"The Definition of Planet" (or, "The IAU is Dumb")

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Soralin » Wed Dec 21, 2011 4:32 pm UTC

Really, what caused the problem is Eris, goddess of discord, and aptly named planetoidish Kuiper belt object.

For a while now, we've been finding objects out past Pluto: Sedna, Quaoar, Makemake, Haumea, Orcus, etc. They've been half the radius of Pluto, or 3/4 the radius of Pluto, or slightly smaller than the radius of Pluto, etc. As long as they were smaller than Pluto, we could sort of defer the question of them being planets, and just go along calling Pluto a planet but not including them, based on the slight difference in size, and simple inertia of definitions.

But then we found Eris. Eris is larger than Pluto is, which meant you couldn't just sweep it aside, it would be the 10th planet in our solar system. But if you did that, then you have to start considering all of those not-quite-Pluto-sized objects that we had found before, and if they were planets or not.

Any way you define it, at that point we knew we no longer lived in a solar system of 9 planets. Either it was 8 planets, or it was 10, or 11, or 12, or wherever you decide to put the cutoff.

Interestingly, this isn't the first time that this sort of thing has happened. In the 19th century we found the planet Ceres, and then the planet Pallas, and Juno, and Vesta, and Astraea, and we started finding more and more of these planets, until we finally decided to kick them out of the planet definition and call them asteroids instead. Pluto, and the rest of them have been made into part of the Kuiper belt, similar to how the Asteroid belt got defined.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Xanthir » Wed Dec 21, 2011 6:27 pm UTC

King Author wrote:I guess I should've made it clear at the outset that I'm neither pro-Pluto nor anti-Pluto. The fact that I think the IAU definition is dumb is based solely on its "clears its neighborhood" nonsense; they chose that definition specifically to strong-arm Pluto out of planethood, and with most of the IAU members not present. That's no way to conduct science; forming a definition just out of spite for an exception (and doing so underhandedly, by making sure to hold a swift vote while those who'd oppose you weren't in attendance). Seriously, the IAU just acted like a buncha eight year olds that day; whether Pluto is or isn't a planet should be based on whether it's actually a planet or not, not IAU politics.

I'm not sure where you heard about this supposed motive. I believe the IAU definition was made specifically to keep us from gaining another dozen "planets" due to our telescopes getting better and finding a bunch of stuff that we had thought of as "asteroids" but that fit our previous definition of "planet". There was a distinct possibility of hundreds more "planets" in the Kuiper Belt under the old definition, too.

If you actually look at the factor used to distinguish planets from non-planets ( mass of body / mass of everything else in the orbit ), it's really stark - there are 8 bodies orbiting the sun whose ratio is much greater than 1, and *everything else* in the solar system (that meets the other two conditions) has a ratio much less than 1. Pluto is certainly pretty high up in the second set, but it's still *way* below a ratio of 1, and thus way below the other 8 bodies. That's why we call it a "dwarf planet", along with a bunch of other objects like Eris.


yurell wrote:
King Author wrote:I think a proper scientific definition of planet should be based upon the way celestial objects form.

Okay, and what are the consequences of this? What happens if I form a planet by your definition, and it gets worn down to the size of a pebble -- is that pebble still a planet? I think it's ludicrous to assume that it is. And what about artificially constructed planet? From your definition they wouldn't be considered planets, despite being identical to one in every conceivable way.

Pluto's identical to any other planet in every conceivable way, and the IAU definition excludes it, so why aren't you complaining about that?

Um, the fact that the IAU definition *can* exclude it shows that Pluto is *not* identical in every conceivable way. In at least one conceivable way (whether or not it has cleared its orbit), it's different from the other 8 bodies we call "planets".

But good points. Outlandish, but good -- what about a planet that gets whittled down, and what about artificial planets.

Has the former ever actually occured? Obviously, in the early solar system, things we'd call planets probably smashed into each other and were completely obliterated, but I've never heard of a planet being whittled down

A planet wouldn't get "whittled down" naturally. It'll only lose significant material through collisions, and that'll form moons or belts around the remainder, or an asteroid belt around the star if the obliteration was complete enough. In the latter case, if you still tried to identify one of the pieces as the "original" planet, it wouldn't have cleared its orbit and thus not be a planet any longer. Plus, it might no longer be in hydrostatic equilibrium.

