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Contents 1 Press coverage 2 Twelve Planets 3 Image:Newplanets.jpg 4 Periodicity 5 Definition of moon aka "satellite" 6 Discussions about the issue 6.1 Definition based on brightness? 6.2 Orbit 6.3 Rogue planets 6.4 Proposed definition is circular 6.5 This whole things reminds me of... 6.6 Size of Our World 6.7 MVEMCJSUNPCU 6.8 My proposed definition 6.9 Atmosphere 6.10 Planet Ordering 6.11 PSR B1257+12 D

[edit] Press coverage

The IAU meeting is underway, and press coverage is beginning. Here is an article I've encountered (Associated Press, at the website for the Boston Globe): http://www.boston.com/news/science/articles/2006/08/14/astronomers_meet_to_define_planet/. GRBerry 21:19, 14 August 2006 (UTC)

[edit] Twelve Planets

The number of planets may need to be expanded to twelve following the news that the International Astronomical Union has recommended to its members that Charon, Xena and Ceres be ratified as new planets. [1] The new definition states that a planet is any star-orbiting object so large that its own gravity pulls in its rough edges, producing a near-perfect sphere. Terjepetersen 06:30, 16 August 2006 (UTC)

What the heck? How does this work? OK. Any round object over 800 km is a planet. Fine. But according to that definition there should be at least 30 planets; not 12. Why are Pluto and ub313 added, but not Quaoar or Sedna? Why is Charon addded, but not the Moon? Both co-orbit the Sun. Why is Ceres added, but not Vesta? Serendipodous 06:25, 16 August 2006 (UTC)

Perhaps there is some variability on how strictly they want to define "round". Even Earth has mountains. As for Charon, it might not qualify as a moon because it is too large relative to the planet it orbits. Algr

I just heard Mike Brown on the radio. He says that it is likely that the current count of 12 will be increased as we determine the precise dimensions of recently discovered objects. 12 could become a hundred before too long. By the end of the 21st century it could become a million. Serendipodous 07:40, 16 August 2006 (UTC)

Yeah, we don't know as much about Quaoar and Sedna. We suspect they probably fit under the roundness definition, but we don't have enough data yet. Charon was added because the barycenter of the pluto-charon system is outside the surface of either planet. Therefore, neither is a satelite of the other, but it would be considered a dual-planet system. The moon is clearly a satelite of the earth. Ceres is added because ceres is large enough to make it's shape stable due to its own gravity. Vesta has an irregular shape, therefore its gravity isn't enough to give it a stable shape. Any other questions? McKay 13:44, 16 August 2006 (UTC)

Actually, Vesta is technically spheroidal. We have enough data on most of the "Plutons" to make a fairly definitive statement on how round they are. Sedna may be far away, but it's not as far away as Xena (not at the moment, anyway), so if we know Xena's round, I'm pretty sure we can figure out if Sedna is. Serendipodous 14:36, 16 August 2006 (UTC)

No, 4 Vesta is not spherical spheroidal. Yes, I think they will quickly add Sedna to the list. McKay 15:18, 16 August 2006 (UTC)

I didn't say it was spherical. I said it was spheroidal. Read the subsection on sphericity. Your picture is right there. Serendipodous 15:47, 16 August 2006 (UTC)

The picture shows that vesta isn't spheroidal. Note the knob in the bottom center. This "cross section" clearly is not an ellipse, therefore, not spheroidal. This also shows that it isn't even an ellipsoid. McKay 15:51, 16 August 2006 (UTC)

Also note the shading on the front center that hints to the fact that there is another knob on the "front". McKay 15:53, 16 August 2006 (UTC)

Believe me, Mckay, I've had this argument before, and argued your side. Just look at the second archive; it's nothing but. It's perfectly possible for someone to claim that Vesta is a spheroid; if it wasn't then I would have changed that table long ago. Serendipodous 15:56, 16 August 2006 (UTC)

okay, I've been through that page, and I don't see anything (maybe I missed it) that shows that Vesta is a spheroid. I can see how it's gravity almost makes it a spheroid, but I don't think that that's enough for the IUA's distinctions. So, I can see how someone could say that it is a spheroid, because it's kinda close, but the same case could be made arguing that it isn't spheroidical, which is the claim that I'm making that I think is valid. McKay 16:04, 16 August 2006 (UTC)

They managed to boot Pluto out (hurray!) by allowing so many dumb rocks to be included, in a while nobody will care anymore. We'll go to a sensible list of 8 (major) planets, and a large number of dwarf planets. Bet you pretty soon planet will come to mean major planet, and therefore: 8 planets in the solar system. -- Jordi·✆ 13:53, 16 August 2006 (UTC)

"Dwarf planet" is to be an unofficial definition. Officially, all classical and dwarf planets and plutons would be planets.--JyriL ^talk 13:56, 16 August 2006 (UTC)

Of course. But I severely doubt the majority of these will be considered real planets by the majority. There may be twelve planets thursday, 24 before long (3 asteroids and at least 8 KOBs are large and round enough to be included), and once we discover more rocks out in the Kuiper Belt, dozens or even hundreds in a few years. With the handy unofficial (but defined by an official body) term "dwarf planet" they've given us a great cutoff point which just happens to only include the classical planets, and excludes the subject Pluto and its kin. -- Jordi·✆ 14:07, 16 August 2006 (UTC)

• that's your imagination at work, i'm happy with these twelve:

Ceres: "the little rocky planet", with a lot of debris around.

