The Epsilon Eridani system, located 10.5 light years from Sol, is a notable slipspace crossroads system of the Human Sphere and formerly one the most notable human-inhabited system outside SolCore.

Cartography

The Epsilon Eridani system located in the Kepler Sector is one of the important slipspace junctions controlled by the Phoenix Initiative. From here, huge amounts of traffic passes through from Sol to either flow down the Via Serena towards the Perseus-side Inner Colonies, the furthest reaches of the Orion-Eridanus Quadrant, and almost a dozen other systems of both minor and major importance. Its position used to be far more important, but the destruction of Reach and decimation of its other major worlds have forced traders to find new routes that bypass the system.

The Via Serena trade route directly connects Epsilon Eridani to Sol and Tau Ceti. The Eridanus Spine links up with the former colony of Verne in the Gliese 185, which used to be the most popular route to the Eridanus-Orion Region. However, the recent discovery and rapid development of the New Eridanus Route, which diverts through the Gliese 86 system, has since eclipsed it. Although not the most loyal of worlds, merchants and tourists frequently make direct trips to the corporate paradise-worlds of Andesia and Gilgamesh in the Asimov and Anu systems, respectively. Epsilon Eridani can also be reached from the Sirius, Procyon, Sigma Octanus, 61 Ursae Majoris, Gliese 176, and UV Ceti systems. The Soell system, home to the wreckage of Halo Installation 04, can be reached by military vessels from Epsilon Eridani as well.

Planetary system

The Epsilon Eridani system is home to four inhabited planets, two asteroid belts, and several gas giants and minor planets. Planets are listed in order of orbital position.

Hadur

A small, metal-rich rocky planet orbiting close to Epsilon Eridani. Hosts a minor mining colony and orbital refineries.

Reach

Main article: Reach

Initially colonized by Hungarian settlers in 2319, the most major industry was titanium mining and refining. A large world, Reach has an above-standard gravity, which initially made the neighboring Tribute more attractive to settlers. However, Reach's natural riches, along with the planet's robust and human-compatible if harsh native ecosystem (and subsequent minimal terraforming requirement) made it attractive to the initial Hungarian group. Initial investments or land claims by other actors were minimal; at the time, Reach's steep gravity well was seen as a hindrance that made the planet unattractive to many colonization firms.

Additional waves of colonists in the 2160s displaced the Hungarians and paved the way for Reach to become the UNSC's headquarters. At the time, there were two major factions among the Hungarian settlers. The first group welcomed the new colonists as a way of invigorating their struggling communities with further, more substantial investments. As a downside, in many cases the pioneers were cheated out of their claims to the local titanium deposits by off-world investors. The second group were hardliner pioneers, who detested the newcomers and their own brethren who collaborated with them. This led to various incidences of violence between various groups over the course of two decades and even one significant conflict known locally as the Settlement War; this was one of many similar conflicts later dubbed the Inner Colony Wars. As new settlers arrived, largely from North America and Central Europe, the majority of the initial pioneer communities assimilated into the newer population, who would go on to adopt some of the cultural characteristics of the Hungarian settlers. While the burgeoning colonies developed into large urban centers, the hardline pioneers withdrew to small farming communities across Reach's harsh wilderness, choosing to eke out a fiercely independent living on their own terms. Despite sporadic attempts at reconciliation, by and large, the relationship between these farming communities and the UNSC remained frosty at best.

In the 2390s, Reach became the UNSC's first major base of operations outside Sol, a development that would continue over the next century as the UNSC spread further on the CMA's former territory in the colonies. A particular characteristic of Reacher culture is the local militia, notable for its exceedingly high participation rate; most of the locals (particularly in the non-urban communities) are part of or involved with the militia in some way.

