So, 12 planets eh?

[Neethis]

The IAU has finnally agreed, Pluto is a planet. So is Ceres, Charon, and Xena (2003 UB313). Solarsys.ssc needs updating I think hehe. They're putting it to a vote next month in Prague, then it becomes official...

http://news.bbc.co.uk/1/hi/sci/tech/4795755.stm

[ANDREA]

The IAC has finnally agreed, Pluto is a planet. So is Ceres, Charon, and Xena (2003 UB313). Solarsys.ssc needs updating I think hehe. They're putting it to a vote next month in Prague, then it becomes official...
http://news.bbc.co.uk/1/hi/sci/tech/4795755.stm

OK, so the "Draft Resolution 5 for GA-XXVI: Definition of a Planet"

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http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_resolution.html

stops this long Celestians debate on the matter:

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http://www.shatters.net/forum/viewtopic.php?t=7719&highlight=

Here you can find the official definition FAQ Sheet:

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http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_Q_A.html

BTW, at the first address you can find many images of the New Solar System composition, the other candidates, a clean movie of it, and other images.
Obviously all the Solar System involving Celestia scripts will have to be modified, so as the Solar System .ssc file
The new "Planet" definition gives room for another dozen "planets", so pupils and teachers will have to memorize a lot of names (wasn't better when they were nine?).
But, seriously speaking, whatever will be our opinion, the new rule, if agreed in Praga Meeting, closes any discussion or doubt on the matter.
It was time!
Bye

Andrea

[selden]

I suspect someone here could generate a much better tour of the 12 planets than the artist's impression that's on the IAU site!

[Malenfant]

The IAU has finnally agreed, Pluto is a planet. So is Ceres, Charon, and Xena (2003 UB313). Solarsys.ssc needs updating I think Laughing hehe. They're putting it to a vote next month in Prague, then it becomes official...

Right. So they haven't agreed to it then, have they - because they haven't voted on it yet.

This is an absolute nightmare if it passes though. What I've seen of this definition is vague and arbitrary, and sure as hell Charon is NOT a planet - it doesn't even orbit a star so it fails their definition, and if Charon's a planet (or a pluton, whatever the hell that is) then so's Earth's moon. Plus, they don't even defined what a "pluton" is.

I'm actually very enraged by all this. So much so that if I get that science education job I'm after, I'm going to refuse point blank to teach this crap.

[Malenfant]

Actually, I found the proposed definitions here:

http://www.newscientistspace.com/article/dn9762

It's still a poorly considered IMO.

Charon is classed as a "pluton" despite the fact that it doesn't orbit a star and therefore cannot be "a planet beyond Neptune with an orbital period of more than 200 years that circles the sun".

And what happens if we find these things in other systems where there's no Neptune? The definition needs to be much more generic than it is.

Oh man, I'm actually embarrassed to be a planetary scientist because of this.

[andrew2364]

I'm with Malenfant on this one...it's ludicrous enough with Ceres being upgraded to planetary status, when we all know that it's just the biggest of the asteroids, but to promote Charon...come on! Then why not the Moon, the Galileans, Titan, even Triton. They certainly have just as much presence to be considered planets as Charon does, and in my opinion, a lot more. Common sense tells you that Pluto should have been downgraded. In twenty years time, no one would even have given it a thought. Now we have this '12 planet solar system' mess.

[Malenfant]

Well they seem to be saying now that Pluto and Charon aren't a planet and moon, but they're a "double planet" instead because the barycentre is outside their bodies (according to the links Andrea posted, which are more detailed):

http://www.iau2006.org/mirror/www.iau.o ... ution.html
http://www.iau2006.org/mirror/www.iau.o ... 1_Q_A.html

But it's totally unnecessary I think. And now it seems they've got "IAU Planet definition, then "IAU Planet Category", and then "Descriptive Category", which is horrendously overcomplicated.

What's even more retarded is the implication that now apparently you can have a planet smack bang in the middle of a belt of bodies, which makes no sense at all.

And after all this, they didn't even bother defining the upper end of the planet scale, so we have no definitions for brown dwarfs or superjovians or gas giants.

[Neethis]

Right. So they haven't agreed to it then, have they - because they haven't voted on it yet.

True, I was just repeating what they said on the news this morning... its still closer to an agreement than they have ever come to before.

Personally, Ive always been a fan of simply demoting Pluto to Kuiper Belt Object status... far easier, lol. Im honestly expecting it to be changed again in a couple of years, when new telescopes get working and they discover a few hundred more objects that fall into this "plutons" category, and they realise its unworkable - I cant see anyone trying to make a mneumonic for hundreds of 'planets', lol. Theres also a bit of a dispute I heard now about whether to add other bodies near Ceres orbit, like Vesta and Pallas

[Scytale]

Well, I guess from now on there's going to be the really interesting inner planets, and the bulls*t planets, remnants of a high-metallicity circumstellar disk.

I wonder how many of these are floating around in the inner Oort cloud.

[ANDREA]

....And after all this, they didn't even bother defining the upper end of the planet scale, so we have no definitions for brown dwarfs or superjovians or gas giants.

Well, in the "Planet Definition?€

[selden]

Also, remember that this is a compromise. Compromises make nobody happy.

It might have been interesting to see some of the arguments (fights?) that went on over the past two years. The fact that it took so long would seem to give some hint as to how hard it was to come up with something that made everyone equally unhappy.

[Malenfant]

The fact that it took so long would seem to give some hint as to how hard it was to come up with something that made everyone equally unhappy.

I love that observation, it's so true! (or as the case may be...)

