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IAU Classifies Pluto & Eris As "Plutoids"
Posted by
timothy
on Wed Jun 11, 2008 02:21 PM
from the once-and-for-all-or-maybe-not dept.
from the once-and-for-all-or-maybe-not dept.
Kligat writes "The International Astronomical Union has decided that Pluto and Eris should be classified as "plutoids," alongside their 2006 classification as dwarf planets. Under the definition, the self-gravity of a plutoid is enough for it to achieve a near-spherical shape, but not enough for it to clear its orbit of its rocky neighbors, and the plutoid orbits the Sun beyond Neptune."
Reader FiReaNGeL links to a
similar story at e! Science News.
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Makemake Becomes the Newest Dwarf Planet 191 comments
Kligat writes "The Kuiper belt object formerly known as (136472) 2005 FY9 has been rechristened Makemake and classified as a dwarf planet and plutoid by the International Astronomical Union, according to the United States Geological Survey. The reclassification occurs just a month after the latter category was created. The object was referred to by the team of discoverers by the codename Easterbunny, and the name Makemake comes from the creation deity of Easter Island, in accordance with IAU rules on naming Kuiper belt objects."
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Plutoids? (Score:2, Funny)
plutoids (Score:2, Funny)
What a pantload (Score:4, Insightful)
Re:What a pantload (Score:4, Insightful)
Parent
Re:What a pantload (Score:4, Insightful)
Of course, as I said below, it's all arbitrary anyway. It is inevitable that someone will be bitching about something no matter what definition we use.
Parent
Re: (Score:3, Insightful)
Rei even said it doesn't matter what you call them. Do you want to call them "binary planets"? Go ahead, from what Rei said in the post it's fine. All Rei said is that they should be prefixed "binary", just like stars are prefixed "binary". And I agree, they should be.
Re: (Score:3, Funny)
Re: (Score:3, Informative)
Re: (Score:3, Informative)
Calimero (Score:3, Informative)
Re: (Score:3, Interesting)
Also, in Pluto's case, I think they should've made an exception for historical reasons. It should have remained the ninth planet while at the same time introducing a system for classifying objects. Every branch of science is riddled with exceptions, and it's nice for, for example, teachers to see their students get angry because there are s
Re:Calimero (Score:4, Funny)
Exceptions for historical reason serve no purpose other than confusing future students, and if that were our goal we would have elected Hillary, followed by Jeb, so that future students could be confused by the "Bush, Clinton, Bush, Clinton, Bush" line of presidents.
Oh, and Hail Eris, of course.
Parent
Re: (Score:3, Insightful)
Yeah, leave all that pesky "classification" and "definition" nonsense to hard sciences like Astrology and leave our fuzzy-wuzzy Astronomy alone!
P.S. Hail Eris!
Re:Calimero (Score:5, Insightful)
This plutoid business is silly though and only serves as some sort of consolation prize to the people who still wish that planets weren't actually defined and Pluto could still be considered among them. I mean, unless we're actually going to be applying this standard to objects we find around other stars (which I think would be silly, but then I'm not a planetary astronomer... so who knows).
I suspect that this has something to do with the upcoming international year of astronomy, which is all about getting the public excited about astronomy, semi-reversing Pluto's demotion (which appears to have been unpopular among non-astronomers) seems to be good for this.
Parent
Re:Calimero (Score:5, Informative)
Now, what I think people are objecting to is the apparent lack of logic for the "planet" classification itself. You get objects as different as gas giants and telluric planets under the same umbrella, "planet". So, why not Kuiper belt objects ?
But regardless of what has been the actual ruling about Pluto, the main problem lies in the redefinition process itself. What is a tomato, a fruit or a vegetable ? For biologists, it's a fruit, for cookers it's a vegetable. Everybody gets on with it. Different names for different fields, it's not uncommon. It has been going for ages.
Now, what went through the mind of the IAU to think that the "planet" word needed a formal science definition ? The ambiguity of this word had been acknowledged for ages, and there was some disagreement among astronomers. They could just as well have kept on using accurate names, such as gas giants or kuiper belts objects. It's as if some day, the "International Biologists Union" decided it was a good time to formally define the word "bug". And ruled that only insects should be called bugs, and not arachnids.
Anyway, it's not a big deal.
