The Castro-Lux system is a star system on the edge of the Treana Molecular Cloud Complex and is home to the capital of the Areial Union, Eiar. It contains 9 bodies with liquids on their surface, a stupendously large amount for such a system.
Two of them are O-class planets, three of them T-class planets and the remaining are all T-class moons. As a result, this system has attracted much attention among civilizations originally descended from T-Class worlds, who actually sort of want to conquer it. However, the the Areial civilization that calls this system home is a member of the galaxy-spanning United Nations of the Flower Galaxy, which would protect the small nation in times of war.
Castro: A small M7.5V red dwarf, a mere 7.9% the mass of Sol. (8 planets)
- Myach: A small desertic dwarf planet, and the most suitable for a colony not on the water-bearing planets of the system.
- Oblachno: A large ringed gas giant with easily differentiable bands, like Jupiter.
- Testament: A tidally locked, puffy waterworld. It has many culturally diverse cities on its surface and is nearly subject to permanent study, in one way or another.
- Ingentis: One of the largest planets in the entire system, Ingentis is a gas giant like Jupiter. It has one moon, and even more magnificent rings than Oblachno.
- Obliqua: A strange world, Obliqua is a T-class world but it is tilted on its side. It has thin rings, and resembles a miniature version of Uranus (when it was discovered).
- Glacipsum: A distant, very cold ice giant.
- Parvastra: Most likely the least significant of Castro's worlds, Parvastra is a tiny iceball.
- Eiar-Ver: A binary planet.
Lux: A small L6.6 brown dwarf. (9 planets)
- Eostre: A tidally locked waterworld. Basically Testament, but orbiting Lux. (Lux b)
- Soranus: An angry-looking desert world that is surprisingly not tidally locked to Lux. (Lux c)
- 5 unnamed ice worlds.
- Imset: A shiny reflective snowball orbiting Lux at 0.69 AU. No jokes please. (Lux i)
- Khione: A completely frigid dwarf planet. It takes 4.39 years to orbit Lux, and is the coldest independently orbiting body of the entire system. (Lux j)
Elorus: A large gas giant with 26 moons. It orbits both Castro and Lux.
- Mote: A small T-class moon orbiting Elorus. It has seas of neon. (Elorus 4)
Ogian: A T-class planet orbiting both Castro and Lux.
Brigid: The largest gas giant and the furthest out, Brigid is only heated by tidal heating from its moons.
- Eurus, Nerthus and Mokosh (Brigid 5, 6, 7): 3 T-class moons orbiting Brigid.
Discovery by Outside Civilizations
Discovered in 82621 by the UNFG-funded Treana Young Fusor Survey Telescope (TY-FuST for short), this star system initially doesn't look special. From the stars' perspective, this is just a somewhat young binary consisting of a red dwarf and a brown dwarf. It wasn't until a multitude of planets had been discovered around Castro, the primary star, that this system gained a bit of interest.
Testament (Castro d) could be habitable and had an absurdly low density, which sparked confusion among scientists. As a result, the UNFG sent a few solar sail probes to investigate Castro's planetary system. What they found out shocked the entire scientific community - Testament was in fact an O-class planet. This was a huge surprise, considering the young age of the system. What surprised scientists even more was that both Obliqua and Eiar, two planets in the Castro system, were Titan analogues! This shocked most of the scientific community, forcing them to slightly re-write some of their planetary formation and cooling models.
The probes were next directed to Lux, the brown dwarf of this system. In fact, the system around Lux seemed like a normal brown dwarf system. But again, this system is young, so it's a slight surprise that Eostre managed to cool down so quickly to become an O-class world.
But the most surprise came from the outer 3 planets. Somehow, there were 5 T-class worlds here! And all of them were below -235 degrees Celsius. Such a young system shouldn't have so many cold worlds.
The probes, when they passed over Eiar, did not notice much at first. Later heat signature scans indicated a concentration of life-forms deep underground, but when they sent drilling probes they were astonished to find a massive, well-lit city on the scale of twenty kilometers across in the deep cave. The inhabitants were also surprised and ran like hell, so time was spent in orbit studying the planet's language so that proper contact could be made. This contact was made in 77,049 CE.