Sol

The Sol system, formally called the Solar System, is humanity's home system and the most populated system of the Human Sphere. It is centered on the G2V-type main sequence star known as Sol both in official contexts and by outsiders, though it is more commonly known as the Sun by the system's inhabitants. The Sol system's immediate region within a five light-year radius is known as SolCore, encompassing the system's Oort Cloud and its closest neighbor, Alpha Centauri.

Planetary system
The Sol planetary system encompasses the four terrestrial Inner Planets, an asteroid belt, and the four Outer Planets, two gas giants and two ice giants. The system is home to numerous small bodies, including the centaurs, whose orbits lie between those of the Outer Planets, and the trojans, which occupy Lagrange points along the orbits of planets, most prominently Jupiter. Beyond the planets lies the Kuiper Belt, a circumstellar disc composed of several dwarf planets and numerous small bodies largely composed of volatiles. A thousand times more distant, beyond Sol's heliopause, is the Oort Cloud, a spherical collection of icy bodies; some of these periodically move near Sol on highly elliptical orbits and are known as comets.

Venus
An inhospitable hothouse world with an atmosphere largely composed of carbon dioxide, Venus has been home to various experimental terraforming efforts throughout humanity's spacefaring history. These efforts fell by the wayside following the invention of slipspace travel and the off-system exodus of the 24th century, and Venus is now a relative backwater. It retains various scientific outposts and floating colonies in the upper atmosphere, which are also the target of a fairly thriving intrasolar tourism business. By 2570, Venus' aerostats and orbitals have a combined population of just below ten million. Construction was started on a solar shield in the late 23rd century in order to cool down the planet; though this was never fully finished, the incomplete shield has managed to lower Venus' temperature somewhat, and now acts as a solar power collector. Various actors have shown interest at terraforming since, but none have had the capital or resources to follow through on the incredibly intensive process.

Earth

 * Luna

Earth's only major natural satellite, Luna is home to the oldest human space colony that continues to be a major shipyard and stopover between Earth and the rest of the Human Sphere.


 * Goddard station

Founded as one of the first commercial development projects in Earth's orbit, Goddard Station played a major role in humanity's earliest expansions through the Sol system. Throughout the Golden Age of Space Colonization, hopeful migrants from all of Earth's nations passed through Goddard to board colony ships and spaceliners bound for Mars, the Jovian moons, and the hundreds of space habitats. Meanwhile, raw materials mined from across the system were processed and then distributed to their final destinations planetside.

Goddard was decommissioned in 2445, though it still remains today, preserved by a devoted non-profit group. It now operates as a tourist destination.

Built in 2499, Fedore Station is the modern passenger terminus for Earth in the 26th century.
 * Fedore Station

Mars
Sol's second-most populous world and humanity's first interplanetary colony.

Asteroid Belt
Commonly known as the Sol Belt or Sol Asteroid Belt to differentiate it from other systems' asteroid belts, the asteroid belt is home to numerous mining efforts and small habitat communities traditionally known for their independent mindsets.

Jupiter
Jupiter's extensive system of moons hosts Sol's most notable subsystem colony network. While none of the Jovian Moons are as notable individually as Mars, as a group they form a formidable collective.

Sol's primary interstellar jump points are located in the Jupiter-Sol L4 and L5 Lagrange points. Several refueling facilities and other waystations have been established trojan asteroids located at said points.

An intensely volcanic world located deep within Jupiter's radiation belt, Io is the industrial powerhouse of the Jovian system, hosting automated mining industries and orbital facilities used to extract energy and zenostium plasma from the Jupiter-Io flux tube. As most of the moon's industries are heavily automated, Io's permanent population is relatively small compared to the other major Jovian moons. Due to the moon's inhospitable conditions, surface habitats on Io have to be shielded against the intense radiation and volcanic activity.
 * Io


 * Europa


 * Ganymede

The first Jovian moon to house a permanent colony, Callisto was initially favored due to its location outside Jupiter's intense radiation belt.
 * Callisto

Saturn
Saturn's orbital space is home to a colony system similar to Jupiter's, albeit less developed or populous; the onset of the Domus Diaspora led to many of the colonies being effectively abandoned. However, Saturn's much less dramatic radiation belt also makes its moons more hospitable than Jupiter's. Saturn's atmosphere is skimmed for various gases, most notably fusion fuels.

Saturn's largest moon, Titan is a cryoworld whose frigid atmosphere makes its conditions ideal for certain specialized industries as well as high-end processing or "cold computing". It is notably home to the ongoing "Titan Experiment", a physically fixed network of Smart AIs operating long past their formal "expiration dates".
 * Titan

Uranus
Since the 24th century, Uranus has been Sol's main source of fusion fuels due to its weaker gravity compared to Jupiter or Saturn and lack of a radiation belt. Though most of these are automated, minor colonies and scientific outposts are located on Uranus' moons and orbital facilities.

Neptune
Houses gas-scooping facilities and fuel plants which experience periodic peaks of activity as Neptune passes near Sol's IJPs. Has been used as a stopover on missions in or out of the Kuiper Belt. Hosts a handful of small colonies and outposts on its moons.

The largest man-made orbital of Neptune, Villaria Station is dwarfed in all respects by the habitats closer to Earth, with most of its facilities specialized for ship repairs. Nevertheless, it is known for its cycle of several years of relative abandonment followed by short, massive business booms, which correspond to when Neptune passes close to Sol's interstellar jump points.
 * Villaria Station

Centaurs and the Kuiper Belt
Several of the small objects of the Outer System were colonized during the 23rd century, after the development of fusion propulsion allowed long-distance travel in economical timeframes. These tend to be small and independent communities colonized precisely for the sake of isolation.

Heliopause
The Heliopause is the point at the edge of the Solar System where the solar wind is no longer strong enough to push back against the stellar winds of nearby stars within the interstellar medium, marking the very edge of the Sun's influence. Hyperborea Station, a scientific UNSC outpost used to study the interstellar medium as well as slipspace travel early on, is located at the edge of the Heliopause.