Talk:Dwarf planet/Archive 2

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"Dwarf planet and other solar system categories" section

I've removed the "Dwarf planet and other solar system categories" section from the article pending discussion. Here is the text in question:

"The categorization of solar system objects into the three categories of planet, dwarf planet, and Small Solar-System Body established by IAU Resolution 5A does not supersede previous classifications based on other criteria, such as a body's location in the Solar System, its composition, or its history. The Resolution itself makes reference to the classes asteroid, Trans-Neptunian object (TNO), and comet (footnote 3)."

"None of these classes (asteroid, TNO, comet) is coterminous with any of the categories of planet, dwarf planet, and Small Solar-System Body. They may or may not be subsets of the latter categories. The language in footnote 3 that Small Solar-System Bodies "currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies," although technically ambiguous, implies that "comets and other small bodies" are subsets of the category "Small Solar-System Body". The use of the word "most", however, indicates that asteroids and TNOs are sets that only partially overlap the category; this is consistent with the naming of asteroid 1 Ceres and TNOs Pluto and Eris as dwarf planets and not Small Solar-System Bodies. A reasonable conclusion is that Ceres continues to be the largest asteroid and Pluto and Eris continue to be Trans-Neptunian objects despite also being categorized as dwarf planets."

It appears that the text is not based on verifiable definitions, but instead sounds like the dreaded "original research". While it would be nice to have a concrete definition of what is what in the solar system, I don't think Wikipedia should be creating that definition. If anyone has thoughts on this, or (more importantly) can provide citations for the conclusions reached in the text, please add them. Thanks! --Ckatz^chat_spy 08:32, 3 October 2006 (UTC)

I agree that it is probably best left out. It's interpreting and drawing conclusions from the text of the IAU resolution etc, not merely setting out interpretations and conclusions made by others. Also, whether (for example) Ceres is still an asteroid is best dealt with in that article. Similarly for Pluto and Eris. --Cuddlyopedia 12:10, 3 October 2006 (UTC)

Archive

Archived talk down to the beginning of September 2006. RandomCritic 00:43, 16 October 2006 (UTC)

Lack of Clarity

Is a dwarf planet a planet that happens to be of type dwarf, or not a planet at all? For example, a berry is a fruit, but a fruit is not necessarily a berry; berry is just a subcategory of fruit. If it is not a planet, I a surprised there is no hyphen, because it dwarf looks to be an adjectives, and nothing more. It seems dwarf is a subcategory of planet, and this article does not explain this clearly, especially to lay people. Nonprof. Frinkus 20:41, 3 November 2006 (UTC)

"Dwarf planet" is that name of a type of solar system object. If the article doesn't say it's a subcategory of "planets", that's because that's not how it's defined. If it helps, think of it as one word that happens to have a space in the middle. TCC (talk) (contribs) 23:50, 3 November 2006 (UTC)

Is it good English to have two words work as one? With such an explanation, it probably would be difficult to get all school children to understand the precise difference between ‘planet’ and ‘dwarf planet’ and yet another possible contradiction in rules in English grammar. As for the science behind this (or severe lack thereof, real science is not a popularity contest and should not be determined by vote) ... “new planet definition that relegates Pluto to "dwarf planet" status is drawing intense criticism from astronomers. It appears likely that the definition will not be widely adopted by astronomers for everyday use, even though it is the International Astronomical Union's (IAU) official position.”. [from New Scientist Space] “"Alan Stern, who heads NASA's New Horizons mission to Pluto and works at the Southwest Research Institute in Boulder, Colorado, US, says the new definition is "awful". "The definition introduced is fundamentally flawed," he told New Scientist. "As a scientist, I'm embarrassed."”.

He goes on to say that only 4 of 8 objects in the IAU's new planetary definition meet their convoluted criteria (Earth and Jupiter for example, do not). He gives technical details for why that is. Another strong point was that “the new definition was pushed by people who are unhappy with having large numbers of planets” (very unscientific). All of that in addition that only astronomers were present, and less than 5% of the total IAU membership voted. Perhaps Richard Conn Henry likes to make a semantical (and only time will show how insignificant) victory to satisfy his own personal opinions.

So, given all of these numerous flaws, why does the main Pluto article now redefine Pluto as a ‘dwarf planet’ when frankly, I yet to see any real consensus (scientific or otherwise) nor any earth shattering supporting logic? Can I change that, or give both the title of ‘planet’ and ‘dwarf planet’ equal standing in all sections of that article?

Nonprof. Frinkus 08:27, 4 November 2006 (UTC)

Well, first off, you should probably pose that question over at Talk:Pluto rather than here, seeing as how it involves changes to that article. Secondly, I don't think the article is "redefining" Pluto - the IAU redefined it. Wikipedia, as an encyclopedia, bases its definitions of "planet" and "dwarf planet" on the decisions of the governing body for a particular field - in this case, the IAU. That doesn't mean that the article can't cover the controversy - in fact, that would be an important part of the coverage, and it is well represented. However, there is a real difference between writing about a controversy and participating in it. By doing what you propose, you would cross that line. (Just my two cents.) --Ckatz^chat_spy 09:34, 4 November 2006 (UTC)

Me controversial … moohey, sorry about that.  :-) Almost all of what I wrote there, was sourced in the same flavour (albeit not exact word for word due to copywrite) is not original by me, so I did not realize I was participating in it. And you are correct, this does not belong here … one question led to another, and I am not sure how to properly transition stuff over.

Ummm, is there a Wikipedia policy that states that each section of subject matter has only one official governing body to make decisions, and that this encyclopædia must be in lock step with that organization for the official take? Some of the complaints of scientists I mentioned there, is the fact some governing bodies could be much more narrow than the community directly researching that type of subject matter as a whole. Unless there is some official policy stating that one organization will be anointed master of each subject matter for official takes … does not Wikipedia participate in the controversy as well (by choosing sides for who gets top billing, even though both sides of issue might be represented when some areas)?

Nonprof. Frinkus 20:07, 4 November 2006 (UTC)

If a Dwarf star is a Star, should not a dwarf planet be a planet?

That's just a grammatical mistake, so it doesn't prove that a dwarf planet is a planet.

Nonprof. Frinkus 06:17, 6 January 2007 (UTC)

What's a grammatical mistake? Dwarf star or a dwarf planet? I believe IAU motivated it's decision by referring to an earlier mistake, but does one wrong rectify the other? I think this kind of terminology should be defined by linguists, not astronomers. Those fools seem to think language rules doesn't matter. I also think that we shouldn't take IAU too seriously, when they don't handle terminology seriously. Said: Rursus 13:54, 19 April 2007 (UTC)

Should this article explain why this definition is required?

Should this article on "Dwarf planet" explain the reasons why it is so important to have a separate definition for the term "Planet"? No where in this article does it seem to clearly justify the why this definition is so importantly required. Could I be wrong here? Nonprof. Frinkus 05:49, 5 November 2006 (UTC)

Doesn't anyone have a clear answer here? That would be helpful for my own research and for inclusion in this article.  :) Nonprof. Frinkus 06:17, 6 January 2007 (UTC)

"As defined, the term "dwarf planet" does not apply to other planetary systems." I think this statement does not make sense as it stands, nor does it's citation support the statement. The definition DOES apply to other systems just fine: if the body has cleared its orbit of most other mass, it is an extrasolar planet, if it has not then it is an extrasolar dwarf planet. There is possibly a problem insofar that extrasolar planets have highly elliptical orbits, so the concept of orbital clearance isn't easily applied, but that should be made clear. That concern would BTW also apply to any undiscovered very large bodies in our system with highly elliptical orbits.