Pluto and Charon: a pair of planets orbiting each other.

UB313: the new outer planet.

the problem are those KBO's around, they need some more criteria such as minimum mass.

Plus, asteroids lost status.

See this simulation with the 3 new planets: http://www.newscientist.com/data/images/ns/av/dn9761V1.mpeg

Mass of UB313: ?! (planet)

Mass of Pluto: 1.305×10^22 (planet)

Mass of Charon: 1.52 ×10^21 (planet)

Mass of Ceres: 9.5×10^20 (planet)

Mass of Orcus: 6.2 - 7.0×10^20 (not a planet)

So anything that is round and has more mass than Ceres?--Pedro 14:36, 16 August 2006 (UTC)

That definition seems pretty arbitrary. If they're going to randomly cut off the mass limit at Ceres, why not Pluto? Or Mercury? Serendipodous 14:58, 16 August 2006 (UTC)

Yes, it it like the "Dwarf planet". Why Ceres is a Dwarf and not the Earth? --Pedro 15:02, 16 August 2006 (UTC)

Likely because the current definition of dwarf planet neatly includes all 8 classical planets, and excludes the problematic Pluto. Any other definition will be harder to sell to the public en large. -- Jordi·✆ 15:10, 16 August 2006 (UTC)

• I doubt it, people just dont know how these objects look like. If they see a picture of it, they will consider it a planet. How can you say Jupiter (a huge ball of gas) is a planet and Pluto (with a surface) is not. I don't understand your criteria. We are in the 21st centuy, probles explored these objects. --Pedro 15:21, 16 August 2006 (UTC)

  They're not "my" criteria ;)

  I can understand the rationale behind them, though. The line must be drawn somewhere: the new definitions allow for just about every roughly round rock not a moon to be a planet. We have 12 now, and hundreds before long. Arbitrarily giving Mercury's mass as a minimum not only neatly avoids all the small ones, but also is identical to the list of planets before Pluto was mistakenly added. (I call it a mistake, just as adding Ceres and the other asteroids was seen as a mistake in the 1850s: Ceres used to be a planet.) -- Jordi·✆ 15:26, 16 August 2006 (UTC)

I'm pretty sure that it has nothing to do with Ceres, it's just that Ceres has enough mass to be a spheroid on it's own right. McKay 15:39, 16 August 2006 (UTC)

• Chinese and Indians are still humans despite you can count billions of them, they have the same human rights has you. One just needs to accept the solar system is not as ordered we used to think, we have pictures and we know they are very different, we have better telescopes, etc. There's no reason to exclud Pluto and others from Planethood. People will like to know there's a tiny planet within the asteroid belt, Ceres, it will make them wonder.--Pedro 15:41, 16 August 2006 (UTC)

Exactly -- it's far more exciting to discover new planets. Very few people care nearly as much (if at all) about extra Trans-Neptunian Objects. The most significant outcome of this debate, IMHO, is that it raises public awareness and excitement about astronomy. --TiroAethra 16:00, 16 August 2006 (UTC)

Pedro, are you accusing us Earthlings of being planetist? Serendipodous 15:52, 16 August 2006 (UTC)

• Some yes: Pluto is a dwarf, Pluto is not a planet, Pluto is a rock, pluto is ice... I wounder what the Jupiterians might think of Earth... --Pedro 16:02, 16 August 2006 (UTC)

I believe the correct term is "Jovians." Most inhabitants of Jupiter would consider your word for them a racial slur. Serendipodous 16:04, 16 August 2006 (UTC)

Silly Americites :D McKay 16:06, 16 August 2006 (UTC)

• Looks like we have two new resolutions to the definition of a planet, the new one would demote pluto and leave 8 planets. [2] Tachyon01 16:36, 18 August 2006 (UTC)

[edit] Image:Newplanets.jpg

At Talk:2006 redefinition of planet#Image removal rationale, concerns have been brought up regarding the use of Image:Newplanets.jpg. I'd like to know what the general opinion here is. I personally would remove the image for the reasons given on the above page. Nick Mks 19:19, 17 August 2006 (UTC)

It's inaccurate. The new ruling by the IAU wouldn't establish nearly the number of planets as that image is claiming. Plus, it's too busy, and frankly, it's ugly. Accuracy issues aside, there has to be a much better and prettier way to show those orbits. --Cyde Weys 19:21, 17 August 2006 (UTC)

Well, as the person who imported that image I should justify my action at least. There has been a great deal of supposition and fudging released by the IAU in the last few days that has been picked up by the media as established fact; the most notable being, of course, that there are now 12 planets. This is wrong. There could be (and indeed should be, if the definition were to be scientific rather than cultural) dozens of planets in our solar system. That image demonstrates a fixed, scientific limit for the total number of planets in our system. Anything below it would have to be justified in some way other than, "But that's just too many!" Serendipodous 19:49, 17 August 2006 (UTC)

I think the image is great. Sure, it's a little rough, but I think it's cool. The rationale for the 12 planets is that those are the ones we have relative certainty of their Hydrostatic equilibrium. The other 53-12=41 Mike Brown thinks are probably round enough, but we don't have enough information. More information will most likely bring the number to around 53 quickly, and several hundred (thousand) in the future. McKay 20:40, 17 August 2006 (UTC)

[edit] Periodicity

Hello anon user. While I admire your dedication to truth, there are several rules involved, particularly WP:NOT. I would imagine that 1 Ceres.com is your page. I'm not sure how I feel about your opinions from a mathematical sense, it doesn't seem right, but it might be true. There does appear to be some credence to your claims. Alas, Wikipedia isn't as interested in Truth, as it is in Verifiability. I'm not here to say that the claim is false, but I'm saying that it isn't verifiable. When 1ceres.com gets reviewed by a major journal or website, it will go in, even if unproven, because Verifiabiliy is more important to Wikipedia than truth.

