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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?"
I remember being so confused about the Pluto controversy. Maybe it's just because I'm not an astronomy nerd but I don't understand the uproar about correcting a miss-classification of a heavenly body... I remember Neil Desgrasse Tyson on the Colbert Report chiming in that it was just a simple fact. Any of you astronomy nerds reading that could explain the emotional reaction? (Not to assume, was it astronomy nerds that were upset? Maybe it was Astrology people that were upset.)
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The argument was as arbitrary as any others. It was basicly "which property is common to both Pluto and Eris, but not found in the other objects traditionally considered planets?".
Pluto always was a weird object to be called a planet, with his density somewhere in the nowhere between the earthlike planets and the gas giants, and being pretty similar to the large moons of the gas giants.
But only when Eris was found, there was a second objekt thought to be similar enough to Pluto to define a new class of "plutolike objects", which allowed Pluto to be demoted from planet status.
So yes, the classification of Pluto in the class of "plutolike objects" (pardon, "Dwarf planets") seems to be on pretty firm ground, considering there are now more objects known in that class (Makemake for instance), though Eris now seems to be a weirdo within this class.
The definition is not about vacuuming the neighborhood - bodies there (including Pluto) are completely dominated by the gravity of Neptune, that's what this is about.
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Apophis would like to have a word with you.
actually, that was the reason they wanted a clear definition of 'Planet'. Pluto not being a planet is the results of those discussion, not the cause.
There would be nothing wrong if the definition included Pluto and all those other similar objects.
That may be true but it's naive to think that the motivation for defining "Planet" didn't color the discussion. The original parent is correct in that this was motivated by the perceived inconvenience of having a large number of bodies that would meet the definition.
The whole vote was a sham in my opinion, because there were other reasonable definitions that got suppressed in discussion because of the issue the parent is raising. The current definition is ridiculous and completely context-dependent, fuzzy, and completely colored by some emotional concern about how many planets there "should" be and how convenient it is for people to ennumerate them. I'd also point out that the hundreds of bodies that caused so much anxiety for so many people haven't become an issue.
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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.
Well if the IAU was going for an IMPRECISE definition they couldn't have done better. Science is all about definitions. Precision is important. The current definition is an utter mess. I couldn't care less that Pluto was named after a Disney character. If we want to be precise it belongs in a different category BUT
1) They created pair of definitions where a "dwarf planet" is not a "planet. That is confusing and ridiculous.
2) They mention "the sun" and therefore the definition as written excludes extrasolar planets. So now we have "dwarf planets" that are not planets and "extrasolar planets" that techincally also are not planets.
3) The clearing the path part of the definition is an arbitrary requirement and a kludge. It is possible we will discover extrasolar planets that cross each other's orbits in a stable way. Fortunately extrasolar planets aren't planets anyway.
There are other things wrong with the definition, but lets just leave it at that shall we? The definition is beauracratic and in terms of science it is PURE JUNK. Science is about understanding things. We humans do this by classifying them, so definitions are important. However in this case everyone was more focused on whether or not Pluto is a planet and was bending the definition to fit their preference.
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