Alternative Term

Is anyone else concerned that astronomers came up with the name 'dwarf planet' which is supposed to make things easier for the public and for schoolkids? Not only is it confusing to say that a dwarf planet is not a planet, but the name could make astronomers a laughing stock. Every smart ass kid in the classroom is going to say: 'Sir/Miss, dwarf planets, is that where dwarfs come from?' and all the kids will fall around laughing. Snow White and the seven Plutonians anyone? Somebody call Peter Jackson, his casting problems for The Hobbit (if it's ever made)are over - all he has to do is go to Pluto haha. It might well be a public relations disaster that would hold astronomers up to ridicule.

All joking aside, it is understandable that scientists like to have precedents for when they coin new terminology but 'dwarf planet' is not the answer. With all the talk of densities of rock and ice etc, the debate moved into the realms of geology and that is where the real precedents lie. Many terms in geology use the suffix 'ule' from Latin and Greek as a dimunitive. Here are some example- note that they have the relevant quality of roundness:

• Globe - globule;
• Sphere - spherule;
• Grain - granule;
• Node - nodule

Also of interest are some terms from biology.

• An 'ovule' is an unfertilised or undeveloped seed (from Latin ovum), and
• 'sporule' is a small spore. It may seem strange for astronomy to borrow from such a source, but with talk of stars being 'born and 'dying' etc, maybe it is not so strange.

How about Planetule to describe Pluto (?), Ceres et al.

To the general public it would be easy to understand as meaning 'a very small or 'undeveloped' planet or planet like object'. It would square the circle of describing something that's like a planet, but doesn't make the grade to being a fully fledged one.

As to how to distinguish a planetule from a planet, that's another day's work, but at least it would solve the 'Snow White' problem!Neelmack 21:08, 17 November 2006 (UTC)Neelmack

Wikipedia:No orginial research. Michaelbusch 20:30, 11 January 2007 (UTC)

I find the proposal very interesting, but I have to agree here is the wrong place to discuss it. You should contact your closest member of the IAU. I hope you will have success. Rgerhards 09:23, 12 January 2007 (UTC)

I emailed several members of the IAU but got no replies. Does anyone know of a suitable website or forum where I can post my suggestion for discussion? Neelmack 19:26, 13 March 2007 (UTC)

I think we need not take the so called terminology (scorn!) determined by IAU too seriously, just wait and see how the humankind use the word planet – I believe that faulty term won't be used, and Wikipedia is obligued to use terms in a way that reflect the actual usage. Said: Rursus 14:01, 19 April 2007 (UTC)

I remind both of you that this is the talk page for the article Dwarf planet, not a forum for discussion of the article's subject. For that debate, please work off-line. Michaelbusch (talk) 18:26, 19 November 2007 (UTC)

Archive

I archived the talk from September-October 2006. RandomCritic 12:11, 22 November 2006 (UTC)

Whether or not a dwarf planet is a planet.

i personally believe that dwarf planets should be considered planets because their relationship to planets is the same as that of dwarf stars to other stars and dwarf stars are considered stars. —The preceding unsigned comment was added by 216.96.73.129 (talk) 18:44, 18 December 2006 (UTC).

According to this http://topics.nytimes.com/top/news/science/topics/dwarfplanet/index.html it isn't. Abtract 18:53, 18 December 2006 (UTC)

Dwarf star means many different things: white dwarf, red dwarf, brown dwarf. A white dwarf weighs within a factor of ten as much as the sun, as does a red dwarf, and both fused hydrogen at some point. A brown dwarf is different: there is no hydrogen fusion, the masses are much lower. If you wish, the relationship between a planet and a dwarf planet is like that between the Sun and a brown dwarf: one important physical boundary in mass has been crossed, but another has not. Personal opinion is also not grounds for inclusion in Wikipedia. Michaelbusch 19:24, 18 December 2006 (UTC)

Red dwarfs have a mass less than 1/3 of the sun--which is itself a yellow dwarf. But are we bere to discuss stars or planets? Arch O. La ^{Grigory Deepdelver} 17:26, 19 December 2006 (UTC)

I don't think that the claim "The category dwarf planet is not a subset of the category planet" can be defended. I feel there are clearly three categories: ("Dwarf planet", "nondwarf planet") both members of the set of planets, and "small solar system bodies." The reason that I say this is that the Earth is currently a nondwarf planet but will become a dwarf planet whenever some clutter (including human clutter and junk) intrudes onto our orbit, until th point the planet cleans it up again; while Pluto is a dwarf planet that could become a nondwarf planet is someone were to pop out there with a big net and clear up its orbit, and Neptune and Jupiter are dwarf planets because of the Trojans at their L4/L5 points. A planet can move from one category to another freely, without changing its own form in any way: and in fact, any dwarf planet, given enough time, will become a nondwarf planet by clearing its own orbit. It is silly to say that a planet can become a nonplanet just by changing the things it shares its orbit with, and vice versa. It is silly to say that two planets at eachothers' L3 points are automatically dwarf planets because they share the same orbit. It is acceptable, however, to say that the categorisation of the TYPE of planet changes depending on its orbital companions, though, just as it can change from being a binary planet to a regular one without changing its essential planettiness. 90.192.153.137 22:07, 16 October 2007 (UTC)

You're letting linguistics fool you. By the IAU's definition of the two terms, dwarf planets are not planets. Also, it'd take a lot more than a few billion tons of debris in our orbit for the Earth to be classified as a dwarf planet. (Mars would be at greater risk.) Look at the cleared the neighbourhood article for more on that. Ben Hocking ^{(talk|contribs)} 22:26, 16 October 2007 (UTC)

The Solar System or Our Solar System

Currently, the second paragraph says:

The term "dwarf planet" applies only to objects in the Solar System.[2] and is quite distinct from "planet" and "small solar system body".

I would like to suggest changing this to

The term "dwarf planet" applies only to objects in our solar system,[2] and is quite distinct from "planet" and "small solar system body".

Yes, I am aware that "the Solar System" (with capital letters) refers to our own solar system, as opposed to any other solar system in the universe. However, the average man on the street might not be aware of such a distinction. Since the intent of this paragraph is to say that the term "dwarf planet" only applies to our own solar system, I feel that it is appropriate for us to make this point clearer in this one specific instance.

I had been bold and made this change myself, but was reverted by Ckatz. I'm therefore bringing the discussion to the Talk page. (Incidentally, Ckatz also restored the incorrect full stop before the reference marker, which I had replaced by a comma.) Bluap 19:24, 5 January 2007 (UTC)

Sorry if it wasn't clear, but I think you misunderstood my edit summary. What I meant was that there is only one system that is properly referred to as "solar" - ours, the "Sol" system. There aren't other "solar systems", so using "our" would be incorrect for either "Solar System" or "solar system". It also means that when we say a term such as "dwarf planet" applies only to "the solar system", we are being specific. That was the basis for undoing your edit. (My apologies for not noticing the comma - minor changes in punctuation aren't easy to see in the diffs.) --Ckatz^chat_spy 19:53, 5 January 2007 (UTC)

Ahh - I see that I was getting confused between solar system and planetary system. (Interestingly stellar system redirects to star system, while I would have thought that a redirect to planetary system might have been more appropriate.) I'll get my thinking cap on, and find a new way of wording those couple of paragraphs. Bluap 21:20, 5 January 2007 (UTC)

"Dwarf planet" … does this definition only apply to this (Sol's) solar system … and is not used for any other planetary star system found in space? I am seeking clarification, thank-you. Nonprof. Frinkus 06:13, 6 January 2007 (UTC)

As per the article (third paragraph), "As defined, the term "dwarf planet" does not apply to other planetary systems." Hope this helps... --Ckatz^chat_spy 06:27, 6 January 2007 (UTC)

