Dossier: Thelion System

18 Scorpii – Thelion system

18 Scorpii has since long been known as a ‘solar twin’ – that is, a star so similar to our sun as to be for all intents and purposes practically indistinguishable from each other. Both the sun and 18 Scorpii share a highly similar age, metallicity (amount of elements heavier than helium), mass and luminosity.

18 Scorpii is located about 45.7 lightyears from the sun, located nearby Antares in the sky from Earths’ point of view.

In the Universe

18 Scorpii – or known as Thelion to the Darnikans – is the host star to the ancient human colony. It is a relatively unremarkable star, with the exception of being a practical twin for the sun. It is orbited by seven major planetary bodies and two significant debris belts.

In order of increasing distance from the star these are Hephaisto, Laina, Merhena, Darnika, Soreta, the Lentikon belt, Aenea, Sirata and the Maigrab belt.



Named for an ancient god of craftmanship and smithing – a clear symbol of a shared cultural heritage with the greek on Earth – Hephaisto is a so called ‘Hot Jupiter’. It orbits Thelion at a scant 19 million kilometers distance, and thus two and a half times closer to its star than Mercury in our own solar system, one revolution taking approximately 16 days.

The proximity to the star puffs up the atmosphere to approximately 180.000 kilometers in diameter, while the planet itself only is fifteen percent more massive than Jupiter. The massive amount of solar heat Hephaisto soaks up creates hellish conditions in its atmosphere – hotspots on the sunlit side reach up to 1600 degrees Kelvin, and data from some probes suggest that the planet has sodium vapor clouds and windspeeds of up to 9500 kilometers per hour.

Parts of the superheated atmosphere are constantly being blown off by the solar wind and form a large tail – in favorable conditions even visible from Darnika, reminding the local populace of the smokestack of a forge.

Based on isotope ratios Darnikan scientists hypothesize that Hephaisto may in fact be an extrasolar capture. While the evidence is not entirely conclusive, the comparatively odd orbits of the remaining planets and the low number of planetary masses in the system as well as their orbital inclinations seem to strengthen the hypothesis.

Hephaisto is of little value. Its position deep within Thelions gravity well as well as the extensive thermal and radiation shielding required to approach this area of the system mean few see a point in venturing this deep into the system. The planet has not been visited by more than a handful of specialized probes sent in scientific curiosity.


The planet Laina [Lah-ee-na] was in ancient times known under another name – an old Darnikan slang word for ‘disappointment’. More recently, during the late age of barbary, a warlord named this wanderer in the sky after his eldest daughter, who he considered a good luck charm. Over time (and in no small part due to threats uttered by the warlord) people started to use this name; In time even his enemies began to use it as a form of mockery or curse words.

Laina to the modern day holds the connotation of being both a curse and a symbol of good luck – a promise so grand that it only can lead to disappointment.

The planet itself is a rocky outcrop with a tenuous krypton and xenon atmosphere, orbiting its parent star at around 79 million kilometers distance. It has an unusually high orbital inclination of nearly 12 degrees from the ecliptic, thought to stem from interactions with Hephaisto in the early days of the system. Laina possesses a strong magnetic field originating from a molten nickel-iron core. The planet has around 20% more mass than Earth, but much of it is canceled out by its significantly larger diameter – Laina clocks in at around 15400 kilometers in diameter. As such it only has 60% of the average density of Earth in spite of its similar composition; Additionally the surface gravity is about 25% lower than on Earth. The planet orbits Thelion in 176 days.

Laina is home to a large cluster of stations in its orbit – about three hundred objects mainly consisting of fuel cracking facilities, ore refining plants as well as large smelters processing raw materials into various products used throughout the system. The orbiting factories almost exclusively rely on the abundant solar power for their operations and are largely automated. Nearly every station resides within the planets magnetosphere for protection against the harsh solar radiation.

The surface of Laina is home to a small robotic mining facility working the few easily accessible mineral deposits worth developing. Despite the lower surface gravity it has become simpler for the Darnikans simply to ship in material from the asteroid mines – material, which is both more highly enriched in the desired elements as well as simpler to process. Few humans live here or in the orbiting stations – at last count less than two thousand souls resided this close to Thelion, most of them concentrated to the largest station Laina-C, a construct nearly five kilometers across (nearly seven if one was to include the actively cooled heat shield and the long heat radiator fins in its shadow).


Merhena [Maer-heh-nah] is a small, Mercury-sized ball of rock with a dense Nitrogen-Carbon Dioxide atmosphere, orbiting its host star at a little over 110 million kilometers. It possesses only a marginal magnetic field, as the planets core is thought to be in its last throes. This magnetic field is the only reason Merhena still has retained such a dense atmosphere so close to Thelion.

The Darnikan fleet operates a large nitrogen harvesting operation, both for refining into fertilizers for Darnikas agriculture as well as nitrogen compounds used in rocket fuels. Several dozen atmospheric scoops regularly descend into the low gravity environment of Merhena to retrieve large batches of its atmosphere for processing.


Darnika [Dar-nee-kaa] is the fourth planet from Thelion and one of the rare planets that is fit for human habitation. Its orbit takes it out to 1.05 AU, which barely balances out the higher activity from the star. Nevertheless, thanks to its lower axial tilt of only 15° the seasons on Darnika are less pronounced when compared to Earth. The planet possesses a Nitrogen-Oxygen atmosphere in a 75-24 relation; It also contains somewhat more Carbon Dioxide which slightly elevates the global temperature beyond what is expected.

