Hail Pluto, well met

Saiph · Aug 25, 2006

Well...I don't remember orbital eccentricity actually being in the definition I've read...so that arguement is moot. as for your 7 tier system...seems rather arbitrary. Mercury has a lot in common with venus and earth...so why is it classified as sub-terrestrial based solely on a rather arbitrary size definition? Neptune, Uranas, Saturn and Jupiter differ really only in size. Composition and behavior vary little between them. So why classify them differently? It's like saying I'm 6ft 4" tall, so I must be something different than my friend, who's 5ft 2", even though we're both brown haired, brown eyes, intillegent, lean build (well, I used to be lean) and like a lot of the same things. Different enough that you would classify us as something entirely different, based solely upon that hieght requirement. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

Saiph · Aug 26, 2006

part of the problem of your multi-tier system, especially when applied to the solar system, is you have 7 categories for less than a dozen objects. There's no real grouping there at all. Now, what does Pluto share in common with mercury (And I can look it up easily, but you brought it up) <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

mithridates · Aug 26, 2006

Pluto and Mercury don't have much in common with each other at all. For starters Mercury is 25 times more massive and has a strong magnetic field. And though Ganymede is larger than size than Mercury it's still only half as massive. <div class="Discussion_UserSignature"> ----- http://mithridates.blogspot.com </div>

lsbd · Aug 28, 2006

Alas poor Pluto...I knew him well!

odysseus145 · Aug 28, 2006

What's the status of Charon now? <div class="Discussion_UserSignature"> </div>

ittiz · Aug 29, 2006

It's a moon

odysseus145 · Aug 29, 2006

Really? In the IAU's initial definition, Pluto and Charon were given equally status because they orbit a point in space. <div class="Discussion_UserSignature"> </div>

ittiz · Aug 29, 2006

Yeah they tabled to whole double planet thing till later with this new definition. So they still consider it a moon.

betelgeuze · Aug 29, 2006

The worst thing is; it took them 2 years to deside a definition and they change it 1 day before the vote. What have they been doing the last 2 years?

MeteorWayne · Aug 29, 2006

Thinking about a very complicated issue. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

cuddlyrocket · Aug 30, 2006

Charon's status is unclear. Whether or not it is a dwarf planet depends on whether or not you consider it a satellite of Pluto or not. Unfortunately, there is no official definition of satellite. Personally I have some sympathy with the view that to be a satellite the barycentre must be within the primary (except I'd add 'at least at some point in the orbit' to take account of any wildly eccentric ones). YMMV.

MeteorWayne · Aug 30, 2006

No matter how wildly eccentric, the barycenter's position does not change. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

odysseus145 · Aug 30, 2006

Is it possible that Charon could have tiny moons of it's own? Now that would make things complicated. <div class="Discussion_UserSignature"> </div>

MeteorWayne · Aug 30, 2006

No, Pluto and Charon have two moons together, Nix and Hydra. All revolve around the barycenter. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

odysseus145 · Aug 30, 2006

Oh, I get it. That makes more sense than what I was thinking. I thought that Pluto and Charon orbited a point in space while Nix and Hydra specifically orbited Pluto. <div class="Discussion_UserSignature"> </div>

MeteorWayne · Aug 30, 2006

Nope, everything orbits the center of mass of the local system in this case. Now for a binary star, there are circumstances where "planets" can appear to orbit one of the stars, but even then they are really orbiting the barycenter. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

derekmcd · Aug 31, 2006

That's not true. Take a binary system of 2 stars with equal mass. They orbit a barycenter that is exactly 1/2 the distance between the center of mass of each star. Now, input a small planet in orbit around 1 of the stars... this will move the barycenter a miniscule amount towards the star/planet, but the planet itself does not orbit (or even come close) the barycenter of the 3 body system. The planet merely adds mass to one side of the equation. <div class="Discussion_UserSignature"> <div> </div> <div>"If something's hard to do, then it's not worth doing." - Homer Simpson</div> </div>

doubletruncation · Aug 31, 2006

Right. It's kind of like the moon orbiting the Earth which is orbiting the Sun, true the Earth and moon are together orbiting the barycenter of the solar system, but they're also doing a mutual dance about their own barycenter. In the limit of two larges bodies and 1 small body, the small body will orbit one of the large bodies if it's deep within one of their Hill spheres. In the limit that its far away from both objects it will only orbit the barycenter of the system. In intermediate cases you can get all the fun orbits of Roche geometry (tadpoles etc). In the case of Nix and Hydra they are farther from Pluto than Charon is and they all orbit the barycenter of the system as MeteorWayne mentioned. You can see an image of their orbit at: http://en.wikipedia.org/wiki/Image

luto_system.jpg You could imagine though a situation in which Nix and Hydra where both very close to Pluto and orbited it specifically (though I think Pluto and Charon would probably have to be farther apart for that to work out). <div class="Discussion_UserSignature"> </div>

falsify · Aug 31, 2006

i was so shocked to learn about the elimination of pluto as being a planet in the solar system.. i mean this is something historical happening here. for centuries we have been believing that it was there counted among the others.. what happens to the theories... and why has it been removed from the solar system...

cuddlyrocket · Aug 31, 2006

"No matter how wildly eccentric, the barycenter's position does not change." The distance from the centre of the primary to the barycentre can vary depending on the details of the orbit - as can easily be demonstrated by considering a two-body system with an eccentric orbit. For instance, take a two-body system where the primary is 10x the mass of the secondary. Then the centre of the primary is always 10x nearer to the barycentre than the centre of the secondary. But the distance of the secondary varies (because the orbit is eccentric). Therefore the distance of the primary must vary. Depending on the relative masses, this can mean the barycentre is sometimes below, and sometimes above, the surface of the primary. (In my example, if the primary has radius R, the barycentre is within the primary where the secondary is within 10R of the barycentre, and above it when it is further away.)

savepluto · Aug 31, 2006

Visit the German site www.save-pluto.de to sign our petition for declaring Pluto as a planet again. We need all help we can get! Thanks a lot!

jmilsom · Aug 31, 2006

Great. I've visited and said my piece! <div class="Discussion_UserSignature"> </div>

savepluto · Aug 31, 2006

Great, thanks! Every single petition is headed to the IAU to show them that we will not take their decision for granted. And thanks for your comment in the vote! See you on www.save-pluto.de - save the ninth planet!

savepluto · Aug 31, 2006

If you also want to make this decision unhappened visit www.save-pluto.de (yes, also the Germans are caring about Pluto ;-)) and sign our petition and take part at our voting. You can also tell us your story with pluto and sign up our guestbook. Help us bringing back the glory for Pluto!

alokmohan · Aug 31, 2006

I am surised that some of us have started save pluto campaign.In 1930 when pluto was dicovered Clyde Tombaugh thought it to be Lowells planet and he was mistaken.Initially pluto was thought to be Lowells planet X ,much larger than jupiter as Lowell had calculated.Now the initial mistake has been corrected.Nothing to feel emotional.

Hail Pluto, well met

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