BlackSails wrote:I really dont see a problem with things being able to become planets, then not become planets. People can alternate between sick and not sick.

But people can't alterante between homo sapiens sapiens and not homo sapiens sapiens.

Sure they could. We happen to define "homo sapiens sapiens" in a way that's difficult to change (roughly, by DNA similarity), but if you had a method to change your DNA significantly, you could switch between being human and not.

There is no analog to DNA for space rocks, though. They're all just balls of ice, rock, and gas, of varying sizes. Any definition we make is necessarily a bit looser than the one we use for mainline humans. Luckily, we've found a set of conditions that gives some *very* clear distinctions, and divides up the mass of our solar system in a reasonable way. It should also work fine for bodies orbiting other stars.
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Re: "The Definition of Planet"

Postby capefeather » Wed Dec 21, 2011 10:26 pm UTC

I feel that someone needs to say this. Every story you tell seems to follow a certain pattern. Watch a "science show" on TV (or read a "science book"), convince yourself into thinking you know shit, post borderline inflammatory piece about what's wrong with how the scientific community does things. Scientific communities have enough trouble staving off attacks from religious zealots and/or people who don't believe in germs/evolution/relativity/anthropogenic climate change for whatever petty reason. I once saw a post on a different forum declaring that "the IPCC is as corrupt as the day is long" with some vague reference to "Climategate". So I hope you can see where I'm coming from when I say I'm very nearly offended by this kind of thing. That's not to say that "scientific dogma" is infallible or should never be challenged, but people have had so many years to discuss and talk about this stuff and it's going to take more than casual criticism to change the establishment. Please don't be that guy.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby mfb » Wed Dec 21, 2011 11:28 pm UTC

@King Author: Your definition of "planet" would probably give us hundreds or even thousands of planets in our solar system. Your definition would be possible. But do you want to put Jupiter in the same category as some random ~200km diameter Kuiper belt object in space?

"Cleared its own orbit" is a nice requirement, as objects which did so dominate the region of their orbit. Large objects (100km++) have a well-defined position in our solar system:
- they orbit a larger object (they are moons)
or
- they do not have objects of similar size (or even larger) in their neighborhood => they are planets (we have 8 of them)
or
- they have larger or similar objects in their neighborhood => they are not planets (asteroid belt, kuiper belt, oort cloud)

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby chenille » Wed Dec 21, 2011 11:59 pm UTC

I'd like to offer what I said on one of the comic threads about other solar systems. For some of these people aren't just finding individual objects, but learning how the system look as a whole, and there you naturally start talking about debris belts and regions cleared by larger masses. Fomalhaut has a thick icy disk with a giant planet keeping the inner edge. Epsilon Eridani has two asteroid belts and an outer disk, probably with three or more planets, though only one has been found. Beta Pictoris has at least four rings and is expected to have a planet for each gap. When you look at these, the IAU definition of a planet becomes a very natural way to think about things.

It's true the same object could change status depending on where it is in the solar system, but that's actually a good feature, because its role in the solar system is part of what you're interested in. It's not an intrinsic category like Escherichia coli or Pan troglodytes, but more something ecological like "canopy tree", "apex predator", or "duke". The question isn't whether one approach or the other makes sense as a concept - both plainly do - but whether one is what we usually mean by "planet". Personally, I'd say the demotion of Ceres suggests people do tend to mean clearing objects, except for a fond attachment to Pluto from when it was thought to be one.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby gmalivuk » Thu Dec 22, 2011 12:08 am UTC

King Author wrote:I guess I should've made it clear at the outset that I'm neither pro-Pluto nor anti-Pluto. The fact that I think the IAU definition is dumb is based solely on its "clears its neighborhood" nonsense; they chose that definition specifically to strong-arm Pluto out of planethood, and with most of the IAU members not present. That's no way to conduct science; forming a definition just out of spite for an exception (and doing so underhandedly, by making sure to hold a swift vote while those who'd oppose you weren't in attendance). Seriously, the IAU just acted like a buncha eight year olds that day; whether Pluto is or isn't a planet should be based on whether it's actually a planet or not, not IAU politics.
[citation needed] on every bit of this.

