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So... What is a Planet Again?

By circletimessquare in Op-Ed
Fri Aug 18, 2006 at 12:00:00 PM EST
Tags: Ceres, Pluto, Charon, Xena, Sedna, Quaoar, 2002 AW197 (all tags)

The IAU's recent decision to retain Pluto as a planet was a political attempt to catch up with two trends: the recent discoveries by Mike Brown and his colleagues of new planetary objects, and a growing unease about Pluto's place in the classical notion of what a planet is. Whether or not they made the right decision about Pluto is rather pointless, as there are certainly more important things astronomers have to worry about. Although it is controversial amongst astronomers. And think of those poor astrologers and their horoscopes: "Your Libra is in the House of Quaoar. So, um, that makes you very cold and distant?"

If Pluto gets called a Planet or a Pluton or a Salami Sandwich in children's textbooks just isn't that important in the larger scheme of things. So certainly, the IAU got it right, for now: just let popular and historical notions hold sway. However, the IAU did not address a third trend on the horizon: we are beginning to discover planets outside of our solar system. This means our traditional notion of what a planet is and isn't is about to be challenged in a whole new bunch of ways that Pluto and Mike Brown could never muster. We are going to be exposed to a whole new cornucopia of exotic objects orbiting other stars in the next few decades. In this regard, the IAU's recent Solar Sytem-centric and politically rendered decisions just don't cut it.


The issue "what is a planet?" will have to be visited again as it becomes more clear just how inadequate the current nomenclature of orbiting objects is. And yes, in many ways it is a trivial concept. And judging how it has grasped the public's imagination, it is also emotional, not just clinical. But as we map more and more orbiting objects, it would be nice to have a system that isn't arbitrary and confusing, like the International Astronomical Union's current decision is.

Some cities, like New York, have an easy-to-grasp layout. Someone who has lived in New York for 10 years is as just as capable as someone who has spent fifteen minutes in Midtown Manhattan in navigating themselves from one address to the next: it's a simple grid, with each avenue and street simply numbered in one direction. Now compare that to Boston, where streets loop around and meet in triangles, and have different arbitrary names... madness. So nomenclature does matter, in the end, when you are dealing with hundreds or thousands of objects. Rather than the mere dozens we are dealing with when it comes to our current portfolio of planet-like objects that we know of. Politics and historical comfort may be a valid basis for the IAU's decisions today, but something more scientifically rigorous needs to come to the fore if we are to deal with our growing portfolio of known objects tomorrow.

The IAU not only allowed Pluto to remain a planet but they said that the moon of Pluto, Charon, should be considered a planet as well. Why? Because Charon and Pluto orbit a common center of gravity, rather than one orbiting the other. So while Earth's own Moon might be larger than both Pluto and Charon put together, and while some consider the Earth and its Moon just as much of a double planet system as Pluto and Charon, it still remains that the common center of gravity between the Earth and the Moon is well inside the Earth. Grumble... seems a rather puny technicality for elevating such a wimpy object as Charon to planethood.

Also, Ceres, the asteroid, got promoted to planethood as well. Why? Well, it's circular. And it's big for its environment, it contains a third of the mass of the entire asteroid belt. And I guess it just wouldn't look good to promote Pluto and Charon and not Ceres. OK, on that rationale: welcome Ceres to the pantheon of planethood. We've known you for awhile, but we just never gave you the recognition you deserved. Fine. But now elementary school students will need a new mnemonic for remembering your place I guess: "My Very Excellent Method: Just Say YoU KNow Planets" would become... "My Very Excellent Memory Concept: Just Say YoU KNow Planets Changing"?

Then there's the cornucopia of new planetoids Mike Brown and his colleagues have been discovering for the last few years: Xena, Sedna, Quaoar, 2002 AW197, etc., and probably a bunch more just lurking in deep exposure pictures on hard drives at some university but not yet properly sifted through computer algorithms and human eyes to be revealed yet. The Oort Cloud/ Kuiper Belt perhaps contains hundreds, maybe thousands of such bodies.

Now the IAU DID propose a new sub-classification for planets: Plutons. Well what is a Pluton? Any small icy object in the Oort Cloud/ Kuiper Belt would make sense to be called so. But no: Ceres is a Pluton says the IAU. Huh? So the IAU's move, in the end, seems to be very arbitrary and politically related rather than scientifically satisfying. Their Pluton designation will help with separating new, small discoveries from what we consider to be the classical eight planets, but it leaves one unsatisfied.

Consider the problems of classifying all orbiting objects we already know of according to their various qualities: Is it a gas giant (is it mostly gas)? Has it undergone nuclear fusion before? Could it? Is it currently undergoing nuclear fusion (like a binary/ tertiary star system)? Does it rotate clockwise or counter clockwise (consider Neptune's captured moon, Triton, and its retrograde orbit)? Does it orbit in the same plane of the other objects? Does it have a noncircular orbit or a complicated multifocal orbit? Is it a Lagrange point companion? Does it have an atmosphere? Is it spherical? Is it unstable? Is it transient? Is it it ice? Is it rock? Is it metal? Is it rock/ice/metal (like comets/ Oort Cloud/ Kuiper Belt objects)? Is it one of thousands/ millions like it (an asteroid belt, or a planetary ring)? What does it orbit: A star? A planet? A moon? A moon of a moon? Is it a binary object? Is it a comet/ does it shed a lot of material? Etc, etc, etc...

As you can see, things get rather mindboggling very quickly. All of these considerations mean that we need to harden our astronomical nomenclature into something less dependent on folk cultural artifacts of Pluto's planethood or not. I've been thinking about this for awhile, so how about this, my homebrew nomenclature, for what it's worth:

  1. Planet = mostly rock/metal/ice sphere with a significant atmosphere. What "significant" means becomes a point of contention then of course. Pluto's atmosphere for example is existent but tenuous, so again Pluto screws with our attempts at classification.
  2. Moon = rock/metal/ice sphere without an atmosphere.
  3. Asteroid = solid rock/metal/ice object that is not spherical.
  4. Comet = loose agglomeration of ice and rock and dust such that it can shed when on a violent orbit... but called a comet regardless of its current violent/ peaceful trajectory. So I am including not just those we see streaming towards the sun on a regular basis, for as we explore the Oort Cloud/ Kuiper Belt, we'll find plenty of these "dormant" comets.
  5. Gas Giant = considered as something different than a planet (mostly gas, obviously spherical). A star is simply a gas giant that has achieved thermonuclear fusion, and in fact, you have binary, tertiary, quaternary, etc. star systems where that is exactly what has happened. And in between you have your brown dwarfs, white dwarfs, and other objects occuring at the end of a star's life time/ before it's lifetime/ malformed and never quite fully fusing, etc. So what I am saying most importantly is that the whole notion of "gas giant" should not only be divorced from being a type of planet, but that it should also be combined with the notion of being a type of star. A gravitationally unignited/ dormant star. Arthur C. Clarke knows what I am talking about.
  6. Star = the root gravitational focal point for a family of rotating objects (besides the galactic center of course, which everything loosely rotates). For now, a star is a large bright fusing object, until we develop the technology in some far off future where we can discover and classify dark, unignited gas giants out there floating by themselves in the galaxy, and their menagerie of what would be very, very cold satellites.

And finally... drumroll please... most importantly... all of these objects should be defined independently of what they orbit. And, also, importantly, all of these objects should be defined independently of their size (I suppose you could talk about moonlets, or planetesimals, or planetoids, or minor planets, etc., if something falls under a certain size threshold that renders them less interesting and more numerous than certain large moons/ planets of obvious greater interest).

So Mercury isn't a planet, it's a moon of the Sun. Likewise, Pluto is a moon of the Sun. And Ceres and Vesta are moons of the Sun (small perfectly spherical "asteroids"). Titan isn't a moon, it's a planet of Saturn (it has a significant atmosphere). Deimos and Phobos are called moons of Mars, but they are clearly NOT moons, but captured asteroids of the Sun. So, represent that: call them asteroids of Mars. Why call them moons? They are not on the same order of objects we can rightfully consider to be moons, ie, spherical but devoid of atmosphere.