On a seperate note, reverting a revert, especially without reasoning, is considered bad form. McKay 04:10, 18 August 2006 (UTC)

Should the following information be included within the definition? See the discussion about the Titius-Bode for the actual equation.

The Periodicity of Planets Recently, a new periodicity of planets was developed by Tyler Granger from the Titius-Bode Law that demonstrates a recognizable accuracy^[1]. Because of this periodicity, planets are defined by a natural phenomena rather than an institution. This new equation was discovered in the late 1990's prior to the discovery of 2003_UB313 (Xena). The discovery of this periodicity has yet to be accepted by the IAU. Yet, the redefinition of 1Ceres and 2003_UB313 would bring the planets of the Solar System into compliance with the periodicity^[2].

Yes or no? Fact or rule breaker? —The preceding unsigned comment was added by PlanetCeres (talk • contribs).

• NO as per the entire community last night. You are also close to getting into trouble for vandalism and WP:3RR violation. Nick Mks 08:47, 18 August 2006 (UTC)
• Yes But, the equation is missing from this section. As per it was deleted from the Titius-Bode_law discussion rather than addressed with fact. Bullying does annoy me. PlanetCeres

Nothing was deleted from Talk:Titius-Bode law in the last 24 hours. Nick Mks 09:41, 18 August 2006 (UTC)

Quite simply, this is a rule breaker because it is original research. If it ever gets accepted in a peer-reviewed science journal like Nature or Science, then yes, it would be worthy of inclusion. Until then, no. Serendipodous 14:13, 18 August 2006 (UTC)

[edit] Definition of moon aka "satellite"

from IAU:

Q: What is a “satellite” of a planet?

A: For a body that is large enough (massive enough) to satisfy the definition of “planet”, an object in orbit around the planet is called a “satellite” of the planet if the point that represents their common centre of gravity (called the “barycentre”) is located inside the surface of the planet.

• so this means that objects smaller than Mimas are no longer considered to be moons?! Or I missunderstood it?!--Pedro 23:32, 17 August 2006 (UTC)

As I read it, all satellites are still satellites even if they are large enough to be planets. But I agree, that is a bit ambiguous. Serendipodous 14:13, 18 August 2006 (UTC)

Maybe the solution is more simple: they could define just two types of objects: stars (objects that sustain or have sustained some form of fusion) and planets (I would discard the term "satellite"). Then we could speak only about systems: a system is a "stellar system" if the more "representative" (normally, the more massive) object in it is a star; and a system is a "planetary system" if the more representative object in it is a planet. So, Ganimedes is a planet in the planetary system of Jupiter, which in turn is in the Sun solar system. Is there a fundamental flaw in this? I see the other definitions too arbitrary.Damien,18-08-2006.

[edit] Discussions about the issue

[edit] Definition based on brightness?

It was said that the proposed definition would be both simple and scientifically accurate. Now the proposal is revealed. The definition based on absolute magnitude: Any object as bright or brighter than Pluto (V = −0.76) would be considered a planet.[3] Therefore Pluto would stay a planet, 2003 UB₃₁₃ would become a new one, and no other TNO found so far would qualify.--JyriL ^talk 01:35, 15 August 2006 (UTC)

It should be noted that the above is a proposal, not the proposal. Derek Balsam 01:47, 15 August 2006 (UTC)

OK, well, at least according to the small article it is just a proposal. I concede it may be the only one presented :) Derek Balsam 01:51, 15 August 2006 (UTC)

If I submitted that article for feature consideration on Wikipedia, it would get slammed. It's virtually incoherent. I can only assume whoever wrote it is not a native English speaker, because his knowledge of English syntax is shaky at best. It is also the worst definition proposal, by far, that I have ever seen. Basically, it's defining planets by their colour. Imagine if we used that criterion to define human beings!

Thankfully, after rereading it for the sixth time, I think I can rest assured that it is not THE proposal, because of this line:

"Letter has been circulated in draft form, but there has been no response from the two naming committees of the IAU."

If their letter was written by the same person who wrote that article, I'm not surprised. Serendipodous 06:55, 15 August 2006 (UTC)

You mean Tom Gehrels? It certainly looks like as if it was devised by an asteroid observer. But remember, nothing has been decided yet. This is only a draft, and as Derek Balsam said, it could be just "a" proposal. It certainly has some appeal (confirming an object as a planet becomes much easier, important as more and more distant large objects are being found), but without additional parameters it would allow huge difference in minimum sizes (1900–10000 km; from an Enceladus-style albedo to an albedo similar the darkest asteroids have).--JyriL ^talk 10:16, 15 August 2006 (UTC)

A rather foolish definition IMHO. You could have an object in an oval orbit that turns 'planet' when far from the sun, and then reverts to 'asteroid' every year when the snow melts. This whole discussion is totally backwards from a scientific viewpoint, as everyone is starting with the result that they want, (8, 9, or 10 planets, but not 30) and then trying to come up with otherwise meaningless distinctions that fit the bill. Algr

[edit] Orbit

I was wondering why the orbit is not included in defining what is a planet ? I'm just a layman but I think the following could define a planet:

a body that is in orbit around a star which is not a star itself (no internal nuclear fusion).

a body which is a spheroid due to its own gravity.

a body which is the only body in its orbit around its parent star (not including satellites).

a body which orbits its parent star in a fairly non-eccentric orbit within the star's ecliptic plane.