Pluto's identical to any other planet in every conceivable way, and the IAU definition excludes it
Which therefore means that is is clearly *not* identical to any other planet in every conceivable way. For example, it isn't big enough, compared to the other stuff out there, to have cleared out its orbit.

Those moons have hydrostatic equillibrium, but they didn't form from the sun, they formed from planets. The Kuiper belt objects formed from the sun, but they don't have hydrostatic equillibrium.
Many of them formed around the same times as their planets, and Earth and the Moon were arguably formed at the same time by the same event. And all the Kuiper belt objects being discussed here *do* have hydrostatic equilibrium. The thing you yourself quoted right there says there are "about 73 potential candidates amongst the population of trans-Neptunian objects".

By my definition, neither would be planets.
So by your definition, there would in reality be up to several hundred new planets.

I read that the sun is going to blow up to red giant state and destroy the Earth before the moon escapes Earth's orbit.
Yes, but no one was talking about escaping Earth's orbit. Rather, the point was explicitly about the Earth+Moon barycenter ending up outside the surface of the Earth.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby LaserGuy » Thu Dec 22, 2011 5:57 am UTC

King Author wrote:...which is why I stipulated the two criteria together are necessary for an object to be a planet, not solely one or the other. Those moons have hydrostatic equillibrium, but they didn't form from the sun, they formed from planets. The Kuiper belt objects formed from the sun, but they don't have hydrostatic equillibrium. By my definition, neither would be planets.


I'm not sure what you mean by moons forming from planets. All bodies in the solar system come from the stellar remnant.

King Author wrote:I read that the sun is going to blow up to red giant state and destroy the Earth before the moon escapes Earth's orbit.


Not the same thing. What I'm saying is that the centre of mass of the Earth-Moon system is currently inside the Earth, but is moving upward. In a couple million years, it will pass above the Earth's surface. The practical effects of this are virtually nothing, but, under some possible definitions of "planet", that might be enough to upgrade the Moon from moon to binary planet. The Moon escaping the Earth's orbit would take much, much longer (it's moving away from us at ~4 cm/year at present), unless something really big happened to hit either us or it and disrupt our orbits.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Mr_Rose » Thu Dec 22, 2011 12:07 pm UTC

LaserGuy wrote:
King Author wrote:...which is why I stipulated the two criteria together are necessary for an object to be a planet, not solely one or the other. Those moons have hydrostatic equillibrium, but they didn't form from the sun, they formed from planets. The Kuiper belt objects formed from the sun, but they don't have hydrostatic equillibrium. By my definition, neither would be planets.

I'm not sure what you mean by moons forming from planets. All bodies in the solar system come from the stellar remnant.

Seems likely to be a reference to the giant impact hypothesis of Earth's Moon's formation. The one where a Mars-sized object hit a proto-Earth and splashed off enough material to form our (relatively) huge moon - if you're not looking too closely that sounds like "didn't form from the sun" I guess.

P.S. on the GIH: Does anyone who is more familiar with it than I know what is supposed to have become of the impactor? I mean, did it carry on its merry way in much reduced form, or merge with the proto-Earth-Moon system or what?
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby mfb » Thu Dec 22, 2011 1:14 pm UTC

It was destroyed, if you call smaller debris parts "much reduced form" or just debris is your choice.
All larger bodies in the solar system formed from collisions of smaller objects, the only interesting thing about the earth/moon-situation is the large size of the impactor. So if that collision would be any problem to call earth and moon as "formed from the protoplanetary disk", nothing visible formed from the protoplanetary disk.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Mr_Rose » Thu Dec 22, 2011 2:02 pm UTC

mfb wrote:It was destroyed, if you call smaller debris parts "much reduced form" or just debris is your choice.

Yeah, Kinda expected that. It doesn't seem likely (quite the opposite in fact) that you'd end up with three bodies emerging from the impact rather than two bodies and a bunch of junk for them to either throw off or eat.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby brenok » Sat Dec 24, 2011 12:50 am UTC

King Author wrote:
BlackSails wrote:I really dont see a problem with things being able to become planets, then not become planets. People can alternate between sick and not sick.

But people can't alterante between homo sapiens sapiens and not homo sapiens sapiens.


