IAU Classifies Pluto & Eris As "Plutoids"

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.

Plutoids?

[Anonymous Coward]

My uncle had a problem with his plutoids, and he had to sit on a big doughnut and use lots of ointment.

Wrong Goddess!

[farrellj]

There is not Goddess But Eris, and Murphy is Her Consort!

HAIL ERIS! ALL HAIL DISCORDIA!

The Law of Fives:

The Law of Fives is one of the oldest Erisian Mysterees. It was first revealed to Good Lord Omar and is one of the great contributions to come from The Hidden Temple of The Happy Jesus.

POEE subscribes to the Law of Fives of Omar's sect. And POEE also recognizes the holy 23 (2+3=5) that is incorporated by Episkopos Dr. Mordecai Malignatus, KNS, into his Discordian sect, The Ancient Illuminated Seers of Bav

plutoids

[unspokenchaos]

pluto contracted plutoids from minnie

What a pantload

[Savior_on_a_Stick]

How they are classified means what to whom? Someone needs their grant pulled for gross misuse of time.

Re:What a pantload

[Jugalator]

I'd normally say it's about what to teach the kids and what's not as important -- a definition makes it easier to draw the line. However... This isn't about planets anymore, but plutoids. I think that moves more into the realms of advanced astronomy rather than schoolbooks, and then the definitions also matter less besides to split up things into smaller tables. :-p

Re:What a pantload

[Skye16]

As an aside, I think it silly that they're no planets solely because their barycenter does not lie inside of them. Do binary stars get classified as "Starloids" because their barycenter is between them? I didn't think so.

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.

Re:

[Cecil]

Um, no, they're called "binary stars", which if you read the damn post is exactly what Rei is saying Pluto and Charon should be called: "binary (insert-appropriate-term-here)"

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:

[AstrumPreliator]

Just to give sort of a visual representation of why Pluto and Charon should be considered binary let's assume for a second that we scale the mass of Pluto and Charon up so that Pluto is the size of Earth. Then Charon would be roughly the size of Mars. That's a REALLY big moon, don't you think?

Now of course defining a binary system in terms of mass is rather arbitrary, but the Barycenter really isn't. If they're orbiting a point that lies between both of them then they should by all rights be a binary syst

Re:

[Skye16]

I'm not really focusing on the binary part so much as the "plutoid" or "dwarf planet" parts of the "binary ..." motif. I'm fine with binary. I never said I wasn't. I just said that it's silly to call them "not planets" just because they're have a barycenter. As I said, you don't have "binary starloids" just because they have a barycenter, you have binary stars. They don't get their passes to the Great Star Convention revoked just because their barycenter is not internal.

If you even bothered to read my

Re:

[Dragonslicer]

Personally, I won't be happy with the classification until they make it a standard to refer to them as a binary. It can be "binary plutoids", or "a binary dwarf planet", or whatever exact terminology they want, but their barycenter lies between them, not inside one of them, and that should make them a binary.

Pluto's moon (or whatever you want to call it today) is Charon, not Eris.

Re:

[Wandering Wombat]

It means a lot to crazy capitalists...

Walter Chang: I got it! Plutoids! [imdb.com]

Re:

[geekoid]

Ignorant person claims someone has misused time, modded +5. News at 11.

Re:

[Abcd1234]

Yeah, I've long said the same thing about geologists classifying rock formations, or biologists classifying life forms...

Re:

[kalidasa]

If the definition some of us preferred had been adopted, a certain Italian [wikipedia.org] would have gotten his planet back, too.

Calimero

[HetMes]

It's a stupid debate altogether. I image all the astronomers involved feel really good about themselves for making an impact. Why couldn't they leave well enough alone? Pluto will always be the ninth planet to me, despite Eris. Definitions be damned!

Re:

[sveard]

IMO classification can be a nice thing. It helps to reduce the clutter. However it seems that every now and then, something is discovered that 'refuses' to be classified.

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

[lgw]

I think this was a wise decision. You can't really aruge that "Pluto is not a plutoid", so maybe this will finally settle things.

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.

Re:

[geekoid]

No, the shouldn't make an exception, it cause confusion for later generations.

The fact that some areas are riddled with exception is no excuse to create more exceptions.

The idea of 'planets' is gone.
I would want a 'planet' to be an object like earth.