Since the Human-Covenant War and the Epsilon Eridani system's recapture in Operation: FORTRESS SIEGE, Reach was prioritized for reclamation. However, even despite the cleanup of the orbital debris field in the decade after the war, damage from the glassing remained extensive. Barring considerable technological leaps, post-war projections put the full recovery of Reach's ecosystem at between 180 and 220 years. In the decades since the war, Reach's surviving population scattered. Most of the urban population resettled on other worlds, especially Earth. A small number remained in Circumstance's orbital communities. Most of the urban population settled on worlds with a UNSC presence. Despite its name, New Reach did not attract a particular Reacher majority; instead, it was so named by the UNSC to symbolize its status as a new military hub in its region of space. In the years after the war, various small settler groups, near-exclusively indigenous Reavians, sought to recolonize the planet, stubbornly braving the inhospitable glasslands.

Turul

The smaller of Reach's moons. Originally inhabited only by research stations, but largely given over to refugee housing.

Csodaszarvas

Reach's largest moon, Csodaszarvas has a frigid, methane-rich atmosphere similar to that of Titan, as well as a peculiar ring system, which is suspected to have been formed as recently as 100,000 years ago. Its unusual traits make the moon the object of considerable scientific interest, as well as a hub of various specialized industries that benefit from readily-available cooling, including AI research and hosting as well as other computation-related functions. For this reason, Csodaszarvas is also the physical location of the UNSC Navy's Reach super-AI network.

Stine's Archipelago

An industrial sector comprised of hundreds of microgravity factories and refineries, the first of which were established by the industrialist Harry Stine.

Tribute

Main article: Tribute

The most prominent civilian colony in the Epsilon Eridani system, and the only one with 'shirtsleeve' weather prior to terraforming. It is smaller than Earth and has a lighter gravity. The first wave of settlers arrived around the same time as those on Reach, in 2319, followed by another colony ship a decade later. At the time, land claims or development were modest and many of the original communities died out before the influx of new settlers in the Domus Diaspora in the 2160s.

Tribute was spared the brunt of the Covenant invasion as the Covenant focused most of their might on Reach. The planet's most significant cities and industries were completely or partially glassed either by the Covenant fleet or by assorted raiding parties afterward, though a number of smaller settlements survive. Most importantly, the glassing was not widespread enough to destroy the planet's ecosystem and climate. In the days and weeks after the Covenant took over the Epsilon Eridani system, several Jiralhanae packs established strongholds on Tribute, along with miscellaneous scavenging operations in the planet's ruined or semi-intact cities and industrial facilities. Thought the concentrated Covenant loyalist opposition was eliminated in Operation: FORTRESS SIEGE in early 2553, a smaller-scale campaign was waged for some time to root out smaller elements of the occupying forces. Shortly thereafter, Tribute was prioritized for reclamation and resettlement. In the years that followed, Tribute became Epsilon Eridani's most notable short-term resettlement project, with hundreds of thousands of refugees flowing in from across the human sphere. Although several large-scale reconstruction projects overseen by the Phoenix Initiative quickly sprang up in the planet's ruined cities and elsewhere, the influx of population still caused various difficulties, and informal settlements with poor infrastructure remained common even two decades after the war.

Circumstance

Main article: Circumstance

A large ocean world that lies at the edge of Epsilon Eridani's Goldilocks zone, Circumstance's surface is entirely covered in a vast ocean which freezes toward the poles, leaving only a narrow temperate band around the planet's equator. While famous in the modern day for high courts and academies of justice, Circumstance was originally important for the resources and the industry needed to tame the Epsilon Eridani system. Its peculiar orbit keeps it near known slipspace jump points, which made the planet a crossroads of the system and the first step for colonists from Earth. Befitting its nature as a waystation, most of Circumstance's settlements are atop its gravity well in several orbital stations, though the planet also hosts surface cities on floating seasteads, along with various undersea research stations. Natively home to a rather primitive aquatic ecosystem, Circumstance also hosted a notable cetacean transplantation and intelligence research project early on in its history.