Parent
Begging the question. (Score:4, Interesting)
You and GP are begging the question. Yes, classifications are "useful" to catalog objects orbiting other stars. But, what is the use of cataloguing objects orbiting stars, in the first place? What does it tell us? Does the classification of an object predict any properties of it that beyond those that were required to successfully classify it?
Two subpoints here:
The response to this is that classifications aren't properties of things in themselves, but rather, are context- and purpose-dependent distinctions that people impose on them.
I've not seen anybody come even close to doing this for "planet." Once you observe all the things you need to observe to decide whether a celestial body is a planet or not, you're not in a position to predict anything else about the object.
This doesn't mean that scientists can't use non-predictive classifications for genuinely useful means; non-predictive classifications can be quite useful for communicating with other people (if somebody says "planet," it may not allow you to predict a lot about the object, but it helps you guess what the other person may be talking about). But usually, those classifications don't really need to be very precise.
In this case, the problem is pretty simple. The ancients charted the movements of the lights in the night sky, and were concerned with formulating laws to explain their motion. The problem you hit right away when you start doing this is that a handful of those lights move in a manner that's very different from the vast majority of the others. Those weird, "wandering" ones are the so-called "planets," in the original sense. This goes back to point (1): the classification of some celestial objects as "planets" responds to the purpose of formulating and solving this problem.
Guess what? We're not the ancients. We don't have their problems in explaining the motion of those things. We have super-powerful telescopes that show us all sorts of funny rocks in space that they could never hope to see, moving in all sorts of weird trajectories. We have a theory of Newtonian mechanics that explains their trajectories as a specific case of more general laws, without having to formulate laws of weird-space-rock-motion. Why are we keen at all to try to get a precise fit between what we see and their vocabulary? The reason we have problems with deciding whether something like Eris is a "planet" is because we know a lot more than the ancients did. Insisting too eagerly on the classification just demonstrates a failure to appreciate how very different and superior our understanding is.
Parent
Re: (Score:3, Funny)
Other solar systems? (Score:4, Insightful)
The new definition of "planet" was quite good. Clear, straight to the point, and easy to apply to any object. Now, they add a new category that applies only to our solar system?
Okay, we won't be seeing objects this small on other star systems, but the point remains. We are already at a time when we know these objects should exist in many other places in the universe. The classification shouldn't depend on their position inside our solar system, it should be generic enough that we won't have to change it (again) when we see one of those around Alpha Centaurii. I thought this was the single most important thing to come out of the previous discussion about what should be considered a "planet".
Re:Other solar systems? (Score:5, Insightful)
"Now, it's at least a plutoid. Happy?"
Yes, from a scientific POV, it's pure bullshit, of course.
Parent
Re:Other solar systems? (Score:5, Funny)
Honestly, if you're just going to say no, say no. This is like saying "no, honey, you can't have a cell phone, you're only 12. but here, i got you this plastic cell phone that holds candy!"
Your daughter would be well within her rights to kick you right between the legs for excessive dickitry.
Parent
Re:Other solar systems? (Score:4, Insightful)
Not only that but the third requirement is NOT easy to apply to an object. Assuming for a minute that the IAU definition of a planet required it to orbit a star, not the sun, it would be near impossible to ascertain whether or not the third criterion has been satisfied for potential planets in other star systems.
While I'm on a bit of a rant, anyone notice that Ceres isn't included in this new definition? Ceres is the third dwarf planet (by the IAU definition) if you don't know, it's orbit is in the asteroid belt. So Ceres, Pluto, and Eris are all dwarf planets. However, Pluto and Eris get to be Plutoids for being beyond Neptune. Good for them. I'm not sure how it's useful to classify trans-Neptunian dwarf planets again just so they can exclude Ceres, but I'm sure there's a reason that's definitely not arbitrary!
Parent
Re: (Score:2)
The Plutoid name may actually be a very good term. Pluto is nothing if not very different from every other planet or that matter all the known bodies in the solar system.
Re: (Score:3, Interesting)
The first part suggest it is in orbit around the Sun. Not a sun. The Sun. Thus, there are no other planets
Just as good as "Alex and Nikki" (Score:5, Funny)
As I recall, they each had "...a near-spherical shape, but not enough for it to clear its orbit of its rocky neighbors..."
-I suppose naming them "Pluto and Eris" would have worked equally as well...