[speedfreek]

I don't really see why Ceres shouldn't be a planet. I know its in the asteroid belt, but it orbits the sun, is certainly big enough and more importantly, spherical! It looks like a planet should look.

Could Ceres not just be a planet thats inside an asteroid belt? That seems plausible to me.

[MKruer]

Man and i got ripped when I posted this topic. 12hrs earlier

[Malenfant]

That was before every news agency jumped on it and treated it as if it was a fait accompli that there'd be 12 planets. Now the story's all over the place rather than confined to a few papers in the Antipodes, there's not much point trying to clamp down on it...

The point's not changed though - the vote still hasn't been made, and it's still not confirmed that this is what they'll decide.

[Malenfant]

I don't really see why Ceres shouldn't be a planet. I know its in the asteroid belt, but it orbits the sun, is certainly big enough and more importantly, spherical! It looks like a planet should look.

Could Ceres not just be a planet thats inside an asteroid belt? That seems plausible to me.

I don't think it is.

It's no different to any other asteroid around it in terms of what it's made of, how it formed, or what kind of orbit it has - the only difference is that it's bigger. It's a big asteroid, that's all. It's not a planet in its own right with a separate identity to the things it orbits among.


This is more like what I was hoping they'd adopt (this is my own definition, not anything official):

1) The object must directly orbit a star. [I guess we can make an exception for "double planets" orbiting a barycentre outside both bodies, but THAT has to be orbiting the star].

2) The upper limit of its mass is 13 Jupiter masses [if it's higher then it's a Brown Dwarf, this is the lowest mass where fusion can be initiated in the interior but not sustained] and the lower mass limit would be where it could pull itself into a sphere [personally I think that's too ambiguous. I'd say call it 1 lunar mass. Yes, it's arbitrary, but this sphere-shape definition is waaaay too fuzzy].

3) It must not have any bodies in nearby orbits (+/- 10% of its semimajor axis from the star) that are of similar mass (+/- 50% of its mass) - if four or more other such bodies are present then it's part of a swarm of bodies in a belt, and is therefore an asteroid (made of rock or ice, it doesn't matter). [the limits here may need tweaking, but you get the idea. Yes, it's arbitrary, but that doesn't matter so long as it's consistent ]

[MackTuesday]

This is how I'd like to see it:

Planet - One of the nine major substellar objects discovered during or before 1930

Masar - Short for Major Substellar object; this is an object that orbits a star and has swept the vicinity of its circumstellar orbit free of material (except, perhaps, for its attracting Lagrange points).

Misar - Short for Minor Substellar object; this is an object that orbits a star but is not a masar.

Masaroid - A geoidal misar

Rogue Substellar Object - A substellar object that does not orbit a star

Type I n-ary Masar - A group of masars that orbit each other, but are more strongly attracted to a star than they are to each other

Type II n-ary Masar - A group of masars that orbit each other around a barycenter that lies outside all of the objects in the group

Type III n-ary Masar - A group of masars that meets the requirements for both type I and type II

Moon - A misar in orbit around a masar; "The Moon" will become a misnomer.

Major Moon - A moon that has swept its circummasar orbit free of material

Minor Moon - All other moons

One thing that isn't clear to me is whether the larger Kuiper Belt objects are masars or misars. Is it known?

[Malenfant]

I think that's an incredibly complicated way to classify things. One of the things I hate about the IAU proposal is that you've got "classical planets", "dwarf planets", "plutons", and all sorts of other crud we don't need.

I think you just need these, from smallest to biggest:

Asteroid: (less than 1 Lunar mass, orbits star, usually in belts)
Planet: (Terrestrial or Gas Giant) (1 Lunar mass to 13 Jupiter masses, orbits star, no fusion in core ever)
Brown Dwarf: (13-73 jupiter masses, can orbit star or be solo, starts fusing in core but can't sustain it)
Star: (can orbit another star, sustained fusion in core over whole lifespan).

That's all we need. No need for subcategories, or categories that you use depending on what mood you're in or who you're talking to.

[MackTuesday]

I think that's an incredibly complicated way to classify things. One of the things I hate about the IAU proposal is that you've got "classical planets", "dwarf planets", "plutons", and all sorts of other crud we don't need.

It's actually very simple compared to stellar classifications.

[Don. Edwards]

I think some of you need to some research on Ceres before you all jump on the Ceres isn't a planet bandwagon. First none of the other asteroids in the belt are even close being as round or the size of Ceres. Ceres has also been found or it is believed that Ceres has a great deal of water in it. From what I have read it is more like a small scaled down version of Europa than a plain old rocky body. I wish I had kept a record of the information I read about it six months ago or so. What they think they are seeing on Ceres is a rocky body with a large layer of water ice, with a very thin outer crust of hardened asteroidal dust.

So this would make it more like a Pluton, or whatever they have come up with than your everyday day average asteroid. Ceres is unique in this way.
I am not advocating the new system at all. I think it needs to be reworked. I am still a fan of calling all bodies that have enough gravity to have crushed there shape into a spherical shape be called planetoids. This of course would make Pluto and other outer objects all planetoids. This would also be fitting for moons up to a certain size. No one can argue that Ganymede isn?€™t a planet just because it orbits Jupiter. It still orbits the sun and is bigger than Mercury and that makes for a very planet like object to me.

I don't think anyone will be happy with whatever they come up with for their definitions. It?€™s just going to cause more debate and infighting in the scientific circles as well as the public refusing to accept this new way of thinking out right.

I say they need to start over and try again.

Don. Edwards