The you have Gas Giants, and rocks.
Categorize each of those based on it's gravitational pull.
For example, if something accelerates between 9.78 and 9.82m/s2 would be class M.

Yes, thatw as a long way to go to get to a Star Trek reference.

Re:

[Convector]

Should we also have made an exception for Ceres for historical reasons? It was thought to be a planet for some 50 years after its discovery until whole bunches of asteroids were discovered.

Re:

[StDoodle]

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

[vajaradakini]

No, definitions of planets are important if you're looking for them elsewhere and wish to classify the objects you find orbiting other stars. Besides, even as a first year astronomy student five years ago I knew Pluto wasn't a planet, they only made it official recently (and properly defined planets).

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.

Re:

[Plutonite]

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.

Yes, and bringing me closer to celebrity status is a good thing too. When the plutoids grow, behold! They become... Plutonite!

Re:Calimero

[Cochonou]

Classyfing Pluto as a Plutoid is not silly. Classifying Jupiter as a gas giant is not silly. Classying Mars as a telluric planet is not silly, either. This is exactly what you pointed out when you said that classifications were useful to catalog objects orbiting other stars.
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.

Begging the question.

[Estanislao Martínez]

Classyfing Pluto as a Plutoid is not silly. Classifying Jupiter as a gas giant is not silly. Classying Mars as a telluric planet is not silly, either. This is exactly what you pointed out when you said that classifications were useful to catalog objects orbiting other stars.

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:

1. You're committing a very common philosophical error, that I'll call ontological essentialism: the belief that there exists such a thing as a context-independent "correct" classification of things according to a given scheme. This error is leading you to think that there really must be a truth of the matter as to whether Pluto, as a thing in itself, is a "planet" or not.

   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.

2. Astronomy is a natural science. Natural science is concerned with making predictions. The most natural use of classifications in natural science is, therefore, as a predictive apparatus: a classification has predictive value if, when you observe the properties of an object required to classify it correctly, you can use the classification to predict further properties that you did not observe.

   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.

3. In any science, it pays to be skeptical about the validity of received vocabulary and classifications. I like the way one of my professors puts it: when faced with terms like "planet," it is often valuable to step back and, instead of seeing them as the names for distinct kinds of things, to see them as the names of distinct kinds of problems that the people who came up with the term were trying to solve.

   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.

Re:

[2short]

"...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)."

Exactly.

"But usually, those classifications don't really need to be very precise."

Sure they do, just not for science. Just because the terms of such a definition are scientific, don't assume the motivation is.

When an astronomer finds an object around a distant star, wh

Re:

[vajaradakini]

Classifying Pluto as a Plutoid and then defining a Plutoid to be a spherical object past the orbit of Neptune is silly. At least gas giants are defined by some intrinsic characteristics (i.e. they're giant and made of gas) which is different than terrestrial planets (i.e. made of rocks) which could be applied to objects in other solar systems while we're not going to find any more Plutoids unless we start naming the furthest planet from every star "Neptune" or re-define the term.

Furthermore, the fact

Re:

[2short]

"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 ?"

The short answer is, if you're trying to draw a sharp line through a big grey area, you've got to draw it somewhere. There's a few places in that grey area that make a little more sense than others though, and one of them is just this side of Pluto.

"It's as if some

Re:

[servognome]

definitions of planets are important if you're looking for

... grant money

Re:

[syousef]

No, definitions of planets are important if you're looking for them elsewhere and wish to classify the objects you find orbiting other stars.

The very first line reads "A planet is a celestial body that (a) is in orbit around the Sun". The Sun. SOL. Our star. Your extra-solar planets aren't planets at all by the agreed upon definition. In fact scientifically the definition is pure garbage.

1) A "dwarf planet" is not a "planet". Calling an entire category by a name so as to misleadingly imply it is a sub-categ

Re:

[vajaradakini]

Yes. I'm sure that it has nothing to do with the fact that Pluto behaves just like all the other Kuiper Belt Objects with its eccentric and highly inclined orbit or the fact that it crosses the orbit of an object that is definitely a planet (Neptune). It's just that everyone in the scientific community hates Americans which is exactly why all other American achievements and discoveries in the sciences are likewise ignored.