It all boils down to this: no matter what nomenclature is agreed upon, as we discover weirder extrasolar objects and orbital arrangements out there, the "what it's made of" part of an object's identity should come to mean something more important than "what it orbits". And for the same reason (the many different exotic configurations), size should no meaning, or much less important tertiary meaning. Then we have to come to grips with direction of orbit, orbits outside the orbital plane, orbits with bizarre shapes, binary/ tertiary objects, binary/ tertiary/ quaternary star systems, ring systems, etc.

How about a tertiary star system orbiting a common gravitational barycenter, each star with it's own planetary system... and one planet that, via natural harmonics between the three stars, switches orbital allegiance every now and then? Unlikely but possible. Well, what do we call such an object then with a nomenclature dependent first and foremost on what something orbits, rather than what it is made of?

How about a trojan planet? Usually objects that are trojans are tiny, a requirement of objects existing at Lagrange points for two much larger objects. But what if those two objects were so massive that they allowed for the existence of a mass large enough to gravitationally become a sphere and retain an atmosphere at the LaGrange point? Yes, a trojan planet. Again, unlikely, but plausible.

You can probably think up some of your own exotic scenarios. So anything with an appreciable atmosphere that is NOT a gas giant should be called a planet ...REGARDLESS of what it orbits. Some other nomenclature can address what it orbits ("a moon of the Sun" or "a planet of Saturn"). And the nomenclature doesn't have to be some German compound word ("thisisamoonnotaplanetbecauseitistooclosetothesuntohaveanatmosphere"). What I mean is that it's just a matter of accepting that you can not capture the object's complete characteristics in one single word, like we can do now with so few objects in our portfolio.

The whole issue is finding and agreeing upon a convenient yardstick for calling a planet a planet. We should detach the pretext for calling something a planet from the classical understanding of things, and we should get a greater pretext of taxonomical rigor on the question. Of course my conception is radical... but only from the classical point of view. But think about it: look at Saturn's or Jupiter's menagerie of objects. In complexity and quantity and variety they rival the Solar System itself. Those ecosystems are quite big, and should get that recognition they deserve. So let's give these large moons with atmospheres there the status of planet. They are moons just because of what they orbit? Nah. I say promote Titan to planet, and demote Mercury to moon.

As we find weirder systems out there: moons orbiting planets orbiting moons orbiting gas giants orbiting gas giants orbiting stars, stars with ring systems, true binary planets of equal size with a shared atmosphere, etc., we are going to need a nomenclature system that is more scientifically grounded, and certainly grounded more than the IAU's recent foray into political appeasement over scientific rigidity.

You can have asteroids of asteroids (Ida and Dactyl) and moons of moons (Pluto and Charon's Nix and Hydra). We can have a binary moon of the sun (Antiope the "asteroid", Pluto and Charon). I firmly believe this nomenclature would be more useful as we will come to see much more planetary systems out there, some quite exotic, with secondary planetary systems orbitting gas giants (which you can say Saturn and Jupiter already have) and maybe even TERTIARY systems (moon of a moon of a moon?). I expect to find planets orbiting nonspherical large asteroids. All sorts of lunacy (no pun intended).

But I am sorry: Pluto is just NOT a planet like the Earth. And Titan is just NOT a moon like some forlorn rock. So we need a new nomenclature for classifying planets, and mine simply stated is:

  1. composition first (spherical, solid, atmosphere: planet),
  2. orbital focus second (planet of Saturn),
  3. size third, or not at all (major planet of Saturn... Titan).


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o recent decision to retain Pluto as a planet
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o politicall y rendered
o it has grasped the public's imagination
o Internatio nal Astronomical Union's current decision
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o Xena, Sedna, Quaoar, 2002 AW197, etc.
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o Also by circletimessquare


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So... What is a Planet Again? | 87 comments (72 topical, 15 editorial, 0 hidden)
Scientific pedantry (2.25 / 4) (#4)
by debacle on Fri Aug 18, 2006 at 01:12:24 AM EST

+1 FP

It tastes sweet.
Ok, looks a good definition (3.00 / 4) (#9)
by jd on Fri Aug 18, 2006 at 02:39:53 AM EST

I have a different definition, which I'll run through here (again! :). The upshot of my long-winded definition is that:


  • ANYONE who knows something about an object should be able to classify it directly
  • ANYONE who hears of the object and its classification can derive a set of useful facts from that
  • Objects should be grouped across multiple dimensions of definition by definite, non-arbritary characteristics - much like the periodic table of the elements is.

My definition attempts to identify the variables and from that derive the groupings that are implicit by those variables. It's not intended to be perfect, it's merely intended to be useful, derivable and apolitical. Yes, there are a lot of terms, and I have argued that there should be many more. However, the terms are almost entirely orthogonal and can be combined to give a meaningful description. This means that the number of things you can describe is vastly greater than the number of terms in the list.

A planet is any body that originated in an accretion disk around a star, is gravitationally rounded, has a single core, is stratified, has a composition that is a direct function of both the distance the body formed from the sun and the abundance of the elements in the Universe, and is not undergoing a process of nuclear fusion.

A rocky planet is any planet in which over 50% of the mass of the planet is solid.

A gas planet is any planet in which 50% or more of the mass of the planet is in the form of a gas or plasma.

Any planet whose mass within a class is close to the minimum should be considered a dwarf. Any planet whose mass within a class is close to the maximum sustainable by the solar system it is in should be considered a giant. Any planet whose mass within a class is close to the maximum possible for that class (regardless of location) should be considered a supergiant.

A planetoid is any body that would qualify for a planet (regardless of type) but has insufficient mass. It must meet the other criteria, however.

A comet is any body that would qualify as a rocky planet but has multiple cores bound by any material that would sublime if heated, and may have any mass.

An ice planet is any body that would qualify as a comet but has a single core.

An asteroid is any body that would qualify for a rocky planet but has no identifiable core, is not stratified, and/or does not have the required composition, regardless of mass. This category should really be split up, as it has too many permutations. Categories should be useful and informative, not catch-alls.

Objects NOT formed in an accretion disk around a star (some exoplanets have been seen with accretion disks, and it's entirely possible that Saturn's rings once fit that category) are moons of whatever the accretion disk is/was around. Even if the object escapes the gravity of the body around which it formed. A moon cannot become a planet under any circumstance.

The moon around the Earth was formed from a piece of Earth splitting off as a result of a gigantic collision with another planet. This should be classified as a native moon, as it is from the body it orbits.

A special case is where both the surviving planet and "native moon" orbit a common point outside of the surface of either, as is the case with Pluto and Charon. This would be better described as a clustered planet, rather than as a planet/moon system, or as a binary planet.

Moons that are captured by a planet or other body should be classified as captured moons.

In the parallel special case, where both the planet and captured moon have comparable masses and orbit a common point, it should be regarded as a binary planet.

(The distinction between a clustered planet and a binary planet allows an observer to understand the relationship between the bodies and therefore deduce something about relative composition, the nature of the orbits, etc. It is therefore a useful distinction as it conveys a great deal of information.)

Planets that are captured by a larger planet, such that the smaller planet orbits the larger one within the larger planet's diameter should remain planets. A classification system that is changed by random events is useless for characterizing or making predictions. (The exception being for asteroids that are captured, as that's so uselessly overgeneralized that it doesn't hurt to reclassify.)

Bodies (whether rock or gas) that do not form in an accretion disk, or whose path cannot be reversed to any point in space where such a disk could have been, get the prefix of pseudo. For example, in a stellar nursary, it is possible to imagine the gas/dust cloud condensing to form a solid or gaseous planet-like object directly, as it must have all the same materials that the accretion disks would have.


my head asplode nt (1.75 / 4) (#10)
by circletimessquare on Fri Aug 18, 2006 at 02:45:38 AM EST



The tigers of wrath are wiser than the horses of instruction.

