Eyes Turned Skywards

[Bahamut-255]

I suppose it's worth a bit of a reader poll: how do you all feel about Pluto's planetary status? Is it a travesty it was stripped? Does the reclassification make sense in general, but Pluto should be excepted due to "historical value" or something? Should it never have been considered a planet the first place? And however you feel, how important is it to you?

The OTL classification of a Dwarf Planet - to which Pluto/Charon was reclassified - is that the body in question directly orbits the Sun, is of sufficient mass for its shape to be controlled by gravitational forces, as opposed to mechanical forces. But has failed to clear its orbital path of other objects.

The critical failing of this particular categorisation system, is that if you put the Earth into the Kuiper Belt. It too, would be incapable of clearing its neighbourhood of all the other objects.

Personally, this is why I feel that Pluto needed to remain a Planet.

 

[NCW8]

The OTL classification of a Dwarf Planet - to which Pluto/Charon was reclassified - is that the body in question directly orbits the Sun, is of sufficient mass for its shape to be controlled by gravitational forces, as opposed to mechanical forces. But has failed to clear its orbital path of other objects.

The critical failing of this particular categorisation system, is that if you put the Earth into the Kuiper Belt. It too, would be incapable of clearing its neighbourhood of all the other objects.

Personally, this is why I feel that Pluto needed to remain a Planet.

I think that the original classification of Pluto as a planet was alright as it was the best decision possible on the evidence available at the time. Ceres was also initially classified as a Planet.

The Dwarf Planet classification is a useful one, except that it doesn't really make sense to distinguish between dwarf planets and the larger moons. Ganymede is about ten times the mass of Pluto and you could argue that it hasn't managed to clear its neighbourhood, so why isn't it regarded as a dwarf planet ?

The part of the IAU definition that I really don't agree with is that it only applies to objects in our solar system. That makes the definition no better than a list. A useful definition is one that would have more universal applicability, especially since extra-solar planets have already been discovered.

Cheers,
Nigel.

 

[Michel Van]

the problem with Pluto is, it was discover 1930 while looking for "Planet X"

Planet X was a suggestion solution on perturbations in the orbit of Uranus and Neptune.
considering Pluto was this Planet X, it must have very big mass,
during 1931 to 1978 the theory what Pluto is, change over the time.

in 1930 Pluto was consider a gas-planet like Neptune,
but the telescope show faint spot in nightsky, so he lost Planet X status soon after his discovery.
during 1931 to 1948 Pluto was consider a earth size black planet of exotic Material.
in 1948 with new Telescope, Pluto was resize to 7000 km ø
until 1978 with discovery of Charon by astronomer James Christy
they could calculate the mass of Pluto and Charon, it was very tiny: 0.24 percent that of the Earth
also it size was calculate now under 3000 km ø and it made from ice and rock.
with help of Hubbletelescope the size was specified now 2322 km.

So for over 76 years the astronomer dispute about what Pluto is and in 2006 they disqualified pluto as planet.

 

[e of pi]

The critical failing of this particular categorisation system, is that if you put the Earth into the Kuiper Belt. It too, would be incapable of clearing its neighbourhood of all the other objects.

Personally, this is why I feel that Pluto needed to remain a Planet.

So that's one vote in favor of remaining a planet? Would you support elevation of Ceres as well, and the other Kuiper belt objects as they're discovered?

I think that the original classification of Pluto as a planet was alright as it was the best decision possible on the evidence available at the time. Ceres was also initially classified as a Planet.

The Dwarf Planet classification is a useful one, except that it doesn't really make sense to distinguish between dwarf planets and the larger moons. Ganymede is about ten times the mass of Pluto and you could argue that it hasn't managed to clear its neighbourhood, so why isn't it regarded as a dwarf planet ?

Well, except that large moons are moons--they orbit a parent body, and must be considered within that context. Understanding, for instance, the formation of Luna depends a lot on understanding the past history of Earth, just as investigating Miranda in depth and at length (a somewhat difficult task, to be sure, given the distance) requires understanding the formation and history of Uranus--and understanding the history of the moons can point to the history of their parent worlds.

The part of the IAU definition that I really don't agree with is that it only applies to objects in our solar system. That makes the definition no better than a list. A useful definition is one that would have more universal applicability, especially since extra-solar planets have already been discovered.

Currently our technology is barely good enough to spot Earth-sized worlds around other stars. It'll be a bit before we'd be able to resolve the existence of anything classifiable as a dwarf planet around other stars. Once we can and do, I'm certain the definition will be revised to include them--just not as members of the sun's solar system, of course. Not sure how to count your vote though--in favor of the new category on balance? Against it? In favor but believe it should be written to also include objects previously counted as moons?

the problem with Pluto is, it was discover 1930 while looking for "Planet X" ....So for over 76 years the astronomer dispute about what Pluto is and in 2006 they disqualified pluto as planet.