How irrelevant my past accomplishments (Score:5, Funny)
What's in a name? (Score:2)
Or in other words, what does the terminology matter? Yes, we like to classify things to organize our thoughts. But this seems a step too far.
What's in a name? A lot actually (Score:5, Funny)
Parent
Re: (Score:2)
> thoughts. But this seems a step too far.
You think adding a sub-classification of dwarf planets is going too far? No; giving even individual plutoids their very own names--like "Eris" and "Pluto"--THAT'S going too far. Next thing you know, they're going to be giving names to FEATURES of Eris and Pluto. Don't even get me started on that level of crazy.
Let me summarize (Score:5, Insightful)
USAcentrism? (Score:2, Interesting)
In Soviet Russia . . . . (Score:2, Funny)
What about Ceres? (Score:3, Interesting)
Re: (Score:3, Informative)
Re: (Score:3, Insightful)
Slight ommission (Score:5, Funny)
The summary fails to mention one further requirement: For an object to be considered a true Plutoid, it must posses a "curiously strong" flavor.
Pluto on its way out? (Score:5, Funny)
Re:Pluto on its way out? (Score:4, Funny)
Parent
I defy that classification, also refuse it (Score:2)
this is not science. pluto is a planet.
Re: (Score:3, Informative)
Whole debate seems bogus (Score:3, Interesting)
For that matter, if you want to be REALLY pedantic - Pluto's orbit overlaps Neptune's, so Neptune apparently isn't large enough to clear it's orbit.
There! We've whittled it down to two planets total: Jupiter and Uranus. That'll be easy to remember...
Galactic Lampoon's Summer Vacation! (Score:4, Funny)
Galactic Overlords: "Tom Tom! Where is this "Earth"?!"
Tom Tom: "Make a left at the 9th Planet."
Galactic Overlord: "WTF?!?! There IS NO NINTH PLANET, Tom Tom!"
Galactic Overlord's Mother-in-law: "I told you, Rory! You should have made a right at Uranus! If you can't find a PLANET, HTF were you able to find my daughter's birth tube?!"
Galactic Overlord Jr.: "Are we there yet?"
Galactic Overlord: "Dammit! Don't make me pull over this Star Destroyer!"
Galactic Overlord Jr.: "I gotta pee!"
Any excuse to make new words. (Score:3, Interesting)
http://www.go-astronomy.com/glossary/astronomy-glossary-p.htm [go-astronomy.com]
"A large asteroid or other celestial body, also called a minor planet."
Call them planetoids. Therefore still remaining a planet but one that is not large enough to remove debris from its orbit. Then throw on mercury and mars and we can have a solar system of six planets and four planetoids (minor planets). This crap about removing debris from its orbit is farcical, how do they not know given another billion or two years it won't remove remaining debris?
Re:WTF is Eris? (Score:5, Informative)
Parent
Re:WTF is Eris? (Score:5, Informative)
Parent
Re:WTF is Eris? (Score:4, Informative)
Many (but not all) of the observed dynamical features of the Kuiper Belt can be explained by giant planet migration.
Parent
Re: (Score:2)
Re:Earth too (Score:4, Insightful)
Specifically, it doesn't say that no other bodies in vicinity are present, but that all of them are dominated by gravitational influence of a planet. And that's definatelly the case with Moon and near Earth asteroids. But not with Pluto - it's in orbital resoncance with Neptune.
I actually really like this definition, fairly precise, universal, and avoids waking up one day in a Solar System with 20 or 30 planets, once we start discovering more Pluto-like objects. But somehow we have this nonsence of people attaching sentimental value to the notion of Pluto beeing a planet, which makes the whole deal unpopular.
And BTW, I don't like this latest "plutoids" thing; looks more like PR stunt. Definatelly doesn't really resolve anything, and if
Parent
Re: (Score:3, Insightful)
There's no hard limit as a number, but there has to be some limit, otherwise every dust particle that orbits the sun should be classified as a planet.
I think the current definition is pretty good. Although I feel some sympathy for Pluto, I feel it's not quite right to classify a small body whose orbit intersects the orbit of a gas giant as a planet.
The irony of it all is that Pluto would never have been considered a planet if it wasn't for
Re: (Score:3, Insightful)
All signs on heaven (and...only on heaven
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