[ Parent ]
Errr... (none / 1) (#62)
by Pseudonym on Sun Aug 20, 2006 at 06:31:11 PM EST

I don't like the "rocky planet" definition, because there's no way to know how much of the mass of a planet is solid. Over 50% of the mass of the Earth is liquid, and we have no idea if that's also true of other planets until we see a volcano actually erupting.


sub f{($f)=@_;print"$f(q{$f});";}f(q{sub f{($f)=@_;print"$f(q{$f});";}f});
[ Parent ]
It's not all that hard (none / 1) (#67)
by godix on Mon Aug 21, 2006 at 11:44:59 AM EST

There are a couple things we can easily look at. First of all if there's no evidence of volcanic activity that lets us know the crust is solid enough that internal forces can't tear it apart so it obviously must be much more solid than the Earth. We can't tell if it's 50% or not but we can tell it's solid enough that the planet acts different than earth which is really the point of classifying it as a 'rocky planet'.

Another fairly easy way to make a decent guess is to look at the planets magnetic field. Currently we believe magnetic fields are caused by the core spinning faster than the mantle (although for very close planets the solar wind plays a role as well). Little or no magnetic field means the planet is pretty solid, solid enough the core can't spin much faster than the mantle at least.



- An egotist is someone who thinks they're almost as good as I am.
[ Parent ]

A planet is (3.00 / 2) (#11)
by Kronecker on Fri Aug 18, 2006 at 04:22:32 AM EST

anything that orbits a star and has been brought into a spherical (surface-) shape by its own gravity.

--
At some point we have to face down a culture in which not only the mob in the street but the highest judges and academics talk like crazies. - Mark Steyn
what is titan? (1.50 / 1) (#12)
by circletimessquare on Fri Aug 18, 2006 at 04:27:26 AM EST

i think that earth has more in common with titan than it does with mercury

i think that when we talk about classifying spherical objects, whether or not it has an atmosphere should be more important than what it orbits

so i say titan: planet

mercury: moon

and i think that as we find more and more exotic orbital configurations out there beyond our solar system, the "what its made of" will indeed become more important of a concept than "what it orbits"


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

Well I don't know (none / 1) (#15)
by Kronecker on Fri Aug 18, 2006 at 05:27:59 AM EST

I think the whole debate is kind of pointless and boring really. Maybe we should just call planets "any spacestuff that we've colonised" for political reasons.

--
At some point we have to face down a culture in which not only the mob in the street but the highest judges and academics talk like crazies. - Mark Steyn
[ Parent ]
If Titan is not a moon, it's... (3.00 / 2) (#17)
by toleransi on Fri Aug 18, 2006 at 08:23:09 AM EST

A platypus?
We use words like moon and comet for the same reason we use animal, mammal, plant and  virus. For humans, what goes around the sun in a relatively orderly fashion has a special importance. That's why Mercury will remain a planet. And that's why some of those rocks flying around out there will be comets if or when we notice they have those tails. This nomenclature will remain until it is obvious to a great number of people that the system is completely off-mark, and ready for a complete overhaul. That day is still a little ways off, I think.

[ Parent ]
i'm telling you man (none / 0) (#38)
by circletimessquare on Fri Aug 18, 2006 at 06:46:56 PM EST

what its made of is more important than what it orbits

a dead rock is not as interesting as titan

titan has an atmosphere

being a sphere and having an atmosphere makes a celestial body immediately of more importance to us, REGARDLESS of what it orbits, and the nomenclature should reflect that

an ant eats plants

an elephant eats plants

but grouping elephants with ants and not other mammals is stupid

because "what it eats" is a bogus primary organizing principle in zoology

so it should be in astrononomy

cl;assifgying planets by "what it orbits" first is just as stupid as classifying animals by "what it eats first

"what it is made of" is far more important to us, it just is, and so our naming conventions should reflect that


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

a dead rock is not as interesting as titan (3.00 / 6) (#58)
by zenofchai on Sun Aug 20, 2006 at 04:33:13 AM EST

first of all, you can't know with certainty whether a dead rock is as interesting as titan. it is possible that titan will not be as useful scientifically as we might think, and it is possible that, say, mercury will contain an abundance of some element that holds the very key to humanity's long-term survival.

secondly, you seem to grossly misunderstand the taxonomy of living things.

http://www.tigerhomes.org/animal/curriculums/lemurs-4.cfm

we say something is living not generally based on what it's composed of (since nearly everything living or non-living is composed mostly of carbon anyway) but whether it can reproduce.

ok, so we've classified living vs. non-living on whether it can reproduce or not (an action, not a composition).

let's go further.

now we've got living things. we classify them into their Kingdom, such as Animal, Plant, etc. surely, now, we go on something as important as composition.

nope. we go by shared traits of behavior.

why?

because if you grind up a big pile of ants, an elephant, or an oak tree, or a shark, or a whale, you're going to get fairly similar results in terms of all the junk that's in there. all have DNA, all have some proteins, some sugar chains, some fat chains, etc. that's why we can eat any of those things and live. (except probably the oak tree; there's such a thing as just too damned much fiber!)

animals are classified animals not because they are made of different things than plants, but because they are seen to be as: "sharing with all other members of this group the need to feed on organic matter (unlike plants which can create energy using light and minerals)".

http://species.wikimedia.org/wiki/Main_Page

(yes i've glossed over eukaryote vs. prokaryote; but nobody is going to mistake a lion for a bacteria any time soon, i think.)

what we really want is a predictable and useful taxonomy for planetary bodies. you seem to be presenting such a taxonomy, but you unfortunately seem to be using words in your taxonomy which are already in use; with nearly opposite meanings existing in a nearly opposite taxonomy already. the word "moon" has no meaning outside this already established taxonomy, because it already depends on the word "planet" which is already defined (again in this already established taxonomy).

how it currently works:

  1. is it a star, or something else?
  2. if it is something else: does it orbit a star, or something else?
  3. if it orbits a star, what shape is it?
  4. if it is a spheroid...

whales and sharks are both useful; even similarly for their copious amounts of flesh for human consumption. they both make their living in the sea. yet one is a fish, one is a mammal. why? because a whale is considered to be, fundamentally, more like a mongoose than a shark. just like titan is, fundamentally, more like our moon that it is like mars.

anyway, fundamentally it matters because the chief consideration is really already composition, where composition is defined as local gravitational significance -- titan is not as locally significant gravitationally speaking as jupiter is. this is why jupiter is a planet and titan is not. if titan were gravitationally speaking more significant than jupiter, jupiter might be a moon of titan. but it's not. that's why it's a moon. why is local gravitational significance so important? so we don't crash our spaceships into the wrong thing, and so we can predict where what mega-billion-ton thing is going to be.

ask yourself: if i want to know where titan is, does it make sense to know that it tends to, oh i don't know, sort of follow jupiter around the sun? you want to say things like "titan is a planet of jupiter" but it just doesn't make sense, it would be like saying "cts is a fan of grammar, fascism, and political correctness" and when you disagree, reply, "oh, yeah, i redefined the word 'fan' to mean something else."

use a different word if you want to create a different taxonomy based on usefulness or composition. it sounds like interesting stuff, and important stuff. sort of like figuring out a tree of categorization that has a shark and a whale handily nearby because both can be found in the ocean and eaten. but we don't try to re-define fish or mammal and destroy the existing body of classification, which exists for its own purposes already.

--
The K5 Interactive Political Compass SVG Graph
[ Parent ]

titan is a moon (none / 1) (#59)
by toleransi on Sun Aug 20, 2006 at 05:46:52 AM EST

being probed quite a bit recently by Cassini.
Change "jupiter" to "saturn" in your comment and you've got yourself an argument, though.
 