Oops, thank-you very much.  :) I thought that was an err, because I've been dumbly lost about the logical requirements for a new yet so awfully specific category, other than naming rock/ice balls to big to ignore. I will update my numbers, merci. Nonprof. Frinkus 06:29, 7 January 2007 (UTC)

New dwarf planet

..According to BBC. See title: http://news.bbc.co.uk/2/hi/science/nature/6268799.stm

--TheFEARgod (Ч) 14:24, 17 January 2007 (UTC)

I think the BBC made a mistake on the headline... I couldn't find any mention online about it being reclassified. Potentially, yes, but that dates back to the fall. --Ckatz^chat_spy 17:40, 17 January 2007 (UTC)

That article is very badly garbled (see Talk:2003 EL61). EL61 is not classified as a dwarf planet by the IAU. Michaelbusch 19:20, 17 January 2007 (UTC)

Besides, classifying anything as a "dwarf planet" is a mistake. Its a planetary body, the size of Pluto. Said: Rursus 14:02, 19 April 2007 (UTC)

Eris' Mass

Can we get a citation for Eris' mass? I have not been able to verify this figure anywhere. All other sources say that it is unknown and astronomers are going to use the moon's orbit to calculate the mass. Notably, the Eris page does not give a figure, either. I'd love to be proven wrong; I just need a source. -- Joshua BishopRoby 00:40, 3 February 2007 (UTC)

I just added the citation, to Mike's 2006 paper on satellites of KBOs. Michaelbusch 00:52, 3 February 2007 (UTC)

I added it to the Eris article as well. Michaelbusch 00:57, 3 February 2007 (UTC)

From the cited article: "One faint source is seen near 2003 UB313 (Eris). ... We thus conclude that the source is a satellite moving with 2003 UB313. With only a single observation of the satellite of 2003 UB313, we cannot yet measure or constrain the mass of 2003 UB313, but we can estimate likely orbital parameters to aid further study." (emphasis mine) The article is about the sighting of the satellite, not the measurement of its orbit or the calculation of the dwarf planet's mass. -- Joshua BishopRoby 01:05, 3 February 2007 (UTC)

Further in the article, they estimate Dysnomia's period as 14 days. I asked Darin Ragozzine, one of Mike's students, if they had an orbit and consequently a mass & density, and he told me they did, and referenced that paper. It may be that I mis-understood him with regards to the reference, but they have the period and the mass. Michaelbusch 03:32, 3 February 2007 (UTC)

Alright, but you can't really cite the conversation that you had with an astronomer. I assume you mean the following passage: "If the semimajor axis is 14% greater than the current separation, and if 2003 UB313 has the size estimated by assuming an albedo and density similar to Pluto's (Brown et al. 2005a), the satellite will have an orbital period of approximately 2 weeks." They're not deriving the mass of Eris based on the orbit, they're deriving the orbit based on the mass of Eris, assuming Eris has the same albedo and density as Pluto, which is a mammoth assumption to make. Michael, can you provide a citation for the mass of Eris, not an estimate of the mass of Eris, or shall we put 'unknown' in there because the mass is, in fact, unknown? -- Joshua BishopRoby 17:40, 5 February 2007 (UTC)

They have the orbit now. I will check for more recent references. Note: we will never have anything other than an estimate for the mass of Eris or any other planet. Michaelbusch 18:05, 5 February 2007 (UTC)

The relevant paper would be M.E. Brown et al., 2007 in prep., which will be a paper giving the mass of Eris. It has not been published yet. Given this, we should place estimated tags (the mass and density given follow from the size and Dysnomia having a 14 day period. Presumably the paper will be more precise). Michaelbusch 18:27, 5 February 2007 (UTC)

Michael, could you please check out the recent addition to Eris (dwarf planet) (specifically the new sub-section "Mass and Density"). I suspect it could use a rewrite, but as it pertains to what you're discussing here, you're probably better suited to check it. Thanks. --Ckatz^chat_spy 20:19, 5 February 2007 (UTC)

I cleaned it up some. Hopefully, Mike will put out his paper giving the better mass value soon. Michaelbusch 20:25, 5 February 2007 (UTC)

Tables

I've noticed that the table showing the dwarf planets and the table showing the dawrf planet candidates do not match, on the dwarf planet table the names of the categories follow the Y-axis along the left while the candidate table has its category names along the X-axis at the top. Could someone change these two tables to make them similar? Ryan shell 18:58, 9 April 2007 (UTC) 18:57, 9 April 2007 (UTC)

That won't really do, both tables have a label column and three content columns, if either one is transposed, there will be far too many columns for the data to fit a sane web page view. Leave it as is. 128.227.68.14 15:35, 10 April 2007 (UTC)

4 dwarf planets?

I've been reading a special ASTRONOMY magazine, the 50 Greatest Mysteries of the Universe, and it says that the solar system has eight planets and 4 dwarf planets. Is it that they've made a typo error, or is it just me cause this article still mentions only 3 dwarf planets. — Alastor Moody _{(T + C + U)} 04:19, 22 May 2007 (UTC)

It's not a typo exactly. It's a common enough statement. Loosely it's true anyhow. Pluto and Charon orbit each other. The IAU because it had two proposals mixed people up. You'll also see some include already without IAU approval other planetoids too like Sedna. Yisraelasper —Preceding comment was added at 11:35, 1 January 2008 (UTC)

Dwarf planet

(I moved this from my talk page in case anyone else wants to participate)

Hello... sorry, but I had to revert your edit at Dwarf planet. Charon is a unique case in that it is thought to possibly be part of a double-planet system (well, double dwarf planet now), based on Charon's large size relative to Pluto. This is not official, as the IAU has made no formal decision in this regard. However, it has been mentioned as a possible candidate for dwarf planet status, and was actually under consideration for designation as a planet under the initial IAU proposal last August. Hope this helps. --Ckatz^chat_spy 07:45, 11 June 2007 (UTC)
P.S. Sorry about the lack of an edit comment at Dwarf planet - my bad.

Thank you for your courteous explanation, but I'm actually aware of these facts. Since the IAU hasn't made an official ruling, Charon is still orbiting Pluto (similar to how Pluto was still a planet while the debate about it's status carried on, and it changed whenn they made it official.) I agree with the proposal because the barycenter of their interaction is actually not inside either one, whereas the Earth/Moon barycenter is inside the diameter of the Earth making it obvious that the Moon is the one orbiting the Earth. However even though the proposal makes sense we ought not act like it has already been announced. Anynobody 07:57, 11 June 2007 (UTC)

Fair enough - the remaining mention of Charon under the table of candidates is probably enough (and less confusing than the text you removed later in the article.) Cheers (and thanks for the nice note on my talk page!) --Ckatz^chat_spy 08:34, 11 June 2007 (UTC)

You're very welcome, I was thinking that mentioning the discussion in the IAU about Pluto/Charon and a brief explanation of why they are possibly(probably IMHO) not in a d. planet/sat relationship would be informative(with a source of course). I was just browsing when I came across the basic issue we're discussing and hadn't planned to do much editing here, right now I'm just taking a quick break from the articles I am editing to see what else is going on Wikipedia so if you want to write something about it in it's own subsection of candidates I'd say go for it. (Reason for giving it a subsection is dwarf planet rule four is no sats so it needs to be made clear this is under debate.) Anynobody 09:05, 11 June 2007 (UTC)

Interesting dwarf planet candidate list

I thought some editors might find this interesting. They figure that 2002 UX25 is not a candidate, and that 1996 TL66 and Huya are. Of course, most of their candidates are up in the air, but just thought it was worth bringing up here. --Patteroast 00:01, 10 July 2007 (UTC)

Are these in our solar system?

