Persephone

Discovery (Ancient 21th Century)

Planet Nine, truncated to P9, is a planet that is responsible for the anomalous behaviours of objects orbiting far beyond the Kuiper belt, 6 times further than the heliopause of its parent star.

Being discovered the same way as Neptune and Pluto, the location of this planet was deduced by using the anomalous belt of minor bodies and maths to figure out the necessary orbit and mass an object would need to reproduce the effects of the anomalabelt.

In 2050, seven moons were discovered around Persephone, Five of them were named Dionysus, Pariahdark, Klemper, Nightmerica, and Terminatra. Two moons had Triton-like retrograde motion were named Femalien and Poindexter.

Modern P9 (200th Millenium)

Planet Nine is not interesting enough to gather much attention, but it does have a spacecraft museum of physical relics of the ancient world orbiting around it at a distance of 0.1 AU.

With all of its population in floating cities in the planet's upper atmosphere, Planet Nine has a relatively low population of 100 billion people.