Re:

[vajaradakini]

Clearing the area refers more to the fact that Pluto intersects Neptune's orbit than the fact that it lives in a debris field. The fact that Pluto crosses the orbit of a much larger object much like how comets and various asteroids cross our (and other planet's) orbit. By the way, how many other KBOs have their own satellites as large as Charon? Quite a number actually (ssee wiki [wikipedia.org]). They're not all as large as Pluto, but some are (some are bigger) and many have moons.

Re:

[PitaBred]

Yeah! The Earth is the center of the universe, and that's the way I likes it, too! Ptolemy's [wikipedia.org] tables were good enough for him, and they're good enough for me!

Other solar systems?

[Steve Max]

*sigh*
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?

[Jugalator]

As ridiculous it may seem, I'm pretty sure that this celestial body class was invented in some sort of weird attempt to satisfy people that didn't want Pluto to lose its planetary status.

"Now, it's at least a plutoid. Happy?"

Yes, from a scientific POV, it's pure bullshit, of course.

Re:Other solar systems?

[Skye16]

Also, it's patronizing. It's like trying to pass off Civil Unions as just as good as Marriage. You can try, but everyone sees through such cheap tricks.

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.

Re:

[uglydog]

I was going to criticize your use of the word dickitry (it's been a slow day). I've heard of dickery, but not dickitry.
Then I checked urbandictionary.com and was enlightened!
dickery: the state of being a dick
dickitry: The art of dicking around

A subtle but very important distinction.

Re:

[Cussin_IT]

Seriously, if your daughter kicks you beteween the legs when you give her candy, I would invest in a cup.

Nope - Not Happy - Pluto is a Planet to me

[gadlaw]

In the realm of things that don't matter except that I've been told for more than 40 years that Pluto is a planet then told by some 'Congress of Ass- tronomers' that it's not - screw those smug smirking bastards. I saw the Nova episode and hate every one of those ass-tronomers who happily conspired and worked on the planet demotion by vote. It's a planet and some power tripping douchebags can't vote otherwise. Now I hate this crop of Ass-tronomers.

Re:Other solar systems?

[AstrumPreliator]

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?

You do realize that the 2006 IAU definition of a planet requires a body to orbit the sun to be considered a planet, right? There are only 8 planets in the universe according to the definition [wikipedia.org] at this time. You can follow the references back to the IAU's site for confirmation if you want.

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!

Re:

[tirerim]

We currently call objects in other stellar systems exoplanets, which seems good enough for me. It will be a long time before we can study them in enough detail for it to really matter in any case.

I think the good reason for keeping plutoids separate from other dwarf planets is that plutoids are Kuiper Belt objects, rather than asteroids (which is a word that has its own issues, of course), so they have quite different origins and compositions

Re:

[LWATCDR]

Except that Pluto really as far as I can tell swept it's orbit clean. I don't think that Pluto eccentric orbit keeps it from being a planet.
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:

[spacemandave]

Pluto is nothing if not very different from every other planet or that matter all the known bodies in the solar system.

Except for the Plutinos [wikipedia.org], which are similar to Pluto in that they are all in 3:2 mean motion resonance with Neptune. Plutinos are themselves just one of several collections of resonant Kuiper Belt objects (the "Twotinos" at the 2:1 resonance being another). The resonant population is just a subclass of the Kuiper Belt, which itself contains other large objects like Eris, Sedna, and many more.

Pluto the 2nd largest of the as yet discovered Kuiper Belt objects. It is also the largest Plutino. In addition

Re:

[Dragonslicer]

Except, of course, that its orbit crosses that of Neptune. That minor technicality relegates Pluto to status as a minor planet.

Wouldn't that imply that Neptune hasn't cleared its orbit either, and therefore isn't a planet?

Re:

[arthurpaliden]

Well if an object is found in orbit around another star that fits the description of a plutoid would it not be "outside the orbit of Neptune" ?

Re:

[PunditGuy]

Not to worry -- when we find such objects in other star systems, we'll be able to refer to them as Class D as the Vulcans intended.

Re:

[Psion]

I don't think it was quite good at all. In fact, it wasn't even good. Calling it half-assed would be complementary. Consider:

...a "planet" is defined as a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

The first part suggest it is in orbit around the Sun. Not a sun. The Sun. Thus, there are no other planets

Re:

[Psion]

Stern (of Stern-Levison) himself says that the Earth hasn't cleared its neighborhood of debris. If there's debate over the interpretation of that parameter by one of the authors, it hardly strikes me as precise. Rather than precise, let's try the word, "arbitrary". As in, Stern-Levison arrived at an arbitrary threshold that once classed whether an orbital path was cleared and have since reconsidered this position.

