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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?"
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This sounds about right; the Eris is a fairly tiny phone.
Oh wait...
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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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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.
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.
I wasn't arguing how arbitrary it was. I was arguing that the people who created the definition were smart enough to define it in such a way that the classification can be determined on a case-by-case basis. A basis that won't be substantively changed by comparative measurements. Discovering anything about any new planetary body will not change Pluto's classification because the discoveries will not be about Pluto.
Professor: "I'm sorry, Fry, but astronomers renamed Uranus in 2620 to end that stupid joke once and for all."
Fry: "Oh. What's it called now?"
Professor: "Urectum. Here, let me locate it for you."
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 ?
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.
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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.
Bigger than 'Er arse? My arse? Yer arse?
'Er arse ain't 'alf bad, as 'tis!
"Flyin' in just a sweet place,
Never been known to fail..."
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.
The enemies of Democracy are
The goddess of discord is certainly living up to her reputation.
"So you think you have me all figured out, do you? Heh, heh, heh."
So how long will it take to get there, how big of a dish will it take to get a signal back, and how much plutonium to power the instrument package and radio to find out what is really going on out there?
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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The battle over the status of dwarf planets has never subsided. Pluto and Eris are both planets and Kuiper Belt Objects. One does not preclude the other. They are planets because they are large enough to be rounded by their own gravity. They are Kuiper Belt Objects because they are located in the Kuiper Belt. Ceres too is a small planet because it is large enough for its gravity to pull it into a spherical shape. The IAU misappropriated the term "dwarf planet," which was first coined by Dr. Alan Stern, Principal Investigator of NASA's New Horizons mission to Pluto, to indicate a third class of planets which are large enough to be rounded by their own gravity but not large enough to gravitationally dominate their orbits. He never intended for "dwarf planets" to be classed as not planets at all. The IAU did not "have" to do anything other than allow Eris's discoverer to name it while holding off on any additional classification until more information is discovered about remote planets in this solar system and all planets in other solar systems. Significantly, there are quite a few exoplanet systems in which multiple planets orbit the host star in various different planes. Some have orbits far more eccentric than Pluto's, yet they are giant planets the size of Jupiter or larger. According to the IAU definition, none of these objects are planets! Saying there are more differences between Pluto and the eight closer planets to the Sun depends on what aspects one considers. Earth actually has far more in common with Pluto than with Jupiter. Both have surfaces on which we can place rovers and landers. Both have a large moon formed by giant impact; both are geologically differentiated into core, mantle, and crust, and both have nitrogen in their atmospheres. Other than orbiting the Sun, what do Earth and Jupiter have in common? It is premature to pronounce declarations that these faraway objects are definitively not like the other planets or that one is larger than the other. We just do not have enough data at this point to do more than make educated estimates. What we really need to do is send robotic missions like New Horizons to Eris as well as Haumea and Makemake. Yes, that will take time and money, but it is a far better investment than the black holes the endless wars in Iraq and Afghanistan have become. Also, memorization is not important. It is much more important to teach the characteristics of each category of planet than to ask kids to memorize a bunch of names. We don't ask them to memorize the names of rivers or mountains on Earth, so why do so with planets, and why allow a need for convenient memorization to determine how we classify them?