They can't on the actual lifespan of a human, but it happens across millions of years.

In the other hand, I don't think anything would change on ours planets in the next 4 billion years.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby mfb » Sat Dec 24, 2011 2:21 pm UTC

brenok wrote:I don't think anything would change on ours planets in the next 4 billion years.

I think there is a non-vanishing probability that life on our planet changes the planet in a significant way in the next 4 billion years.
It could change to orbit, modify the complete crust to something new, or even disassemble large parts of it to use them in another way. Or destroy the whole planet...

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby brenok » Sat Dec 24, 2011 4:18 pm UTC

mfb wrote:
brenok wrote:I don't think anything would change on ours planets in the next 4 billion years.

I think there is a non-vanishing probability that life on our planet changes the planet in a significant way in the next 4 billion years.
It could change to orbit, modify the complete crust to something new, or even disassemble large parts of it to use them in another way. Or destroy the whole planet...


I believe the human race will be extinct before we reach the level of planetary engineering, but I was talking about that the fact that the OP was accusing the IAU classification of being "short-sighted".

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Ghona » Sat Dec 24, 2011 9:09 pm UTC

Eh, it's not like the IAU has the authority to declare that sort of stuff.

And even if they did, the vote was only attended by 4% of the IAU since votes were conducted in person at the Prague meeting. Of the thousands of people who were present at the conference, only a few hundred were left on the last day (the conference lasts two weeks, and since most General Assembly attendees pay their own way, most do not stay the entire two weeks.)

And even if that was sufficient, it was in violation of IAU bylaws, since the resolution wasn't drafted by the planet definition committee before voting. Heck, the chair of that committee (Dr. Owen Gingerich) had already gone home when the vote was suddenly brought up.


So basically, the IAU doesn't have the authority, and even if it did they didn't have quorum, and even if they did the vote on the proposal was invalid. Without even getting into the actual technical details (let alone the dynamicist vs geologist feud or the anti-Iraq war sentiment commonly held by the remaining European astronomers), it's already dead in the water for purely formal reasons.


If they want to define kittens as planets, that's fine by me, but they should at least have the decency to do it properly.


That said, my personal preference is to make 'planet' either a fuzzy historical term denoting a fixed set of objects (like how we define what a 'continent' is), or a more general category with specific subgroups based on composition (like the broader historical use of 'planet').

I personally think it's far weirder to lump Jupiter together with Mars than it is to lump Mars with Pluto. Of course, I'm more towards the geologist side of astronomy, so you have to take that into account.

And excluding extrasolar objects from the category of 'planet' (as the IAU currently does) is just dumb. That's the part I most dislike about the definition.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby brenok » Sun Dec 25, 2011 12:45 am UTC

Ghona wrote:And excluding extrasolar objects from the category of 'planet' (as the IAU currently does) is just dumb. That's the part I most dislike about the definition.


As far as I know, IAU don't excludes extrasolar object from the category of planet, just don't classify them, no?

Edit: About Mars, Jupiter and Pluto; well, there's Giant Gas Planets like Jupiter and Saturn, Rochous Planets like Mars and Earth, and Dwarf Planets like Pluto, Eris, Ceres, etc. What's the problem?

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby chenille » Sun Dec 25, 2011 8:50 pm UTC

Ghona wrote:Eh, it's not like the IAU has the authority to declare that sort of stuff.

The IAU keeps track of nomenclature for the solar system, and has different rules for planets and non-planets, where numbers are only given to the latter. As such, it's absolutely necessary that they have a working definition of planet for their own use. If you want to use the word differently in every day speech, I don't know that anyone will stop you, beyond the usual "starfish aren't fish" type of thing.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Eebster the Great » Tue Dec 27, 2011 5:28 am UTC

brenok wrote:
King Author wrote:
BlackSails wrote:I really dont see a problem with things being able to become planets, then not become planets. People can alternate between sick and not sick.

But people can't alterante between homo sapiens sapiens and not homo sapiens sapiens.


They can't on the actual lifespan of a human, but it happens across millions of years.

In the other hand, I don't think anything would change on ours planets in the next 4 billion years.

I'm pretty sure he was referencing cladistics, although he didn't make that clear at all.

By definition, if an organism is in a given clade, so will all its descendants be.

