Sirius is a binary star system and one of the closest inhabited systems to Sol. It consists of the brilliant blue-white main-sequence star Sirius A and its smaller companion, Sirius B, a dense white dwarf that is the remnant core of a once much larger star.
Despite its proximity to Earth, Sirius proved to be a difficult target for early colonization efforts. Sirius A, an A-type star, emits intense ultraviolet radiation that bathes much of the inner system in harsh stellar light. Early settlers relied on extensive radiation shielding, enclosed habitats, and advanced environmental engineering before permanent settlements could thrive.
While the system contains only a handful of small, Mars-sized worlds, it is exceptionally rich in metals and industrial resources. Astronomers believe that much of Sirius's original planetary system was disrupted when Sirius B expanded into a red giant billions of years ago. During this turbulent period, planets were likely consumed, ejected from the system, or shattered by gravitational interactions.
The prevailing theory suggests that many of the smaller worlds and asteroid populations seen today formed later from material shed during Sirius B's stellar evolution. This unusual origin left the system with scattered mineral wealth, compact worlds, and massive outer belts that became central to the Sirius economy.
Orbiting closest to Sirius A is the Sirius Independent Rotating Infrastructure Settlement, more commonly known as SIRIS. This enormous rotating ring habitat encloses a sprawling urban environment beneath a transparent protective canopy. Home to millions of residents, SIRIS serves as the commercial, industrial, and transportation hub of the system.
Near Sirius B lies Tiberius, a small icy world believed to have formed from material expelled during the star's transformation from a red giant into a white dwarf. Its largest settlement, Tiberius City, is built into the walls of a vast crevasse and sheltered beneath a colossal glass dome.
Tiberius City is one of humanity's most impressive engineering achievements. The city's dome uses photonic crystal composites to filter harmful radiation while maximizing usable light, creating a stable environment beneath the harsh glare of the white dwarf. From this protected capital, mining fleets coordinate operations throughout the resource-rich outer belts, transforming Sirius into one of the Inner Sphere's most important resource-exporting systems.