This'll all be cleared up in August 2009.

I hope.

Re:

[syousef]

The new definition of "planet" was quite good. Clear, straight to the point, and easy to apply to any object.

Quite good???? It infuriates me that sane rational people keep saying this. It's terrible science. It's inconsistent nonsense. It's a poster child for confusing obfuscated science.

1) A "dwarf planet" is not a "planet". Calling an entire category by a name so as to misleadingly imply it is a sub-category is confusing and thus very very bad.

2) Arbitrary distinction that a planet orbits our own star (th

Re:

[mcvos]

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?

We have lots of categories that apply only to our solar system. Near earth asteroids, for example.

Pluto's status as a planet was only an issue because "planet" happens to be the most prestigious category an object can be in. All other categories just need to be meaningful and useful to the people who need it. Apparently the IAU thinks plutoid is a meaningful category.

Just as good as "Alex and Nikki"

[Zymergy]

In college I knew a 'dancer' who had named her 2 breasts "Alex and Nikki"!
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

[Anonymous Coward]

my award-winning 5th grade planet mobile becomes even more irrelevant.

What's in a name?

[truthsearch]

"What's in a name? That which we call a rose / By any other name would smell as sweet."

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

[jamrock]

Or in other words, what does the terminology matter?

Imagine if the former ninth planet had been named after Hemos, and then a class of similar objects given a derivative of that name. We'd have to put up with "Hemorrhoids circling Uranus" jokes until the heat death of the Universe.

Re:

[Chysn]

> Yes, we like to classify things to organize our
> 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.

Re:

[truthsearch]

Naming an individual object seems to make more sense than this sub-classification. I would think astronomers would speak more of each object than this particular subclass.

Re:

[Chysn]

I dunno... you give 'em a subclass, and they'll fill it. It's getting mighty crowded out there. It scares me.

Re:

[Omestes]

Short people are people.
Dwarfs are short.
Dwarfs are people.

Small planets are planets. (Mercury)
Dwarf Planets are small.
Dwarf Planets aren't... er... planets.

Let me summarize

[Bryansix]

They didn't do any more research. Nothing scientific was done. No more information was found out or cataloged. Nothing interesting happened. Just a bunch of people with too much time on their hands gave yet another name to a celestial body that orbits the sun. Frankly, who cares?

Taxonomy

[Kozar_The_Malignant]

And in the taxonomy of taxonomists, we find that taxonomists can be sorted into "lumpers" and "splitters". There tend to be more splitters, because it is easier to write papers arguing for splitting an existing taxon than it is to write papers arguing for combining two or more existing taxa, particularly if the original namers are still alive (and possibly the dean of your department.)

It gets complicated when nature doesn't cooperate by forming things in easily sorted groups. Then you get long, ongoing a

USAcentrism?

[papabob]

When Pluto lost its status of planet a couple of years ago I was shocked reading that the USA was lobying against that definition just because Pluto is the only planet discovered by an american scientist. Please, oh please, tell me that IAU hasn't produced this new denomination just for political reasons. It would be very sad...

In Soviet Russia . . . .

[Eg0Death]

plutoids classify you!

Re:

[Akardam]

As others have pointed out, the USA lobbying isn't entirely accurate.

That aside, I don't see this as being a IAU political decision. We have literally thousands of designations in science that are based on the 1st "thing" to be classified (and sometimes to be discovered, too). So, in this case, since a new designation of a thing has been created, and Pluto is essentially the first to be classified, I see no problem with calling it and others like it "Plutoids". Actually, I think the definition makes a lot o

Re:

[Omestes]

But... but...

Pluto was discovered at the Lowell Observatory, on Mars Hill, in Flagstaff, Arizona...

Not in New Mexico. New Mexico doesn't come into this story at all.

Percival Lowell, who started the search was from Boston. Clyde Tombaugh, who actually discovered Pluto was from Illinois.

Re:

[Omestes]

Ahh.. you, sir, are correct. sorry about that, all I really remembered from slumming about Lowell in college (nice, but dangerous bike ride, beautiful short hike though) was the Flagstaff and Illinois connect. I stand corrected.

