the distance between them increases considerably, the further one travels from the ecliptic.
As the Unified Government is concurrently searching for colonisable planets and Protoculture Ruins (or actual Protoculture beings,) it has decided to focus on the 'prime' layer due to the greater number of star systems; thus the greater chance of success. This is not to say that the Greek and Roman layers are being ignored, they too are being explored, but at a far lower rate.
*Note: not the Galactic_plane, which is actually the proper center-line of the Orion Arm.
© Aaron Sketchley