Expanded Colonies refers to newer colonies that are farther from the reach of the Key Worlds. The few colonies in the Expansion Region resented more prosperous worlds and wanted to strike against them with private militias and stolen weapons. These tensions would boil over into the Colony Wars.
Mithras is a world in the Luyten system. It is unique in that its orbit borders both the Prosperous and Expanded Regions. This has led to disputes about where the loyalties of its government lies, though Mithras sees itself to be outside the Circle of Prosperity.
Chiron III is a planet in the Teegarden system. It is the third planet from its star.
Gliese is a colony in the Gliese 667C system. It is also the third planet from its star. Gliese was the base of operations for the shadow government that rose up against the UCG - One Liberty. By consolidating the private military forces of each of the Expanded Colonies, the government ensured the Colony Wars would last to inflict as much damage as possible to the PALM forces of both the Key Worlds and the Prosperous Colonies.
Aurora is the only world in the TRAPPIST-1 system inhabited by humanity. While the majority of the colony used to be covered in water, the newly-developed terraforming technologies of the post-war UCG has allowed Aurora to transform into a popular holiday destination for civilians who are willing to travel to the farthest edge of Human Space.
Next week, we will take a look at the some of the characters from The Stars of Aspiria...