There is a big difference between Planet and Dwarf Planet, right? So, it did lose its status as a planet, I think. That was the whole point of the IAU decision, wasn't it?

dgavin,
It's a start... a step in the right direction. This is the first official subclassification of planets, at least in our lifetime, but it sets a precedent for future subclassifications.

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No... the point was to correctly classify 2003 UB313 so that it could be named properly. Seriously!

This debate has been building since the discovery of Varuna. But since 2003 UB313 was the first KBO bigger than Pluto, clarification had to finally be reached on whether a Kuiper Belt Object can be a planet. The IAU decided it could not.

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Not really, anything at Hydrostatic Equalibrium (round) is now a Planet.

To prevent having to number our planets in the 30's or more once all the large KBO's are confirmed, they split Planets into two catagories. One for mainstream and one for Dwarf's. I think that was the point behind the decision, to avoid adding a mass of tiny planets to the major solar system count.

So it's now 8 mainstream Planets, and 5 (officialy named) Dwarf Planets. So were sitting at 13 planets total, and counting.

Yes totaly agree there. But with over 170 other planets around other solar systems, I was hoping the working group on extrasolar planets would get a better classification scheme pushed through.

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I know you're serious The debate started long before that, and you know it. The decision about whether a KBO could be a planet started with Pluto, long before the other was discovered.I see that you are trying to make a distinction between Planet and planet, but there is none, according to the IAU. Gillianren!

Ehh? Where did you get that from?

All i'm saying is the IAU didn't remove the word Planet from Dwarf Planet.

It's still a planet according to thier definition, of which now has has two classifications. Those that have cleared thier orbits of other objects, and those that havent.

It's a bit disconcerting when IAU's definition of a planet says any object in Hydrostatic Equlibrium, (with the two classes) and NASA and the press go and say it's no longer a planet.

Don't they even -READ- the definitions?

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I just saw Hayley's comet, she waved, Said "why you always running in place? Even the man in the moon disappeared, Somewhere in the stratosphere" - Shinedown

http://worldsofothersuns.home.comcast.net/

When you said "8 mainstream Planets, ... 13 planets", but I understand now that that is not your intention.As I read the definition, Pluto does not seem to qualify under their definition of planet. I don't think that that is the fault of NASA or the press. I think that was the intent of the IAU.

After all, you seem to be ignoring the IAU's use of the term "Minor Planet" to refer to asteroids--so wouldn't there now be a lot more than 13 planets, and always have been?

You're incorrect. A dwarf planet is not a planet, regardless of what you may consider to be the usual rules of English grammar. 'Dwarf planet' is here regarded as a compound noun (and such compound nouns do exist in English). Minor planets are not planets either.

The IAU specified in the resolution that there were eight planets in the solar system (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune).

There was a resolution that 'planet' in (1) be replaced by 'classical planet'. This was specifically to put forward the idea that there were two classes of planet (classical and dwarf), rather than have planets and dearf planets as distinct classes of object. This was well understood at the Congress and there was a great deal of debate. The Congress voted not to put in the word 'classical', but to have them as two seperate categories.

Let the record show that CuddlySkyGazer is talking to dgavin

I just re-read it. They specified that those 8 planets Belong in the Planet(1) classification. They never ever said that it ment there was only 8 planets in the solar system.

And they never said Pluto wasn't a planet, just that it's in a different catagory of planet.

I also find it highly unlikely it was IAU's intention to remove Pluto from the planet classification altogether.

But yea, to bad that Classical planet resolution didn't pass, that probably would of been less confusing to have Classical and Dwarf classifications within the definition of all planets.

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There is no problem that cannot be solved by a suitable application of high explosives - US Army Demolitions School

I just saw Hayley's comet, she waved, Said "why you always running in place? Even the man in the moon disappeared, Somewhere in the stratosphere" - Shinedown

http://worldsofothersuns.home.comcast.net/

Which is it at the present time though? Are there 8 planets, or hundreds? There can't be just 13.

There are 8 Planets and 5 (named) Dwarf Planets. That makes 13 of something.

For lack of a better term maybe 13 planets of all types would sound better?

And yes, there are quite a few that haven't been named. I was only including the named planets in my Dwarf Planet count.

I think the count of hydrostaticly equal solar system objects on mike browns site is 53 (51 which are still unnamed). So could say we have 8 Planets, and and 56 Dwarf Planets for a total count of 64 planets of all types?

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http://worldsofothersuns.home.comcast.net/

And NOW we Know Why they've Capped The Definition of Planet ...

I Can Imagine Memorizing Fewer than 10 Objects, But Dozens!

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My point was, you are missing the minor planets in that count. Either you only have 8, or you have hundreds, you can't have 13.

And regardless, the IAU seems to be clear that it does not consider Pluto a planet.

No need, you don't memorize all the stars, do you? They could have come up with an inclusive definition of the term "planet" and assign distinctive attributes like "principal planet" vs. "hive planet" or something alike. That's what the (rejected) "classical" part was presumably about. It was just a decision between an inclusive and an exclusive definition, and they decided in favour of the latter. By taste.

When 5B failed to pass, it was decided that a 'Dwarf Planet' (compound noun basically meaning Planetoid) would be excluded from the list of 'Planets'.