And one vote for an info dump? I know the history of the decision, Michel, I was curious about your thoughts about it. Anyone else care to chime in? Now's your chance to not only shape the fate of Eyes--but the fate of the VERY SOLAR SYSTEM ITSELF.

 

[Brainbin]

As oddly romantic and mindful of historical precedent as I usually am, I can't say I wept much for Pluto's demotion. Honestly, everything pointed to it not really being a planet in any conventional sense of the word, and it probably retained that status as long as it did IOTL because it had been grandfathered as such, along with sheer inertia and (perhaps) some sentimental attachment in the astronomical community. But the writing was on the wall with Sedna, and once they discovered Eris, it was all over.

My only real complaint as it stands now is that "dwarf planet" is an awful name for that class of celestial body; they should really use a distinct term for it. After all, a dwarf star is still a star, just as a dwarf galaxy is still a galaxy. Looking way down the line, Pluto will probably be remembered only as a historical anomaly, rather than being visited for its sheer beauty (any of the gas giants) or because of its (relatively) close proximity to useful resources (Ceres). Pluto had its moment in the sun (fittingly, during some of which time it actually was closer to the sun than Neptune), and now it should be lain to rest (again fittingly, considering just what Pluto reigns over in the classical pantheon).

Just my two credits. You can take that to the bank. Or buy one-fifth of a tribble.

 

[Shadow Knight]

Outstanding TL and work guys. Top notch.

 

[e of pi]

Outstanding TL and work guys. Top notch.

Thanks! Any thoughts on Pluto as a planet?

 

[Shadow Knight]

Thanks! Any thoughts on Pluto as a planet?

You're welcome.

While I can see both sides wasn't particularly attached to it being a planet aside from tradition.

Personally though I think they should have classified anything that obtains a roughly spherical shape that orbits anything as a planet, and if it happens to orbit another such object it could be classified as a moon as well. (Moons could also be asteroid objects but couldn't also be classified as planets.)

For ease of things they could just teach in schools the 8 classical planets (for general reference) with some throw away liner about there being more out there.

But I'm not an expert or anything just an engineer.

 

[Predictably.Damaged]

I approve of pluto's demotion.

Also, great timeline, really enjoying it.

 

[AndyC]

Well, the definition of "planet" is defective in any case - the "orbit clearing" criterion is artificial and arguable. Do we need a definition of planet? We got by without a definition of "continent", after all (how come Europe is a continent?)

Define "planet" as anything round orbiting the Sun (ie with dominance over the barycentre of its own system) of Pluto-size or larger and we're there. That makes Eris a planet too - so be it. Any other KBOs of larger than Pluto-size give us more planets. If this becomes a problem in time, we can revisit it then.

We can then categorise planets as "gas giant", "terrestrial" (rocky and inside the orbit of the most dominant planet, Jupiter) and "plutonian" (rocky, icy and outside the orbit of the most dominant planet), and we're away.

 

[NCW8]

Well, except that large moons are moons--they orbit a parent body, and must be considered within that context. Understanding, for instance, the formation of Luna depends a lot on understanding the past history of Earth, just as investigating Miranda in depth and at length (a somewhat difficult task, to be sure, given the distance) requires understanding the formation and history of Uranus--and understanding the history of the moons can point to the history of their parent worlds.

It's a good argument. However the formation of Luna, involving the collision of another planet-sized object with the Earth, is not the same as the formation of other moons. At the other end of the scale you have the smaller moons of Jupiter which might be captured asteroids. It seems strange to lump all of these objects together when you are trying to draw a distinction between planets and dwarf planets.

There's also a certain amount of fudging of the definition to count Charon as a dwarf planet rather than a moon. The argument seems to be that the centre of mass of the Pluto-Charon system lies between the two bodies, which means that Charon isn't actually in orbit about Pluto. However the same argument can be used to show that Jupiter isn't actually in orbit about the Sun and so, according to the definition, isn't really a planet

Currently our technology is barely good enough to spot Earth-sized worlds around other stars. It'll be a bit before we'd be able to resolve the existence of anything classifiable as a dwarf planet around other stars. Once we can and do, I'm certain the definition will be revised to include them--just not as members of the sun's solar system, of course.

A definition that we already know needs to be revised isn't a particularly useful definition. Especially since astronomers spend some of their time speculating about objects that we haven't yet observed and then trying to observe them.

Not sure how to count your vote though--in favor of the new category on balance? Against it? In favor but believe it should be written to also include objects previously counted as moons?

On balance I'm in favour, but it's obvious that the current definitions of planet and dwarf planet are fudged and parochial. When they are rewritten, I wouldn't be surprised if the larger moons fall into the dwarf planet category.

Cheers,
Nigel.

 

[Expat]

Well, scientists are emotionless, calculating joy-killers, right? So I'd suppose they would take Pluto from its adoring public no matter what.