Today, Circumstance hosts several aquatic farms created during the Covenant War to feed the rest of the Epsilon Eridani system due to shortages created by the loss of out-system agri-worlds. During the Covenant invasion of the Epsilon Eridani system, Circumstance was attacked by Jiralhanae-led raiding parties, though it never received the attention given to the larger colonies in the system. Still, much of the population either escaped or were killed, and many of the seaborne arcologies were destroyed. After the retake of the Epsilon Eridani system, plans were laid for the recolonization of the planet and the restoration of the more intact seastead cities and orbital habitats. The surface colonies expanded in the post-war era as a dumping ground for refugees from Reach and Tribute, as well as migrants and refugees from elsewhere in the human sphere. A portion of the refugees who did not go on to settle on other worlds now inhabit vast raft-cities built in and around the ruins of the world's seastead arcologies, as the influx of population too fast for the formal rebuilding and expansion of those seasteads to accommodate. Yet more have crowded the orbital communities awaiting for the Phoenix Initiative's resettlement plans to come to fruition.

Niven Station

One of the original stations built to support the colonization of the Epsilon Eridani system. Niven Station is also the largest spin-gravity station ever built in Human territory, having been built with three 770-meter rings and expanded until the Dzhanibekov Effect threatened its stability.

Inner Asteroid Belt

The system's inner asteroid belt houses Epsilon Eridani's longest-lasting asteroid mining operations. While these operations are largely automated, a handful of more developed asteroid colonies exist there, serving as waystations between the inner and outer system.

Aegir

A gas giant classically designated Epsilon Eridani b. Orbiting fairly close to the system's inner asteroid belt, Aegir (formally Ægir) is home to the system's primary helium-3 and hydrogen scooping operations and several lesser colonies on its moons. The most prominent moons are named after figures associated with Ægir from Norse mythology.

Snaer

The second-largest moon of Aegir, Snaer (formally Snær) is an icy moon hosting a relatively small surface colony in the form of various subsurface warrens and domes.

Beta Gabriel

Main article: Beta Gabriel

A small, uninhabitable ice planet with a subsurface ocean. A smattering of arcologies (including a peculiar domed-off artificial 'wilderness preserve' created by a private corporation as a retreat for the wealthy) brought the planetary population up to a few hundred thousand. Prohibitive cost of development prevented settlement even by desperate evacuees from the outer colonies.

Outer Asteroid Belt

While the mining claims in the outer belt are more recent than those in the inner one, development of the infrastructure at Tantalus has steadily increased interest in the outer belt's riches since the mid-25th century.

Tantalus

Gas/ice giant classically designated Epsilon Eridani c. Tantalus serves as the hub of commercial operations in the outer Epsilon Eridani system. The planet is scooped for fusion fuels, largely serving mining efforts in the outer asteroid belt. Tantalus houses various mining and scientific colonies and outposts on its moons and in orbit. Despite Covenant raids, these emerged relatively unscathed from the invasion, though small groups of Kig-Yar and Unggoy set up shop on the moon-colonies of Broteas and Niobe; shortly after Operation: FORTRESS SIEGE, these groups surrendered with little resistance. The most prominent moons are named after figures associated with Tantalus from Greek mythology. Was defended by a Naval flotilla before the Fall of Reach.

Jericho

Gas/ice giant classically designated Epsilon Eridani d. Scooped for fusion fuels for local use and housed orbital UNSC outposts along with a defense flotilla. Jericho had no civilian presence; following the initial surveys of the planet in the 24th century, the UNSC promptly declared it off-limits, followed by the establishment of an Office of Naval Intelligence base, Teller Station, on the moon cryptically designated Site 17. Numerous rumors surround this facility and Jericho, with many conspiracy theories claiming that the planet was sequestered due to the presence of ancient alien technology or questionable experimentation.

Early-warning system

The Epsilon Eridani early-warning network was extensive, comprising various automated and manned remote-sensing and reporting satellites with a focus on monitoring likely slipspace entry points and inbound trajectories. In the 2550s, these systems were supplemented with early wavespace communicators connected to the system's nascent slipstream comm buoy network, enabling them to get messages across to Reach much faster than before. Some of the more notable platforms included:

• RSOs Fermion, Boson, Axino, and Dyon in the inner cometary belt.
• RSOs Hadron, Baryon, and Meson in the L3, L4, and L5 Lagrange points, respectively, between Aegir and Epsilon Eridani.

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