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Proserpine - Realistic Planet Nine with Moons

A realistic interpretation of the hypothetical planet nine.

The mass and orbital parameters are based off of the 2019 revised estimates( https://arxiv.org/abs/1902.10103 ). Other parameters were estimated based off of this. Proserpine is cold enough for atmospheric nitrogen to condense and form clouds, giving it a purplish grey color rather than the popularly depicted blue.

Rather than just work on Proserpine itself, I decided to give it 25 moons and a ring system. The inner system is largely inspired by Uranus. It has 13 regular moons, 9 ring moons and 4 major moons. The largest of these is just slightly larger the Ceres.

It also has 12 irrgular moons on distant orbits. Proserpine has captured a number of TNOs, some of which being rather large. The largest of the irregular moons is big enough to be a major moon, being comparable in size to Mimas. There is also a binary (formerly trinary) TNO pair that was captured, which now sits on a very distant orbit.

Regarding the name I went with for Planet Nine, it was also chosen to be as realistic as possible. Proserpine is an alternate spelling of the roman goddess Proserpina, whom is the roman equilvelant of Persephone. Persephone is a very common option for a planet beyond Neptune, having been used in science-fiction on numberous occasions, as well as being one of the proposed names for the dwarf planet Eris. However, all the planets in our solar system are named after Roman gods, a trend which has continued past antiquity with Uranus, Neptune, and at the time of naming, Pluto, Ceres, Vesta, and Juno. It stands to reason that any subsequent planets should also be named after roman deities for consistancy, which is why Proserpine is used instead. The reason why it's not Proserpina is a little more recent. The IAU, which is responsible for naming bodies, doesn't like to reuse names. Both Persephone and Proserpina are already in use for asteroids, so cannot be used for planet nine. In recent times, they have been able to skirt around this by using alternate spelling (Aegir and AEgir, Nyx and Nix, Cerebus and Kerberos). Proserpine being an alternate spelling of Proserpina, and roman equlivent of Persephone, makes the most sense for a name.