[ Parent ]
yeah well (none / 0) (#61)
by zenofchai on Sun Aug 20, 2006 at 10:24:01 AM EST

nobody's perfect. least of all my stupid ass. but thanks, it is good to know that i misplaced something as important as titan :(
--
The K5 Interactive Political Compass SVG Graph
[ Parent ]
"dead rocks" are just as interesting (none / 0) (#73)
by CanSpice on Mon Aug 21, 2006 at 07:11:25 PM EST

Actually, "dead rocks" are just as interesting as rocks with atmospheres, because they can give us greater insight into the composition of the early Solar System. Rocks with atmospheres (like Titan, or Mars) have had their surfaces modified by their atmospheres; it's next to impossible to determine what that rock was originally made of. Rocks without atmospheres are essentially pristine; neglecting cosmic ray interactions at the very surface, underneath is essentially primordial Solar System stuff.

And by finding out what the Solar System was originally made from leads us to the composition of the pre-stellar nebula, which is important in the study of how stars (and planetary systems) form.

[ Parent ]

no, wrong (none / 0) (#74)
by circletimessquare on Mon Aug 21, 2006 at 10:02:40 PM EST

i mean, we can wax and wane poetic and scientific about how interesting the sahara desert is for all sorts of reasons

but it just is not as interesting as the amazon rain forest

it's simply isn't

simply on a measure of complexity

and so, things with atmospheres are more interesting than things without atmospheres, no matter how you cut it

The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

no, wrong (none / 0) (#75)
by CanSpice on Mon Aug 21, 2006 at 10:13:54 PM EST

You're confusing "complex" with "interesting". A rock with an atmosphere is more complex than a rock without, but that doesn't necessarily imply it's more interesting.

[ Parent ]
it DOES imply it is more interesting (none / 0) (#76)
by circletimessquare on Mon Aug 21, 2006 at 11:06:41 PM EST

i mean you could find someone who is more interested in a pile of sand than human psychology, but so what?

it is a solid fact that human psychology is more complex than a pile of sand and therefore more "interesting", meaning something capable of and holding a random person's interest and attention for discovering more and more things

so i say interesting is directly proporitonal to complexity, for strictly objective reasons

of course, SUBJECTIVELY, you could find someone more interested in staring at a plain brick wall than listening to complex music, but who the fuck cares?

The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

Yawn (2.50 / 4) (#13)
by BJH on Fri Aug 18, 2006 at 04:37:24 AM EST

OK, here's my definition: a planet is something that I occasionally wish cts wasn't on. Like right now. Can you say BOOOORING?
--
Roses are red, violets are blue.
I'm schizophrenic, and so am I.
-- Oscar Levant

Boring, (none / 0) (#66)
by wuckers on Mon Aug 21, 2006 at 10:30:01 AM EST

awckward and unnecessarily verbose syntax, sentence fragments, no evidence of proofreading.  Why bother writing if you're not going to take pride in it?

[ Parent ]
...says the person who can't spell awkward. [nt] (none / 0) (#78)
by BJH on Tue Aug 22, 2006 at 10:50:27 AM EST


--
Roses are red, violets are blue.
I'm schizophrenic, and so am I.
-- Oscar Levant

[ Parent ]
asteroids aren't star-like (none / 1) (#14)
by toleransi on Fri Aug 18, 2006 at 04:43:03 AM EST

>3. Asteroid = solid rock/metal/ice object that is not spherical.

For consistancy, you shouldn't be using the word asteroid like that, should you?

What is a planet? (2.25 / 4) (#16)
by United Fools on Fri Aug 18, 2006 at 07:24:54 AM EST

That is a difficult question!
Something like the moon?

We are united, we are fools, and we are America!
Chang-E the moon goddess says so (none / 0) (#46)
by badvogato on Sat Aug 19, 2006 at 05:49:34 AM EST

Moon can rise higher than the Sun.

[ Parent ]
My Very Excellent Memory Concept: Just Say YoU KNo (2.50 / 6) (#19)
by GhostOfTiber on Fri Aug 18, 2006 at 09:46:24 AM EST

My Vagina Excretes Messy Crap, Just So You kNow, Prince Charming.

[Nimey's] wife's ass is my cocksheath. - undermyne

Good stuff. (3.00 / 2) (#20)
by daveybaby on Fri Aug 18, 2006 at 10:29:44 AM EST

I dont give a monkeys whether somethings called a planet or not, but this is still a very interesting read.

Bonus points for mentioning the Oort cloud multiple times, 'oort' is one of my favourite words, and it's always nice to have a part of the solar system that sounds like it might be  
controlled by a sinister alien race.

whatever idiot (2.77 / 9) (#21)
by Mylakovich on Fri Aug 18, 2006 at 11:31:06 AM EST

i'm gonna spell it out, since you are obviously incabable of thinking clearly (Snicker)

you are missing the point of living in this new age of ours

your insignificant local problems mean nothing

only global sociopolitical issues are relivant today

how do you like the taste of REALITY moron?

(snicker)
[+1 FP]

you stupid motherfucker (1.66 / 3) (#37)
by circletimessquare on Fri Aug 18, 2006 at 06:42:46 PM EST

you understand where i'm coming from asshole?

listen to my fucking words

or i'm going to have to stick a boot in your face

capisce fuckwad?

now follow the bouncing ball you twat

i'm going to have smack some fucking common sense into you

you blind stupid useless turd

singing in your ivory tower of ignorance

we're down her ein the mud duking it out with real evil

don't you fucking understand the fucking obvious?

etc

...


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

Awesome. nt (none / 0) (#64)
by Mylakovich on Mon Aug 21, 2006 at 09:01:20 AM EST



[ Parent ]
now that you know it's just an act (none / 0) (#69)
by circletimessquare on Mon Aug 21, 2006 at 04:23:28 PM EST

don't tell anyone, they might get less upset, and ruin all of our fun ;-)


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]
One minor problem (3.00 / 3) (#24)
by godix on Fri Aug 18, 2006 at 02:15:46 PM EST

if a planet gets far enough from the sun it's atmosphere will freeze and effectively change it's classification from 'planet' to 'moon' under your idea. If the idea is composition first then distance from the star shouldn't change the classification. Perhaps you should toss in 'would have an atmosphere if it recieved enough energy that oxygen/hydrogen/etc wouldn't freeze'.

Even this doesn't help that much, there are objects in the solar system that aren't massive enough to hold an atmosphere except in unusual circumstances. IIRC Io couldn't hold it's atmosphere but because it's orbiting Jupiter close enough to be volcanically active from tidal forces and the other moons act as shepard moons Io regenerates it's atmosphere and tends to pick up any it loses again the next time it goes around. Remove the shepard moons or put it at 1 AU from it's primary and it'd be a dead rocky ball. AFAIK Mars is pretty near the lowest mass object that can still be said to have an atomosphere without unusual conditions.