The third qualification would eliminate Ceres which is a member of the asteroid belt. The fourth qualification would eliminate all Kuiper Belt objects including Pluto as they have highly eccentric orbits and with significant inclinations relative to the ecliptic plane of the solar system.

All of your proposed definitions are discussed somewhere in the article. The first is discussed in the "Extrasolar planets" section. The second is discussed in the "Sphericity" section. The third is discussed in the "Shared orbit" section. The fourth is discussed in the "History and Etymology" section, near the bottom. Serendipodous 18:25, 16 August 2006 (UTC)

Specifically, the third qualification would also eliminate from the list of planets Mars, Jupiter, Saturn, and Neptune (see Lagrangian point#Natural examples) and possibly even Earth (see Lagrangian point#Other co-orbitals). Co-orbitals are quite common.Derek Balsam 18:31, 16 August 2006 (UTC)

Yes but my question is if the orbit is be considered in the official definition by the IAU and if not then why not ? That seems to be an important parameter, at least to me. The official definition shouldn't be about what's popular it should be about good science. There seems to be a bit of a desperate attempt to keep Pluto as a planet just to satisfy popular culture when it is really a Kuiper Belt object (or trans-Neptunian object).

As for the third point, the satellites are gravitationally linked to their planets so that wouldn't count. The bodies in the asteroid belt generally are not.

Which definition do you mean? The IAU specified that a planet orbit its star, be big enough to be spherical, and not be big enough to fuse (in its earlier definition concerning brown dwarfs). That's three of your criteria right there. The last one is more to do with manner of orbit and has little to do with the object itself.Serendipodous 19:01, 16 August 2006 (UTC)

Actually that's only 2.5 of my definitions as that would still include Ceres and any other asteroid which happens to be spherodial. Also why shouldn't the orbit be considered ? Kuiper Belt objects have irregular and highly inclined orbits and are at the edge of the solar system so why shouldn't they considered their own class because of this ? Clearly they're different from the eight planets which aren't in question.

No object in orbit around the Sun, planet or otherwise, as an entirely circular orbit. Some are more circular than others, but none is more "regular." Quaoar has a nearly circular orbit, almost on the ecliptic. That definition wouldn't excuse every KBO or other such object we may find. The third option, orbital dominance, is not really scientific. It's precident is largely historical. It's really just a means to keep the solar system tidy rather than an inherent scientific criterion.Serendipodous 19:16, 16 August 2006 (UTC)

Instead of "regular" I should say non-eccentric. Pluto's orbit is highly eccentric. As for orbital dominance, consider the Earth and Moon. Clearly the Earth is the planet and the Moon the satellite by virute of size. As for Quaoar then maybe it qualifies as a planet though it's not on the proposed list of 12 but can a KBO be a planet ? Also if tidyness is considered then the solar system should be as follows: Sun, inner (rocky) planets, asteroid belt, outer (gas giant) planets, Kuiper Belt objects, Oort cloud. Eight planets, lots of asteroids, probably lots of KBOs.

Again, all planets' orbits are, to a greater or lesser degree, eccentric. Orbital eccentricity is a measured planetary characteristic. As for KBOs being planets, well Pluto and Xena are both KBOs, so the answer would appear to be yes. The Moon is a satellite because it orbits the Earth. Size has nothing to do with it. Serendipodous 19:36, 16 August 2006 (UTC)

Yes that was my point about being the only object directly in orbit around a star, satellites orbit the planet. As for the IAU considering Pluto and Xena planets, it seems based much more on what the public wants (Pluto historically and Xena because of the popular culture reference). Why not Quaror as well which is spheroidal and has a much more typically "planetary" orbit (not highly eccentric and very close to the ecliptic plane) ? Pluto's orbit takes it in within Neptune's at perihelion and beyond Quaror's at aphelion. Considering Ceres a planet seems even more ridiculous, that's definitely an asteroid in the asteroid belt, albeit the largest asteroid.

I don't think that they're considering "Xena" because of the pop culture reference. Partially because the IAU doesn't acknowledge the name Xena, it is officially 2003 UB₃₁₃. I think this also means that we'll have a new name for 2003 UB₃₁₃ soon. I think that it's because we know more about 2003 UB₃₁₃, and we have greater reason to know that it's spheroidical. McKay 20:31, 16 August 2006 (UTC)

Xena and not Quaror ? Not buying it. Xena has an even more eccentric and more inclined orbit than Pluto. All of these objects just don't seem like they should be considered planets. Certainly not Ceres which is definitely an asteroid and Charon which is a satellite. While you're probably right about the IAU not considering Xena for that reason they certainly seem to be trying to come up with a definition that fits Pluto instead of just coming up with a good definition.