This page doesn't make it clear if dwarf planets have only been discovered in our solar system, or if they've been discovered in other solar systems, too. It would be nice if someone could fix this so it's more clear. Thanks, Fredsmith2 20:13, 7 October 2007 (UTC)

Currently, the ability to discover dwarf planets outside of our solar system is beyond our abilities (other than possibly through a very lucky transit event). So, the question remains though (and I don't know the answer to this) does the definition of dwarf planet necessitate that the object be in our solar system (as the lede suggests)? Clearly, the definition as put forth by the IAU suggests this is the case ("is in orbit around the Sun"), but the definition of planet has the same wording, so I'm not sure what's appropriate here. Ben Hocking ^{(talk|contribs)} 20:36, 7 October 2007 (UTC)

I think what the resolutions mean is that the IAU has adopted actual definitions only for objects orbiting our Sun. If you look at the IAU document that is referenced in the article Extrasolar planets, you will see that they are far less precise regarding objects orbiting other stars. They use terms like "planetary companion" and mention that some of these objects may be "brown dwarfs" or other types of objects. It makes sense not to classify these objects, since we humans are really still at the very beginning of discovering them and figuring out what they are, and in most cases we haven't even "seen" them. The history of planetary discovery in our own Solar system suggests that caution is the correct approach; when Ceres, Pluto and other objects were first discovered, they were immediately classified as "planets", then eventually, as new objects were discovered, the astronomers figured out that this approach was not working. There's no rush in defining these things, we've got the rest of eternity. 6SJ7 01:31, 8 October 2007 (UTC)

Makes sense. Could someone who knows how to word it, please reword the first paragraph so that it reads that these are in our solar system? I'm a surgeon, not a bricklayer or an astronaut. Fredsmith2 00:45, 9 October 2007 (UTC)

It's already in the first sentence. Ben Hocking ^{(talk|contribs)} 01:20, 9 October 2007 (UTC)

Actually it's not beyond our abilities. The condition is, it has to orbit a pulsar. And yes, the IAU definition requires it to be in the Solar System, and so the planet. There is a draft resolution (2003) for the definition of planet outside the Solar System. 132.205.99.122 (talk) 23:14, 22 November 2007 (UTC)

sizes

I did a quick search to get diameter estimates. I left something of a mess, with multiple estimates, some of which are probably dated, in the hopes that someone who knows the reliability of the data would be able to clean it up a bit. kwami 14:28, 7 November 2007 (UTC)

nomination

The article has been nominated for Wikipedia:Article Collaboration and Improvement Drive.Nergaal (talk) 20:17, 20 November 2007 (UTC)

One of the things to clean up is the sortable table. The sorting doesn't work with exponentials. kwami (talk) 21:01, 20 November 2007 (UTC)

Somebody should check this link and update the article

http://www.sc.eso.org/santiago/science/OPSWorkshop/Contributions/Oral/S2_Tancredi_talk.pdf —Preceding unsigned comment added by Nergaal (talk • contribs) 17:35, 6 September 2007 (UTC)

Not a Satellite?

What does the IAU mean by "is not a satellite" in its definition of dwarf planet? This seems to directly contradict the first clause of the definition stating that it "is in orbit around the Sun."[[1]] By the standard definition of satellite, "a celestial body orbiting another of larger size," a dwarf planet orbiting the sun should indeed be considered a satellite.[[2]]
Cgnu 08:40, 6 May 2007 (UTC)

I noticed this too. The IAU website only lists the first three conditions. The fourth condition is mentioned on the NASA website but not on IAU. Can someone with more knowledge in the field enlighten us? My understaning is that satellites are in orbit around the sun (as well as a planet) and therefore the fourth condition is necessary to exclude the satellites from the definition of dwarf planets. Alex.g 22:36, 10 December 2007 (UTC) —Preceding unsigned comment added by Alex.g (talk • contribs)

"Dwarf" is the wrong term for what the IAU had in mind

The use of "dwarf" in this context is an adjective so a "Dwarf Planet" is still a Planet and not a separate classification of solar system objects.

This leads to the conclusion that all of the so called "Dwarf Planets" really are extra planets above the traditional 9 we all used to know about before this change in classification. —Preceding unsigned comment added by 81.174.240.178 (talk) 18:39, 26 November 2007 (UTC)

You are interpreting "dwarf planet" in an English context. "dwarf planet" is a single term, without an adjective. Sure, if astronomers were English majors, they might have though of doing it a different way... but they're not. 132.205.99.122 (talk) 22:40, 26 November 2007 (UTC)

Just the same in any other language. For example Russian "karlikovaya planeta", a direct translation of "dwarf planet" reads even more ugly than Eglish one (because it's too long in my mind) and can be interpreted as "very small planet". This is confusing both because dwarf planets are not too small (if to compare with minor planets for example) and are not planets at all in the current classification.--Dojarca (talk) 20:46, 28 November 2007 (UTC)

I agree though (with the section title) that the word 'dwarf' is a poor choice. But then, there are lots of poor wording choices that have become idiomatic in English. kwami (talk) 23:09, 28 November 2007 (UTC)

Isn't the use of dwarf in the English version kind of... offensive in regards to the perception of "dwarves" culturally? I know that calling a little person dwarf or midget is considered pejorative, for instance. —Preceding unsigned comment added by 24.148.118.190 (talk) 03:36, 2 December 2007 (UTC)

"dwarf" is very common in astronomy. white dwarf star, dwarf galaxy, red dwarf star... The Sun is a yellow dwarf. There's also a term called "degenerate dwarf" 132.205.99.122 (talk) 23:17, 6 December 2007 (UTC)

The word Dwarf Planet

The word Dwarf Planet is properly only for our solar system but it has gotten a looser usage too just like many words

Hello I realize that properly a Dwarf Planet is an object in the solar system. I was surprised and dismayed when I first learned that to a lesser degree it is being used for outside our solar system. That it has such a usage is all that is being pointed out by me. Yisraelasper (talk) —Preceding unsigned comment added by 67.171.69.206 (talk) 10:58, 1 January 2008 (UTC)

Preparing for GA/FA

I have worked on the article quite a bit. I need to add citations to where I allready placed the tags myself (i.e. the text is good but references are required for GA). If you have tips you are welcome to leave them here, or if you want to contrigute with references you are welcome too. Nergaal (talk) 10:40, 26 January 2008 (UTC)

I am done with the article. You are welcome to wikify it. Once the review is done, I am going to nominate it for GA/FA.Nergaal (talk) 13:52, 26 January 2008 (UTC)

merge section?

The "largest objects" section of Trans-Neptunian object duplicates the "candidate objects" section of this article. Since the physical parameters of these bodies are so uncertain, and there are so many estimates floating around, I think we should merge here to keep our account and references consistent. kwami (talk) 23:52, 26 January 2008 (UTC)

Sounds ok. There is also the option of transforming the table into a template; this could mean that it might be harder to edit the values (a good thing against vandalizations?).Nergaal (talk) 00:33, 27 January 2008 (UTC)

I think a template would be better. kwami (talk) 02:34, 27 January 2008 (UTC)

Successful good article nomination

I am glad to report that this article nomination for good article status has been promoted. This is how the article, as of January 28, 2008, compares against the six good article criteria:

1. Well written?: Pass. The article is very easy-to-follow and user-friendly, while still offering technical data

2. Factually accurate?: Pass. The inclusion of citations is very good, although a few sections still require citation

possible citation [3]Nergaal (talk) 03:16, 28 January 2008 (UTC)

3. Broad in coverage?: Pass. The article properly addresses the topic in all respects

4. Neutral point of view?: Pass. The discussion of the controversy was written with a very neutral POV.

5. Article stability? Pass. Although the article has undergone SIGNIFICANT changes recently, it is a new article and this is understandable. As the article is largely complete now, I expect it will stabilize.