What about Ceres?

[kfort]

I'm not sure why but they seem trying to purposefully exclude Ceres which is spherical in shape (able to overcome hydrostatic force) and exists in the asteroid belt

Re:

[AstrumPreliator]

I skimmed TFA and the release on the IAU's website. It looks as though they think Ceres is unique and so made the definition encompassing only trans-Neptunian dwarf planets. I'm not defending their reasoning, but that appears to be it.

Re:

[kfort]

Yeah, I just question the decision to include 'clear the orbit' in the definition for a planet, which is what started this whole mess. If they had just stuck with the simplest definition of hydrostatic equilibrium (round shape) they could upgrade Ceres, keep Pluto, and deal with Eris. I think it would be a lot more exciting to have new planets than this constant squabbling over the status of Pluto

Slight ommission

[Waffle Iron]

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.

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?

[jeiler]

First it got demoted, then given a brand new (and largely meaningless) title. I expect Pluto to get a pink slip any day now.

Re:Pluto on its way out?

[lysse]

Nah, they'll just stop paying it and let the problem work itself out naturally.

I defy that classification, also refuse it

[unity100]

this whole thing has become a charade. first, they have 'declassified' a damn heavenly body that is orbiting the sun as a planet for billions of years, then invented a new classification to fill in the gap.

this is not science. pluto is a planet.

Re:

[magicchex]

2 Skinnee J's - Pluto! lyrics

With depravity,
I break lots of gravity
Blast past the atmosphere
to the last frontier
I go boldly through space and time
The sky's the limit,
but the limit isn't the sky
I break orbit by habit,
I ignite satellites and leave rings round the planets
A flying ace like that beagle,
nevertheless this alien remains illegal
Cause their discovery don't cover me
the immigrants been left in the cold
to grow old
and disintegrate
Discriminate
against the distant and disclaimers,
Cause small minds can't see

Re:

[Omestes]

Yes, a definition that was VOTED on, and mainly to keep the amount of "planets" to a neat, tidy, manageable level.

Last I checked, science wasn't democratic. Or can instate a vote to redifine "element" as to remove Plutonium, since its dangerous, and we already have too many of the silly things.

Re:

[snuf23]

We call rocky planets also terrestrial or telluric. We call the other ones gas giants or jovian planets.

Whole debate seems bogus

[93 Escort Wagon]

Pluto isn't large enough to clear it's orbit of "rocky neighbors". Well, here's a news flash - neither Earth, nor Mars, nor Venus, nor Mercury have orbits that've been cleared of rocky neighbors. So apparently the bias only applies to the outer regions of our solar system?

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...

Hail Eris, All Hail Discordia!

[argent]

Agreed. Pluto is a planet, so is Eris. Naming the latter after the goddess of chaos and discord was a splendid idea (as well as a lovely if possibly unintended homage to the late Robert Anton Wilson, though not as good as naming it Mickey would have been).

Re:

[geekoid]

And Linux is Windows.

Re:

[kalidasa]

Um, no, that's more like saying that Windows Mobile is Windows.

Re:

[geekoid]

I love when ignorant people rant. I mean, just seeing you be that foolish warms my heart~

Stupid git.

Galactic Lampoon's Summer Vacation!

[mandark1967]

Let's be honest here. We all know the reason Pluto was re-classified to throw off the Tom Tom of our, now lost, Galactic Overlords.

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!"
 

are we on an "earthik," then?

[swschrad]

after all, who can name one other planet in which allegedly intelligent life is in contact with us? only one? maybe earth is not a REAL planet, itself, if everything else that IS a planet has no allegedly intelligent life.

Any excuse to make new words.

[Merls the Sneaky]

WTF is a plutoid? We already have a definition that could easily fit pluto and other celectial bodies like it
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?

there is only one solution to this debate

[circletimessquare]

we must fund a NASA mission to go to Pluto, and nuke it into gravel

we are wasting far too much time and thought over this frivolous disagreement. the obvious solution is to simply destroy the object of this disagreement, and move forward again in peace and unity. we must salve the wounds we have savaged on each other in this truly barbaric and vicious debate

In other news

[whoami-ky]

Pluto officially defined as Pluto.
Eris officially seen as similar to Pluto.

Who really gives a flip?