[edit] Rogue planets

This may be a silly question, but what happens if a planet-like object that maybe once was in orbit around a star but was ripped out of orbit by some passing star and is now kind of floating around is discovered? What's that? --Elliskev 19:23, 16 August 2006 (UTC)

Not a planet. But we already know objects that are way too small to be even brown dwarfs (>13 M_Jupiter). There are several suggested terms like sub-brown dwarfs (hardly apt in this case), rogue planet and planemo.--JyriL ^talk 19:29, 16 August 2006 (UTC)

One thing it's not is a silly question :). In fact this is considered one of the major flaws in the IAU's definition by some see here, for example. The issue of what constitutes a star and what constitutes a "rogue planet" is not dealt with by this definition, the main purpose of which was to decide what to do about "Xena." Serendipodous 19:32, 16 August 2006 (UTC)

[edit] Proposed definition is circular

Lol, the IAU have blundered big-time: in defining a planet, check out condition (b). Hopefully, they realise this and will finally decide on a definition that is at least logically sound. MP (talk) 18:40, 16 August 2006 (UTC)

I don't see what's circular about it. Stars orbit stars. Serendipodous 18:55, 16 August 2006 (UTC)

Stars orbit stars, yes, but you can't define a star to be an object around which another star orbits (or otherwise):

“A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet.”

MP (talk) 08:27, 17 August 2006 (UTC)

I wouldn't describe such a definition as "circular." It would be circular if a planet was defined as something in orbit around a star, and a star was defined as something with planets around it. But a star has always had a very rigid definition independent of planets. I agree that defining a planet by the fact that it orbits a star is certainly silly, (as do a lot of professional astronomers) since it means that if a planet were ejected from its system it wouldn't be a planet anymore, but that doesn't make it circular.

Re your edit: No, that's not circular either; it's just redundant. Satellites do not orbit stars; they orbit objects in orbit around stars, so obviously by the above definition they would not be planets. There's no need to specify that a planet cannot be a satellite. Serendipodous 08:31, 17 August 2006 (UTC)

[edit] This whole things reminds me of...

When Ceres was discovered in 1801. At first, everyone was like "Oh, it definently a planet! It's right where we excpected it to be! In the huge empty gap between Mars and Jupiter!" And it was obvious. Sure, the best telescopes couldn't resolved it as anything more then a point of light, but that's ok. And everyone was happy. Until Pallas was discovered. "Well, that's ok. We'll have another planet!" And then came Juno. "And another!" After some time, they eventually realised that thousands of these odd "Asteroids" would be found, and that they couldn't fit in well with the big planets known at the time (Mercury to Neptune). So then the planet count went back down to 8. Until Pluto was discovered. Pretty much the same thing happened, it was definently a planet, although an oddball too. Until 1992. Something else was found beyond Neptune. It was smaller, but it was in the same area. Doubt lingered, but then along came some others. Sedna, Quaoar, and then "X". We face the same problem today. We know that out there is something like an asteroid belt, but with ice instead of rock. Perhaps "X" and Pluto would just be really big comets in the Kuiper Belt. Maybe if something is mostly made of ice, it can't be a planet, because if brought close to the Sun, it vanishes pretty quickly. It would look nice sure, in it's death pangs, but when all is said and done... the system I thought they'd choose wouldn't have an arbitrary barrier at 800 km for size, but at say... Mercury. It's made of rock, round, big, is very close to the Sun, but still not vaporised. Seems logical to me. But what do I know? I'm not one in the commitee of "7 elderly astronomers who decide the faith of the Sol-system". When we discovered about say, 50 of these things, just "Nuke and Pave" the bloated list, with Mercury being the smallest.--Planetary 18:59, 16 August 2006 (UTC)

We already have discovered over 50 of them. This definition, love it or shove it, is for the long haul. Serendipodous 19:05, 16 August 2006 (UTC)

• Planetary, i guess you never heard of this: Hot jupiter. If you put Earth or Mercury even closer they would also evaporate. In fact, that will occur to Earth, and these planets will continue "living". Pluto is also made of rock, ice in that region is hard as rock. The problem of Plutons is that those are not translatable, I cant translate Pluton to have the same meaning as in English. If I translate directly I'll get the name of planet Pluto. I would prefer Ice planets or Tartarus planets or something else... Plutons?! what a lack of imagination, that razes translation issues. --Pedro 19:40, 16 August 2006 (UTC)

I already know about Hot Jupiters. That isn't what I really meant. If you could push Pluto inside Mars's orbit, say, it would evaporate pretty quickly (relatively speaking). That probably won't happened, though. Pluto's still pretty big, and hard to move. By 50, I meant 50 planet-sized KBOs, not all of them. I know there are almost 1000 already. I just think the current definition for planet isn't strict enough. IMHO, Mercury should be the smallest planet. We can call the others "planetoids". If something is discovered out there larger then Mercury, I'm all for it. Just my opinion. Just noting similarities now to about 200 years ago, when this sort fo thing was happening with the asteroids. I think making Ceres a planet would just make things worse. If they wanted to, they could even set the limit at "X"'s size, but Ceres is just much too small. As for translation issues, I can already think of something in my native language that says the same thing as Plutons. But I recommend planetoids or minor planets. --Planetary 20:13, 16 August 2006 (UTC)

We have already found more that 50 planet-sized KBOs. At least according to Mike Brown, and he should know. Serendipodous 20:51, 16 August 2006 (UTC)

Planetary, your comparison of this to Ceres and the asteroids is a good one. I agree Ceres should not be considered a planet as it is clearly part of the asteroid belt. Also what about Quaror and other KBOs ? The list of "planets" is just going to increase simply to serve the generally public opinion of keeping Pluto on the list and that's ridiculous. If there's any doubt that this decision is about public opinion then consider the following quote:

“If we were starting from present knowledge we probably would not have classified Pluto as a planet. But this is a very sensible compromise.”

