Resolution 5a states:

(1) A "planet"¹ is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

Neptune is not a planet by that definition because it has NOT cleared Pluto from it's neighborhood.

Jupiter is not a planet by that definition because it has NOT cleared all of the Trojon asteroids from it's neighborhood.

I'm not sure, but Earth may fail the test also.

The IAU argument puzzled me on that count, too, because they didn't offer a definition of "neighborhood".

I think it could be argued that all planets could have Trojan/Lagrangian point bodies, and that the more massive the planet the more likely objects could be trapped at those points.

And it could surely be argued that Pluto is only very rarely in danger of being swept away by Neptune, so that Pluto's orbit wouldn't automatically be assumed  to be within its neighborhood.

But I haven't seen a good definition of what constitutes "neighborhoodness" in general and of Pluto's neighborhood in particular.

Writing definitions is a tricky business ...

start a worldwide protest for pluto having planet status- ill sign it- this is an good as any place to start one for the pro-plutonians!!-       something like this

Dear idiots, pluto is a planet

                                                    regards-us

I think the part about clearing out the neighborhood is aimed at the asteroid belt and Kuyper Belt.  They will proably never be cleared out so no object within them can be called a planet.

 

 

I thought that any Celestial body containing some sort of atmosphere would be considered a planet.  They should keep pluto, add Charon and 2003 UB₃₁₃ , and knock off Ceres.

This technical paper http://xxx.lanl.gov/abs/astro-ph/0608359 defines "clearing out the neighbourhood" as being at least 100 times the size of any object sharing your orbit. Or words to that effect!

I'm wondering if this will be the basis of the official definition?

The "clearing out the neighborhood" definition is referring to the formation of the Solar System over 5 billion years ago.

During there formation, the gas giants litterally cleared out almost all of the objects in there gravitized orbital path. Beyond the gravitational influence of Neptune, the many remaining objects in a fixed orbit were safe from crashing into any Planet.

Therefore there are much more objects spread out at great various distances in the KB than within the gas giants regions. Many we haven't discovered yet because there very small and far away but every now and then we see them as comets.

The very few objects still remaining between the Planets are rogue asteroids or comets. In comparison to the Asteroid or Kuiper Belts there are much less and they are more likely to crash into the Planets much sooner.

Get it through your thick skulls people it's called the Kuiper Belt and Pluto in it's safe
200+ year orbit is part of it.

Glacius wrote:

The "clearing out the neighborhood" definition is referring to the formation of the Solar System over 5 billion years ago. During there formation, the gas giants litterally cleared out almost all of the objects in there gravitized orbital path. Beyond the gravitational influence of Neptune, the many remaining objects in a fixed orbit were safe from crashing into any Planet. Therefore there are much more objects spread out at great various distances in the KB than within the gas giants regions. Many we haven't discovered yet because there very small and far away but every now and then we see them as comets. The very few objects still remaining between the Planets are rogue asteroids or comets. In comparison to the Asteroid or Kuiper Belts there are much less and they are more likely to crash into the Planets much sooner. Get it through your thick skulls people it's called the Kuiper Belt and Pluto in it's safe 200+ year orbit is part of it.

The problem is that you have to qualify the defintion in trying to keep the outer planets - well - "planets". And even then you fail!

They (the former "Outer Planets") all have rings, and by defintion have not cleared their orbital paths as evidenced by these rings. The defintion of a planet does NOT clarify that this orbital debris may be orbiting the Sun in sync with the object that may or may not be a "planet" itself.

Hey, a rose by any other name is still a rose but something not a rose will never be a rose unless you change the defintion to include it. Or you can make a rose not a rose by changing the definition too. They changed the defintion of "planet" to exclude Pluto and went to far.

Now we have no outer planets and our Moon is now a planet, we went from 9 planets to 5, getting rid of 5 and adding 1. Mercury, Venus, Earth, the Moon and Mars. And we got a lot of "stuff" out past the Asteroid Belt!

James

PS- they eliminated exosolar planets completely since to be a planet it must be a member of our solar system. So now we have exosolar "stuff"...

 

Glacius wrote:

The "clearing out the neighborhood" definition is referring to the formation of the Solar System over 5 billion years ago. During there formation, the gas giants litterally cleared out almost all of the objects in there gravitized orbital path. Beyond the gravitational influence of Neptune, the many remaining objects in a fixed orbit were safe from crashing into any Planet. Therefore there are much more objects spread out at great various distances in the KB than within the gas giants regions. Many we haven't discovered yet because there very small and far away but every now and then we see them as comets. The very few objects still remaining between the Planets are rogue asteroids or comets. In comparison to the Asteroid or Kuiper Belts there are much less and they are more likely to crash into the Planets much sooner. Get it through your thick skulls people it's called the Kuiper Belt and Pluto in it's safe 200+ year orbit is part of it.

There is nothing stating that the clearing out HAD to occur 5 billion years ago.

Literally cleared out is not the same as cleared. Either it is cleared or it is not.

The Trojan asteroids are not rogue asteroids.

Whether they are more or less populous that the Kuiper Belt is not relevant. They exist, so therefore, they have NOT been cleared.

Thick skulls? You obviously are not intent on having an intelligent discussion and a comment like that renders your entire post moot.

i ask you all, what have the Plutonians ever done to us?

-4A ; )