(In case you haven't heard, scientists have some convincing evidence that somewhere far beyond Neptune, there is a super-Earth disrupting the orbits of some smaller icy bodies.)
In any case, we got ahead of ourselves and decided that "Planet Nine" was a pretty lame name. You all really came through with a list of great names and a discussion on whether we should keep the tradition of naming these bodies after classical mythology.
In my mind, fgeorgeharris ended that argument when he commented: "It seems that so many Greco-Roman mythological names are taken by minor planets, dwarf planets, asteroids, etc., and seeing as the name of our own planet already breaks the 'tradition' anyway, I would suggest that we call this planet Sagan. For obvious reasons."
With that, here are the four of the best suggestions:
-- Janus was suggested many times. Here's how TymmConner explained it: "As it is found at the end of the solar system, thus the beginning of the vast unknown cosmos, it should be named accordingly. The Roman Deity for endings and beginnings is Janus."
-- Celo. BillGoodwin explains: "Latin meaning conceal, heaven, keep secret, be silent, cover, hide, keep back, veil, hush"
-- Proserpina. AndreaBlankiship writes: "The planet name definitely has to remain Roman. You can't break up a set. To that end I suggest Proserpina. She is in the underworld and not seen for great lengths of time, near Pluto, master of the underworld." And Dean Lovett adds: "She was abducted by Pluto (god of the underworld). Her mother's search for her are subject of Roman art and literature."
-- Black Star. User33297 writes: "In honor of David Bowie."
And here is where you vote. We'll be in touch with the winner so we can send them some NPR swag: