Sol System

The Sol System, also known as the Terran System or Solar System, is the name given to the home solar system of Mankind during the Age of the Imperium. The system is named after sun, Sol, and lies at the direct astro-cartographic center of the Segmentum Solar, and is part of the Sub-Sector Solar and Sector Solar respectively. Its primary planets include Terra and Mars, the twin capitals of Imperium. There are a total of eight major planets and many dwarf planets in the Sol System, some of which are also orbited by heavily settled moons, such as Luna and Titan.

The Sol System is home to the governing body of the Imperium of Mankind; including the High Lords of Terra, the Fabricator-General of Mars, and the Emperor Himself. The Sol System, and the entirety of the Sector Solar is guarded by Battlefleet Solar, the mightiest Battlefleet of the Imperial Navy.

Notable Planets and Moons

 * Mercury - Mercury is a small planet that orbits very close to Sol. Despite its conditions, shoal facilities operate in Mercury's orbit. During the Horus Heresy, Alpha Legion infiltrators worked with anti-Imperial scavenger clans in the area.


 * Venus- Venus is an inner planet of the Sol System, and the second closest to Sol. During the early stages of the Great Crusade, Venus was conquered by the Iron Warriors Space Marine Legion during the Mehr Yasht Campaign. The planet was dominated by War Witches who fielded armies of Litho-Gholem. Venus would later play host to a wide variety of luxury resort orbitals, for the elite of the Sol System to find respite and relaxation.


 * Terra (Hive World) - Terra is the throne world of the Imperium of Man and the original homeworld of Mankind and of the Emperor. It is the most sacred and revered place in all the million worlds that comprise the Imperium. Terra is a Ecumenopolis, with its vast Hives covering the entirety of its surface, and is home to over four-quadrillion humans.
 * Luna (Dead World/Civilised World) - Luna, Terra's only natural satellite, is a densely settled Civilised World of the Imperium. Its massive population lives in great cities built deep below the lunar regolith. Luna is most famous for its gene-laboratories where the Emperor of Mankind made the genetic breakthroughs that would ultimately culminate in the massive number of Legionaries of the Space Marine Legions of the late 30th Millennium. Luna also boasted a massive series of orbital dockyards, although these were destroyed during the Horus Heresy.


 * Mars (Forge World) - Mars is the greatest Forge World of the Imperium of Man, producing vast numbers of weapons, vehicles and other technology for the Imperial war efforts throughout the galaxy. Mars is also the ancestral home of the Mechanicum and their Cult Mechanicus.
 * Phobos - Phobos is Mars' only remaining natural satellite. A small moon only 11 kilometres in diameter, Phobos' surface is completely covered in gun-studded fortifications and is used as an orbital fortress that protects the Red Planet and its Ring of Iron.


 * Ceres - Ceres is a small dwarf planet located within the Sol System's inner asteroid belt. During the Horus Heresy era, Ceres was home to relay and communication stations that helped with communications between the inner and outer reaches of the system. Ceres was also home to various habitat stations for industrial mining of the Asteroid Belt.


 * Jupiter (Gas Giant) - Jupiter is a massive gas giant and is the fifth planet in the Sol System. The space docks and workshops that orbit Jupiter are home to massive Imperial Navy Shipyards controlled by the Tech-Priests of Mars. During the time of the Horus Heresy, the moons of Jupiter were known to have habitats for the workers of the shipyards in Jupiter's orbit, all of which were powered by the radiation from Jupiter. It was here that the infamous Word Bearers ship, the Furious Abyss, was constructed, before it turned its guns upon its shipyards in order to maintain the secrecy of its existence.
 * Ananke - A small moon known to have had habitats on its surface by the time of the Horus Heresy.
 * Iocaste - This moon is known to have had habitats on its surface by the era of the Horus Heresy.
 * Europa - Located within the Galilean range, by the time of the Horus Heresy Europa had been geo-engineered into an ocean-moon.
 * Io - The seething orange mass of Io was home to a uninhabitable volcanic wasteland.
 * Ganymede: Another of the moons of Jupiter with the shipyards centering around it as well as the dozen other smaller moons.
 * Thule - An asteroid moon that served as the clandestine shipyard for the Furious Abyss and was destroyed by renegade members of the Mechanicum during the Horus Heresy.
 * Callisto - A moon of Jupiter known to hold residential orbitals above its surface by the time of the Horus Heresy.
 * Saros Station - Saros Station was a space station that orbited Jupiter during the time of the Great Crusade and Horus Heresy. The station resembled a vast spindle bathing in crimson glow which made it appear as if it were crystal chandelier that had been severed from its mounting and thus cast free into the void. Unlike the majority of the gas giant's other industrial and colonial stations, Saros had been a resort platform before the Horus Heresy, where the Jovian elite found respite as well as diversion from the works of the shipyards and manufactorums. It was said that only the Venus orbitals could surpass Saros Station in luxury with its avenues of gold and silver, null-gardens, auditoriums along with the finest opera houses outside the Imperial Palace.
 * Kadal: Kadal was the name of a satellite munitions fortress during the time of the Great Crusade and Horus Heresy. During the Horus Heresy Kadal would be the site of an Alpha Legion-instigated anti-Imperial revolt and would be subsequently destroyed during the Solar War.