- An egotist is someone who thinks they're almost as good as I am.

same with mercury (1.50 / 1) (#25)
by circletimessquare on Fri Aug 18, 2006 at 02:22:13 PM EST

it pretty much got its atmosphere boiled off and blasted away

but i'm not concerning myself with the WHY, just the WHAT

i'm sayin gno atmosphere=moon, regardless of why

sound arbitrary to you? hardly as arbitrary as the IAU

and what are people interested in? what are humans interested in?

places with an atmosphere, because they resemble earth

so elevate those more interesting objects with a word: planet

promote titan

demote mercury

certainly titan is more interesting than mercury

surely titan doesn't deserve the same designation as some captured asteroid


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

i'm not sure i understand (none / 0) (#26)
by zenofchai on Fri Aug 18, 2006 at 03:09:42 PM EST

why you want to confuse the definitions of atmosphere and planet. we have two words here and you are trying to make them the same.

is it a planet? well yes, it has an atmosphere after all.

does it have an atmosphere? well yes, it is a planet after all.

by all that is unholy, i submit that i must agree that Klonecker's definition is the post palatable. anything orbiting a star that is a formed sphere due to its gravitation. your "my head asplode" comment's parent was also quite fetching in its usefulness.

thus, mercury is a planet. titan isn't because it orbits something other than a star. as far as "deserving the same designation as some captured asteroid" see the "my head asplode" comment's parent with its "native moon" and "capture moon", etc.

you seem to be defining "useful planet" or "interesting planet" or "potentially habitable planet" or "planet with an atmosphere". yes, that's it, you're defining a "planet with an atmosphere" as a "planet with an atmosphere".

but it's still +1 ;]
--
The K5 Interactive Political Compass SVG Graph
[ Parent ]

as we find extrasolar planets (2.00 / 3) (#27)
by circletimessquare on Fri Aug 18, 2006 at 03:18:19 PM EST

the what its made of will be more interesting to us than the what it orbits

it already is in fact

titan is far more interesting than mercury

that difference needs to be recognized in the nomenclature

look at it this way: ants eat plants. elephants eat plants. should we classify ants close to elephants because they both eat plants? and not elephants with lions because lions eat meat? no, that's silly

honestly, the what it orbits being more important than the what its made of is just as silly a clasification methodology

deimos is a little useless captured rock around mars. it's a moon. titan is a large spherical body with an atmosphere and a complex environment. also a moon. that's just as stupid as classifying ants with elephants

The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

useless captured rock (none / 0) (#32)
by zenofchai on Fri Aug 18, 2006 at 05:31:30 PM EST

deimos is a little useless captured rock around mars. it's a moon. titan is a large spherical body with an atmosphere and a complex environment. also a moon. that's just as stupid as classifying ants with elephants

deimos is an uninteresting barren rock moon;

titan is an interesting atmosphered moon.

planets orbit stars, cts.

as we discover extrasolar bodies, be they planets or moons or comets, we are well equipped with the vocabular to describe them as interesting or not; barren or not; having atmosphere or not; being a moon (orbiting a planet) or being a planet (orbiting a star) or neither.

and believe me, if there were volunteer applications for manned missions to titan, my name would be on there. i'd initial all 5 freaking initials wherever i needed to initial. but i'd be heading to a moon, not a planet.
--
The K5 Interactive Political Compass SVG Graph
[ Parent ]

an ant is an interesting plant eater (1.50 / 1) (#34)
by circletimessquare on Fri Aug 18, 2006 at 05:46:37 PM EST

an elephant is an interesting plant eater

but i think its wiser to classify elephants with other mammals than with ants


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

exactly (none / 0) (#35)
by zenofchai on Fri Aug 18, 2006 at 05:59:06 PM EST

that's why we DO classify elephants as large mammals, and ants as insects.

and that's why we DO classify moons, even interesting ones, as moons; and planets, even uninteresting ones, as planets. because that's what they are.
--
The K5 Interactive Political Compass SVG Graph
[ Parent ]

if it has an atmosphere or not (none / 0) (#36)
by circletimessquare on Fri Aug 18, 2006 at 06:10:10 PM EST

is more important than what it orbits

titan has more in common with venus/ mars/ earth than mercury does

yes or no?

titan is more interesting to us than mercury: yes or no?


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

answering questions: (none / 0) (#39)
by zenofchai on Fri Aug 18, 2006 at 08:18:23 PM EST

titan has more in common with venus/ mars/ earth than mercury does: yes or no?

no. titan orbits jupter. venus, mars, and earth do not orbit jupiter.

titan is more interesting to us than mercury: yes or no?

from the perspective of searching for life (that we can presently understand) yes. from other perspectives, who knows.
--
The K5 Interactive Political Compass SVG Graph
[ Parent ]

so an elephant is more like an ant (none / 0) (#40)
by circletimessquare on Fri Aug 18, 2006 at 08:25:25 PM EST

than a lion

because they both eat plants?

you're saying what they ARE MADE OF, they're COMPOSITION, is less important than what they ORBIT, right?

i say bullshit

i say titan and earth are close in COMPOSITION

and that is a SOUNDER taxonomic basis than what they orbit

and as we find more objects out there in more exotic arrangements outside the solar system, i am going to be vindicated


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

i said not a word about composition (none / 0) (#41)
by zenofchai on Fri Aug 18, 2006 at 08:49:09 PM EST

so an elephant is more like an ant than a lion because they both eat plants?

i've never said this. we have a huge stratified sorted set of classification of living creatures.

you're saying what they ARE MADE OF, they're COMPOSITION, is less important than what they ORBIT, right?

i didn't say a word about composition. i said the fundamental thing about planets are that they orbit stars, and the fundamental thing about moons are that they orbit planets. this is the top of the taxonomy.

sharks and tigers are both interesting carnivores. yet one is a cold-blooded fish and the other is a mammal.

and as we find more objects out there in more exotic arrangements outside the solar system, i am going to be vindicated

vindicated? i'm not sure i understand. we'll call them objects until we figure out what they orbit; we'll call them moons if they orbit planets, and planets if they orbit stars, and various other things if they orbit various other things.
--
The K5 Interactive Political Compass SVG Graph
[ Parent ]

that's retarded (none / 0) (#42)
by circletimessquare on Fri Aug 18, 2006 at 09:07:41 PM EST

"i didn't say a word about composition. i said the fundamental thing about planets are that they orbit stars, and the fundamental thing about moons are that they orbit planets. this is the top of the taxonomy."

bullshit

titan is interesting

ceres is not

why?

because of it's COMPOSITION

what it orbits is LESS important

the FUNDAMENTAL issue is composition, not what it orbits

and as we discover more and more out extrasolar objects, i will be vindicated

"we found a rock orbiting beteljuese today"

"OMFG A ROCK! A NEW PLANET!"

"we found a large spherical object with a significant atmosphere today too... but it orbits a gas giant, so its not as significant, it's a just a moon"

"yeah, who cares about just another moon"

pffffffffft

COMPOSITION IS MORTE IMPORTANT THAN ORBITAL FOCUS

TITAN IS MORE INTERESTING THAN MERCURY

solid facts

our nomenclature should reflect that

and it will


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

who the hell says (3.00 / 2) (#57)
by zenofchai on Sun Aug 20, 2006 at 12:26:27 AM EST

"we found a large spherical object with a significant atmosphere today too... but it orbits a gas giant, so its not as significant, it's a just a moon"

"yeah, who cares about just another moon"

who says that? who calls titan "just a moon"? really?

what's retarded is taking perfectly fine and classically used words and violently and wantonly redefining them with near randomness.

nobody calls an interesting, atmosphered planetary body "just another X" at this point.
--
The K5 Interactive Political Compass SVG Graph
[ Parent ]

Classification (none / 0) (#83)
by joto on Thu Aug 24, 2006 at 03:41:28 PM EST

look at it this way: ants eat plants. elephants eat plants. should we classify ants close to elephants because they both eat plants?

Yes. We already do, and we should continue to do so. There's even a word for it: herbivores!

[...] and not elephants with lions because lions eat meat? no, that's silly

There's no single "best" way of classification. Scientific naming of animals happen to choose evolutionary origin as the basis. But depending on what the purpose of the classification is, there are other classifications that are just as useful.

Here are just some examples of other useful criteria for classification of animals: edible, poisonous, disease-causing, dangerous, damages human artifacts, protein-rich, has ivory, has wool, tastes good, can be tamed, can carry humans, can plow fields, can guard human territory, easy to catch, disgusting or slimey, etc...

honestly, the what it orbits being more important than the what its made of is just as silly a clasification methodology

All classification is silly. Classification is a futile attempt by humans to simplify the real world. The real world is complex. Which classification scheme you choose depends upon what you intend to use it for. If you want to calculate planet orbits, the current definition of "planet" and "moon" is just fine. If you want to do other things, your suggestion might have some advantages, as would any number of other more or less arbitrary classification schemes.

deimos is a little useless captured rock around mars. it's a moon. titan is a large spherical body with an atmosphere and a complex environment. also a moon. that's just as stupid as classifying ants with elephants

I think by now that you know what I think of your statement.

