But to the eyes of the political purse holders... They may not be smart enough to understand that. Still... it seems like a stupid thing to say in the article.

The following questions jump to my skeptical mind:

1. Is this decision based largely on political expedience? Is it is easier to relagate one body from planetary status, than to promote a number of others to same?

2. The new bodies that some might consider planets are in the Kuiper belt regions. Are we sure that there actually is a Kuiper belt, or is this a hypothesis driven by BBT ideas and not actually witnessed as yet?

3. Is a planet now defined purely on the basis of size? Is this sensible?

That's enough for now.

1) There are zillion ways to define a planet. Depending on a definition, some are harder to confirm as planets, some are not. According to this one, if there's massive gas giant very far from the Sun, they probably would be included as planets, but no Pluto- or Mercury sized bodies.
2) Kuiper Belt exists, that is known. Currently there are roughly about 1000 known Kuiper belt objects.
3) The definition of a planet is primarily based on approximate roughness (more accurate, it must be massive enough to become round). A planet is an object that is round and it must have "cleared its orbit", according to the IAU that means it is not a dominant member of a population. Objects that don't fulfill the second criteria are dwarf planets (Ceres, Pluto, 2003 UB313). Is this sensible? If the rules are to be followed exactly, one could argue that there are no planets in the Solar System (failing the clearing criteria; Footnote 1, however, explicitly lists the eight planets). Clearly common sense must be included when decided which object is a planet or a dwarf planet.

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Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

OK, so we have:

1) Terrestrial planets - Mercury, Venus, Earth and Mars.
2) Asteroids, the largest of which (Ceres) is also a dwarf planet.
3) Giant planets - Jupiter, Saturn, Uranus and Neptune.
4) Trans Neptunian Objects, which can be further broken down to:
4a) Kuiper Belt Objects, the largest of which (Pluto, Sedna, Xena, etc.) are dwarf planets.
4b) Oort Cloud Objects.

Most asteroids and TNOs are to be called Small Solar System Objects.

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

My conclusion from that is that Neptune isn't a planet, since it hasn't cleared Pluto from its orbit.

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Everything I need to know I learned through Googling.

The good news are that we have a new class of objects "the dwarf planets" that are distinct from "small solar system bodies" and that this distinction is indeed based on roundness.

The other good news is to have a planet definition (and a dwarf planet one) definition for the first time.

The bad news is that it doesn't solve the problem of using orbit-based arguments to define what is a planet
....whereas a galaxy, a star or an asteroid is defined as such no matter what and how it is orbiting.

Let us just wait until more discoveries (inside or outside the solar system) spells troubles for this orbit-based definition.

Agreed. The definition doesn't seem like it'll be relevant for long, especially in that it is only concentrating on our solar system.

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Of all the things I've ever lost, I miss my mind the most!

Dwarf planets can be divided into "normal" dwarf planets (Ceres, maybe some of the largest asteroids), and trans-Neptunian dwarf planets (of which Pluto is the first member).

You're missing satellites, and surprisingly, so did the creators of the draft (it was fixed before the voting, however). There is no formal definition of a satellite.

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Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

Kind of dumb to replace "dominant body" with "clearing". But they mean dominant body. Neptune clearly dominates the Kuiper belt (many objects there are in resonant orbits).

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Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

Given that its written to define only eight of over two hundred bodies, its already irrelevent.

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The last time I felt a warm fuzzy feeling, I was informed by my doctor that it was just gas.

???
The science most astronomers subscribe to: Astronomy. Xena discoverer Mike Brown's science, which has nothing to do with what you're bringing up.

So now, according to Astronomy, there are only eight planets in the entire universe?

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The last time I felt a warm fuzzy feeling, I was informed by my doctor that it was just gas.

That must be the most idiotic bit of contentless journalism I've seen in a long time.

Grant Hutchison

I think the orbit-based arguments are the best. A planet is essentially a star-orbiting body [and so are "asteroids", which, ipso facto, should be regarded as planets too]. The primary characteristic of a planet is to orbit a star. Everything else [shape, size] comes [or should] after.

Demoting Pluto was an unhappy move.

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What brings us together is stronger than what pulls us apart

Ah, ah, ah! A planet is an object orbiting the Sun, so sayeth the definition.

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The last time I felt a warm fuzzy feeling, I was informed by my doctor that it was just gas.

I thought my idea (following on from Steven Wrights 'Its a small world, but I wouldn't want to paint it' quote) to define a planet as being an object 'too large for one person to paint in an Earth year' was far better than the IAU's!

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Of all the things I've ever lost, I miss my mind the most!

Argos: I´m baffled by the awkwardness of this entire episode. IAU has found a way to displease everybody. I think we should forget all this and start over.

Scientists threaten not to use the new definition

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What brings us together is stronger than what pulls us apart

Yeah, its pretty rotten, no matter how you slice it.

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The last time I felt a warm fuzzy feeling, I was informed by my doctor that it was just gas.

Yeah, it does sound like Douglas Adams wrote it in one of his books doesn't it!

'In 2006 the IAU came together after many months of debate. The outcome of this meeting was to alienate absolutely everyone on the planet Earth by fudging the planet definition. In the next meeting the IAU resolved to strip Earth of its planetary status on the grounds that it didn't fulfil the previous meeting's criteria. They then all voted themselves out of existence before disappearing up their own.........'!!

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Of all the things I've ever lost, I miss my mind the most!

Frankly, they pleased me. I like the definition. It will require some later refinement when we look at other planetary systems, but this is a great start.

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Forming opinions as we speak

They will be the first against the wall when the Revolution comes.

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You're a coward and a liar and a thOOF - Bart Sibrel

I don't see why not... After all, asteroids have moons. (See Ida and Dactyl)

Now the Death Star? That's not a moon, it's a space station!

I agree with Jakenorrish, an opportunity was lost here, in favor of nice tidy packages. It was a triumph of nomenclature over understanding, trivia over knowledge. Planet should be a more general term, with many subclasses to recognize the wide variety of physics involved, not just "planet" and "dwarf planet". Yuck.

"What's in a name? That which we call a rose by any other word would smell as sweet."

-- Romeo and Juliet (II, ii, 1-2)

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The proceeding post was brought to you by NASA, the National Association of the Sellers of Alcohol.

Alls I know is it's time to call my congressman. There is no reason to spend billions of dollars sending worthless probes to itty bitty chunks of ice way out in the atmosphere while one poor baby is starving thanks to the ravages of Katrina, the onslaught of Radical Islam war and any other load I can think of. Why spend billions on a chunk of dirty ice when that money can be used here in my own country. And since there is no real chance of finding another planet out in the nether-regions of our little neighborhood, I want funding to all those projects canceled as well. Nature of the Universe, who cares. I have roads and bridges that are crumbling right here in KC probably because we've been funding joy rides for PHDs on that piece of junk ISS and space shuttle. CLOSE IT ALL DOWN FELLERS its just a waste of money.

To hell with them all. Think I'll just go over and read some CT garbage and see what I really should believe in.

...and still have thorns!

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

It is OVER. Let's finally stop the eternal what is a planet wrangle!

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Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

Indeed.

Now we can call it Brown's Dwarf!

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I was just sitting here contemplating the immortal words of Socrates who said, "I drank what?"

"Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot." --Carl Sagan "Pale Blue Dot"

Yep, time for the Northern hemisphere autumn, longer nights, so I'll be getting out there with my small telescope, and enjoying the best of the British weather during the next few months - about 3 nights without cloud I expect!

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Of all the things I've ever lost, I miss my mind the most!