Why did scientists decide Pluto wasn't a planet?

Answer 1

i'm not happy with their decision----so what it still remains in orbit-------what about the 10th planet just discovered a short time ago---some call it a phantom ......but something's there in orbit....

Answer 2

Pluto did not obey Bode's law. And they never were really able to determines its mass ,hence they considered it a large asteroid revolving as a planetary motion but yet did not considered it a planet. This disappointed a lot of would be astronomers who where very interested in pluto.
Never the less the quest for new planets moves on. However none have been found in the likeness of the earth.It behoves all the inhabitants of the earth to apreciate it because the earth so far is the best planet in the solar system. It was just too bad for Pluto.

Answer 3

I don't think anyone here has actually stated the IAU's definition of a planet. Basically, in order to be a planet, a body must:

1. Orbit the Sun. Pluto does, so no problem here.
2. Have enough mass that it forms a ball/sphere. Unlike what was previously stated, Pluto is in fact massive enough to have gathered itself into a sphere, so again, no problem here.

Ah, but then we come to
3. The body must have "cleared the neighborhood" of its orbit. This is where Pluto falls short. All of our other planets orbit alone (or with their respective moons/satellites), but Pluto does indeed orbit our sun with hundreds of other rocky, icy bodies in an area known as the Kuiper Belt. Because of this, Pluto was demoted to dwarf planet status.

I hope this makes things a bit clearer.

Answer 4

The International Astronomical Union decided that Pluto was no longer a planet. The reason is that while Pluto is round, orbits the sun, and has three moons, it has not cleared (via gravity) its own orbit of debris. Instead, they decided to classify it as a "dwarf planet".

See the details below.

RESOLUTION 5A
The IAU therefore resolves that "planets" and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:

(1) A "planet" [footnote 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.

(2) A "dwarf planet" 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 [footnote 2] , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects [footnote 3] except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".


Footnote 1: The eight "planets" are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Footnote 2: An IAU process will be established to assign borderline objects into either dwarf planet and other categories.

Footnote 3: These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

RESOLUTION 6A
The IAU further resolves:

Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.

Answer 5

To put it simply Pluto is a kuiper object. I should have never been deemed as a planet to begin with. There are thousands of kuiper objects just beyond the orbit of Pluto. Pluto just so happens to be one of the biggest and the closest again a kuiper object non the less.

Answer 6

Pluto is actually a dwarf planet. The astroid belt also contains a dwarf planet but is not counted in which the other 8.

Answer 7

that was because pluto was becomming smaller and smaller.. it was not big enough to be a planet.

Answer 8

It is not big enough for it's gravity to crush it into a sphere. it is shaped like a potato so it is an asteroid.

Answer 9

they think that people arnet asking a lot about why we need the sun,


and the other answer is they think it might be the sun,s moon

Answer 10

Because Mickey decided that pluto would be better off on another planet DUH!