[ Parent ]

He has a point (3.00 / 2) (#55)
by boxed on Sat Aug 19, 2006 at 10:01:36 PM EST

There can definitely be bodies that orbit a sun with an eccentric enough orbit that the atmosphere freezes during part of the orbit. This thing would fluctuate between "moon" and "planet".

But you know, fuck it. You can get all lawyer on it's ass and say "if it has an atmosphere during any point of it's orbit" but just ignore that extra sentence for normal use.

[ Parent ]

Mercury and Pluto have atmospheres (none / 0) (#72)
by CanSpice on Mon Aug 21, 2006 at 07:06:51 PM EST

Actually Mercury has an atmosphere. It's extremely tenuous, but it has one.

Ditto Pluto. It has an atmosphere made up of nitrogen, carbon dioxide, and methane.

[ Parent ]

Just as silly. (3.00 / 2) (#29)
by rpresser on Fri Aug 18, 2006 at 05:20:58 PM EST

What about Sirius? Sirius A and B orbit a common center of gravity that lies outside of either one, so neither is the "root gravitational focal point for a family of rotating objects."  So what are they, gas giants?

------------
"In terms of both hyperbolic overreaching and eventual wrongness, the Permanent [Republican] Majority has set a new, and truly difficult to beat, standard." --rusty
the astronomers AGREE with me asshole (1.75 / 4) (#30)
by circletimessquare on Fri Aug 18, 2006 at 05:24:09 PM EST

or at least the one who DISCOVERED THE FUCKING "PLANETS" they are talking about, mike brown

he doesn't even think they should be called planets!

What should the public think about 53 planets?

Most people, when first confronted with a proposal to make 44 new planets in the solar system, seem to react by looking blankly for a second, then shaking their heads and muttering something about astronomers being crazy. Astronomers are not actually crazy, at least most of them. Astronomers have needed a good scientific definition of the word "planet" for many years now and this one works well for scientists. It doesn't, however, work terribly well for the rest of the world. The solution is the one that should have happened long ago: a divorce of the scientific term "planet" for the cultural term "planet." No one expects school children to name the 53 planets (most, in fact, don't even have names). If I were a school teacher I would teach 8, or 9, or perhaps 10 planets and then say "scientists consider many more things to be planets too" and use that opportunity to talk about how much more there is in the solar system. But at the end of the day I would talk about 8 or 9 or 10. Not 53.

Culture and science have always meant something different when they use the word planet, and with this new scientific definition so clearly far removed from what the rest of the world things a planet is there will no longer be any need to confuse the scientific word with the cultural one.

How am I going to vote on the IAU resolution?

This one is easy to answer. I am not an IAU member, I took no part in drafting the resolution, and I get no vote. If I were to vote, however, I would have to decide that while the definition itself is viable the extra non-scientific beauracratic barrage attached to the resolution would doom it for me.

so now you know the facts, so now you can open your mouth asshole


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]

Now that you've called me an asshole (none / 1) (#31)
by rpresser on Fri Aug 18, 2006 at 05:30:23 PM EST

and made yourself feel important, how about answering my question?

Is an object not a star just because it isn't the center of a system?
------------
"In terms of both hyperbolic overreaching and eventual wrongness, the Permanent [Republican] Majority has set a new, and truly difficult to beat, standard." --rusty
[ Parent ]

i dont feel important (2.00 / 2) (#33)
by circletimessquare on Fri Aug 18, 2006 at 05:45:41 PM EST

i feel angry, because you ask without reading


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]
christ (none / 1) (#44)
by rhiannon on Sat Aug 19, 2006 at 01:20:36 AM EST

are you sure you're responding to the right post?

-----------------------------------------
I continued to rebuff the advances... so many advances... of so many attractive women. -MC
[ Parent ]
Why that order? (3.00 / 3) (#47)
by anno1602 on Sat Aug 19, 2006 at 06:56:13 AM EST

  1. composition first (spherical, solid, atmosphere: planet),
  2. orbital focus second (planet of Saturn),
  3. size third, or not at all (major planet of Saturn... Titan).

I agree that composition, orbit and size are all three important factors to classify an object. I fail to see why one should be more relevant than another. For example, the relation of a lump-o-cold-material to a star is at least as, if not more important to its habitability than what it is made of or whether it has an atmosphere. Venus has an atmosphere, too, but it's uninhabitable. The gas giants can be argued to mostly be atmosphere. Pluto has a - very thin - atmosphere, which doesn't make it any more interesting.

How about a tertiary star system orbiting a common gravitational barycenter, each star with it's own planetary system... and one planet that, via natural harmonics between the three stars, switches orbital allegiance every now and then? Unlikely but possible. Well, what do we call such an object then with a nomenclature dependent first and foremost on what something orbits, rather than what it is made of?

A planet. You say so yourself.
--
"Where you stand on an issue depends on where you sit." - Murphy
Those poor astrologers (3.00 / 3) (#48)
by localroger on Sat Aug 19, 2006 at 09:42:46 AM EST

Astrologers are ahead of the curve on this; they classify everything that moves against the backdrop of stars, including the Sun and Moon, as a planet. (Indeed, the word "planet" itself comes from the Greek word for "wanderer," reflecting this.) This would mean that Ceres, Pluto, and all that crap in the Oort cloud are all planets too.

Things that revolve around other planets, like Phobos, Deimos, Ganymede, and Titan don't matter because they effectively share the motion of the planet they orbit. They would be called moons mainly because they have nothing of their own to contribute to an Astrological chart.

In the case of dual planets such as Pluto/Charon the larger member of the pair would be taken as the parent body. Again there really isn't any Astrological system for considering the motion of moons of planets, so it really doesn't matter if the "planet" is one body or fifteen.

See kids? The Universe really is simpler if you ignore science :-)

I am become Death, Destroyer of Worlds -- J. Robert Oppenheimer

Simpler? (none / 0) (#63)
by roystgnr on Sun Aug 20, 2006 at 09:37:30 PM EST

Kids, just try to imagine your next astronomy test!

Question 1.  Name all the planets in the solar system:

Mercury
Venus
 (a couple more lines)
Ceres
Pallas
Juno
 (a thousand more lines)
Gaussia
Olbersia
Lilofee
 (nine thousand more lines)
Palermo
1969 TQ1
1971 UD1
 (ninety thousand more lines)
1982 UC3
1983 QC1
1983 RN3
...

And after all that, you still get marked wrong, because you didn't know that the ESA was launching the Corot satellite (now known as Planet Corot) while you were taking the test!

[ Parent ]

this is so fucking stupid (1.50 / 2) (#50)
by balsamic vinigga on Sat Aug 19, 2006 at 04:24:19 PM EST

The solution is simple.  Keep the planets exactly as is, and don't name anything else a planet.  Any further discoveries in our solar system or other solar systems can get a new scientific classification...  and just let the word planet be a romantic and unscientific word.

Before other planets were disocvered we called our own planet Earth.  In non scientific terms other planets have been caled "earths" but science isn't down with that so they just came up with a new word... called them all planets and limited the name Earth to our own planet.  It's the same thing..  these other satellites can get better scientific names that can also be adapted to our planets, but just leave the word planet alone...  there's no reason to change its definition.

Proposed definition for planet:

One of these satellites of our sun:

Mercury, Venus, Earth, Mars, Jupiter, Uranus, Neptune, Pluto.

Any other things tentatively called planets can be named some other shit..  I don't give a shit what they're named call them anything you like, and classify the planets as that too..  who gives a shit.

