why isn't pluto a planet any more?

Question

why?!?!?!?

Answer 1

http://en.wikipedia.org/wiki/Pluto

on 24 august 2006, the international astronomical union reclassified pluto.

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

this same thing happened has happened before. in 1800, an astronomer found a body orbiting between the orbits of mars and jupiter and thought it was a planet. astronomers finally stopped classifying them as planets after they found several other bodies with similar orbits, and no one thinks ceres, pallas, juno, and vesta are planets today.

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 2

The posters who said Pluto was reclassified as a "dwarf planet" because it is too small are incorrect. True, size is one criteria astromomers use to classify a planet. But Pluto was downgraded from planet status primarily because of its orbit. In a very controversial decision by the International Astronomical Union earlier this year, astronomers decided that Pluto doesn't meet one of the new "rules" for a planet: it must "clear the neighborhood around its orbit." Pluto has an oblong orbit that cuts in front of (and overlaps with) Neptune. It also orbits around the sun on an angle that takes it well above and beyond the main plane of our solar system. So it was disqualified as a planet.

Answer 3

The scientific community has downgraded Pluto from a planet to a Moon because Pluto does not meet the new standards as to what is classified as a planet.

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

Pluto has never really been a planet. It is too small, too unlike all the other planets. It does not meet the definition of a planet.

Answer 6

Because it's too small - there are larger objects orbiting the Sun which are not classified as planets (mainly some of the larger asteroids in the asteroid belt between Mars and Jupiter).

Therefore Pluto, it's binary neighbour Charon, and the as-yet unamed object further out than Pluto have been re-classified and "Dwarf Planets"

Answer 7

Pluto is not a planet anymore because scientists stated that it was a dwarf planet and that it was not part of our solar system but instead part of the kuiper belt which begins where pluto is at . the kuiper belt is a place paast our solar system where comets ,asteroids and dwarf planets are found.

Answer 8

I agree with gab500.

It's true, Pluto runs around here interfering with my orbit. It makes me so mad sometimes! Now, since he was downgraded from being a planet, all I hear is him whine about it. Stay out of my orbit and people will like you again Pluto!!!


Wow..thumbs down. Smeone needs to lighten up and take a joke.

"Our 5 senses are useless without the 6th sense............A sense of humor"

Answer 9

pluto is not a planet anymore because 1it is too small 2itis only made of ice and it also lacks the general characteristics of a planet such as atmosphere gas and gravity etc.

Answer 10

Too small. I guess you gotta draw a line somewhere; otherwise, every hunk of rock would be a planet.