International Astronomical Union XXVIth General Assembly

[The Last Conformist]

Well to be fair, they want to include Pluto and the like in a set of smaller planets called "Plutons".

That's not the same thing at all - "minor planet" is a catch-all term for everything that's directly orbiting the Sun, too small to be a regular planet, and too big to be a meteoroid (the cutoff being ~10m).

 

[Perfection]

Hm. I think I'm starting to see why you think this is a bad definition.

Yeah it's gonna end up being a real mess

Well to be fair, they want to include Pluto and the like in a set of smaller planets called "Plutons".

Well maybe if they made Ceres a "Ceron" too we could talk. The fact is there's no differentiation between large field/belt objects (Pluto Ceres and thier ilk) and traditional orbit dominating objects like the traditional 8 planets.

Another thing that really sucks about this definition is the need for close observation of borderline cases sticking many objects into a sort of status limbo until we can get out and get a closer look

One of the properties of a pluton is that it uses more than 200 years to complete one orbit... Yep, basing the definition on how long time the Earth takes to complete one orbit.

Well, years is just a conveniant measure of time. They could easily use some other system. I really don't have much a problem with this

The two other properties are that they orbit in a plane on a different angle than the classic planets, and that their paths are highly elliptic.

it would be interesting to see how they classify a Pluto-like body that by chance has a circular orbit in the planetary plane

 

[The Last Conformist]

Yeah it's gonna end up being a real mess
Well maybe if they made Ceres a "Ceron" too we could talk.

I suppose that should be a "cereron", the stem of Ceres being Cerer- (eg. genitive Cereris). Then again, in the age of "twotinos" I suppose they would borrow with such detail. Just a question of time, I fear, before we see "jupiterian".

it would be interesting to see how they classify a Pluto-like body that by chance has a circular orbit in the planetary plane

Quaoar fits that description - it's excentricity of 0.034 is smaller than that of most classical planets, and it's inclination of ~8 deg is at the upper end of the span for the classicals. Granted, it's much smaller than Pluto, but it's bigger than Ceres, and apparently spherical.

 

[Perfection]

I suppose that should be a "cereron", the stem of Ceres being Cerer- (eg. genitive Cereris). Then again, in the age of "twotinos" I suppose they would borrow with such detail. Just a question of time, I fear, before we see "jupiterian".

Yeah, it's all kinda silly

Quaoar fits that description - it's excentricity of 0.034 is smaller than that of most classical planets, and it's inclination of ~8 deg is at the upper end of the span for the classicals. Granted, it's much smaller than Pluto, but it's bigger than Ceres, and apparently spherical.

Must not be a Pluton then!

 

[The Last Conformist]

Even better, some plutinos, but not all, will be plutons, while some plutons, but not all, will be plutinos.

 

[kryszcztov]

- Will "plutons" (new definition) be "planets" (new definition) ? If yes, what's the point in having a "pluton" sub-category ?

- The problem with their new definition is that it is based on our own Solar System, which is unique of course. At the age of the "exoplanets" ( ), this is rather annoying. I think they should come with a universal definition, that we could use for every system in the universe (even if we're years from finding out if an Earth-sized object light-years from us is round or not). What are "classical planets" and "plutons" in other solar systems ?

 

[Perfection]

- Will "plutons" (new definition) be "planets" (new definition) ? If yes, what's the point in having a "pluton" sub-category ?

Yes, the catagory is to differentiate between the classically formed eight and the KBO stuff. Of course, Ceres throws a wrench into the works

- The problem with their new definition is that it is based on our own Solar System, which is unique of course. At the age of the "exoplanets" ( ), this is rather annoying. I think they should come with a universal definition, that we could use for every system in the universe (even if we're years from finding out if an Earth-sized object light-years from us is round or not). What are "classical planets" and "plutons" in other solar systems ?

There are none, just Planets. Plutons are only things that orbit Sol, and the Classical Planets are undefined by the IAU, just reccomended as a general term for the first 8.