---
Please help fund a Filipino Horror Movie. It's been in limbo since 2007 due to lack of funding. Please donate today!

oh lol and Saturn too $ (none / 1) (#51)
by balsamic vinigga on Sat Aug 19, 2006 at 04:25:58 PM EST



---
Please help fund a Filipino Horror Movie. It's been in limbo since 2007 due to lack of funding. Please donate today!
[ Parent ]
You should have forgot Pluto instead $ (3.00 / 2) (#53)
by localroger on Sat Aug 19, 2006 at 07:17:14 PM EST



I am become Death, Destroyer of Worlds -- J. Robert Oppenheimer
[ Parent ]
i actually like that nt (none / 0) (#54)
by circletimessquare on Sat Aug 19, 2006 at 09:10:45 PM EST



The tigers of wrath are wiser than the horses of instruction.

[ Parent ]
Planet Politics (none / 1) (#52)
by Orion Blastar Again on Sat Aug 19, 2006 at 05:44:42 PM EST

This is all a massive conspiracy by the left, to change the definition of what a planet is, in order to impeach George W. Bush. I ain't buying it!

I can see the propaganda now "George W. Bush and other Republicans think that there are only nine planets. The Republicans are discriminating against Ceres, Charon, Xena, Sedna, Quaoar, 2002 AW197, etc, which is Unconstitutional. This is an impeachable offense. They would have you think that these planets are asteroids, moons, and other things. Vote for Democrats in 2006 and 2008, and help end the discrimination of planets."

Learn how to be a liberal.
I can't believe it's not Liberalism!
"Thanks for the pointers on using the internet. You're links to uncylopedia have turned my life around." -zenador

IAU Conspiracy Theory (3.00 / 3) (#60)
by wji on Sun Aug 20, 2006 at 10:21:04 AM EST

See, the astronomers have been trying for decades to bump off Pluto: clearly it's not a planet in the sense that, say, Venus is a planet. It's got a whacky orbit and it's very small. The most common argument against Pluto's planethood has been, "If Pluto's a planet, all this other crap that nobody thinks are planets must be planets!".

But when the IAU has tried to "demote" Pluto it's run into, of all things, public oppostion. People want there to be nine planets, including Pluto. People have an emotional attachement to Pluto for some reason. Maybe it's the Walt Disney thing.

Solution: a "poison pill" proposal that the public will get upset about, reject, and replace with the only natural alternative: there are eight planets and change. It's all so Machiavellian!

I have no idea if this is true, but it makes a strange kind of sense.

In conclusion, the Powerpuff Girls are a reactionary, pseudo-feminist enterprise.

"People" (none / 1) (#65)
by linca on Mon Aug 21, 2006 at 09:21:09 AM EST

The "people" who want Pluto to remain a planet tend to be some American astronomers ; because it is The Planet Discovered By An American TM.

That's why the Union of Astronomers won't vote for a new definition of "planet" that excludes Pluto, and why all the others will have to be included too.

[ Parent ]

potential solutions (none / 1) (#68)
by zenofchai on Mon Aug 21, 2006 at 03:18:23 PM EST

"the 9 classical planets" or "traditional" planets.

"Pluto, a dwarf planet in a binary planet system with its sister Charon, was one of the 9 classical planets. It was originally discovered by ..."

I'm not sure I understand why pluto isn't a "technical" planet. It's spheroid. It's held together by its own mass. It orbits the sun. It isn't composed entirely of ice and so shouldn't be called a tailless comet.

its primary objections seem to be its: size, inclination of orbit, binary nature with charon, and composition (potentially, if you say that an object with N% of ice is a comet, i suppose).

would you call it an asteroid? not sure... don't think so, because it is spheroid.
--
The K5 Interactive Political Compass SVG Graph
[ Parent ]

potential solution (none / 1) (#70)
by circletimessquare on Mon Aug 21, 2006 at 04:24:59 PM EST

its a moon of the sun


The tigers of wrath are wiser than the horses of instruction.

[ Parent ]
touche -nt (none / 1) (#71)
by zenofchai on Mon Aug 21, 2006 at 04:27:32 PM EST


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The K5 Interactive Political Compass SVG Graph
[ Parent ]
Aha! (none / 0) (#77)
by wji on Tue Aug 22, 2006 at 10:17:21 AM EST

Now it's an anti-American conspiracy theory, too!

Marvelous!

In conclusion, the Powerpuff Girls are a reactionary, pseudo-feminist enterprise.
[ Parent ]

Orbital eccentricity & Inclination (3.00 / 2) (#79)
by hentai on Tue Aug 22, 2006 at 03:07:12 PM EST

Personally, I'd prefer Ceres to be a planet before Pluto. At least it's in the right place.

Mercury - eccentricity 0.206, inclination +5.00 degrees, diameter 4880 km
Venus - eccentricity 0.007, inclination +1.39 degrees, diameter 12,100 km
Earth - eccentricity 0.017, inclination -2.00 degrees, diameter 12,750 km
Mars - eccentricity 0.093, inclination -0.15 degrees, diameter 6,800 km
Ceres - eccentricity 0.020, inclination +8.60 degrees, diameter 950 km
Jupiter - eccentricity 0.049, inclination -0.70 degrees, diameter 143,000 km
Saturn - eccentricity 0.056, inclination 1.49 degrees, diameter 120,500 km
Uranus - eccentricity 0.047, inclination -1.33 degrees, diameter 51,120 KM
Neptune - eccentricity 0.009, inclination -0.33 degrees, diameter 49,530 km
Pluto - eccentricity 0.250, inclination 15.2 degrees, diameter 2,300 km

Note Pluto's extreme orbital inclination and eccentricity. Ceres and Mercury also each have substantial eccentricity and/or inclination, but with Mercury it's somewhat understandable (given how close to the sun Mercury is).

interesting developments (none / 0) (#80)
by circletimessquare on Tue Aug 22, 2006 at 11:50:51 PM EST

Astronomers in a Quandary Over Pluto's Status

August 23, 2006

Astronomers in a Quandary Over Pluto's Status

By DENNIS OVERBYE

Pluto was looking more and more like a goner yesterday as astronomers meeting in Prague continued to debate the definition of a planet.

"I think that today can go down as the `day we lost Pluto,' " said Jay Pasachoff of Williams College in Williamstown, Mass., in an e-mail message from Prague.

Under fire from other astronomers and the public, a committee appointed by the International Astronomical Union revised and then revised again a definition proposed last week that would have expanded the number of official planets to 12, locking in Pluto as well as the newly discovered Xena in the outer solar system, as well as the asteroid Ceres and Pluto's moon Charon.

The new definition offered yesterday would set up a three-tiered classification scheme with eight "planets"; a group of "dwarf planets" that would include Pluto, Ceres, Xena and many other icy balls in the outer solar system; and thousands of "smaller solar system bodies," like comets and asteroids.

The bottom line, said the Harvard astronomer Owen Gingerich, chairman of the Planet Definition Committee of the union, is that in the new definition, "Pluto is not a planet."

"There's not happiness all around, believe me," he added.

The new proposal was hashed out in a couple of open meetings, the first of which was described by participants as tumultuous, and the second as more congenial. Astronomers are supposed to vote Thursday on this or some other definition, but whether or not a consensus is emerging depends on whom you ask. Some astronomers expressed anger that the original definition of a planet had been developed in isolation and then dropped on them only a week before the big vote. Others continued to question whether it was so important to decide the question now.

Among its defects, some astronomers say, the newer definition abandons any pretense of being applicable to planetary systems beyond our own solar system.

To many astronomers, Pluto's tiny size and unusually tilted orbit make it a better match to the icy balls floating in the outskirts of the solar system in what is known as the Kuiper Belt than to the traditional planets like Jupiter and Mars. The issue has been forced on astronomers by the discovery of such a ball even larger than Pluto, nicknamed Xena by its discoverer, Mike Brown of the California Institute of Technology.

If Pluto is a planet, Xena should be, too, Dr. Brown has argued.

The committee's original prime criterion was roundness, meaning that a planet had to be big enough so that gravity would overcome internal forces and squash it into a roughly spherical shape. But a large contingent of astronomers, led by Julio Fernández of the University of the Republic in Montevideo, Uruguay, has argued that a planet must also be massive enough to clear other objects out of its orbital zone. Dr. Gingerich admitted, "They are in control of things."