This type of classification makes a lot of sense for studying an evolutionary system like life (ignoring the complexity introduced by horizontal gene transfer), but it makes no sense when studying most other things, such as rocks or chemicals or astronomical bodies.

Even in classifying life, people most often prefer more traditional (and slightly arbitrary) paraphyletic taxonomic divisions. For instance, people like to say that apes are not monkeys and birds are not dinosaurs and none of those are fish.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Gagundathar The Inexplicable » Tue Jan 17, 2012 5:25 pm UTC

Gosh, I SO glad to have found this place.
The IAU, like all other scientific bureaucratic bodies, has its weaknesses.
The demotion of poor old Pluto has probably bothered almost .0001% of the planet's population.
Even Disney enthusiasts haven't picked up torches and pitchforks.

Weirdly, we, as scientists still cling to the terms we used when we didn't understand as much as we do now.
We still use the term 'species' even though it has a very plastic meaning.
It is not especially extraordinary for us to redefine the names of bodies of the solar system when we discover an entirely new category of them.
But, we cling to the 9 planets. Poor old Pluto.
The word 'planet' needs to mean something.
It used to mean 'wanderer' as in 'planetos' in Greek.

Maybe we could upgrade Pluto's status to 'twin planet', because Charon is pretty dang large in comparison.
Maybe we should accord the same assignment to Terra-Luna.

Now that would be a head shaker, wouldn't it?

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Fire Brns » Thu Jan 19, 2012 3:49 pm UTC

As much as I disagree with OP, I do have a reservation: Many classification systems and rules have exeptions. The exception I would propose to The IAU is:
5-) Pluto is a planet, despite above rules.

I say this as I believe Pluto an "honorary" planet being the first of the dwarf planets to be discovered.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby firechicago » Thu Jan 19, 2012 3:54 pm UTC

Fire Brns wrote:I say this as I believe Pluto an "honorary" planet being the first of the dwarf planets to be discovered.


Except it's not

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Fire Brns » Thu Jan 19, 2012 4:10 pm UTC

The wording was odd. Was it originally classified an asteroid then reclassified a dwarf planet? IMO Pluto should be an honorary planet, regardless of the IAU system.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby firechicago » Thu Jan 19, 2012 7:57 pm UTC

Fire Brns wrote:The wording was odd. Was it originally classified an asteroid then reclassified a dwarf planet? IMO Pluto should be an honorary planet, regardless of the IAU system.


The point is that Pluto is definitely not the first dwarf planet discovered. Ceres was discovered over a hundred years earlier. And Pluto is also not the first planet to have that title stripped from it.

Ceres (along with even smaller objects, like Pallas and Vesta) was originally classified as a planet. If you were to take a basic astronomy course in the early 19th century you would have been told that there were 11 planets, including Vesta, Pallas, Ceres and Juno. Then in the 19th century a distinction was drawn between "major planets" and smaller objects called "minor planets" or asteroids, when people realized that there were an awful lot of the latter floating around, with the term "minor planets" gradually falling out of favor.

The only reason that Pluto was classified as a "major" planet in the first place, rather than being classed with objects like Ceres which are much closer to it in size and mass, was that early estimates of its mass and radius were off by two orders of magnitude.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Gagundathar The Inexplicable » Thu Jan 19, 2012 10:06 pm UTC

Well, then, doggone it (there is a pun there y'all) then all of that group should classified as 'planets'. Not 'dwarf planets' but fully fledged planets.

If they are big enough to get real names, then they should be planets.

I have no problem teaching my grandchildren that there are 13 planets in the solar system.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Copper Bezel » Thu Jan 19, 2012 10:36 pm UTC

Except that it would be more like 40, or more. I mean, it could be any number, depending on where you decided to draw the line.

"Big enough to get real names" doesn't really make sense. People decided to name things, and some of those things are bigger than others. All the moons are named, of course.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby idobox » Thu Jan 19, 2012 11:37 pm UTC

Rocky planets are not the same as gas giants.
Dwarf planets are not the same as "normal" rocky planets, in that they do not dominate their area.
Dwarf planets are not the same as asteroids, in that they achieve hydrostatic equilibrium.
I have no problem with having a few more categories.

