Pluto Might Be Bigger Than Eris 257
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?"
Re:Pluto controversy (Score:4, Insightful)
I also seem to remember Neil blaming most of the uproar on Disney. Paraphrasing - "if they hadn't named that darned dog Pluto nobody would have cared".
It's hard to tell with Neil how serious he was on that one. :-)
Re:Pluto controversy (Score:5, Insightful)
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.
Re:No. (Score:2, Insightful)
Re:still not a planet per the IAU (Score:5, Insightful)
Please compare the total mass of all Neptune-crossing bodies to those gravitationally bound to Neptune. You will clearly find that Neptune has cleared the neighborhood. Neptune has a planetary discriminant of 2.4 x 10^4. A body with discriminant >= 1 is considered a planet.
-molo
What does being old have to do with it? (Score:5, Insightful)
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?"
Re:No. (Score:5, Insightful)
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?
Re:still not a planet per the IAU (Score:4, Insightful)
Yes, let's come up with a definition that excludes Pluto - that way we can exclude Pluto. Makes sense.
Re:still not a planet per the IAU (Score:5, Insightful)
Don't forget the real reason that they wanted to change the definition in the first place: current theory predicts that there are probably hundreds, if not thousands of bodies in the outer solar system with basically the same composition and orbit as pluto, and only slightly smaller. There would be no logical reason to exclude those hundreds of bodies from the list of planets without also excluding Pluto, since there is little qualitative difference between them.
Eris is more massive and may still be bigger (Score:5, Insightful)
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 ?
Re:To rephrase it... (Score:3, Insightful)
So, in other words, the question is not which one is bigger - Eris or Pluto, but which one is denser - Eris or the astronomers?
Why the insults? Why are people so emotionally attached to the old order in which the term "planet" didn't have a solid, scientific definition which included Pluto (but in which kids didn't learn about similar bodies like Ceres) that they are willing to lash out at astronomers for attempting to put some kind of reason and order into the system?
I honestly can't think of any better demonstration of why humans should never achieve immortality. Look at how attached people are as minor of a belief that they were taught in childhood as whether or not Pluto is a planet. It's like the whole "debate" is a microcosm of how irrationally attached some people become to resisting change in their understanding of the world.
And people wonder why politics is so entrenched and partisan. If people can't adapt over Pluto just think of how stuck they are on the things that actually matter.
Re:Judgment Day? (Score:3, Insightful)
It seems perfectly acceptable for a religion that advocates the murder by magical bears of 42 children for the sin of pointing at a man, laughing and calling him bald.
Re:What does being old have to do with it? (Score:4, Insightful)
Re:Pluto controversy (Score:3, Insightful)
> It's a fact.
No it isn't. It's a definition, and an arbitrary one since the class "planet" as currently defined has no particular physical significance. "Member of the list of planets of Sol" is no less (and no more) "factual".
Re:still not a planet per the IAU (Score:2, Insightful)
It's spherical. Some KBOs aren't, like my favorite Haumea. Yes, I'm an unscientific idiot.
Re:Hey you guys (Score:3, Insightful)
Bigger than 'Er arse? My arse? Yer arse?
'Er arse ain't 'alf bad, as 'tis!
Re:No. (Score:5, Insightful)
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 [wikipedia.org] (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.