There are objects out there of every size shape and configuration possible.

At least we can be glad...

[mpthompson]

...they didn't name the last planet Hermes.

Re:WTF is Eris?

[MRe_nl]

Eris, which measures about 70 miles wider than Pluto, is the farthest known object in the solar system at 9 billion miles away from sun. It is also the third brightest object located in the Kuiper belt, a disc of icy debris beyond the orbit of Neptune.

Re:

[Pr0xY]

IIRC it is a kuiper belt object that actually isn't on the same plane as the other planets.

I think I actually recall it being found by accident because it isn't where we would expected it to be, most likely it is a captured object not formed by our suns accretion disk.

Re:WTF is Eris?

[spacemandave]

IIRC it is a kuiper belt object that actually isn't on the same plane as the other planets. I think I actually recall it being found by accident because it isn't where we would expected it to be, most likely it is a captured object not formed by our suns accretion disk.

It is unlikely that any of the Kuiper Belt objects were captured from somewhere else. The Kuiper Belt is thought to have formed from the same accretion disk that formed the planets. However, it is thought that the original Kuiper Belt contained far more material than it does today, and that the objects were in more circular and coplanar orbits than we find them today. Due to an episode of giant planet migration, this original disk was scattered and depleted.

Many (but not all) of the observed dynamical features of the Kuiper Belt can be explained by giant planet migration.

Re:

[Pr0xY]

OK, I could ben wring about it being a captured object. But does giant planet migration address the orbit of Eris being 44 degrees tilted compared to the other planets and the like?

Re:

[davolfman]

"You forget Peter I was there for an kuiper-belt, unexplained massive planet migration." "Ray, the planet migrated about a foot and a half."

Re:WTF is Eris?

[spacemandave]

Eris, which measures about 70 miles wider than Pluto, is the farthest known object in the solar system at 9 billion miles away from sun.

Eris is not the farthest known object in the solar system. It is a member of the "scattered disk," a subclass of Kuiper Belt objects (KBOs). It is the largest scattered disk object (SDO) discovered so far, but by no means the farthest away. This [wikipedia.org] article has some nice diagrams that show the location of Eris relative to other known SDOs. There is another subclass of KBOs, called the "detached" objects, that are even further away. Sedna [wikipedia.org] is a member of this family.

Re:

[modmans2ndcoming]

eris, also known as the reason pluto is no longer a planet.

Re:

[Skye16]

Ditto with every other planet with a satellite. And don't even get me started with Saturn; just LOOK at that mess of rocky neighbors it left floating in a circle around it!

Re:Earth too

[sznupi]

By saying this you (and people agreeing with you - yes, you know who you are!) show you didn't put any effort into understanding what "clearing neighbourhood" in planet definition means.

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 /. summary is to be trusted, is specific to our system.

Re:

[Omestes]

Who really cares if we have 30 extra planets. I didn't know there was a hard limit of 10 planets in a solar system. Can some one please cite where it says this?

Re:

[mangu]

I didn't know there was a hard limit of 10 planets in a solar system

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:

[sznupi]

You have to draw the line somewhere, especially if there's a chance that we'll end up with a lot more than 30 (it shows the signifance of given object for the Solar System as a whole vs. the significance of a lot of objects as quite homogonous group). For example, Ceres was ALSO initially considered a planet...right until the point when we started to discover the rest of asteroid belt.

All signs on heaven (and...only on heaven ;P ) hint that Pluto is simply a similar "first", discovered by chance because it

Re:

[John Meacham]

There isn't any such limit. but it dillutes the usefulness of 'planet' as a term. This is astronomy, a science, it benefits from clear, precice, and _useful_ definitions. We can call everything that orbits the sun a planet if we like and lose its usefulness as a term, or we can just drop 'planet' as a scientific term and demote it to an historical anachronism. But neither of those are very good. If 'planet' is to be a useful term, it needs to have a precise and useful definition. There wasn't any such one

Re:

[ricebowl]

Thanks; I now feel thoroughly chastised. *sigh*

Re:

[Omestes]

Actually, your half right. It also is a derivitive of the initials P.L., for Percival Lowell, the founder of the observatory. And it fits into the Greek God motif of the existing planets, especially since it is the god of the underworld, which is somewhat fitting.

The initial suggestion was based on the character, but the above reason were why it was actually selected.