Source: http://www.timesonline.co.uk/article/0,,3-2314926,00.html

Since when is science about compromise with opinion ??

Since there is the odd belief the removing Pluto's planethood will result in riots. But then, cartoons can result in riots.--Planetary 21:05, 16 August 2006 (UTC)

• maybe that is also a pressure they had to deal with. Almost everyone likes to read the horoscope, and I bet that some people that has Pluto as planet would become pretty mad. LOL. Roundness is a physical aspect and what really distinguish asteroids from planets, thus you are not making very scientific statements. All that you say for Pluto will also turn Earth into an asteroid. Planets are all different: Jupiter != Earth != Pluto. Ceres was removed from planethood, because in the 1800s people wanted order in the skies.--Pedro 22:29, 16 August 2006 (UTC)

Horoscope ?!? That's an absolutely stupid reason which has nothing to do with science. I don't know anyone who reads that sort of unscientific garbage. Your weak arguments are a good example of why science should not pander to public opinion. Science is about understanding the true nature of things, not capitulating to public opinion or silly traditions.

Agreed. And how can Earth be an asteroid just because Pluto is a comet? I don't see the connection. It would be simpler to set the limit at Mercury.--Planetary 03:09, 17 August 2006 (UTC)

• reply to anonymous: maybe you don't know anyone. We've got a new Einstein! There are scientific studies that show that most people read horoscopes. And that was not part of my arguments (but possible reasons for protests), the roundness is the only valid scientific argument that comes by in these discussions and it was studied by a group of 7 prestigious astronomers for more than two years. And they came up with a valid scientific, historical and international definition. Mass is the key: if you have enough mass you'll get a star, and more and more, you can even get a black hole. If they didn't do it, in a few years different countries would have different counting of planets. Why set the limit at Mercury?! One of the reasons for Ceres being classified as a planet: Ceres An Embryonic World. BTW, I've read that the diameter cut-off would be 772.5 km (but that doesnt show up in the IAU site: [4]

-Pedro 10:55, 17 August 2006 (UTC)

Well, the unsigned comment above (about opinion) reminds me about the decision made to turn pounds into a unit of mass and not force (discussion at weight). Even though officially according to virtually standards organization, the pound (and ounce and ton...) are units of mass, even the top class scientists use them the old way. Regardless of whether they like it or not, no matter what they say, Pluto will remain a planet. As I've been thinking about this discussion, I can't help but think about how I would make the distinction. I personally like taking away the status of Pluto, because I don't think it's very scientific. So, giving it the smaller status is a reasonable compromise. A couple sentances ago, I made the statement that I didn't think that calling pluto a planet was very scientific. Until the past couple days, my reasoning for thinking that it wasn't very scientific, wasn't very scientific. See, within the past 20 years, we've found other objects within the gravitational well of Sol that seem more like planets than Pluto does. (most notably "Xena"). But within the past couple of days, I've thought about it more. And I've been thinking, "Well, how would someone who wasn't familiar with just the Sol System define the term. This is hard for us – as humans who haven't left our system – to do, but picking a size and sticking to it is kinda stupid. (anything smaller than 2000km?) As it's very arbitrary. I liked the "larger than the combined masses of other objects in the same orbit" definition (which would kick out pluto), but it would kick out other planets just because some other masses got a little larger. I really do like the current proposed definition of having enough gravity to maintain Hydrostatic equilibrium. It doesn't seem arbitrary. sure, badastronomy.com likes to say that if a material is made of a softer substance like pluto, (cf 4 Vesta), it attains this status easier, but it isn't arbitrary, it's an established phenomenon. I want to say something (potentially about size) to exclude the potentially millions of KB or OC objects that might attain this status, but either it's too arbitrary, or excludes planets like earth. Pedro is right, all other characteristics of celestial bodies are characteristics based on mass. A black hole is an object that is so massive that the escape velocity is greater than the speed of light. A star is an object not a black hole that's so massive that it generates internal fusion. Why not, A planet is something not a star that's so massive that it attains hydrostatic equilibrium. It think it makes perfect sense the more I think about it. McKay 13:20, 17 August 2006 (UTC)

Foolish unscientific garbage like horoscopes shouldn't be part of a discussion about astronomy. Anyway mass is still an arbitary parameter, Ceres has less mass than many satellites. Also shouldn't an object have only one definition ? Ceres is an asteroid and is officially designated as such: 1 Ceres. Why shouldn't Pluto which is a Kuiper Belt object be officially designated as "1 Pluto" (first discovered member of the Kuiper Belt) ? That seems much more logical than simply pandering to opinion especially considering there are many known KBOs already and this number will very likely grow. Having specific classes of objects in the solar system makes more sense: Sun, planets, satellites, asteroids, KBOs, comets. 16:31, 17 August 2006 (UTC)

