After the IAU shares its wisdom, how many official planets will we have in our solar system?

Either 8, or no definition (they have to talk about something on those astro boards after all).

My best guess is 8, though - The Definition will somehow involve near-circularity of orbit and history of formation - thus demoting Pluto/Charon, sadly.

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Non sunt multiplicanda entia praeter necessitatem.

I think that we'll be up to 11 or more.

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Quaeso quousque humi defixa tua mens erit? Nonne aspicis, quae in templa veneris?

Ten, but the number will rise soon.

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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

I think that Quaoar will be in immediately as well. Not to mention Sedna, Orcus, and the others.

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Quaeso quousque humi defixa tua mens erit? Nonne aspicis, quae in templa veneris?

8 they're clever people, I don't want to have to remember the name of 300 or more planets

I have a feeling they will go 10....but I really don't know what I'd like to happen myself. :-?

with regards

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I disagree....such a definition would be ridiculous. Consider we discover a large Earth to Neptune sized with a high eccentricity? And what about exoplanets?

I don't think they will go that far....too many becoming planets at once..

But it was an interesting idea somebody mentioned in a previous post about having:

Rocky inner-planets: Mercury - Mars
Gas planets: Jupiter - Neptune
Kuipter belt planets (or something similar): Pluto and others

It will be very interesting to see what they have to say...

with regards

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Hey, that's no problem, just remember the mnemonic:

Many
Very
Erudite
Men
Just
Shut
Up and
Number the
Planets
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12...300.

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There´s a few thousand planets in this system, according to Argos.

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"As truth is gathered, I rearrange,
Inside out, outside in - Perpetual change." - A British rock band

Forgive my cave habitation, but is the IAU actually going to come up with an official definition that will decide the fate of Pluto? Wow! This is like waiting for the Hutton report.

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Where's the cut-off point then? 1000km diameter? There are many 'others' that range in size from UB313 ~2500km down to objects under 500....where do you draw the line?

Good luck, IAU.

=D>

with regards

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Sure hope so...this is the current definition they have:

http://www.iau.org/IAU/FAQ/sedna.html

with regards

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Well, only if you are into lists. Pluto will have the same size, shape, orbit, etc., no matter what the decision...

We need a definition that´s suitable for all stars. When you consider that, things like size and shape lose their meaning. Our definition of "planet" must take solely orbital characteristics into account.

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"As truth is gathered, I rearrange,
Inside out, outside in - Perpetual change." - A British rock band

I disagree. What if we discover a solar system that has planets in erratic orbits, not all in the same plane? Large objects... gas giants, even? What would you call them?

with regards

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Current theories on planetary formation would rule out this possibility. If components of a planetary system are formed from a primeval disc [i.e. a roughly co-planar collection of objects] of dust an gas a round a star, then one would expect at least one planet (whatever its size and shape) with a stable orbit (whatever the orbit´s shape, except hyperbolic). Erratic objects would be called "planetoids" (whatever their shapes and sizes).

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"As truth is gathered, I rearrange,
Inside out, outside in - Perpetual change." - A British rock band

Well, obviously objects can have erratic orbits (KBO's in our own solar system) but where do you draw the line? If Earth had an eccentric orbit (if say, a large jupiter-sized body was closeby and knocked it out of a 'regular' orbit), would it then be no longer classified as a planet?

And what if we discover another Earth to Neptune sized object beyond the kuiper belt ... is distance going to be an issue as well?

with regards

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How about any spherical body with an appreciable (say... Mercury/Pluto) atmosphere orbiting a star is a planet?

Mercury and Pluto would qualify. Titan and Ceres would not.