New Tenth Planet Has a Moon

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?"

Comments

Smaller object orbiting a larger...

[Caine]

so what do you call a moon with no planet?

Do people never think about why the flimsy pieces of metal flying about above us are called what they are? The answer to your question is: A satellite.

Re:Smaller object orbiting a larger...

[mOdQuArK!]

Aren't they technically orbiting the center of the galaxy (along with the rest of the solar system)? Or do we know that their trajectory will eventually take them out of the galaxy?

What is a planet?

[Starker_Kull]

For some reason, there has been a bit of a dispute about what constitutes a planet vs. an asteroid, comet, other thing orbiting the sun, etc. Some astronomers have said the origin of the object should decide, others give maximum orbital eccentricities and size, etc.

Here is an easy idea for what should be called a planet, that is a somewhat "natural" definition. We first noticed planets were different from stars because we could resolve them into DISCS, not merely points of light - in other words, (aside from being close) planets are ROUND. This is not just an accident, but an indication that they had sufficient gravity to pull themselves into such a shape; thus their surfaces at some point were probably molten, there was a chance for various elements to sort into layers, etc. So why not just say if it's big enough to have pulled itself into a spherodial shape, and it's orbiting the sun, it's a planet?

Re:What is a planet?

[hattig]

Don't try to bring sense into this debate.

Because someone will reply "if it is not part of an orbiting belt of material" to try and cut out Ceres and this new planet, to keep the status quo.

Never mind the fact that the asteroid belt is in fact very sparsely populated, and merely a bunch of bodies in space in a reasonably common orbit, possibly created from the destruction of a single larger body or two.

I'm happy with our solar system having 5 rocky planets, 4 gas planets and 2+ remote ice planets.

Re:What is a planet?

[at_18]

It excludes Pluto (twin planet with Charon). It doesn't exclude Earth by a hair, since the center of orbit of the Earth-Moon system is only 1/6 of the way down from the crust.

Amusingly, it would exclude Jupiter as a planet of the Sun (!), since the center of orbit of the Sun-Jupiter system falls outside the Sun itself.

Re:A Satellite?

[RAMMS EIN]

``The really interesting question for me is whether there are a lot more planet-sized bodies so far outside the ecliptic.''

Probably not. Otherwise, they would probably have found them sooner; if not because of the more measurable gravitational effect, then simply because there were more of them.

Rupert

[Alioth]

Come on, don't any of these guys read Douglas Adams books? At least one of these objects has to be named Rupert!

Re:Not a planet Yet

[hattig]

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

Are we going to be scientific about this, or are we stopping the planetary count because most people can't count in the double digits?

So what if it is in a belt? Does the fact that it is in a belt (with bodies in the belt being many millions of miles apart) somehow stop a massive body being a planet?

Either: Pluto is a planet, alongside Xena (and Quaaarorora and Sedna, if they meet other planetary requirement) (and Ceres), or none of them are. Scientifically. Popular culture can still call it a planet, and in 50 years time with new school books popular culture will finally catch up.

Re:Not a planet Yet

[Anonymous Coward]

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

I hope you don't mean that. If you did, then by historical and cultural points of view, the sun revolves around the Earth and we are the center of the universe. They were wrong then, and we are wrong now to consider pluto to be a planet.

Re:Meaning of "Satellite"

[moonbender]

Etymology is amusing, but it's really fairly irrelevant when it comes to the actual, current meaning.