Why is pluto not concidered as a planet?

Answer 1

The debate came to a head in 2006 with an IAU resolution that created an official definition for the term "planet". According to this resolution, there are three main conditions for an object to be considered a 'planet':

1 The object must be in orbit around the Sun.
2 The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
3 It must have cleared the neighbourhood around its orbit.

Pluto fails to meet the third condition. The IAU further resolved that Pluto be classified in the simultaneously created dwarf planet category, and that it act as prototype for a yet-to-be-named category of trans-Neptunian objects, in which it would be separately, but concurrently, classified

Answer 2

Is Pluto a planet???? Yes and no...

Well for starters, Pluto is just too small. In the neighborhood where Pluto lives? Planets are supposed to be huge. The Jovian planets, Jupiter, Saturn, Uranus and Neptune are 20 to 300 times the size of the Earth, and Pluto is really small compared to the Earth, smaller than our Moon. Kind of stands out.

And Pluto is not made out the same material as the Jovians. The large planets are mostly gigantic spheres of gas, mostly hydrogen and helium. Likely there are no solid surfaces, only denser and denser gas all the way in. Pluto is a small solid world of methane, water, carbon dioxide and ammonia ices, maybe a little rock and with a just hint of atmosphere (that freezes out and falls as snow in her "winter").

And third, Pluto's orbit is the most eccentric (oval shaped) and the most tilted to the plane that the rest of the planets orbit in. Also, Pluto is locked in a resonance with Neptune's orbit and comes closer to the sun than Neptune sometimes.

There were theories that Pluto was a lost moon of Neptune but that was before we discovered she a has one large moon (Charon) half her size (pretty much, this system is a double planet) and recently two other teeny-tiney moons (Nix and Hydra).

Pluto seems like she cant be an ejected moon-she must have formed on her own and seems to be part of an entire army of small icey-dwarf objects that circle just outside Neptune's orbit in what is known as the Kuiper belt. We have no idea of how many or how large these objects may be, hundreds???? NOT "planets" proper, hence the new term "dwarf planet" where Pluto is king.

But... I still think Pluto SHOULD be called a planet because of historical reasons (discovered by an American, financed by Percival Lowell, Tombaugh's life story, etc).

Answer 3

Because it does not dominate it's orbit. Pluto drifts around debris at the edge of the Kuiper belt and it's orbit comes inside that of Neptune which is dominant.

Ceres is also called a dwarf planet since it is big enough to have become round, but is in among the debris of the asteroid belt.

Answer 4

It's part of the Kuiper belt instead. Pluto is both highly inclined to the ecliptic and highly eccentric in its orbit, typical of Kuiper belt objects. At the time of Pluto's discovery, it was not even known that the Kuiper belt existed, but recently there have been larger objects than tiny Pluto found in that region beyond Neptune.

Answer 5

We all know that Goofy is Goofy, and the Man in the Moon is a Newfy ... but Pluto is "different"

;-)

Answer 6

'cause its a moon...>.>