6. Images?: Pass. Some articles simply can't have that many photos, and this topic is one of them. The few present photos accurately provide the necessary information, so there is no reason to fail this section.

If you feel that this review is in error, feel free to take it to Good article reassessment. Thank you to all of the editors who worked hard to bring it to this status, and congratulations.— Codharris (talk) 00:43, 28 January 2008 (UTC)

FAC

Anyone got any final suggestions before a FAC? Nergaal (talk) 11:41, 29 January 2008 (UTC)

Lead

Hi Nergaal.
In the lead: "it is suspected that more than 70 other objects in the Solar System might belong in this category" and
"there are estimates that the number might increase to 200 when the region known as Kuiper belt will be fully explored, and might be around 2000 when also objects outside this region will be accounted for"
These claims should be clarified. Indeed, what kind of numbers are we talking about? We first estimate 70 more dwarf planets in the Solar System but then correct this estimate? This seems contradictory unless the first claim is tweaked to something like: Ignoring the Kuiper belt and other regions of the Solar System, it is suspected that more than 70 other objects in the Solar System might belong in this category. Randomblue (talk) 11:20, 10 February 2008 (UTC)

How is it now? Nergaal (talk) 08:16, 11 February 2008 (UTC)

disambig planetoid

Randomblue (talk) 15:12, 15 February 2008 (UTC)

why? it is just that the linked article is a stub.Nergaal (talk) 15:59, 15 February 2008 (UTC)

Map request

A plot of the orbits of the known dwarf planets would be helpful. -- Beland (talk) 08:44, 2 January 2008 (UTC)

Pluto

I belive that Pluto... STILL IS FREAKING A PLANET!! —Preceding unsigned comment added by 66.32.5.212 (talk) 21:36, 21 February 2008 (UTC)

Pluto was declared a Dwarf planet during 2006. I guess it depends on what you mean by planet. Planets are planets, but the mid-sized dwarf planets and the smaller minor planets (AKA asteroids) are not planets by the current definition, even though they have "planet" in their name. Confused yet?

When Pluto was first discovered, it was thought to be larger than Mars and was thus categorized as a planet...but it turned out to be an icy body (high albedo) and thus was much smaller than the other planets, although still much larger than the asteroids. Then the Kuiper belt (sort of an asteroid/comet belt at the edge of the solar system) was discovered, and Pluto was labeled a Kuiper Belt Object. Still a planet? Then Eris (AKA Xena) was discovered, and suddenly there were ten planets...or perhaps eight.

If Pluto was as large as was originally thought, it would definitely be a planet. As it is, it's smaller than the other planets and much bigger than non-spherical asteroids (AKA the "minor planets." The debate on Pluto's status has been raging for some time. Twenty years ago, Isaac Asimov suggested the category of mesoplanet for objects bigger than Ceres and smaller than Mercury, which at the time would have put Pluto in its own category. With all these KBOs being discovered, however, it's likely that the register of dwarf planets will continue to grow. Arch O. La ^{Grigory Deepdelver} 18:05, 27 February 2008 (UTC)

I agree, Pluto is still a planet. Why is Wikipedia still using the discredited IAU definition of planet? There are other Astronomical organizations out there with different definition of Planet. Use a organization that is creditable. Not one that waited until only 400 people were left before taking a vote. Thats my opinion on the matter. Magnum Serpentine (talk) 14:28, 23 May 2008 (UTC)

As regards to definitions used in Wikipedia, if it after some years, happenstance occurs that humans cannot use the IAU definition because of it's linguistic flaws, we should consider disusing the IAU definition, but that will take a while, and personally I consider Pluto and Ceres being nice "sub-planets" - thingies that share some planet qualities but are too small to really be regarded as planets. "Sub" usually means "too small", "under" and "below". Said: Rursus ☻ 20:44, 15 July 2008 (UTC)

This is not the place to discuss whether or no Pluto is a planet. If you have information relating to the IAU being discredited or other large astronomical organizations that use a different definition of planet, make the edits and cite your sources. Remember that Wikipedia is not a forum.shaggy (talk) 00:03, 18 July 2008 (UTC)

Maybe, but the topic here is whether it is freaking a planet, and now we discuss terminology to be used. Rursus dixit. (^mbork³!) 16:42, 28 January 2010 (UTC)

Broken reference

Perhaps someone who can edit this page could update the broken reference to "The IAU draft definition of 'planet' and 'plutons'". The new location seems to be http://www.iau.org/public_press/news/release/iau0601/

Thanks! —Preceding unsigned comment added by 86.142.111.14 (talk) 19:49, 16 May 2008 (UTC)

I added new link. Ruslik (talk) 08:46, 17 May 2008 (UTC)

Plutoid

Looks like "dwarf planet" has been replaced with "plutoid" for objects beyond Neptune.

http://www.space.com/scienceastronomy/080611-plutoid-planets.html

What verification is needed before making the appropriate changes to this article? Daveharr (talk) 15:30, 11 June 2008 (UTC)

I think it hasn't, I think the taxo tree is:

• "Dwarf Planet" - a not-cleared-the-neighborhood "sub-planet",
  • Plutoid - a not-cleared-the-neighborhood "sub-planet" in the "outer solar system"
  • the rest - Ceres.

Said: Rursus ☻ 20:29, 15 July 2008 (UTC)

(A dwarf elephant is a non-elephant that hasn't cleared his neighborhood, such as Joe, Jim and Bill) Said: Rursus ☻ 20:31, 15 July 2008 (UTC)

Sorry, again: I think it hasn't, I think the taxo tree is:

• "Dwarf Planet" - a not-cleared-the-neighborhood roundish non-planet which is not a star,
  • Plutoid - a not-cleared-the-neighborhood roundish non-planet which is not a star, and that is in the "outer solar system"
  • the rest - Ceres.

Said: Rursus ☻ 20:34, 15 July 2008 (UTC)

Sorry, again: replace "star" with "fusor"! A "fusor" is a star or a Brown Dwarf. Said: Rursus ☻ 20:39, 15 July 2008 (UTC)

Neptune

Is it not true that Neptune shares its orbit with Pluto in some fashion? If Pluto is a KBO and a dwarf planet, would not that mean that Neptune, which crosses Pluto's orbit, has not cleared its neighborhood of KBOs? Should not then Neptune be considered a dwarf planet? I have 2 points here: 1, There is no upper limit on the size or mass of dwarf planets. 2, Neptune, by virtue of Pluto and other KBOs in the vicinity, has not cleared its neighborhood. Therefore, Neptune is a dwarf planet.

It seems to me that the definition of "Dwarf Planet" was tailored specifically to stop debates about Pluto and other "Dwarf Planets" but they failed to try to apply the definition to the other planets to see if they would be reclassified as well.

If the IAU's word is authority (there are not authorities in science), then I say that Neptune is infact a dwarf planet. If the Trojan Asteroids were not in Jupiter's Lagrange Points, I would venture so far as to declare it a dwarf planet as well. But even then, this means that Neptune, having not cleared its vicinity of smaller objects and even failing to clear it of planetesimals such as Pluto, is a dwarf planet. Meanwhile, Earth, having even gone so far as to absorb a Mars sized planet (or as commonly theorized for the creation of the moon), is a Super Planet. Doesn't this seem a little disproportionate?