Agree on horoscopes, Yes, mass is an arbitrary parameter Hydrostatic Equilibrium isn't. Sure, Ceres is kinda an asteroid, but an asteroid Usually considered a hunk of rock, and usually not really in hydrostatic equilibrium, because there isn't a liquid core. So, Ceres isn't really an asteroid. It may have been one at one point, but because of it's size it compressed its core, and reached a state of hydrostatic equilibrium. So, unless you can define asteroid differently, then that might be something. Also, mercury is smaller than many moons, should we have a new designator for Planets that are smaller than moons? McKay 18:37, 17 August 2006 (UTC)

Let's see, what's know about Ceres? Not much. Pluto is about 2 and a half times larger the Ceres. If we set the limit at Pluto exact size (will be known very well in 2015), we'd have 11 planets, with Pluto and "X" the new editions (2003 UB313 is too long a name, Xena is hideous, so for me it's just "X"). If we set the limit at Mercury, there would be 8. Yes, there are 2 larger moons in the solar system, one of which has a significant atmosphere. However, they all very clearly can't be planets by basically all definitions, because the center of mass of the system is deep inside the gaseous planet, which is much more massive. If Titan or Ganymede were free-orbiting objects, yes they'd definently be planets, based on sheer size. But they aren't. They're deep in the gravity well of their parent bodies. Another bonus of setting the universal lower limit for planethood at Mercury is that we don't have to wonder about Pluto-Charon counting as 2 planets or not. The difficulty with this whole issue is that we don;t know very much about the objects in question. "X" is just a point of light at best. Ceres is a ball of pixels. Pluto and Charon no better. We might just have to wait a few years, until New Horizons and Dawn reach their mission objectives.--Planetary 20:26, 17 August 2006 (UTC)

[edit] Size of Our World

I tried to put this up as a new article, but it gets deleted. This is interesting anyway so feel free to put it somewhere appropriate.

http://www.rense.com/general72/size.htm

This seems non-notable. Also because of the nature of the site, incorporating its images into wikipedia is probably a copyright violation without express consent from the author of the images. McKay 20:31, 16 August 2006 (UTC)

• nice link, loved it.---Pedro 13:08, 17 August 2006 (UTC)

No McKay... I just wanted to incorporate the link not the entire picture, and why is it non-notable?

Pages linking to that page according to google. Seems very non-notable to me. It's very cool, but Wikipedia is not a place for original research. see WP:Notable. I think that those images would be good in wikipedia if they were copyleft somehow. McKay 20:25, 17 August 2006 (UTC)

Original research? This shows the relative size of planets to other celestial bodies, maybe it does not belong here, but when relative size is discussed it seems this link is just what the doctor ordered.

[edit] MVEMCJSUNPCU

Why this obsession with roundness? We don't define "moon" based on shape, which is why Jupiter and Saturn have so many of them.

For the traditionalists who want to keep 9 planets because they don't want to memorize more, I have a new mnemonic, good at least until they rename UB313 or add more planets:

My Very Educated Mother Considers Just Slightly Understood Nine Planet Concept Uneducated Roger 20:43, 16 August 2006 (UTC)

• This is Very Clever. Love it. Žena Dhark…·°º•ø®@» 03:17, 17 August 2006 (UTC)

Man Very Early Made Clay Jars Stand Up Nearly Perpendicular, Clearly Upright. GBC 17:03, 17 August 2006 (UTC)

[edit] My proposed definition

I doubt anyone in the IAU will read this, but I'm curious what other people think.

A planet is:

• anything large enough to be spherical under it's own gravity AND
• is significantly larger then the other objects in it's general area (orbit), excepting it's moons.

Anything large enough, but not 'unique' in it's orbit shall be called a 'minor planet' or 'planetoid' (or moon if applicable).

Tell me what you think. 71.199.123.24 01:04, 17 August 2006 (UTC)

• Yes! I think the uniqueness is what defines a Planet from a Planetoid. Žena Dhark…·°º•ø®@» 03:14, 17 August 2006 (UTC)

What is the limit on "spherical"ness? Nothing natural can be a perfect sphere. The Earth has a slight bugle, almost not noticable. Saturn is football shaped. What is the limit? And how wide is the "general area"? Look here [5]. That seems rather "messy", doesn't it? The limit will have to be arbitrary, or else nature will always find a way to keep us humans from categorising everything. --Planetary 07:36, 17 August 2006 (UTC)

I'd like to lead an expedition to find the Earth's Bugle. It can be like Christopher Robin searching for the North Pole. THanks for that link, by the way; I'm gonna swap one of refs with it. Serendipodous 08:04, 17 August 2006 (UTC)

Hmmm, I don't think the Earth has a Bugle. There is a Cape Horn, but that has been discovered.

[edit] Atmosphere

Sorry for my ignorance on this, but how much mass does a body need to hold in an atmosphere? That could be another factor that could be added to the IAU's current proposal so that tiny round objects aren't added later.

