Why is pluto no longer considered a real planet?

I haven't followed the science debate at all, but I'd like to know. Why is pluto no longer considered a real planet?

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Last Updated: Thursday, 24 August 2006, 13:34 GMT 14:34 UK
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Pluto loses status as a planet

Pluto was discovered in 1930 by US astronomer Clyde Tombaugh

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Astronomers have voted to strip Pluto of its status as a planet.

About 2,500 scientists meeting in Prague have adopted historic new guidelines that see the small, distant world demoted to a secondary category.

The researchers said Pluto failed to dominate its orbit around the Sun in the same way as the other planets.

The International Astronomical Union's (IAU) decision means textbooks will now have to describe a Solar System with just eight major planetary bodies.

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I don't see the need to redefine the solar system
Siraj Ahsan, Dubai

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See the new Solar System
Pluto, which was discovered in 1930 by the American Clyde Tombaugh, will be referred to as a "dwarf planet".

There is a recognition that the demotion is likely to upset the public, who have become accustomed to a particular view of the Solar System.

Teary-eyed

"I have a slight tear in my eye today, yes; but at the end of the day we have to describe the Solar System as it really is, not as we would like it to be," said Professor Iwan Williams, chair of the IAU panel that has been working over recent months to define the term "planet".

Voting and the IAU meeting (IAU)
The meeting had seen some fierce arguments before final voting
The need for a strict definition was deemed necessary after new telescope technologies began to reveal far-off objects that rivalled Pluto in size.

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It is no longer considered a planet becuase it is so small that they think that it may disappear or something one day...I am only recalling what I read. but there are many answers to that

because..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................I DONT NO.................................................................................................

Hm..I guess I've been out of school too long. I didn't know they weren't considering it a planet anymore. I need to do some research I guess.

because, the astronots came and decided
that pluto would not be a planet any more.
and I think they destroed it.

for one it has an eliptical orbit, not a circular one, for two it is smaller than out moon, for three, its orbuital field is tilted like a comet's

Because it's so small!! and to far away!! it is considered as a dwarf planet now!!

"I have a slight tear in my eye today, yes; but at the end of the day we have to describe the Solar System as it really is, not as we would like it to be," said Professor Iwan Williams, chair of the IAU panel that has been working over recent months to define the term "planet".

This is bogus. The IAU definition does not describe the solar system "as it really is" but as one group of astronomers, namely dynamicists, interpret it. Their definition is flawed in multiple ways. First, it makes no linguistic sense by stating that dwarf planets are not planets at all. Second, it classifies objects solely by where they are while ignoring what they are. Planet should remain a broad category with multiple subcategories such as terrestrial planets, gas giants, ice giants, dwarf planets, super Earths, hot Jupiters, etc., with more likely to come. Dwarf planets are simply a subclass of planets, and while they may not dominate their orbits, their geophysical composition is far more akin to those of planets than those of shapeless, inert asteroids.

Professor Williams is also likely aware that the IAU did not follow its own bylaws in adopting this definition. Its committee, which worked on this issue for months, proposed a very different planet definition which included Pluto, Ceres, and Eris. IAU rules prohibit the introduction of a resolution at the General Assembly if that resolution has not been properly vetted in advance by the appropriate committee, yet in this case, a small group railroaded through this resolution, which they introduced on the convention floor without having it go through the required process.

Describe the solar system as it really is? The IAU definition gets an F if that was its goal. All this definition does is blur the distinction between dwarf planets and asteroids and artificially narrow the scope of the concept of planet. It is nothing more than an interpretation of what the solar system is and a very poor one at that.