Why did we downgrade pluto from a planet?

Answer 1

Because a bunch of idiot geniuses got together and decided that they didn't like all those kids who already knew the MVEMJSUNP things.

Answer 2

http://www.iau.org/fileadmin/content/pdfs/Resolution_GA26-5-6.pdf
http://en.wikipedia.org/wiki/Pluto

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. astronomers then added numerals to the names, and pluto recently got its numeral. 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. "1 ceres" and "136199 eris" are other dwarf planets.

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.

Answer 3

Another "planet" was found recently, UB313. It is bigger than Pluto and farther away. It was found in the Kuiper Belt, a region of space where there could be 200 more objects that could be considered planets. Pluto is also in the Kuiper Belt. So they had to figure out a formal definition of a planet before more discoveries are made. It was either have 200+ planets or have 8. They chose to have 8.

Answer 4

Much to my surprise, the International Astronomical Union has indeed voted on a resolution that defines exactly what a planet is and Pluto no longer qualifies. This means that Pluto is indeed not a planet any more and that our solar system no longer has the nine planets I learned about as a kid, but only eight!

Don't worry, though, Pluto is now to be known as a dwarf planet, so it's not been completely ejected from our solar system, just relabeled. The eight planets in our solar system are now, in order from the Sun outwards, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

As The Planetary Society explains, "a “planet” is now 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 neighborhood around its orbit."

"A dwarf planet, according to the new definition, 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, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite."

Got it?

There are now three dwarf planets in our solar system, so Pluto isn't alone. It's joined by the asteroids Ceres and Xena (aka UB313), though more than a dozen are on the IAU's dwarf planet watch list, if you can believe it.

One key reason that Pluto has been given the boot is because its orbit is not in the same ecliptic plane as the rest of the planets and isn't circular as are the planets, but is rather "eccentric". Indeed, at certain points in its orbit, Pluto is actually closer to the sun than Neptune.

Answer 5

There are three main conditions for an object to be called a 'planet', according to the IAU resolution passed August 24, 2006.

1. The object must be in orbit around the Sun.
2. The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
3. It must have cleared the neighborhood around its orbit.

Pluto fails to meet the third condition.

EDIT: Wow, every single person above me is absolutely wrong. It wasn't downgraded because of it's size, niether is it like a "moon".

Answer 6

Because some retard decided that pluto is not a planet after they set some new rules for the definition planet.

The new rules require a planet to orbit the Sun (pluto does, kinda), be big enough to be roundish (gravity does that), and have enough mass to clear out its solar neighborhood (gravity does that, too). Now, the problem was about gravity. Pluto lives in a crowd, it doesn't clear out it's solar neighborhood.

Answer 7

In my mind Pluto was never a planet, its orbit is simply too elipitical to be considered one. Also, with the discovery of new objects in the kuiper belt the same size or bigger than pluto we would either have to add planets or redefine what a planet really was. Thankfully they chose the latter. Maybe eventually we will find a planet out there even further (the mysterious Planet X, ohhhh) so who knows.

Answer 8

When the Khyber objects were discovered, it was realized that Pluto was too small and in the wrong orbit to be considered a planet. It was too close to Uranus, and it was not aligned with the plane of the ecliptic.

Answer 9

because they have found of lot of objects ion space that are the same size as pluto and pluto does not fit the descripionof a planet

Answer 10

I watch a Discovery Channel show on this last night. They said, because with the increased power of our telescopes....astronomers found that Pluto was actually part of a second belt of asteroids....so it is not a planet, but one of the millions of asteroids circling in that same orbit.

*L*

Answer 11

the alliens instructed us to, it appears they are taking pluto away to another system and they don't want the rest of humanity to ask questions later about the lost planet