The Five Worlds

The Five Worlds are a set of five star systems in the Milky Way galaxy that have a human presence, which include Sol (our star), 130 Piscium (Natak / Akash), 71 Andromedae (Bolarui), 201 Aquarii (Tabaaler) and HR 2431 (Tonzierke). All of the stars are located within 500 parsecs of Sol.

Discovery
The first of the worlds to be discovered was Kishiv (130 Piscium D, the fourth planet in the 130 Piscium system) in 2078, after an archaeological colony based on the Moon unearthed a large, 20-meter-tall obelisk buried deep within the Martian soil. Carbon dating revealed that the obelisk was about 3 million years old, and the obelisk appeared to have a control panel on it that had five buttons arranged in a circle. One of the younger researchers studying the artifact, Alec Feist, pressed one of the buttons, which caused him and all of the researchers within fifty meters of the obelisk (about five people, since most of the other researchers were at the base at the time) to be transported to a similar obelisk on the planet known as Kishiv.

Obelisks
Main article: Obelisks

The obelisks, sometimes called pillars or gates, are a set of five monuments built by a very old civilization known simply as the Ancients that allowed early travel between the five worlds. The obelisks were studied in great detail after their discovery; they contain scriptures in the language of the Ancients (known in the linguistic community as Ancient Common, as it's considered unlikely that they spoke only one language). The obelisk on the Moon is the only one to not exist on an inhabited planet. They were used exclusively for inter-world travel until 2102, when the warp drive technology left behind by the Ancients was recovered and successfully reverse-engineered.

The worlds and their characteristics
All of the worlds are considered "Earth-like"; that is, they are all within the circumstellar habitable zone, have the same gravitational pull as Earth, have large moons, their atmospheres are similar, and their flora and fauna are similar to Earth's. Each planet, however, has a unique characteristic or two that separates it from the others:
 * Earth: is the only world that doesn't have an obelisk directly on it (it's on the Moon instead), and also has the highest amount of CO2 in its atmosphere out of any of the planets.
 * Kishiv: the first world to be discovered by the Terrans. It has the longest year, at 1.6 earth years, and has the lowest racially-motivated crime rate amongst its registered citizens out of all of the worlds, due to a lack of racism in general.
 * Ishnakei: well known for its humans being very racist towards the humans of the other worlds. They are also the only world with a second intelligent species, the Alcatān.
 * Doleeshi: known for its inhabitants being extremely aggressive and war-like. They almost started a war with Earth in 2081 over a misinterpretation of one of the prerequisites in the Inter-system Alliance application form.
 * Tlaberke: The warmest planet out of the five worlds, with an average temperature of 19.7oC (compared to Earth's 15oC). Also known for their rather "primitive" technology (compared to the other worlds, at least; they still had tech comparable to the 60's on Earth.)