If you want to teach your kids a list of 13 planets, it's okay. But what if there are 20 or 30 of them in a few years?
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Gagundathar The Inexplicable » Fri Jan 20, 2012 12:02 am UTC

Then we just add the new planets to the mix.
Yes, I really do see how absurd this will be.

Starting serious mode...


Using the term minor planets, is, as a term a bit confusing.
Without context, it could describe the smaller planets that we know of: Ceres, Pallas, Vesta, Mars, Terra-Luna, Venus, Mercury.
And, of course the outer orbit of similarly sized planets: Pluto-Charon, Eris, Makemake and Haumea.

What makes Pluto a minor planet when Mercury isn't?

I suggest an outer distance limit from Sol.
Defined radius is ... 35 AU. That takes it a bit out of the Neptunian orbit, but well with the outer Kuiper and Oort objects.

It would NOT include the outer Kieper belt objects with one important special exception: Pluto-Charon.
Because of its really weird orbit, it comes into the category of a 'special' category.
It has more in common (apparently) with the larger accreated asteroids like Ceres, Pallas, and Vesta.

Again... apparently because we don't have enough info yet to make a determination.
Pluto-Charon is a very interesting target for a hard probe. One that actually lands on the primary (Pluto) and sends back data from the real surface of the trans-Neptunian object. Heh See, we already have a name for this kind of 'solar-orbiting object''.

What ever happened to the term 'planetoid'?
Seems like that would come in handy here.
Minor planet is clumsy. Planetoid is a superior term.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby yurell » Fri Jan 20, 2012 12:21 am UTC

Gagundathar The Inexplicable wrote:What makes Pluto a minor planet when Mercury isn't?


The fact that Mercury has cleared its orbit, while Pluto hasn't come close.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Gagundathar The Inexplicable » Fri Jan 20, 2012 2:51 am UTC

yurell wrote:
Gagundathar The Inexplicable wrote:What makes Pluto a minor planet when Mercury isn't?


The fact that Mercury has cleared its orbit, while Pluto hasn't come close.


Hmmm... well there is that.

Carry on.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby gmalivuk » Fri Jan 20, 2012 6:03 am UTC

Also the fact that Mercury is about 25 times more massive than Pluto makes it seem somewhat less "minor"...
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Fire Brns » Fri Jan 20, 2012 3:11 pm UTC

As long as people are making an arguement about the mass I am fine but don't say we can't learn them all when we eventually have 30.
For starter's we teach the alphabet and solar system near simultaeously in school: We can remember 26 letters, the Russians remember 33, the Chinese remember hundreds and hundreds. In fiction and general society we teach people to remember dozens of objects in a system: talk to any pokemon fan or gun collector.

Worse case we teach the important ones and then leave the rest(solid ice balls by themselves) to whoever will remember them like countries.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby idobox » Fri Jan 20, 2012 6:29 pm UTC

Fire Brns wrote:Worse case we teach the important ones and then leave the rest(solid ice balls by themselves) to whoever will remember them like countries.

That's exactly what we do when we teach the 8 ones, and not the rest.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby gmalivuk » Fri Jan 20, 2012 6:55 pm UTC

Fire Brns wrote:As long as people are making an arguement about the mass I am fine but don't say we can't learn them all when we eventually have 30.
And if we have 50 or 75 or 100?
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby chenille » Fri Jan 20, 2012 11:39 pm UTC

Gagundathar The Inexplicable wrote:It would NOT include the outer Kieper belt objects with one important special exception: Pluto-Charon.
Because of its really weird orbit, it comes into the category of a 'special' category.

Adding special exceptions is a sign that either the objects in question don't lend themselves to easy categorization, or you're using a bad system. Here the underlying scheme is pretty simple:

1. There are four giant gas objects, all with relatively circularly orbits of low inclination and without much else in the same region.
2. There are four moderate-sized rocky objects with orbits of the same type, but near the sun.
3. There are a lot of smaller objects scattered in the regions between and outside these, with varying and often overlapping orbits, some large enough to be round and others not.