The high solar activity and atmospheric composition mean that Darnika experiences extensive, near constant aurorae at both magnetic poles; The rotational poles also have no ice caps (save for some smaller glaciers on the northern continent):

Two small moons orbit the planet, named Carindan and Resnos, revolving around Darnika in 10 and 4 days respectively. Resnos at some point in the past experienced an impact that nearly shattered the small moon and left a prominent impact scar on its leading hemisphere. Carindan on the other hand possesses a faint rust-red colour that can be traced back to iron compounds in the lunar regolith.

The planet is now home to approximately 620 million humans, all of whom are descended from an original settler population of 15.000 individuals that came to Darnika around twelve- to thirteenthousand years ago.

For more details, see the dossier on Darnika.


Soreta [So-reh-tah] is the stepchild of Darnikan space development. Located at the inner edge of the Lentikon belt, the airless, heavily cratered world offers little to the larger system. Frequent impacts from stray debris of the belt, combined with the lack of air and materials that would make any effort to develop the planet worthwile meant that it never was elevated beyond the status of a fuel stop for ships moving towards other destinations in the system.

Some scholars argue that with its small size of barely 4.800 kilometers in diameter and its low mass it shouldn’t qualify as a planet at all. This is quickly rebuffed by the opposing side pointing out that the planet [sic] is the dominant mass of its orbit as well as causing a clear inner cutoff of the Lentikon belt, and planetary status should not be determined by its usefulness to science or other endeavours.

Lentikon belt

The Lentikon [Len-tee-kon] belt is a conglomeration of asteroids shepherded by Soreta and Aenea, totalling about 3.5 million rocks of 1 kilometer or more in size, with objects smaller than that numbering in the tens of millions. Similar to the main asteroid belt in the solar system, however, it is not a navigational hazard at all. Overall there are about 620 objects larger than 100 kilometers. The largest – and the object the belt was named after – is the location of several manned stations involved in deep space research. Aside from those manned installations, nearly 2000 asteroids have been converted into robotic mines, literally tearing apart the rocks to be loaded into automated cargo barges headed towards Laina. While the Darnikans possess FTL technology, they see little point in wasting precious energy when sending the goods. The automated sublight barges are sent on Hohmann transfer orbits towards Laina, often arriving there more than two years after departure – the high number of automated barges in transit at any time however mean that there is never a shortage of material at the destination.


Aenea [Ah-eh-neh-ah] is the dominating presence of the Darnikan solar system. An old saying among the Darnikans, referring to the ‘lazy god’, notes that it is ‘simpler to change the mind of a rock than nudge Aenea from his place’. Whether conscious or not, it accurately reflects Aeneas massive presence of four Jupiter masses in a single planet, giving it an unusually high density of 2.4g/cm³ for a gas giant.

The planet has a striking blue colour with prominent white cloud bands – the former most likely due to a presence of methane in the atmosphere, the latter surmised to be ammonium clouds. Like many gas giants, Aenea gives off more heat than it receives from its parent star thanks to heat generated by the continued gravitational contraction of the planet.

Aeneas’ L5 point has been largely cleared of debris by the Darnikans, which is now home to a complex of 40 stations serving as shipyards for the navy. While the majority is designated to produce small craft and automated vessels for the ever-expanding mining and manufacturing industries, around a dozen of the stations are permanently tasked with building new capital vessels for the navy. The efficiency of Darnikan shipbuilding technology is evident by the sheer speed of production – from the laid-down keel to a finished hull with engines it takes the larger yards less than four months to assemble a Kerberos class heavy cruiser – a bulwark measuring 500 meters in length. Once transferred to a secondary yard the ship is outfitted with its final arament and equipment in another four months.

Another unique peculiarity of Aenea is one of its 83 moons and moonlets. Officially only known by its catalogue number of 6-21, it is orbiting Aenea on a polar orbit – a clear sign that it wasn’t originally a moon of the gas giant. A fourhundred kilometer rock, it’s been surmised that Aenea has captured this moon during the past fifteen thousand years – anything further back than that would be impossible to explain due to the inherent instability of an orbit like this.

6-21 will likely collide with one of the larger moons of Aenea in a century or two. The collision will create a massive debris field, forming a new ring system around the gas giant.

There is a small research outpost located on one of the outer moons of Aenea, Dina, which monitors the planet and its extensive system of moons. The massive radiation belts caused by the planets extensive magnetic field makes it mostly impossible for anything but the most hardened probes or heavily shielded vessels to approach the gas giant more than 12 million kilometers.


The older sister to Soreta in Darnikan mythology, it is a small ice giant in the outer reaches of the system. At 89.000km in diameter it is the most modest gas giant of the Thelion system, with fifteen moons. It is a frigid, featureless turquoise ball orbiting at a distance of 15 AUs, which only distinguishing mark is the Helium-3 mining operation the Darnikans have set up to fuel many of their power needs.

The largest moon is called Ison, a 2500km conglomeration of loose rocks and ice with a fractured surface.

Maigrab belt

The outer debris belt of the Thelion system is extensive. Starting at a sharp inner edge at around 17 AU, it extends to at least 200 AU and contains massive amounts of dust and ice dwarfs. There is a slight concentration of objects at around 100 AU, in roughly the spot where Thelions magnetic field and exotic physics create a ‘weak spot’ in altspace where it is particularly easy to enter the system from FTL speeds.

The Darnikans have set up extensive automated defense networks around those weak spots and patrol each with a sizable fleet, with reinforcements available within 35 minutes if the need would arise. The extent of the debris field and the amount of dust make it fairly imperative to enter the system in one of those four spots, as any attempt to enter the outer system runs the hazard of collision, and jumps deeper into a system from the outside are prohibitive in both terms of energy consumption as well as stealth.

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