So... 1) orbits a star, and not another object (like a moon), 2) has enough mass to form a round shape, and 3) has enough mass to hold in an atmosphere. ? i dunno... -- Zeroyon 05:43, 17 August 2006 (UTC)

It depends how cold the planet is. Pluto has an atmosphere, but much larger Mercury don't. Our Moon doesn't have atmosphere, Jupiter's Galilean satellites' atmospheres are almost nonexistant, whereas colder but similar-sized Titan has thicker than Earth's. On the other hand, 2003 UB₃₁₃ most likely currently (like Pluto most of its time) don't have atmosphere, because it is now too cold.--JyriL ^talk 09:37, 17 August 2006 (UTC)

• Yes! 4 Point Planets, Not 3 Žena Dhark…·°º•ø®@» 05:47, 17 August 2006 (UTC)

Actually the Earth's moon has an atmophere, very thin, but mostly Argon. So does Ganymede and Europa. The question is, how thick does it have to be to count as an atmosphere?

[edit] Planet Ordering

So, I was reading Real Life (webcomic) today, and he was calling 2003 UB₃₁₃ the tenth planet, which I thought was wrong, so I went to the Xena page, to get look at the page. The Xena page actually references the Xena: Warrior princess character, but at the top it said that 2003 UB₃₁₃ was a potential tenth planet also (has been modified since), so I went to the Tenth planet article. It will definitely need some work when the decision has been made, but it got me thinking about the ordering of the planets. Here's a couple possible numberings, LMK what you think: "Planetary order"

1. Mercury
2. Venus
3. Earth
4. Mars
5. Ceres
6. Jupiter
7. Saturn
8. Uranus
9. Neptune
10. Pluto
11. Charon
12. 2003 UB₃₁₃ (we really need a real name for this one)

• Disadvantages, Renumbering. This also has the effect of making Pluto, the Tenth planet

or Order in which they became planets (ties go to closeness and discovery)

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune
9. Pluto
10. Ceres
11. Charon
12. 2003 UB₃₁₃ (we really need a real name for this one)

• Disadvantages, splits up Pluto and Charon. Ceres is way out of place

discovery

1. Mercury*
2. Venus*
3. Earth*
4. Mars*
5. Jupiter*
6. Saturn*
7. Uranus 13 March 1781
8. Ceres 1 January 1801
9. Neptune 23 September 1846
10. Pluto 18 February 1930
11. Charon 22 June 1978
12. 2003 UB₃₁₃ 21 October 2003(we really need a real name for this one)

• Classical planets, (doh, that term means something) planets discovered anciently
  • feel free to move Earth to #1, but that's kinda silly.

So, now that I've typed all this, I realize that planetary order is the only real order, you're just going to have to get used to saying "...mars, ceres, jupiter..." McKay 14:44, 17 August 2006 (UTC)

Or just use the classical planets (all 8 in the classic order) and forget about the rest, since it is likely more asteroids will become accepted as dwarf planets, and it is without doubt that many more plutons will be added to the list.... -- Jordi·✆ 14:53, 17 August 2006 (UTC)

Eh, yes, I think the first one will have to be the new planet order, although because Pluto-Charon is a double planet they might both share the 10th (or 11th) position. Which is a bit confusing, but I'm sure it will be worked out in due time. There is also the possibility that other objects (like other big asteroids and other KBOs) will be upgraded to planet status, which will again change the number arrangement. I think the only thing for sure is the Earth will remain 3rd Rock from the Sun. --Hibernian 14:53, 17 August 2006 (UTC)

I think easiest is to forget about the small ones. The IAU is going to give us a nice order which fits both the historical and the --imnsho-- logical definition of planet by creating the term classical planet which nicely eliminates not only Ceres and the plutons, but also any other rocks from the list without need for re-ordering.

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus
8. Neptune

-- Jordi·✆ 14:59, 17 August 2006 (UTC)

• UB313 will get a name after it is officially declared a planet, in some weeks time. --Pedro 15:04, 17 August 2006 (UTC)

  Which will certainly not be Xena, by the way. 2003 UB₃₁₃ must be named after a deity. -- Jordi·✆ 15:09, 17 August 2006 (UTC)

So, My question is in regards to the Tenth planet article, (which doesn't have much conversation). What will happen there? McKay 15:19, 17 August 2006 (UTC)

Well, since the whole concept of a "tenth planet" will soon be out of date, I think it probably should be merged with "hypothetical planet." As regards the ordering of disovery: Ceres, technically, is a classical planet, because it was discovered before Neptune. Earth wasn't "discovered" to be a planet until long after Saturn. Serendipodous 15:23, 17 August 2006 (UTC)

Well, we're either going to end up with 12-and-soon-more planets, so the "tenth planet" bit is somewhat moot (if you want to be anal about it, Pluto is the tenth, since Ceres was discovered long before it), or 8 "classical planets" (i.e. non-dwarfs) so the "tenth planet" will be the second planet we discover which is larger than Mercurius. I don't think current theories about the Kuiper Belt or Oort Cloud allow for two objects the size of non-dwarf planets there, so there likely won't be one. (edit conflict with Serendipodous, so some duplication) -- Jordi·✆ 15:27, 17 August 2006 (UTC)

And if more asteroids are upgraded to dwarf planet status, Neptune will become the 'Tenth planet' in order of discovery and distance from the sun, or even a higher number. Most planet-candidate asteroids were discovered before Neptune was. -- Jordi·✆ 15:30, 17 August 2006 (UTC)

[edit] PSR B1257+12 D

PSR B1257+12 D could be defined as a planet if this passes... it's larger than Ceres. 132.205.93.195 03:23, 18 August 2006 (UTC)