Why is Pluto not considered a major planet, and what other peculiarity

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Billy Jane

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distinguishes it from other major plane? Why is Pluto not considered a major planet, and what other peculiarity distinguishes it from other major planets?

I don't need a huge post, just something simple.
 
A bunch of Frenchmen got their skivvies twisted in a knot and passed some resolution insulting one of the finest planets in our solar system.

Don't pay any attention to their nonsense. Pluto is and always will be a major player among planets.
 
A planet must have cleared the neighborhood of its orbit. That means that as a planet travels, its gravity sweeps the space around it clean of other objects. Some of those objects may crash into the planet or even become moons. thats why pluto isnt one i hope this isnt too long
 
Pluto is still a planet. Just a particular type of planet. The word "dwarf" is an adjective; we add the qualifier "dwarf" to the noun "planet", specifying the sub-categorization.

Its like saying "gas giants" are still planets. People that say Pluto isnt a planet might as well say Jupiter isnt either.

With that in mind, though, we can now say there are four more planets in our solar system than we last thought before Pluto was reclassified.

We have Ceres, Haumea, Makemake, and Eris; all of which are dwarf planets. Along with Pluto, and the gas giants, we have 13 planets in our solar system.
 
1) Pluto's diameter is less than 3000 kilometers

2) Pluto has not "cleared its neighborhood" of other objects.

Neptune has not cleared its orbit of Pluto, but Neptune's diameter is greater than 3000 kilometers.
Most people are tripping over that 3000 kilometer diameter criterion. They don't realize it's part of having enough mass to be spheroidal.
 
Many other planets were being discovered at an alarming rate, such that it was felt by the IAU that school children would have difficulty memorising 20 or more planets with more being discovered all the time. The final straw that meant pluto could no longer be a planet was the discovery of the Koiper belt of which Pluto was just another member. This is just like what happened with Ceres which was once thought to be a planet but was later downgraded to an asteroid.

Now Pluto has been demoted to dwarf planet but Ceres has had a promotion from asteroid to dwarf planet.

The somewhat controversial decision arose after days of debate and finally the definition of a planet (though not uniformly accepted) is:

1. It has to independently orbit the sun, it can't orbit another body and the two bodies orbit the sun.
2. It has to be large enough to pull itself into a vaguely spherical shape under its own gravity.
3. It has to have cleared its orbit.

The third criteria is what most of the fuss is about, as technically the earth hasn't met the third criteria as evidenced by the huge number of near earth asteroids. Those who support Pluto being reinstated as a planet jump on this third criteria to argue that a strict application of the IAUs definition of a planet should exclude earth from being considered a planet.
 
Pluto has not cleared its orbit of debris.

A planet has to conform to 3 rules.

1/ It has to be a non-luminous body orbiting a central star or star system.
2/ It must have sufficient mass to form itself into a sphere.
3/ It must have cleared its orbit of major debris.

If Pluto had a clear orbit, it would be a planet. It is not too small, it has sufficient mass to be a sphere.
 
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