Why isn't PLUTO a planet no more?

Question

Can somebody please explain to me why Pluto is not a planet anymore! I am very confussed!

Answer 1

cus its too small

Answer 2

The International Astronomical Union (all hail) has decreed, by a vote of it's members:

A planet must uphold ALL three of the following:
1) Must orbit a star
2) Must achieve hydrostatic equilibrium (Gravity must pull it into round shape)
3) Must be by far the most dominant mass in it's region of the solar system.
4) Must be below the deuterium fusion limit.

Pluto is not a planet because it does not satisfy #3. Pluto is certainly not the largest thing in it's region of the solar system. It's in the middle of the Kuiper asteroid belt, where some of the asteroids are even larger than Pluto, namely Eris. Pluto is now comparable to asteroid Pallas. Ever heard of it? Probably not. The same will be with Pluto. Another large object, but certainly not planet-like, in the Kuiper Belt.

Answer 3

In the summer of 2006, the International Astonomical Union created a definition of "planet" for the first time. Pluto's status was then changed to "dwarf planet" because it satisfies all the new requirements to be a planet, except that it has not cleared the neighborhood of its orbit. A planet must be large enough to be rounded by its own gravity but must not experience any nuclear fusion at its core. In addition, a planet must be orbiting a star directly; it cannot itself be oribiting a planet. Any object that satisfies these requirements and also has "cleared the neighborhood of its orbit" is classified as a planet. An object that does not meet this final requirement but satisfies the others is a dwarf planet. Pluto is a dwarf planet because many other objects criss-cross its orbit, which is resonantly controlled by the planet Neptune. The asteroid Ceres is also a dwarf planet, because it is spheroidal but shares its orbital space with many other asteroids.

Answer 4

Congradulations! You are the 1000th person to ask this question. You win an answer:
According to the International Astronomical Union, a celestial body must satisfy these 3 criterias to be considered a planet:

1 It must be in orbit around the Sun.
2 It must be large enough that it takes on a nearly round shape.
3 It has cleared its orbit of other objects.

According to the AIU Pluto does not satisfy number 3

Answer 5

This has been asked before, I don't remember the details but I think the official answer has to do with the size of other objects in similar orbits, there are asteroids out there that are large enough that Pluto doesn't seem so very special, or something like that.

The real reason is his publicists wasn't very good.

Answer 6

Pluto is a smallest planet in the solar system. it is very small so that scientices noticed that it is not a planet any more.A planet must be at least three time bigger than pluto to be a planet.

Answer 7

As stated by a recent astronomers agreement (Praga meeting, august 2006) to precisely define the terms of solar system bodies, now that a lot of are known and will be known thank to probes, telescopes, etc. Here down are the specs:

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"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) shape2,
(c) has not cleared the neighbourhood around its orbit, and
(d) is not a satellite.

(3) All other objects3, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

1The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
2An IAU process will be established to assign borderline objects into either dwarf planet and other categories.
3These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

RESOLUTION 5B
Insert the word "classical" before the word "planet" in Resolution 5A, Section (1), and footnote 1. Thus reading:

(1) A classical "planet"1 is a celestial body . . .

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

Take a look at the IAU home page for further info:

http://www.iau.org/iau0602.423.0.html......

Answer 8

Pluto was never a planet, unfortunately 5 billion people thought it was, until we were all corrected by a bunch of fuzzy headed scientists that needed a reason to revise all the astronmy textbooks.

Gotta prove they are good for something.

Answer 9

Okay, double negative. So, if you add them together it equals a positive... now I'm confussed. It is really confusing when you are confussed.

Answer 10

It's still a planet, no matter what some fraking scientist calls it!

Answer 11

Princess Leia deceived the empire into thinking that was where there rebel base was - so they destroyed it with the death star. The Force still has remnants of the distrubance.