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Pluto Might Be Bigger Than Eris
astroengine writes "Look out, the battle of the dwarf planets is about to re-ignite! During last weekend's rare occultation of a star by Eris, astronomers managed to gain one of the most accurate measurements of Eris' physical size. When three Chilean telescopes watched the star blink out of sight, astronomers were shocked to find that Eris is actually a lot smaller than originally thought. So small that it might be smaller than Pluto. On speaking with Discovery News, Eris' discoverer Mike Brown said, 'While everyone is more interested in the "mine is bigger than yours" aspect, the real science is the shockingly large density of Eris.' The mass of Eris is well known, so this means the object is more dense than Pluto. Does this mean the two mini-worlds have different compositions? Did they evolve differently? In light of this finding, is the underlying argument for Pluto being demoted from the planetary club on wobbly ground?"
Size does not matter. Clearing its path matters. Per the IAU Pluto has not cleared its orbital path and can not be considered a planet by the current definition.
I think that it has a lot to do with the fact that a shockingly large number of people confuse nomenclature with knowledge. Because of that, a fairly fiddly technical discussion over how best to handle astronomical nomenclature hit the popular press as "zOMG pointy-headed scientists don't even know if Pluto is a planet!!!!!"
Naming is not a trivial thing, good nomenclature makes the world a much easier place, crap nomenclature makes it a mess wholly without reason; but either way it seduces people into forgetting that names are simply constructs, assigned for our convenience to bundles of real things. Sometimes, you have to revise the constructs to make the nomenclature better, simpler, more expressive, whatever; but that is very different from changing the bundle of real things and attributes.
At least we can be certain it will pass - I don't see any people lamenting that Ceres, Pallas, Juno and Vesta have lost their planetary status.
Status which they had, for half a century after their discovery. Similar to Pluto.
(for that matter, the same applies to the Sun - it was also classified as a planet at some point)
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Ask just about anyone geeky and my age,, and they'll telll you so: "yes, Pluto is a Fucking Planet, now stop trying to change things".
What does being geeky have to do with being old and too set in your ways to listen to reason?
Give us an argument why the IAU's definitions of a planet and of a dwarf planet are unreasonable. Please avoid any Appeal to Tradition. Also, can you craft a definition of a planet that covers Pluto but not Eris and Ceres other than "just what we used to arbitrarily call a planet?"
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It's perfectly simple: Humans are not animals, Humans are fucking special. Ask just about anyone religious and my age, they'll tell you so: "No, humans aren't animals, now stop trying to change things".
See how ridiculous your non-argument sounds?
Don't give Eris out yet. There was a lot of discussion on the MPML about this.
First, Eris is definitely more massive, by about 28%. They both have satellites with good orbits, so their masses are pretty well determined.
Second, it is not really that clear that Pluto is really larger than Eris. There have been a number of estimates of Puto's size; by the most recent one presented by Angela Zalucha at the DPS meeting (a radius fit to occultation measurements with a new atmospheric model), Pluto and Eris have roughly the same radius within the respective error bars (1146 +-20 km in diameter for Pluto versus 1170 km for Eris).
What is more interesting to me is that Eris is dense and very bright - could something as rare as Deuterium snow be covering its surface ?
The rest of the definition is noise because they failed to define "clearing the neighborhood".
Noise?!
There's FIVE ORDERS OF MAGNITUDE difference in planetary discriminant (mass ratio between the body and all other masses in that orbit) between the highest value for a dwarf planet (Ceres) and the lowest value for a planet (Neptune).
When the difference is a factor of 10,000, there's absolutely no need to create a precise definition, and it would be foolish to do so.
It's like you're arguing that the definition of what is or isn't ocean is useless because it doesn't precisely define at what point of the tide cycle, or how far up a river mouth, it transitions from ocean to not ocean. But the question we're asking is whether Topeka, Kansas is in the ocean or not and the answer is obviously NO!
You might as well argue that it's completely arbitrary to say that you are alive and Benjamin Franklin is dead, because science has not precisely defined the exact line between dead and not dead. Um, I think it's still pretty clear which is which in this case.
You see, if they did actually define "clearing the neighborhood" in a precise manner, that would be the truly arbitrary choice. But when you look at the bodies in our solar system, and you see that there's a small set of objects which outweigh everything else in their orbits by at least a thousand-to-1, and then a great many objects which weigh less than the rest of the objects in their orbit, then yes that actually makes a clear dividing line. You don't have to draw it with infinite precision to see that it's there.
The definiton of Pluto as a planet is far more "noise" than the definition that it isn't. We only called it a planet because we didn't know it was so different from the other ones. It's like when we first discovered Ceres. Only we changed that one pretty quick, even though it's more planet-like than Pluto is.
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