If Pluto's not a planet then what is it?

Answer 1

pluto is not a planet, but pluto orbits the sun, is round, does not have an isolated orbit (a bunch of other similar bodies have similar orbits.), and is not a satellite so it is a dwarf planet. this does not change anything about the solar system or pluto. it just corrects the mistake of classifying pluto as a planet initially.

this same thing has happened before. beginning in 1800, astronomers found a few bodies orbiting between the orbits of mars and jupiter, and they finally stopped calling them planets after the fourth discovery. 150 years from now, no one will think of "134340 pluto" as a planet. very few will even know we classified it as a planet.

i have been waiting for this since i was about twelve. i feel somewhat satisfied. i knew that pluto didn't fit the pattern set by the major bodies in the solar system so it was an anomaly. it just felt illogical and "out of place". this was the right thing to do, believe me. i don't understand why so many are having such a problem with this.

i don't know how long this will drag on tho. many planetary scientists are not satisfied that the definition is rigorous enough.

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

Answer 2

Pluto, the last planet to join the heavenly pantheon, became the first to leave it. The status of Pluto had been under discussion for some time, but with the discovery of 2003 UB313, nicknamed Xena, the question became acute, for it seemingly had as much right as Pluto to be called a planet.

On August 24, 2006, the International Astronomical Union surprised the world by voting in a new definition of planet, one that would exclude Pluto and bring the total number down to eight. (There had previously been been strong speculation that the redefinition would bring the total up to 12 instead of down.)

Pluto was instead classified as a dwarf planet, along with Ceres and the aforementioned Xena. The main difference between a dwarf planet and the real thing is that the dwarf variety has not cleared the area of its orbital path.

This redefinition met with a wave of protests from those who wanted to see the ninth planet grandfathered in, including but not limited to supporters of the late Clyde Tombaugh, who discovered Pluto in 1930. His widow, however, said he would have been accepting of the IAU's decision since "he was a scientist" and understood that astronomers had to take into account newly discovered objects in the Kuiper Belt (where Pluto is located).

But opponents of Pluto's demotion remain unconsoled and have generated a thriving industry in T-shirts, mugs and other memorabilia. Among the many slogans of this movement was one which played on the mnemonic for the names of the erstwhile nine:

Answer 3

The IAU members gathered at the 2006 General Assembly agreed that a "planet" is defined as 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.

This means that the Solar System consists of eight "planets" Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. A new distinct class of objects called "dwarf planets" was also decided. It was agreed that "planets" and "dwarf planets" are two distinct classes of objects. The first members of the "dwarf planet" category are Ceres, Pluto and 2003 UB313 (temporary name). More "dwarf planets" are expected to be announced by the IAU in the coming months and years. 

Aloha

Answer 4

The International Austronomical Union defines a planet as celestial body that
(a) is in orbit around the Sun,
(b) is round, and
(c) has cleared the neighbourhood around its orbit.

A "dwarf planet" is defined as a celestial body that
(a) is in orbit around the Sun,
(b) is round
(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".


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 is now a dwarf planet.

Answer 6

since Pluto discovered in 1930 or so , it had only finished 1/3 of it's orbit !!!!

And it's orbit intersects with Uranus orbit ...

It's size is smaller than the earth's moon !!

So scientistes decided to put a new definition of a planet
so Pluto isn't a planet any more and kicked out of our solar system !

Answer 7

It has been downgraded to a dwarf planet due to its elliptical rotation intersecting with Neptunes. Pluto fits the other requirements of a planet (circular, etc) but does not have its own elliptical plane.

Answer 8

Its now considered a sub planet! As far as the change in what we call it, if we are going to be politically correct when it comes to planets, we need to get rid of the Greek names too!

Answer 9

Dwarf planet

Answer 10

Officially, it's a dwarf planet. So are Eris (formerly called Xena) and Ceres (an asteroid).