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New Tenth Planet Has a Moon

Posted by CmdrTaco on from the everybody's-doin'-it dept.

starexplorer writes "SPACE.com is reporting that the recently discovered 10th planet of our solar system has a neighbor - a moon. The discovery team also have nicknamed the planet 'Xena' and the moon 'Gabrielle'. Many scientists are objecting to whether the new planet really is a new planet - so what do you call a moon with no planet?"

3 of 223 comments (clear)

  1. A Satellite? by kalidasa · · Score: 5, Interesting

    A body that orbits another body is a satellite in all cases. It is a moon if the body it orbits is a planet. Either "Xena" is a planet, or Pluto isn't (in which case Charon isn't a moon, either). The really interesting question for me is whether there are a lot more planet-sized bodies so far outside the ecliptic.

    1. Re:A Satellite? by kalidasa · · Score: 5, Interesting

      I'm not so sure. "Xena" is pretty far out, so its gravitational effect is probably negligible. And look at all the KBOs they've found at least a quarter the size of Pluto. (On your other posting, to ignore the joke and pretend it's serious - I don't know enough about extrasolar systems to know if they've found that the "ecliptic" arrangement is the norm, but I imagine it is - so extrasolar planets outside their local ecliptic are interesting, too.)

  2. Not a planet Yet by Anonymous Coward · · Score: 5, Interesting

    As far as I known, Xena (2003 UB313) is not a planet yet.

    Mike Brown, who discovered it said "If Pluto is a planet, so is 2003 UB313". (And he said 6 months earlier that Pluto should not be considered a planet !)

    But in fact, they are both transneptunian objects. Along with some big ones we discovered earlier like Quaoar and Sedna. So what's the difference with Xena ? It's that Xena is the first transneptunian object larger than Pluto. But note that it's possible to have transneptunian objects the size of Mars. Size don't matter as they are still transneptunian objects, part of the Kuiper Belt.

    But you say "Xena has a moon". So what ? Even asteroids can have moons. No big deal.

    So the true question is "Is Pluto still a planet ?".

    A lot can be said, but I'd say Xena and other transneptunian objects aren't planets while Pluto is.

    Why Pluto ? Only because from an historical and cultural point of view, it's a planet.