|Satellite(s):||Nibiru (sister planet), Numskul (Transient Satellite), Exhenge|
Thought to be completely mythological until well into the Great War, Planet X and its odd sister Nibiru were the butt of astronomical jokes until their earth-shattering discoveries in 2304 and 2305, respectively. Even though many theories and potential evidence of their existence had been put forward since the early 21st century, it wasn't until the dawn of the 24th century that early GCN starships were able to solidly confirm and eventually nail their precise location and capture the first, indisputable images of the mysterious pair.
Both true giants, these planets sit on the very edge of the solar system, hidden from sight because of their dim surfaces and surprisingly low gravity for their sizes.
Planet X has two satellites, one permanent and one transient, though its sister planet Nibiru is considered by some astronomers to be a giant satellite of the planet, as the two orbit a barycenter.
Exhenge, its sole "true" moon, has almost no atmosphere, but a noticeable two-tone appearance (due to being made up of two highly disparate halves), the origin of which remains a puzzle to science.
Numskul, a dwarf planet and transient satellite, orbits Planet X periodically (usually for a period of between 10 to 40 years) as the two make their long trek around the sun. Since Nubskul orbits the sun faster than the larger Planet X, and in a more elliptical orbit, the two planets interact multiple times during their multi-century orbits. It has been estimated by some models that Numskul will one day either be ejected from the solar system, or sent flying toward the sun (and thus dangerously close to other planets in the system) due to its interaction with Planet X and (less frequently) Nibiru.