Seriously, though, if there's anything like scientific consensus for un-planetating Pluto, best to do it while you've got your best lobbying team alive (though I disagree on Sagan's imminent death- cancer is absolutely subjective to butterflies.)

If the best argument you can make against stripping Pluto's planetary status is that the best lobbyists are against it, I imagine the scientific community will say, "more study is needed," and just strip it later after its discoverer is dead. Best to do it now.

Fantastic update, btw, really sweeping scale!

 

[Dathi THorfinnsson]

Sweeping your orbit clear is a very, very subjective kind of thing. They are going to have to revisit that definition, I'm sure, when we understand how more solar systems look.

I'd rather have kept 'dwarf planet' as a subset of 'planet' - as somebody pointed out, above, dwarf stars are a subset of stars.

Yes, that means there's a dozen or more planets in the solar system. I don't mind relabeling Ceres back to being a planet, now that we know more.

We're going to find Earth size planets in Trojan positions in other solar systems, for instance, and calling the earth a 'dwarf planet' or some such won't make sense. IMO.

 

[Athelstane]

Well, it's really just semantic anyway

But there has always been the sense that Pluto is...rather marginal and odd as planets go, even before the definition wars heated up.

I always liked the term minor planet, "minor" being less pejorative than "dwarf"...but it has been used under such a broad definition that it seems pointless - there are hundreds of thousands of minor planets, and the overwhelming majority strike us as being hardly planet-like at all. Virtually any dinky rock can merit the title.

A line has to be drawn somewhere, and I really don't mind moving Pluto to the other side of it.

 

[Workable Goblin]

So how about the Marsden proposal OTL which would have given Pluto a minor planet number (100000) without, IIRC, saying that it wasn't a planet?

 

[Brainbin]

So how about the Marsden proposal OTL which would have given Pluto a minor planet number (100000) without, IIRC, saying that it wasn't a planet?

You know, oddly enough, I thought that milestone number proposal was entirely warranted, and it's a shame it didn't go through.

Something to think about for TTL, perhaps

 

[Workable Goblin]

Anyways, if I was in charge of defining planets--which I am not, either in Eyes Turned Skyward or in real life--I would define a planet as anything big enough to be spherical, but too small to have nuclear fusion occur in its core naturally. Those are nice clear markers which have no degree of arbitrariness to them. Within the category "planet," there would be multiple subcategories, but these would tend to be functional, differentiating bodies based on their physical characteristics. For instance, gas giants, ice giants, rock dwarfs, ice dwarfs, etc., using similar nomenclature to the long-established stellar standards.

Obviously, in this case the Solar System would have a large number of planets (up to as many as several thousand, based on the Wikipedia dwarf planets article), but I don't see this as being a particular problem.

Bodies too small to be a "planet" would be numbered and called "minor bodies," with, again, multiple subcategories (like "comet" and "asteroid"). Bodies too large would, of course, be stars, brown dwarfs or larger, and already have a reasonably well-functioning system to handle them.

 

[Bahamut-255]

Fair point Truth. Though personally for me, my definition of a Planet would be:

A body of sufficient mass to form a spherical shape and be able to differentiate its structure into layers. That is, heavy core, light crust.

A Dwarf Planet would be one that can only do the first, but not the second.

This seems to me to be a fair method of defining the difference. Although defining the critical points may not be easy.


As for the various groups:


Dwarf Ice Planet

Ice Planet

Giant Ice Planet

Dwarf Terrestrial Planet

Terrestrial Planet

Giant Terrestrial Planet

Dwarf Cannonball Planet

Cannonball Planet

Giant Cannonball Planet

Dwarf Carbon Planet

Carbon Planet

Giant Carbon Planet

Waterworld Planet

Giant Waterworld Planet

Cold Ice Giant

Hot Ice Giant

Cold Gas Giant

Hot Gas Giant


So what does everyone else think of this classification system? Everything covered?

 

[e of pi]

Fair point Truth. Though personally for me, my definition of a Planet would be:

A body of sufficient mass to form a spherical shape and be able to differentiate its structure into layers. That is, heavy core, light crust.

A Dwarf Planet would be one that can only do the first, but not the second.

I'm not sure how useful that would be as a system to distinguish--remarkably small bodies actually have structured layers. Dawn's investigations at Vesta, for instance, showed a crust, mantle, and core despite it not being not quite large enough to form into a sphere (it's just slightly too small). We'll see about Ceres when Dawn makes orbit there in 2015, but I'm thinking they'll find similar structured composition. So you'd actually be more likely to have that without spherical shape than spherical shape without layers--and you can only determine about layers for sure through orbital observations. That makes it a troublesome point of separation--we'd have to visit every minor body in the solar system to know whether to call it a planet.

 

[Bahamut-255]

And that same source referred to Vesta as being a Protoplanet. I missed that one.

In any case, it was an idea that tried to make more sense than the IAU method.