 * Saturn (Gas Giant) - Saturn is a massive, ringed gas giant and the sixth planet of the Sol System. Unlike most of the Sol System, Saturn never hosted a large population, due in-part to xenos activity, thus making it the perfect candidate to house to newly created Inquisition when it was first established at the end of the Horus Heresy. The moons of Saturn serve as the location for a massive complex of military bases and orbital shipyards run by the Inquisition. All of these areas are off-limits to anyone who does not serve or have clearance from the Ordos of the Inquisition, any unidentified vessels nearing Saturn are promptly destroyed by its sophisticated orbital defenses.
 * Titan (Inquisition Fortress World/Space Marine Chapter Homeworld) - Titan is the largest moon of the gas giant Saturn in the Sol System and is wholly controlled by the Grey Knights Chapter of psychically-active Space Marines who serve as the Chamber Militant of the Inquisition's Ordo Malleus. The Fortress-Monastery of the Grey Knights is based on Titan, and is carved entirely of basalt.
 * Deimos (Forge World) - Deimos was previously a moon that orbited Mars and served as a small Forge World with smog-ridden manufactorums that produce weapons and armour. When Malcador the Sigillite created the Grey Knights Chapter during the Horus Heresy, the moon was displaced from realspace and into the Warp, after the Battle of Terra it reappeared, its orbit relocated to Titan by way of unknown arcane technologies.
 * Mimas (Inquisition Prison World) - Mimas is the closest major moon to Saturn, with its surface suffering from an immense impact scar covering a quarter of the surface. This crater houses the Inquisitorial Prison Complex which contains the worst criminals hunted down by the Inquisition, who are kept in isolated cells with psychic wards woven into the walls and guarded by gun-Servitors and an Inquisitorial Stormtrooper regiment.
 * Encaladus - Encaladus houses a citadel of the Inquisition and is a vast palace from which Lord Inquisitors of the Ordo Malleus hold court, and also where many of these Lords maintain their personal estates. The primary citadel used by the Inquisition is known as the Encaladus Fortress. In the libraries of the Encaladus Fortress, there are countless volumes of forbidden lore on the subject of Chaos and Daemons. The Encaladus Fortress also incorporates the Admiralty Spire, where the empire of Saturn's rulers signed their treaty with the Emperor during the Great Crusade.
 * Tethys - Tethys is the site of the hidden archive of the Librarium Daemonicum, access to which is restricted to Lord Inquisitors. Tethys is home to a number of Daemons trapped on its surface. One of the set trials for all aspiring Paladins of the Grey Knights is to survive on its surface without their armour.
 * Iapetus - Iapetus is the furthermost major moon, and home to a vast Naval Fortress and series of dockyards that serves the various strike fleets of the Grey Knights Chapter, along with the starships requisitioned from Battlefleet Solar by the Inquisition. As it is under Inquisitorial command, it serves as the only reliable means of getting into and out of the rings of Saturn. Iapetus was a stronghold of the Ringers before the coming of the Emperor and the Imperium.


