yes Pluto is not a planet:
The resolution
The decision establishes three main categories of objects in our solar system.
Planets: The eight worlds starting with Mercury and moving out to Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
Dwarf planets: Pluto and any other round object that "has not cleared the neighborhood around its orbit, and is not a satellite."
Small solar system bodies: All other objects orbiting the sun.
Pluto and its moon Charon, which would both have been planets under the initial definition proposed Aug. 16, now get demoted because they are part of a sea of other objects that occupy the same region of space. Earth and the other eight large planets have, on the other hand, cleared broad swaths of space of any other large objects.
"Pluto is a dwarf planet by the ... definition and is recognized as the prototype of a new category of trans-Neptunian objects," states the approved resolution.
Dwarf planets are not planets under the definition, however.
"There will be hundreds of dwarf planets," Brown predicted. He has already found dozens that fit the category
2006-12-18 04:49:33
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answer #1
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answered by Anonymous
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A lot of what has been said already is true. So I won't add yet another answer. I'll just ramble on about history and feelings.
When Pluto was discovered, it was thought to be bigger than Earth and big enough to affect the orbit of Neptune (the search was based in discrepancies in the calculated orbit of Neptune).
As time went on, Pluto was found to be a lot smaller than first thought and certainly not massive enough to account for the errors in calculation of the orbit of Neptune.
There was a debate at the IAU in Prague which actually began as an attempt to define planets in such as way as to ensure than Pluto would be included, as well as some other "key" bodies, like Ceres, the first asteroid discovered.
Actually, when Ceres was discovered, it was called a planet. When it became apparent that it was only one of many objects in the asteroid belt, it -- and all other similar bodies -- were demoted to minor planets.
The proposed definition was not very good. It got modified, changed, cancelled and redrawn until there was a vote on the definition as it existed on the last day of the meeting. That definition was accepted, and its wording excludes Pluto (and Ceres, and Sedna, and...) from being full-fledged planets.
However, many astronomers agree that the definition still has problems (e.g., it is not completely clear if it includes Neptune as a planet). Therefore, it is very likely that the debate will start again and that the definition will change again.
In North America, the debate (and the result of the vote) has left a sour taste for a variety of reasons. Here are 3:
1) Many North American delegates has planned their return flight for the last day of the meeting (when, normally, very little business is conducted). They missed the vote.
2) Pluto is the only planet that was discovered in North America. It is a little more painful for us to see it lose its status.
3) NASA was sending a probe to Pluto. There was concern that the mission would not get the same amount of attention (and budget!) if it were a mission to a "dwarf" planet instead of the furthermost planet.
Within a decade or two (a long time in a career, a short time on the astronomical scale), we will have automated telescopes which will be able to find, in a month, as many objects as we presently know about in our own solar system.
When the data starts pouring in, we will have a better idea what to call a planet and what is mere rock.
For all we know, when we get to compare our system with thousands of others (in the future), we may decide that our system is better understood if we consider it a 4-planet system (Jupiter, Saturn, Uranus and Neptune) or even a one-planet system (Jupiter -- it has an 11 year orbit and the Sun has an 11 year cycle; coincidence?)
2006-12-18 13:38:22
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answer #2
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answered by Raymond 7
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Because powerful telescopes have found dozens of objects on the edges of the solar system that are around the same size as Pluto (and there are probably a lot more that we haven't found yet). If we call Pluto a planet, logically we have to add all these dozens (or more) of objects as planets as well. And nobody wants there to be dozens (or maybe even thousands) of planets in the solar system.
Of course some people say that Pluto should be a planet because it was found first, and all these others have only been found in the last few years.
Some of the largest asteroids in the asteroid belt used to be called planets before we found the rest of the asteroids. A planet should be something unique, not just one of a huge group.
2006-12-18 13:08:19
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answer #3
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answered by jrr7_05_02 2
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There are two "belts" of millions of small objects that orbit our sun. Between Mars and Jupiter is the "asteroid belt." We normally do not consider an asteroid to be a planet even if it is very large. Beyond Neptune is the "Kyber belt," which is where most comets come from.
Pluto is actually just a large rock within the Kyber belt, and it's not even the largest rock in the belt. It's smaller than our own moon.
Scientists decided that a planet must clear its immediate neighborhood of debris in order to be considered a planet and must be of a certain minimum size. Otherwise, we would have to start naming countless asteroids and comets as planets.
Over millions of years, Pluto's gravity may eventually clear most of the debris of other Kyber belt objects from its orbital path. As it grows and clears its orbital path, it would then qualify as a planet.
To distinguish objects like Pluto from smaller objects like asteroids and comets, astronomers created a new classification called "dwarf planets." Pluto is now considered a dwarf planet.
2006-12-18 15:19:09
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answer #4
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answered by jordannadunn 2
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Unfortunately too small. Astronomers had found a planetoid a little further than Pluto and they called it Setuna. There was a big debate about whether or not they it was planet. They decided it wasn't. Unfortunately Pluto was smaller than Setuna, so technically they couldn't call Pluto a planet. So they had to demote poor Pluto.
2006-12-18 12:48:05
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answer #5
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answered by Ruthie 1
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please check out this NASA link for some explanation. NASA still classifies Pluto as a planet. That will probably change sometime in the near future, because Pluto really is not a planet.
To see the reason for their decision, follow the 2nd link.
2006-12-18 13:04:40
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answer #6
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answered by scrapmetal 2
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Quasi-intellectuals? Does he mean the people with Ph.D.'s who spent 10 years in grad school who actually define what things mean? Yeah, I thought.
Pluto is too small and hasn't cleared it's orbit, that's why it is no longer a planet under the new definition. The old definition was too broad.
2006-12-18 12:50:35
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answer #7
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answered by eri 7
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A bunch of guys who decide those things decided it was too small because they were starting to find more objects about the same size and we would have wound up with a bunch of planets eventually.
2006-12-18 12:45:31
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answer #8
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answered by Gene 7
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Because a bunch of quasi-intellectuals says so. For me, it's been a planet for my whole life, and will remain that way.
2006-12-18 12:45:17
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answer #9
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answered by FRANKFUSS 6
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It doesn't meet the criteria
2006-12-18 12:44:27
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answer #10
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answered by Anonymous
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