http://www.space.com/scienceastronom...7_chrx73b.html

There it is, a cold admission. Special conditions applicable to one example in the universe, meant to be used nowhere else. This definition is utterly bogus. Its the fundamental equivalent of saying the Sun is some object other than a star because it happens to be at the center of this star system, and isn't a twinkling background object in the sky.

Bad Astronomy if there ever were.

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I'm not completely heartless, the doctor who removed it told me he'd never be able to get it all.

It is extremely unscientific to make a definition for just one area. Considering the high amount of other stellar systems we know of, and that our knowledge of them is rapidly increasing...it should be a rule to make a definition that can be applied anywhere.

The arguement that "we should wait and deal with the issues when the come" is ludicrous. Conquer the issues now. This is an opportunity to make a definition that could stick for centuries to come. Forget culture, forget arbitrary limits, focus on the science.

In simple terms...my view is that a planet is anything that is shaped into hydrostatic equilibrium by gravity and is not or never was a star. There can be as many sub-categories as needed, based on orbit, size, features, whatever. The point is...it's simple, scientific, and universally applicable. Frankly, that should be the goal.

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This space is for rent.

I've argued for that same definition too. Note we don't even care if it's a moon (I'l bet the Apollo astronauts thought they were walking on a planet, and if life is ever found on Europa, we'll want it to be a planet too), or an orphan in deep space. A planet should be internally defined, like everything else in astronomy, and the definition should be inclusive (so that a "dwarf planet" would still be a planet!). Did anyone ever say "oh, we can't define a star that way, there'll be too many in our own galaxy!" It's kind of ludicrous. Now, a major planet, that's another story, and can be heliocentric.

How does that not define planets around other stars?

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PW -- Plant Whisperer

The possibility exists that around some other star there could be multiple very large (mars-size or bigger) objects in crossing orbits. We might want to consider them planets even though none of them has cleared their orbits yet. Hypothetical, but possible.

The part about "clearing its path" was added only to prevent our solar system planet tally from reaching into the dozens. It's not applicable to other systems for many reasons. For one, we have no way of knowing whether extrasolar objects have cleared their region or not. Furthermore, it's not based on size...so a Ceres-sized object that has cleared its orbit would be a planet but a region of Earth-sized objects would remain dwarf planets. Such scenarios, which are very feasible, really make the definition useless. Location should not matter at all.

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This space is for rent.

Ironically, there's evidence in the Beta Pictaurus and Epsilon Eridani accretion disks seeming to indicate a large object is in the process. Both have rather impressive, and fairly stable, gaps in the debris field. Nothing confirmed, but strong strong suspicion of a planet.

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I'm not completely heartless, the doctor who removed it told me he'd never be able to get it all.

So, I wonder what the evolutionary tree looks like, now? Would you call it a protoplanet if you don't really know it will ever be a planet, or call it a protodwarfplanet which is too much a mouthful? A protoplanetoid sounds more scientific and could be considered planet-like by one definition.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

What you've quoted is not what the IAU has decided.

Sun with a capital S is our sun. The definition only applies to objects in our solar system.

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"The plan does not involve mayonaise."
"... I knew there was a catch."

You can't take the sky from me.

Important quote from the article:
That's very important to realize. Just because our classifications will not be perfect does not mean we should not attempt to classify.

Who cares if "dwarf planets" are called planets, or not? In a way, they ARE planets.... dwarf planets. But are they qualitatively different than the classical planets? Absolutely, because they did not accrete to a large enough size to clear their orbit.

Too much of the planet debate revolved around nomenclature, when it really was an issue of classification.

It could be that the IAU used "Sun" in their definition instead of the general "a star" simply because they realized that they had far too little information to make a generalized rule.

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"Barbarism is the natural state of mankind. Civilization is unnatural. It is a whim of circumstance. And barbarism must always ultimately triumph" -- Conan

It was my observation that much of the debate revolved around dynamics vs inherent properties of the object itself.

And what good is a classification scheme when the nomenclature is so poor as to be confusing?

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"The plan does not involve mayonaise."
"... I knew there was a catch."

You can't take the sky from me.

That is the exact reason.

As extrasolar planets are not going to be named or numbered, letting them without definition now doesn't matter much.

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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

Dynamics has a lot to do with the term planet. After all, planets are objects which orbit stars and don't orbit other planets. If only the roundness criterion was accepted, all large moons would have become planets.

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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

Of course. What the debate came down to, when all of the rhetoric is stripped away, was formation proceses (dynamics) vs intrinsic properties (geology). I'm sure many of us who are both disappointed and annoyed with the definition approved by the IAU would be placated if we had other official planetary categories as well. By giving us a distinction between "Real Planet" vs "Large, Planety Objects That There Are Too Many Of For Some People To Take Seriously," but tacking the word Planet on for good measure, they IAU has effectively muddied their definition of "Real Planet".

I still stand by the idea that "Planet" should be based on intrinsic properties of the body, while "Dwarf", "Gas Giant", "Ice Giant", "Terrestrial", or whatever other adjective one wants to tack on could deal with the issues of dynamics. And the IAU's definition can be interpreted as doing this, or at least it could be if it didn't have the stench of "Real Planet" vs "Insignificant Ice Cube" all over it.

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"The plan does not involve mayonaise."
"... I knew there was a catch."

You can't take the sky from me.