In closing, I declare the IAU about as schizophrenic as any committee can possibly get. 9,664 voices in the IAU's head, apparently it's too noisy to actually come up with anything that actually makes sense. 24.254.163.150 (talk) 16:25, 11 June 2008 (UTC)

Actually, Neptune has cleared the neighborhood. Pluto is in a resonant orbit, which means it is dominated by Neptune. Read cleared the neighborhood for the practical meaning of the phrase. kwami (talk) 18:54, 11 June 2008 (UTC)

As far as I'm concerned, Pluto's orbit is too close to Neptune's orbit to let Neptune off the hook. Neptune hasn't cleared out Pluto or any of the other stuff that Pluto hasn't cleared out. It's a dwarf planet, ironic considering it's probably also a super planet. As for the "orbital resonance" nonsense. That's explicitly defining an arbitrary exception. I'm sorry, but REAL scientists have no room for needless use of arbitrary definitions. The only time science needs to get arbitrary is when dealing with a purely arbitrary subject, not making excuses for definitions. Such as defining a planet's meridian. But even then, the equator would still be defined on a non-arbitrary piece of data. I reject the definition of "dwarf planet" and "plutoid" because of its silliness. Neptune is a dwarf planet, but not a plutoid, as Neptune cannot be beyond Neptune. And if the IAU had it's way, there are no extra solar planets, just a bunch of silly people measuring star wobbles. If we brought Richard Feynman back to life, he likely wouldn't even be interested in the IAU's recent incoherent babbling. That's because zombies are attracted to brains, and the IAU has very little of that it seems. In closing, I am also not adding "plutoid" to the spell checking dictionary on FireFox as it's not even a valid scientific concept, let alone a real word. 24.254.163.150 (talk) 17:28, 14 June 2008 (UTC)

You didn't bother to read the article, did you? kwami (talk) 17:58, 14 June 2008 (UTC)

Makemake

Here are the numbers for the "Planetary discriminants" table for Makemake: mass 6.7e-4; Λ/ΛE 1.447e-9; µ 0.02. I used wiki's data on Makemake's mass. For µ, both the Pluto and Eris entries seem to assume the "other mass" is about 1.7e23kg, so that's what I used. —Preceding unsigned comment added by 65.94.6.168 (talk) 14:59, 14 July 2008 (UTC)

Since this is a FA, I would prefer a reference for these numbers... :( Nergaal (talk) 15:43, 14 July 2008 (UTC)

I think the table is from some scientific paper published like 8 years ago. The authors are not going to deliver an updated version for us. It's not Forbidden Original Research to divide "2" by "4" and get "0.5". This isn't even a matter of unnecessary information in an extra paragraph, it's a big blank space in a table, the info should only be removed if it's wrong. 64.122.41.167 (talk) 04:31, 21 July 2008 (UTC)

Hence the un-smiley in Nergaal's post... From my point of view, we should reference the Makemake data, and give a note in the cite saying which value we are using for the "other mass". Simple calculations are, of course, not original research. For example, see this section of the Wikiproject Physics guidelines. Bluap (talk) 04:56, 21 July 2008 (UTC)

Inconsistancy Concern

I've started a discussion at Talk:Ceres_(dwarf_planet)#Inconsistancy_Concern over problems relating to information consistancey between this and two other articles. Gnangarra 06:00, 15 July 2008 (UTC)

Incorrect parenthetical note

I can't edit the page so I'll mention that in the "Current members" section the parenthetical referenece to Neptune's discovery is wrong: Ceres was discovered 45 years before Neptune, not 16. —Preceding unsigned comment added by 129.162.1.41 (talk) 13:24, 23 July 2008 (UTC)

Thank you for taking the time to note that. -- Kheider (talk) 14:23, 23 July 2008 (UTC)

Stern

According to the current text of the article, Stern recognizes dwarf planets as planets, & counts Pluto as the 9th planet. This appears to be inconsistent:

• Pluto would not be the 9th planet from the sun; Neptune would
• Pluto would not be the 9th planet in size; Eris would
• Pluto would not be the 9th planet to be discovered; Neptune would

In what sense would Stern count Pluto as the 9th planet if dwarf planets count as planets? I tried following the link given in the ref note, but it seems irrelevant; perhaps changed since retrieval. Peter jackson (talk) 08:27, 31 July 2008 (UTC)

Stern recognizes Pluto as a planet. The problem disappears if we don't assume he recognizes Ceres as a planet just because people he doesn't agree with have classified Pluto and Ceres under one label. kwami (talk) 08:56, 31 July 2008 (UTC)

But that's not what the article says. It says he counts dwarf planets as planets. Peter jackson (talk) 08:12, 1 August 2008 (UTC)

Nowhere the article says that he counts all dwarf planets as planets. Ruslik (talk) 11:12, 6 August 2008 (UTC)

No, he doesn't recognize that 'dwarf planet' is a valid category distinct from 'planet'. Ceres is still an asteroid, and Pluto the 9th planet. I don't know if he considers Eris the 10th planet, but for him it doesn't affect the status of Pluto. kwami (talk) 08:22, 1 August 2008 (UTC)

Again, I repeat: that's not what the article says. It says he recognizes dwarf planets as planets. If you think that's wrong, change the article & supply a reference. If somebody thinks the article is right, could they supply a reference? If nobody can find a reference, the material should be deleted.

More generally, if you go back to the proceedings at the IAU Congress, you find there were only 2 proposals on the table:

1. final official decision
   1. planets
   2. dwarf planets
   3. SSSBs
2. committee recommendation
   1. classical planets
   2. dwarf planets
   3. SSSBs

The only difference is on the 1 word "classical". Virtually nobody voted against both proposals. Unless something's changed since then, it seems reasonable to assume that virtually all astronomers follow 1 of these. Peter jackson (talk) 10:14, 6 August 2008 (UTC)

I'm sorry, I just don't see anywhere in the article where it says Stern recognizes dwarf planets as planets, so I don't know how to answer this. kwami (talk) 16:49, 6 August 2008 (UTC)

"Thus, he and his team still refer to Pluto as the ninth planet, while accepting the characterization of dwarf planet for Ceres and Eris (dwarf planet in this case meaning just a small planet)." Doesn't the bracketed material clearly imply that? Peter jackson (talk) 17:25, 7 August 2008 (UTC)

History of the name

That's what the section's called, but it seems to be mainly about the history of the concept. It doesn't even mention that the name was proposed in the original committe recommendation. Peter jackson (talk) 10:27, 6 August 2008 (UTC)

move 2003 EL61 to 'dwarf planet'

2003 EL61 is a dwarf planet "for naming purposes". That's all Makemake is too, but we've moved that to Makemake (dwarf planet). I propose we do the same here: the only difference with 2003 EL61 is the dispute over who discovered it, which prevents it from going through the naming process. That has absolutely nothing to do with the nature of the object.

I placed a Move? tag on the article's talk page. kwami (talk) 06:48, 27 August 2008 (UTC)

Makemake was categorized as a dwarf planet officially; 2003 EL61 was not. We have to wait for the IAU. --Ckatz^chat_spy 07:27, 27 August 2008 (UTC)

But it is a dwarf planet according to the IAU definition of a dwarf planet. Effectively, then, the phrase is not a scientific term at all if the body cannot be demonstrated to have achieved h-equilibrium, but a bureaucratic one. Perhaps we should reword this article to make that clear? kwami (talk) 07:44, 27 August 2008 (UTC)

I prefer to wait until it receives a name. EL61_(dwarf_planet) is not a good title for the article. Ruslik (talk) 09:30, 27 August 2008 (UTC)

I agree with the idea of WAITING until it has a real name. The public will appreciate it more when it has a real name. License plate numbers do not go well with the public. Besides, as a minimum, we need an official IAU statement declaring it as a plutoid or dwarf planet. In twenty years few will remember "2003 UB313", "2005 FY9", or "2003 EL61" by their license plate names. I see no problem with it being the top candidate. -- Kheider (talk) 16:11, 27 August 2008 (UTC)

I think this is a case where the No Original Research rule comes in. We can't decide for ourselves whether something is a dwarf planet. Peter jackson (talk) 17:11, 27 August 2008 (UTC)

Haumea (2003 EL61) is now officially a dwarf planet: http://planetarynames.wr.usgs.gov/append7.html#DwarfPlanets —Preceding unsigned comment added by 65.94.39.95 (talk) 19:49, 17 September 2008 (UTC)

Spherical?

