Ninth? Did they let Pluto back in? Nope, American astronomers at Caltech have found evidence for a new ninth planet beyond the Kuiper Belt, 10 times as massive as Earth, either a super-Earth or mini-Neptune.
*"The group’s calculations suggest the object orbits 20 times farther from the Sun on average than does the eighth - and currently outermost - planet, Neptune, which moves about 4.5 billion km from our star.
But unlike the near-circular paths traced by the main planets, this novel object would be in a highly elliptical trajectory, taking between 10,000 and 20,000 years to complete one full lap around the Sun."*
But what do we call it? Personally I think the sisterhood is a bit underrepresented in the planets, so I’d call it Juno. Or you could complete the Archaic Triad with Mars and Jupiter and call it Quirinus.
Keeping with the Roman mythology theme, how about Orcus? (Oh, crap, looking it up, looks like there already is a trans-Neptunian object named that.)
I like Hades, but that kind of breaks the Roman god tradition, and the Roman equivalent, whether you go with Pluto or Orcus, well, those are taken, too. How about Avernus, the entrance to the underworld?
I was going to suggest that, in a turnabout, we could start naming planets after elements on the periodic table, since elements are being found faster than planets. But we are now up to Ununoctium, so thats obviously a non-starter. Naming elements has also exhausted the capacity of the scientific mind to produce names.