The Cyrannus Star System

The Twelve Colonies are situated within the star system Cyrannus, located some 2,000 light years from Kobol, where humanity presumably first evolved. All in all, Cyrannus is a vast and complex system, comprised of four 4 stars: Helios Alpha, Helios Beta, Helios Gamma, and Helios Delta.

Each star is orbited by its own family of planets and other astronomical bodies. The stars come together to form two binary systems (Alpha/Beta and Gamma/Delta). Both pairs of stars then orbit each other around a third, central barycenter every 546,892 years. Both binary systems are separated by 0.16 light years or 10,091 Stellar Units, shortened to SU (In this case, 1 SU being equal to the average distance between Helios Alpha and the barycenter of the Caprica-Gemenon binary, roughly 150 million km).

Helios Alpha

Helios Alpha is a main sequence star of spectral class G2V and has a mass of 1.0, and was the first system settled by the Colonials after the exodus from Kobol, having first set foot on Gemenon. It shares its orbit with Helios Beta at a distance of 63 SU. The pair complete an orbit once every 373 years.

Planets and Other Astronomical Bodies

Icarus – A small planet located close to the star. It has a molten surface which makes mining and exploration impossible.

Picon – This colony has an inclined orbit.
Caprica and Gemenon – These two colonies form a binary planet.

Tauron – One of only three colonies to feature a moon, named Minos. It is the only moon with a ring, and home to several mining and scientific outposts.

Erebos asteroid belt – This asteroid belt is rich in minerals, which were mined by Tauran prospectors for hundreds of years.

Zeus – A gas giant located at the outer edge of the system. This gas giant is the largest planet in the four systems, with a diameter of 153,000 km at the equator. The planet has 74 moons, the largest of which are Nike and Hebe. Constant upper atmosphere lightning creates an aurora effect that can be seen with the naked eye.

Persephone – Classified as a dwarf planet, Persephone is the outermost planet in the system and features an inclined and eccentric orbit. Colonial scientists believe this planet could be an escaped moon of Zeus.

This system is unique in the fact that Caprica and Gemenon share an orbit around a common barycenter. According to the Colonial map, the planets orbit each other once every 28.2 days, and are separated by a distance of 493,000 km. Based on these numbers, Kepler’s Third Law learns us that the combined mass of these colonies is about twice that of Earth.

Helios Beta

Helios Beta is a main sequence star of spectral class K1V and has a mass of 0.79. It was the second system settled by the Colonials after the exodus from Kobol. It shares its orbit with Helios Alpha at a distance of 63 SU. The pair complete an orbit once every 373 years.

Planets and Other Astronomical Bodies

Troy – A small, metal-rich planet, mined extensively by Virgon and Leonis since the founding of those two colonies.

Leonis – The largest inhabited planet of the Twelve Colonies.

Pallas – A small world with an inclined orbit once believed to hold a life sustaining atmosphere. It is no longer tectonically active. However, the Colonials have set up several small colonies and a military research station on the planet. Efforts to kobolform the planet have failed.

Ouranos asteroid belt – This dense asteroid belt separates long-time rivals Leonis and Virgon, and has been a source of minerals for both colonies.

Virgon – One of only three colonies to feature a moon, named Hibernia, and the only naturally habitable moon in the 12 Colonies. It was settled several centuries ago by the Celtans, an ethnic group opposed to Virgon rule.

Hera – A gas giant, approximately 75,000 km in diameter, and the third largest planet in the Cyrannus system. It has 29 moons, the largest of which are Iris and Eubora.

Helios Gamma

Helios Gamma is a main sequence star of spectral class G9V and has a mass of 0.89. It was presumably the third system settled by the Colonials. Helios Gamma shares its orbit with Helios Delta at a distance of 70 SU, and completes an orbit once every 456 years.

Planets and Other Astronomical Bodies

Thanatos – This planet, named after the god of death, has a corrosive ‘sulphur’ dioxide atmosphere and is tidally locked to its star.

Acheron asteroid belt – A broad asteroid belt, named after Sagittaron’s largest river.

Libran – Features two small moons, Herse and Pandrossos, which are thought to be captured asteroids. The moons orbit so close to each other, they periodically swap positions.

Scorpia – Home to the Scorpia Fleet ship yards. The planet features a half ring, thought to be a moon that broke apart nearly 100,000 years ago.

Sagittaron – A barren, mountainous world.

Ophion – A frigid gas giant with a diameter of 51,000 km, and an inclined orbit. The planet has 14 moons, all smaller than 10 km in diameter. Studies on the planet have Colonial scientists thinking that Ragnar was originally a member of the Helios Gamma system, while Ophion was not. Scientists think that Ophion was a rogue planet that passed close to Ragnar and was caught by the star, pushing Ragnar into its current orbit around the entire Gamma/Delta system.

Helios Delta

Helios Delta is a reddish main sequence star of spectral class K2V and has a mass of 0.74. It was the last of the four systems to be settled by the Colonials. Helios Delta shares its orbit with Helios Gamma at a distance of 70 SU, and completes an orbit once every 456 years.

Planets and Other Astronomical Bodies

Phoebe – A small world with a high surface temperature and thin atmosphere.

Styx – A planet with a dense, reducing atmosphere of carbon dioxide and sulfides.

Aeolus asteroid belt – This asteroid belt features ‘gaps’, likely caused by tidal influences with Hestia and its two orbital companions.

Aerilon, Hestia, and Canceron – These planets share the same orbit.

Hestia – The smallest gas giant in the Cyrannian star system, Hestia only has a diameter of 47,000 km. It has 17 moons, the largest of which, Kronos and Rhea, share the same orbit.

Aquaria – An arctic world, with the most inclined orbit of all the Twelve Colonies.

This system is unique in the fact that Aerilon, Hestia, and Canceron share the same orbit. The two colonies are positioned at Hestia’s Lagrangian points, meaning that the gravitational pull of Helios Delta and Hestia are balanced, allowing two smaller bodies (Aerilon and Canceron) to share the same orbit in a “fixed” position, maintaining the same distance apart at all times. Aerilon sits at the (leading) L4 point, and Canceron at the (trailing) L5 point.

Ragnar
A gas giant with a diameter of 138,000 km, orbits the entire Helios Gamma and Delta system in a 899.75 year period. It is about 110 SU away from the central barycenter. The Colonials use the planet as host to Ragnar Anchorage, an orbital refueling station and naval armory that distills hydrocarbons from the planet’s upper atmosphere. It has one moon, Sigurd.

The Cyrannus Star System

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