There are some references to spherical, near-spherical or spheroidal shape as a requirement for being classified as a planet. However eg Haumea is none of these, but ellipsoidal (triaxial, longest axis = 2x shortest), and according to the first paragraph the requirement is only to be rounded by its own gravity.--87.162.18.193 (talk) 16:00, 18 September 2008 (UTC)

Yes, that's better wording. kwami (talk) 19:47, 18 September 2008 (UTC)

Link Error

Discusion of link error obviated by fix.
The following discussion has been closed. Please do not modify it.
The link for Reference item #50 is broken. The "/" at the end of the link needs to be removed. VirtualDave (talk) 05:15, 6 December 2008 (UTC) I tried to fix it. It's in a template for the table. I edited and saved the template, and the diff shows in my contributions [4], but the same error still appears on the main page. Someone else will have to do it. -- Another Stickler (talk) 12:41, 6 December 2008 (UTC) Links fine for me. Maybe you just needed to clear your cache. kwami (talk) 12:46, 6 December 2008 (UTC) It works now for me now too, so it must have been the cache showing me the old version. I'm folding up this section. If anyone knows how to archive it, I think that will save some load time. -- Another Stickler (talk) 17:32, 7 December 2008 (UTC)

Pluto is smaller than the moon

This is probably the best reason for Pluto not to be a real planet anymore. People are always assuming that it is larger than it is. Pluto (radius 1195km) is physically smaller than the Earth's moon (radius 1738.1 km). That would give Pluto only 68.7% the diameter of the moon. -- Kheider (talk) 17:55, 31 December 2008 (UTC)

If the Moon were in its own orbit, it would almost certainly considered to be a planet. There are a number of moons in the solar system which would be planets if they were in their own orbit, so I don't think being smaller than the moon is relevant.--RLent (talk) 20:04, 31 December 2008 (UTC)

Actually I mainly posted the above statement because someone had incorrectly updated the Physical attributes of dwarf planets table using the radius of the moon compared to the diameter of Pluto, and came up with Pluto and Eris being larger than the moon. I see this common mistake all the time. Since Pluto was known as a planet everyone seems to subconsciously perceive it as larger (and thus more exciting?) than our moon. -- Kheider (talk) 20:17, 31 December 2008 (UTC)

Dead link

Reference [26] does not work.--Roentgenium111 (talk) 22:45, 2 February 2009 (UTC)

Fixed. ... said: Rursus (bork²) 15:19, 5 February 2009 (UTC)

presentation order

There are two presentation orders that make sense to me: physically, by orbital period, and historically, by date. Discovery date doesn't work very well, though: do we use the IAU email date, the observation date, the precovery date, the date s.o. realized how big the object was, etc. I think the date the object was classified as a DP works best. That's what we all remember, at least, when the official announcement was made by the IAU. However, that causes some problems with the first three, which maybe we can discuss here? Ceres was the first demoted planet, so in my mind it should be first on the list. The difference in announcement date between Ceres, Pluto, and Eris was at a time when the whole DP concept was being ironed out, and speaks more of politics than history IMO. So the most natural order to me is Ceres, Pluto, Eris, Haumea, and Makemake. kwami (talk) 10:39, 16 February 2009 (UTC)

M was announced before H. Peter jackson (talk) 10:58, 30 March 2009 (UTC)

Haumea's orbital period: 283 or 285.4 years?

This article gives Haumea an orbital period of 285.4 years, while the Haumea (dwarf planet) and Makemake (dwarf planet) articles give around 283 years. Which is correct? The Haumea article suggests that the 283 figure is more consistent with a 12 : 7 resonance between Haumea and Neptune, whose orbital period is 165 years. Glenn L (talk) 15:33, 29 March 2009 (UTC)

The orbital peroid of all bodies is dynamic and varies depeding on the Epoch (astronomy) used, ie 1950 vs 2000. JPL currently uses an epoch of 2009 and shows a peroid of 283 years. Buie and the Deep Ecliptic Survey (DES) use an epoch of 1955 show an orbital period of 285 years. Neither is wrong because they are using different dates. -- Kheider (talk) 17:06, 29 March 2009 (UTC)

Grammatical error in section: History of the concept

The following line refers to a plural subject but uses the singular artical "a". For correct grammar, please remove the "a".

"...started to be used for the bodies now known as a dwarf planets." —Preceding unsigned comment added by Mrbynum (talk • contribs) 17:29, 6 May 2009 (UTC)

Logically inconsistent definition

The very first sentence of this article presents a logically inconsistent definition of "dwarf planet". It states:

"A dwarf planet, as defined by the International Astronomical Union (IAU), is a celestial body orbiting the Sun that is massive enough to be rounded by its own gravity but has not cleared its neighbouring region of planetesimals and is not a satellite."

This definition includes these propositions: A - A dwarf planet orbits the Sun. B - A dwarf planet is not a sattelite.

Now, a satellite is an object in orbit around another object*. So the intersection of A and B is the empty set. Okay, fine, maybe it's not technically logically inconsistent, but it is vacuous. Then the article goes on to list some specific examples of dwarf planets, none of which satisfy the definition (of course since nothing could possibly satisfy the definition).

*Technically object A is a sattelite of object B if and only if the they orbit a center of gravity of the two object system that is located within the volume occupied by object B.

How do they not satisfy the definition?

Satellites orbit the Sun. They just do so while simultaneously orbiting another body. Maybe the IAU felt they had to spell this out for the overly literal.

That is not the technical definition of a satellite. It has been proposed, but AFAIK has never been adopted by the IAU. It causes problems because a distant object might not qualify as a satellite despite being small. For example, the center of mass of the Sun-Jupiter system lies outside the Sun, so if we took your technical definition as a general statement of one body orbiting another, Jupiter would not qualify as a planet, but instead would be one component of a failed double star system.

Hey, this is fun! Let's take your technical definition as a general definition of "orbit". Then we have seven planets, and Jupiter is presumably a failed star. Since the Galileans have cleared their orbits, they are planets, bringing the total to eleven. However, the IAU definition of a planet is that it orbits the Sun, but the IAU still speaks of extra-Solar planets, so the logical conclusion is that the Sol system consists of 11 planets: 7 Solar planets, and 4 extra-Solar planets.

Another problem with the IAU ruling is that planets are satellites by definition, since they orbit their primary, and that's all a satellite is.

