When mankind first began traveling through the Relay Network, the first stop was the Arcturus System, heart of the Arcturus Stream. Within that system they discovered many more Relays, each going to a new Cluster, each thousands of light years away, a distance near insurmountable by even the FTL mankind had achieved. The Arcturus Stream made mankind's expansion across the galaxy possible. Today the Arcturus Stream acts as the main nexus of human space, the number of Clusters connected to it only rivaled by a few Clusters and none equal its level of traffic. The Arcturus Stream connects to the Apollo Alpha, Mkali Pool, Exodus Cluster, and Flame Nebula via Primary Relays, with the Local Cluster and Hyades Cluster reached using Secondary Relays. The Arcturus Stream itself boasts a not insubstantial population of over a million.
ARCTURUS:
Stars: 1 (K1.5)
Planets: 3 (1 terrestrial, 2 gaseous,)
Asteroid Belts: 1
Population: 175,000
Description: The crossroads of human space, Arcturus holds several vital Mass Relays that connect the dominions of humanity together. Arcturus sees a large amount of travel, though its low metallicity and lack of quality worlds has led to minimal colonization. Most of those who live full time within the system work for the Alliance on ships, defensive installations, and gateway stations, or are the crews of the gas extractors within the atmospheres of Themis or Eirene. Arcturus has risen to the second highest producer of Helium-3 within human space, behind only Sol itself.
Arcturus-Themis Belt: Existing between Arcturus itself and the world of Themis, the Arcturus-Themis Belt is filled with a mixture of icy bodies and some lighter elements, though anything heavier than iron is rare. Mining operations in the area have not proven fruitful, so it has mostly been ignored.
Themis: A large gas giant in orbit of Arcturus, while the world itself is valuable due to its gasses, what is of greater value are the six Mass Relays at the plant's L5 LaGrange Point. So important are those Relays, the Alliance began construction of a massive space station near them. The Arcturus Station is meant to act as a defensive installation and anchorage for the Alliance, securing its control over access to both the Sol System, and the rest of human space from threats both without and within. The world has several gas extraction operations within its atmosphere, providing vast amounts of He-3 and other gasses.
Eirene: A gas giant slightly smaller than Themis, Eirene is less important than its sister world, but still has a large amount of gas extraction operations upon it.
Eunomia: A small, insignificant ice world at the outer edges of the system, Eunomia has seen no development by humanity, and is rarely visited, usually as a discharge point for smaller ships on the Arcturus-Muphrid route.
ETA BOOTIS:
Stars: 2 (1 G0, 1 M7)
Planets: 3 (2 terrestrial, 1 gaseous)
Asteroid Belts: 2
Population: 189,000
Description: Eta Bootis is a system close to Arcturus that has seen some development, mostly for mining. It is thought that the system used to have more worlds, but they were consumed by Eta Bootis A. All the planets in the system are named after Islamic Scholars/Astronomers.
Ibn Yunus: A large terrestrial world about half again the mass of Earth, Ibn Yunus is very rich in metals in orbit of Eta Bootis A, leading to it holding several large mining operations. The world's three moons also hold several mining operations each, while they also act as ports for mining ships going into the Ibn Yunus-Ibn Rushd Belt.
Ibn Yunus-Ibn Rushd Belt: A large asteroid belt between Ibn Yunus and Ibn Rushd. The belt holds a great amount of materials, leading to a large amount of mining. It is also a minor hotbed of piracy, though it is mostly kept in check by Alliance patrols.
Ibn Rushd: A massive super earth with a mass five times that of Earth in orbit of Eta Bootis A, Ibn Rushd's gravity is too high for economical mining, but it does have several operations on its moons.
Al-Khwarizmi: A large gas giant twice the mass of Jupiter in orbit of both Eta Bootis A and B, Al-Khwarizmi has seen no human development.
Trans-Al-Khwarizmi Belt: A vast asteroid belt beyond even the orbit of Al-Khwarizmi, this belt consists of mostly icy bodies like the Kuiper Belts. No human activity is known to exist in the area, though Alliance Intelligence believes several pirate groups have built bases in the belt.
EULER:
Stars: 1 (K4)
Planets: 4 (3 terrestrial, 1 gaseous )
Asteroid Belts: 0
Population: 915,000
Description: Home to the Garden World Benning and a Secondary Relay, Euler is home to several colonies and supplies much of the food needed within the Arcturus and Eta Bootis Systems. All the planets in the system are named for physicists and mathematicians, with the exception of Silva.
Fermi: A small rocky world about a fourth the mass of Earth, Fermi is surrounded by a large amount of moons and debris, leading researchers to believe that at some point Fermi was impacted by another object, launching pieces of the world into space. Some mining operations exist on Fermi's moons.
Benning: A vibrant Garden World and holder of the system's Relay within its orbit, Benning has seen a decent amount of colonization, though not as much as some other worlds like Eden Prime and Terra Nova. The farms of Benning provide large amounts of food to the rest of the Stream due to its close proximity to the Relay, with it being common to launch a Dropship directly from Benning's orbit beyond the Relay into the Arcturus System. Almost 900 thousand people call Benning home, mostly in small communities of a few hundred or thousand.
Yukawa: A small rocky world with little of interest, only a few mining operations exist on the planet's surface, extracting materials for the construction of Arcturus Station and other projects across the Stream.
Silva: A large ice giant about thrice the mass of Neptune, Silva is the only world in the system to deviate from the naming convention set out in the other world's of the system. This is due to the death of Mateus Silva, leader of the prospecting team that discovered the Mars Ruins, to eezo poisoning just before the planet's discovery. The world was thus named in honor of the man whose discovery made its surveying a possibility. The world has extensive gas extraction operations within its atmosphere, alongside mining operations on its moons. Something of note is the colony of Freeland on the planet's largest moon, Oliverira. Freeland holds a relatively high population of 10 thousand people spread out across several habitat domes, though the surprisingly hospitable conditions of the world allow for the colonists to walk outside with only a gas mask without much harm, though a sealed suit is still recommended. The colony was founded in 2154 and has a thriving economy focused on mining and being the main port for the planet, providing repair, recreation and resupply services to ships coming and going from Silva (its main brothel, Endless Dawn, is somewhat famous for being the first brothel to use mass effect field to provide a zero g sexual experience on a planetary surface).