 * Uranus (Gas Giant) - Uranus is a massive gas giant located in the Sol System. Though never habitable, it is home to orbiting Human colonies most notably the Azurites. The moons of Uranus are used mostly for mining by the Imperium. By the time of the Horus Heresy, Uranus's moons were repopulated contained Human colonists.
 * Ariel - One of Uranus' major moons, Ariel is home to Imperial mining operations.


 * Neptune (Gas Giant) - Neptune is a massive gas giant, and furthest major planet from Sol. Neptune was first colonized by humanity during the time known as the Age of Terra. By the time the Emperor reconquered Neptune during the Great Crusade, its inhabitants had mutated into mutants, which caused them to be destroyed by the forces of the Emperor.


 * Pluto - Pluto is a small dwarf planet located in the outer rim of the Sol System. During the Great Crusade era, Pluto was home to relay stations that were responsible for warning Terra of any imminent invasion. During the Horus Heresy, the world and its accompanying moons was the site of a major Alpha Legion attack in what became the first major engagement of the Solar War.
 * Charon - Charon is the largest natural satellite of Pluto.
 * Styx - Styx is a natural satellite of Pluto.
 * Nix - Nix is a natural satellite of Pluto.
 * Kerberos - Kerberos natural satellite of Pluto and is used as a heavily armed orbital fortress.
 * Hydra - Hydra is a natural satellite of Pluto and houses an Astropathic-relay station.


 * Sedna - Sedna was a planetoid sized trans-Neptunian object of xenos origin located within the Sol System's inner Oort Cloud. During the early Great Crusade eight Space Marine Legions fought against an unremembered xenos species on the dark surface of Sedna, finally leaving the entire Sol System in human hands for the first time since the start of the Age of Strife.

Notable Celestial Objects

 * Astroid Belt - The Asteroid Belt lies between Mars and Jupiter and separates the inner and outer solar system. Ceres is part of the Asteroid Belt. During the 31st Millennium the Asteroid Belt was populated by various mining operations and habitat stations, some of which were controlled by Belter Coalitions.


 * Kuiper Belt - Another asteroid belt, the Kuiper Belt is nearly 20 times wider and 200 times larger than the inner Asteroid Belt. The Kuiper Belt reaches from the orbit of Neptune and out towards the Sol System's Oort Cloud. Several celestial bodies reside within the Kuiper Belt, including Pluto and its moons, and the dwarf planets Haumea and Makemake.


 * Shrine Comet - The Shrine Comet is an artificial construct built by unknown persons during the Dark Age of Technology that orbits the Sol System every thousand years, tracking an irregular elliptical route around the sun. In millennia past, when its trajectory was stable and more accurately predicted, it had worn a different name, but what it was had been lost in the murky fog of time. During one such appearance, the Unification Wars of Terra were coming to an end and the Emperor decided to intercept the Comet and modify it as a shrine for his victory. Known as the Shrine of Unity, it was a potent symbol of Imperial strength and unified purpose. During that time, the zealous XVII Legion (the Word Bearers) had secretly built a shrine deifying the Emperor. Following their chastisement by the Emperor at Monarchia, the Primarch Lorgar had charged Captain Sor Talgron to secretly tear down the shrine, before anyone found out, so as not to risk further embarrassment. But in reality, this mission was a cover story to conceal the Word Bearers' true intentions - to sabotage the Imperial Palace.


 * Artefact 9-Kappa-Mu - Artefact 9-Kappa-Mu is a mysterious relic of the Sol System that orbits around the sun between Terra and Venus. A geodesic sphere of black metal nearly 30 kilometres in diameter, the artefact is marked by honeycombed passages and catacombs. The artefact's origin is completely unknown, and may even predate the Dark Age of Technology.


 * Centaurs - Small minor planets that usually feature unstable orbits due to previous encounters with larger planetary bodies. Centaurs mostly exist in the outer reaches of the Sol System, although due to their unstable orbits they sometimes cross into the inner solar system.


 * Comets - Comets are small icy bodies that usually have highly eccentric elliptical orbits, entering the inner solar system and then leaving for many hundreds or thousands of years.


 * Oort Cloud - The Oort Cloud is a massive spherical cloud of predominantly icy planetesimals that surrounds the entire Sol System.