Before 5A Section (3) passed we had 136,000+ Minor Planets

Pluto is no longer considered a 'Planet'. Hopefully 'Dwarf Planets' will come to be known as Planetoids.

-- Kevin Heider

Or, maybe "planettes"

PS: I just did a BAUT search for "planette" which came up with one use by montebianco referring to "a small plan", and a few references to "planettes" the show. I think Pluto is a great planette.

This is why I dislike the definition they came up with. There is now no way to refer to Planets and Dwarf Planets by calling them planets, planets of all types, or something similar, without an ensuing debate.

So someone either needs to invent a word that includes both types of objects, the definition needs to be changed again, or people need to accept that the word planets has multiple meanings depending on usage.

I'm not disagreeing with your statement above. "Planet" and "Dwarf Planet" are the two definitions. Pluto doesn't fall into the "Planet" definition.

However those two definitions share a common root of "any object in hydrostatic equalibrium" and a common word of Planet. By any language context that means the plural, planets, can refer to either multiples of one definition or used to group both types.

Again another point to why this definition is lacking. To much confusion and debate of what the IAU had intended with it.

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http://worldsofothersuns.home.comcast.net/

Did you re-read all of the resolution? It starts as follows: "The IAU therefore resolves that "planets" and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:" (my italics). 'Distinct' means the categories don't overlap, so dwarf planets are not planets.

The note to the planet definition states: "The eight "planets" are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune." Exactly eight planets, not 'eight of the planets are'.

The IAU's press release announcing the resolutions passed says: "This means that the Solar System consists of eight "planets" Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. A new distinct class of objects called "dwarf planets" was also decided. It was agreed that "planets" and "dwarf planets" are two distinct classes of objects." (my italics)

There was some unhappiness at the wording of the resolution, because it was felt some people might confusedly think a dwarf planet was a planet on the grounds of the normal (but not universal) English language construction. However, this got short shrift from other delegates who pointed out that if a dwarf planet must be a planet, then a minor planet must be one by the same reasoning.

Hello everyone, I appologize if this has been posted or something like this...

But my opinion when Solar system was evolving, a big cloud of dust started to rotate around the future Sun. So, close to the Sun developed planets with solid surface, and as you go further away, gas giants were created. So rocky ones first and gas giants last.. So.. Why the hell's Pluto the last?!

He probably wandered around for a while or something and then got snapped by the Sun and started to revolve around it... Make any sense?

Anyway, that's just my opinion why Pluto shouldn't be a planet in solar system, at least not "big" like others.

Cheers,

Gaj

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Exactly what i've been pointing out. Maybe some people don't want to describe these two classes together, but that isn't universal either.

So again we either need a new word that can be used to describe both Planets and Dwarf Planets together inclusively, or they need to change the definition with that Classical Planet or Main Planet classification for main solar system objects, and simplify the word planet to mean anything in Hydrostatic Equalibrium.

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There is no problem that cannot be solved by a suitable application of high explosives - US Army Demolitions School

I just saw Hayley's comet, she waved, Said "why you always running in place? Even the man in the moon disappeared, Somewhere in the stratosphere" - Shinedown

http://worldsofothersuns.home.comcast.net/

Ironically, they're in a bloodbath over what is a planet versus what isn't at the other end of the spectrum. Seems the breakpoint between brown dwarf and planet isn't any prettier than what's a planet versus an iceball/dirtball.

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Correct. 'Dwarf Planets' are different then Planets. Planets have to clear their orbits of comparable objects.

We call them Worlds or Spheroids, if you prefer. This also applies to the larger moons that deserve to be categorized by 'what they are' and not 'where they are'.

It was decided that a Planet has to be more than just in "Hydrostatic Equalibrium". In 2009, the IAU could just rename 'Dwarf Planets' to a single word (planetoid, planette) avoiding the whole compound noun concern.

'Dwarf Planets' are defined by 'where they are' just as moons are.

-- Kevin Heider

The suggested word is planemo, although it does include other objects.

Um, In a Word, NO ...

Juust as Asteroid Belt-Type Objects Were The Building Blocks of The Inner Solar System, So Too Kuiper Belt-Type Objects Were The Building Blocks of The Outer Solar System ...

By The Way, If you Wiish to Discuss your Theory Further Try In Against The Mainstream, This Really Isn't The Place for it!

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For those of you who would like to keep Pluto as a non-minor planet, you now can have t-shirts and bumperstickers, to identify your fellow travelers.
LINKY
(And no, this is not a statement of my position on this, nor a commercial)

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<< (1) A "planet" 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, and (c) has cleared the neighbourhood around its orbit. >>


Seems to me that Neptune has not cleared it's orbit of pluto and it's moons yet either...

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Yep, that point has been made before Murff. It shows what a fudge the IAU made when coming up with this definition.

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At the risk of repeating for one time too many the answers to this, given here previously: There are no other objects even close to Neptune's mass in Neptune's orbit zone. Neptune's mass is almost eight thousand times the mass of Pluto. Can you name a significantly sized body that Neptune has not cleared out?

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It seems to me that you both are talking past each other. Isn't it just a question of what is meant by "significant" or "cleared out"? Of course, Neptune has not cleared out Pluto, but Pluto is nowhere near Neptune. Of course, Pluto is insignificant with respect to Neptune, but I would consider Pluto to be signficant.