Pluto's orbit doesn't really make it special, it makes it typical of the third group, since lots of asteroids and Kuiper belt objects have similarly inclined or eccentric orbits. The processes that ensured the eight large objects have a relatively regular arrangement don't apply to these smaller things. As far as making an exception for historical reasons goes, that's the one idea I dislike most; it's saying you're more interested in tradition than you are in the world around you, which is bad for science.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Gagundathar The Inexplicable » Sun Jan 22, 2012 1:35 am UTC

chenille wrote:
Gagundathar The Inexplicable wrote:It would NOT include the outer Kieper belt objects with one important special exception: Pluto-Charon.
Because of its really weird orbit, it comes into the category of a 'special' category.

Adding special exceptions is a sign that either the objects in question don't lend themselves to easy categorization, or you're using a bad system. Here the underlying scheme is pretty simple:

1. There are four giant gas objects, all with relatively circularly orbits of low inclination and without much else in the same region.
2. There are four moderate-sized rocky objects with orbits of the same type, but near the sun.
3. There are a lot of smaller objects scattered in the regions between and outside these, with varying and often overlapping orbits, some large enough to be round and others not.

Pluto's orbit doesn't really make it special, it makes it typical of the third group, since lots of asteroids and Kuiper belt objects have similarly inclined or eccentric orbits. The processes that ensured the eight large objects have a relatively regular arrangement don't apply to these smaller things. As far as making an exception for historical reasons goes, that's the one idea I dislike most; it's saying you're more interested in tradition than you are in the world around you, which is bad for science.


Curiously, this is the best argument for eight planets. I agree.
This is the first time this has made sense to me.

Just because one Kuiper belt dual-object decided to intrude into trans-Neptunian space on a weird orbit that clearly was perturbed by something outside of the system, doesn't mean it should be considered a planet.


BUT

What about those poor astrologers who have spent decades trying to shoehorn Pluto into their charts?

AND

Will Mickey lose his dog now?
Will the poor fellow be put into a shelter for dogs named after minor planets?
Think about the children!


<sniff>

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby idobox » Sun Jan 22, 2012 11:11 pm UTC

I'm sure the IAU spent a long time thinking about the implications for the credibility of astrology.

And Pluto still exist, and is still the latin god of death.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Fire Brns » Mon Jan 23, 2012 3:06 am UTC

gmalivuk wrote:
Fire Brns wrote:As long as people are making an arguement about the mass I am fine but don't say we can't learn them all when we eventually have 30.
And if we have 50 or 75 or 100?

Again, not everybody knows all the countries and those matter in our everyday lives. Put the names out there instead of saying "they are not worth learning the names of, even once". If there was to be a school test on the dwarf planets anyway it would be along the lines of "name 10".
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Ibid » Tue Jan 24, 2012 11:58 pm UTC

Fire Brns wrote:
gmalivuk wrote:
Fire Brns wrote:As long as people are making an arguement about the mass I am fine but don't say we can't learn them all when we eventually have 30.
And if we have 50 or 75 or 100?

Again, not everybody knows all the countries and those matter in our everyday lives. Put the names out there instead of saying "they are not worth learning the names of, even once". If there was to be a school test on the dwarf planets anyway it would be along the lines of "name 10".


Except, Burkina Faso has considerably more chance to affect the average person than Sedna, unless we're giving the astrologers credit.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Fire Brns » Fri Jan 27, 2012 4:39 pm UTC

This doesn't counter my arguement. For the most part, astronomy is a hobby or something to fill memory space in your brain, even if space travel was commercialized sucessfully within the next 10 years Mars would still be irrelivent to mankind's everyday lives.

If we are going to decide only solar bodies (excluding stars and moons) that effect our lives significantly are planets then only Earth would qualify.
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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby mfb » Fri Jan 27, 2012 6:04 pm UTC

An object can influence your life even when it is not falling down on your head. Apart from the obvious part (scientists, engineers, ... for telescopes, mars probes, ...): There is quite some public interest in other planets. In Europe, a new mars rover gets more news(paper) articles than a new government in Burkina Faso.

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Re: "The Definition of Planet" (or, "The IAU is Dumb")

Postby Tomlidich » Fri Jan 27, 2012 6:10 pm UTC

i believe the last explanation i heard was:

pluto was a moon, but was ejected from its orbit around one of the gas giants when something struck it.

which would make the OP's definition very resolute in the fact that pluto is not a planet.

i like it. it's the way science should be. facts, not here say


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