What is the reason that Pluto is no longer a planet?

Question

Questions need answers, people!! Also, does anyone know the other two "dwarf planets" names?

I found out the three dwarf planets. Pluto, Ceres, and Xena.

Answer 1

Something less than 400 members of the 10,000 member IAU voted under a veil of assumed authority to downgrade Pluto's status as a planet after they rewrote the rule book. Most of the new criteria they established that must be met in order for an object to be considered a planet is met by Pluto. It orbits a star, it has a moon, and it is generally spherical in shape. The disqualifying new rule was that Pluto has not cleared its orbital path around the sun and there are other objects sharing the same orbit. This would mean that if another object enters or is found to exist in the same orbital path of the Earth, the Earth would not be a planet. The IAU also failed to take into consideration as to whether or not Pluto is in the process of clearing its orbital path and just needs a few billion more years.

Answer 2

http://en.wikipedia.org/wiki/Pluto
http://en.wikipedia.org/wiki/Eris_%28dwarf_planet%29
http://en.wikipedia.org/wiki/Ceres_%28dwarf_planet%29

pluto does orbit the sun, is ball-shaped, does not have an isolated orbit (a bunch of other similar bodies have similar orbits.), and is not a satellite so it is not a planet.

i have been waiting for this since i was about ten when i learned that pluto didn't fit the pattern set by the major bodies in the solar system so it was an anomaly. it just felt "out of place". now that astronomers have found hundreds of other bodies with similar orbits, classifying "134340 pluto" as a planet is even more irrational. i feel somewhat satisfied, but i don't know how long this will drag on tho. many planetary astronomers are satisfied that the definition is rigorous enuf. i can accept that the definition is flawed, but i can not accept that "134340 pluto" is a planet.

this was the right thing to do, believe me. this does not change anything about pluto or the solar system. this just corrects the mistake of classifying pluto as a planet initially.

the names of the two additional "dwarf planets" are "1 ceres" and "136199 eris".

many astronomers consider pluto and charon to be a binary system, but two small bodies orbit that system. they are called nix and hydra.

incidentally, "134340 pluto" was never a moon of neptune. neptune did capture triton. this is why triton has a retrograde orbit.

Answer 3

Ceres, Pluto, and Eris are the three dwarf planets.

The International Astronomical Union decided that Pluto was no longer a planet. Instead, they decided to classify it as a "dwarf planet". The reason is that it has not cleared its own orbit of debris.

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 4

The main reasons are:
- Its orbit is so eccentric that crosses the orbit of Neptune
- It orbits lies on a different plane in comparison to other planets
- It is not so close to a spheric shape.

Answer 5

A planet should virtually clear its orbit of other debris (asteroids...etc)

Answer 6

It's small.

It's shape is not spherical.

It's orbit is not circular but highly elliptical.

Answer 7

it did not 'clear its neighborhood'

Answer 8

it is a planet...