So the newest resolution includes the requirement for orbital dominance as a condition for full-fledged planethood, Dr. Gingerich said. That knocks out Pluto, which crosses the orbit of Neptune; Xena, which orbits among the icy wrecks of the Kuiper Belt, and Ceres, which is in the asteroid belt.

"Vociferous objectors have said they could accept this," Dr. Gingerich said.

Reached in his office at Caltech, Dr. Brown, who as the discoverer of Xena has the most to lose by its and Pluto's demotion, said he thought he could live with the new proposal. "It essentially demotes Pluto to something other than a real planet, which is reasonable," he wrote in an e-mail message.

Dr. Gingerich cautioned that there were still many things to be sorted out. For example, the I.A.U. may or may not create a special name for Pluto and other dwarf planets, like Xena and others yet to be discovered, that dwell beyond Neptune. If so, he said that "plutonians" seemed a likelier choice than the previous suggestion "plutons." That term was protested by geologists, who pointed out that it was already used in earth science for nuggets of molten rock that have solidified and reached the surface.

With two more days before the scheduled vote, there was no guarantee that Pluto would not make a comeback and that the definition of planethood might be rewritten again.

"Some people think that the astronomers will look stupid if we can't agree on a definition or if we don't even know what a planet is," said Dr. Pasachoff of Williams College. "But someone pointed out that this definition will hold for all time and that it is more important to get it right."



The tigers of wrath are wiser than the horses of instruction.

PLUTO DEMOTED (none / 1) (#81)
by circletimessquare on Thu Aug 24, 2006 at 10:44:02 AM EST

SUCK IT BITCH

The tigers of wrath are wiser than the horses of instruction.

Poor Pluto... (none / 1) (#82)
by Niha on Thu Aug 24, 2006 at 01:02:19 PM EST



[ Parent ]
so long, Pluto! (none / 1) (#84)
by tetsuwan on Fri Aug 25, 2006 at 10:03:21 PM EST

don't let the door hit you on the way out!

Njal's Saga: Just like Romeo & Juliet without the romance
[ Parent ]

Bass-Ackwards (none / 0) (#85)
by m50d on Mon Sep 04, 2006 at 04:22:37 PM EST

How about a tertiary star system orbiting a common gravitational barycenter, each star with it's own planetary system... and one planet that, via natural harmonics between the three stars, switches orbital allegiance every now and then? Unlikely but possible. Well, what do we call such an object then with a nomenclature dependent first and foremost on what something orbits, rather than what it is made of?


 How about a trojan planet? Usually objects that are trojans are tiny, a requirement of objects existing at Lagrange points for two much larger objects. But what if those two objects were so massive that they allowed for the existence of a mass large enough to gravitationally become a sphere and retain an atmosphere at the LaGrange point? Yes, a trojan planet. Again, unlikely, but plausible.

They're planets, because they orbit stars and are round. This is not broken, and it is a far more useful definition than what you are proposing. It may need a little attention to the definition of "orbits", sure, but that's not grounds to throw it out the window.

Some other nomenclature can address what it orbits ("a moon of the Sun" or "a planet of Saturn").

Or we can use other nomenclature to discuss what it's made of ("A rocky planet", "A gaseous planet"), like we currently do.

But I am sorry: Pluto is just NOT a planet like the Earth.And Titan is just NOT a moon like some forlorn rock.

Pluto is a planet - it's big enough to be spherical, and orbiting a star. Likewise Titan is a moon, it orbits a planet, though it may be worth introducing a term for moons large enough to be spherical. These are perfectly good and above all useful definitions; there is no reason at all to prefer yours.

yup (none / 0) (#86)
by circletimessquare on Fri Sep 08, 2006 at 07:36:03 PM EST

http://space.com/scienceastronomy/060907_chrx73b.html

Newfound Object Further Blurs Planet Definition

By Ker Than

Staff Writer

posted: 07 September 2006

01:00 pm ET

The Hubble Space Telescope has spied one of the smallest objects ever detected around a normal star. The object further blurs the line between stars and planets and raises new questions about how planets should be defined outside our solar system.

Announcement of the discovery comes two weeks after the International Astronomical Union (IAU) approved the first official definition of "planet" for our solar system and downgraded Pluto to dwarf planet status.

The newly spotted object is a companion to CHXR 73, a low-mass red dwarf star located 500 light-years from Earth, and is itself called CHXR 73 B.

With 12 times the mass of Jupiter, CHXR 73 B straddles the line between the largest planets and the smallest stars. The latter, called brown dwarfs or "failed stars," don't have enough mass to sustain the types of thermonuclear reactions that keep larger stars alight for billions of years.

The finding will be detailed in the Sept. 20 issue of Astrophysical Journal.

Formation history

CHXR 73 B is located about 19.5 billion miles (31.3 billion km) from its parent star, or roughly 200 times farther than Earth is from our Sun. This distance is so great that even though CHXR 73 B has about the right mass to be a planet, it likely didn't form in the same way that planets in our solar system did, scientists say.

According to standard planet formation theories, planets are created from the disks of gas and dust surrounding newborn stars. But the circumstellar disks of red dwarf stars are typically no more than 10 billion miles (16 billion km) in diameter. Furthermore, theory predicts that gas-giant planets like Jupiter should form no more than about 3 billion miles (4.8 billion km) from their stars. CHXR 73 B is located far beyond both these limits.

"This object is too far from the star to have formed within a disk of gas and dust," said Kevin Luhman of Pennsylvania State University, leader of the international team that discovered CHXR 73 B.

More likely, scientists say, CHXR 73 B formed in the manner of stars: from the gravitational collapse of large, diffuse clouds of hydrogen gas.

For this reason, Luhman believes CHXR 73 B should be regarded as a brown dwarf. Luhman believes an extrasolar object's formation history is more important than mass when determining whether it is a planet or not.

Planet or Star?

In a twist that surprised many astronomers, the definition of planet recently adopted by the IAU is not meant to apply to objects around other stars. Also, it does not take formation history into account. According to the new definition, an object is a planet if it is round, orbits a star but does not orbit a planet, and clears a path around its star.

CHXR 73 B "certainly fulfills all three of those criteria, but the IAU definition was never meant to be applied to other solar systems," Luhman told SPACE.com. "It was just for our solar system."

The new discovery is a reminder that objects in nature do not always fit into the neat categories created by scientists. Recently, astronomers spied even stranger planetary-mass objects that drift freely through space, far away from any star. Some scientists are calling the bizarre objects "planemos," but Luhman says the name is unnecessary and that the objects are really just brown dwarfs.

Next step

Scientists say the question of whether or not CHXR 73 B is a planet could be settled when the James Webb Space Telescope launches, sometime around 2013. The high resolution Webb telescope would be sharp enough to determine if, like some other brown dwarfs, CHXR 73 B has a circumstellar disk of its own.

"If it does, it's clearly an object that did not form in a disk around the star, because it wouldn't have a disk by itself then," Luhman said.

He added that if CHXR 73 B does have a disk, it would be some 5 AU in diameter, much wider than the debris rings found around gas giant planets like Saturn and Jupiter. One AU is equal to the distance between Earth and the Sun.



The tigers of wrath are wiser than the horses of instruction.

right on (none / 0) (#87)
by oki on Sat Sep 09, 2006 at 11:51:51 AM EST

cts, no offence dude, but sometimes I think you fly off the handle a bit .  OTOH, this time you have hit the nail on the head. You can argue all day about where the lines can be drawn (like you said - how significant is pluto's atmosphere) but this is definitely the way to do it.

I loved the biological alegory in one of your other posts. The ancient greeks had one system for naming celestial bodies (did the wander around or not) but hopefully we can do a little better after >2k years.

These are now my criteria for celestial nomenclature.  Pluto is not a planet. Even though it makes us a little sad.

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So... What is a Planet Again? | 87 comments (72 topical, 15 editorial, 0 hidden)
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