(Lest anyone take me too seriously, I am not proposing that we make the claim that the Solar system has eleven planets.) kwami (talk) 06:29, 18 May 2009 (UTC)

Perhaps worse yet, using the barycenter definition, some satellites on an elliptical orbit could travel in and out of the "definition zone" with every orbit... There will never be a perfect definition of a planet. -- Kheider (talk) 13:34, 18 May 2009 (UTC)

Someone did point that out to them, & they changed the wording to say the majority of the time, or some such. Academic anyway, as the definition was never adopted. Peter jackson (talk) 17:38, 27 August 2009 (UTC)

The definition is simply incomplete. The word Sun is used when the more general term of "a star" would be more appropriate. The writers of the definition simply assumed that anyone would realize that. The IAU also assumed that it would be obvious that a satellite orbits another body that, in turn, orbits a star. If an object directly orbits a star it is a planet(or dwarf planet, or planetessimal, etc.) Khajidha (talk) 22:58, 23 October 2009 (UTC)

Yes, it's incomplete. It was intended to define only planets of our sun. Why, I don't know. The 2nd part of your remark is correct. Peter jackson (talk) 09:31, 24 October 2009 (UTC)

Honestly I think we shouldn't get too bogged down in the definition of a satellite and use a clearly stated explanation of our own that follows the *intent* of the IAU ruling but makes it clearer to the average user of Wikipedia. Something along the lines of "is a celestial body that primarily orbits a star rather than a planet, and is massive enough to be rounded by its own gravity but has not cleared its neighbouring region of planetesimals." —Preceding unsigned comment added by 86.50.88.77 (talk) 13:23, 1 January 2010 (UTC)

Since we're getting off base here in debating the science ( a good thing) rather than critiquing the article (which can also be a good thing) let me add: astonomically a satellite is understood to be a natural object that orbits a planet. The term is synonymous for moon, which as I understand it is officially reserved for the Moon, which orbits our earth. True, planets are "satellites" of the sun and satellites of planets, i.e. moons do orbit the sun along with their planets, and smaller stars in binary pairs do orbit larger stars as so too are satellites. But that's not what is to be understood when the term is seen.

As for Jupiter, yes it could be oonsidered a failed star, not because the berycenter is outside the sun, but because its mass appraches that necessary to begin deuterium burning. As it stands it falls well within the sensible definition of a planet.

cheers and regards J.H.McDonnell (talk) 00:47, 25 October 2009 (UTC)

Weasel words; Describing the reaction to the IAU definitions

As of the time I accessed this page, the second paragraph of the introduction contained weasel words. "The definition officially adopted by the IAU in 2006 has been both praised and criticized, and remains disputed by some scientists." This unsourced, weasel word claim does not belong in the introduction to a Featured Article. MathEconMajor (talk) 13:48, 27 August 2009 (UTC)

Nonesense; evem though I wouldn't rate this as a featured article in the first place. Interesting, informative, and debative maybe J.H.McDonnell (talk) 00:29, 25 October 2009 (UTC)

I know it has been criticised, f.ex. by Alan Stern, I also believe the definition has been defended, f.ex. by the Eris discoverer Mike Brown, so the statement is simply true. Although a few more citations would make the support for the statement better. ... said: Rursus (^mbork³) 15:50, 8 December 2009 (UTC)

The fact that, after 3 years of criticism, the next IAU Congress apparently didn't even discuss changing the definition suggests it's been accepted by most astronomers. It seems reasonable to mention opposition, but not to give it any sort of equal treatment. Peter jackson (talk) 10:51, 9 December 2009 (UTC)

I believe you're wrong about it being "accepted". The troubles will occur when major exoplanets that haven't cleaned up their orbits will be discovered. I think that most astronomers find the definition only being an "administrative one", not touching their research and being a futile thing to discuss. Nevertheless, we can await future troubles silently too. Rursus dixit. (^mbork³!) 16:52, 28 January 2010 (UTC)

The line between a protoplanet (still undergoing significant growth and and clearing its orbit) and a grown-up planet will always be somewhat blurry. For example, when exactly did Jupiter move from a protoplanet to a planet? You could base an answer on mass, how clear Jupiter's orbit is, or how clear the solar system is as a whole. -- Kheider (talk) 18:28, 28 January 2010 (UTC)

I don't think Rursus' remarks contradict mine. There can be various sorts of & reasons for acceptance. Peter jackson (talk) 14:34, 29 January 2010 (UTC)

Sorting

For some reason, when the table is sorted from most massive to least, Saturn comes first. The list works when sorting in the other direction, though.128.211.167.139 (talk) 22:46, 1 September 2009 (UTC)

Not in my browser. Either there was some trouble that have been fixed, or the trouble is still there, but doesn't occur in the Gecko engine (same as Mozilla Firefox) on Epiphany 2.22.3. The sortable tables are implemented in JavaScript/JScript/EcmaScript, and the behavior might vary depending on bugs in the WWW browser used. In the later case: just wait and upgrade your browser to get the old bugs substituted for brand new ones. Exciting, isn't it!? ... said: Rursus (^mbork³) 15:55, 8 December 2009 (UTC)

Ahistory

In the section History of the concept, second paragraph:

In the 1990s, astronomers began to find objects ...

and later same paragraph:

Several terms including minor planet, subplanet, and planetoid started to be used for the bodies now known as dwarf planets.

gives the reader a very distinct impression that the terms minor planet etc. were starting being used after 1990, which is of course quite wrong: at least the terms minor planet and planetoid were used maybe starting in the 19th century as aliases for asteroid. The trouble is, that if the terms are to be introduced at that place in the paragraph, the grammatical verb tense must be Present perfect tense or Pluperfect tense to indicate that the terms were coined early in the place where they're mentioned. Rursus dixit. (^mbork³!) 17:03, 28 January 2010 (UTC)

Yes, those terms were both used in the early 19th century. Peter jackson (talk) 17:37, 28 January 2010 (UTC)

Eris link

I believe the link in the "Eris" image would better point to: Eris (dwarf planet), instead of simply Eris. thanks. —Preceding unsigned comment added by 189.63.148.139 (talk) 10:54, 18 February 2010 (UTC)

 Done. -- Kheider (talk) 11:15, 18 February 2010 (UTC)

Consistency

Is it actually so hard to keep it consistent even inside of one article? The tables have somewhat different facts; Current members section tables vs Prime plutoid candidates table. Pluto's stats are close enough, but
-Haumea has 1050-1400 for diameter and 41-43 for mass in the first, 1436 and 40 in the latter.
-Makemake has 45.79 for distance and ~40 for mass (first), 45.3 and 30 (latter)
-Eris 67.67 for distance and 2300-2500 for diameter (first), 68.0 and 2600 in the latter.
Which ones are the right? The Current members section's 'Physical attributes' table has two citations marked for each, so those could be the right ones... 85.217.20.77 (talk) 22:49, 27 September 2010 (UTC)

The orbits will vary based on the epoch used to retrieve the data and to a less extent orbital refinement as a result of larger observation arcs. Pluto varies somewhat less simply because it has a better determined orbit and whips around the Sun relatively fast and stable 3:2 resonance. Using a 1954 epoch Eris has a semi-major axis of 67.7, using a 2010 epoch you get a semi-major axis of 68.0. Makemake: 1995=45.79 and 2010=45.3. The orbital values are not fixed numbers with only one correct solution. -- Kheider (talk) 06:39, 28 September 2010 (UTC)

WP:CLEANER

I've ran WikiCleaner through this and simplified a lot of redirects (piping them), so if there's any problems with them, just go-ahead and fix them.
Thanks
--George2001hi (Discussion) 18:17, 15 October 2010 (UTC)

Asteroids

About a quarter of the asteroids are known to be spherical because they are presumably loose rubble remaining from outgassed comets and/or gravitational aggregations of smaller asteroids, or collision fragments, etc. Are they all technically dwarf planets under the present definition? Ginger Conspiracy (talk) 21:06, 14 November 2010 (UTC)

It would appear not. They'd still have to clear an orbit, & most asteroids aren't in "clean" orbits. TREKphiler ^{any time you're ready, Uhura} 21:36, 14 November 2010 (UTC)

A quarter of the asteroids are known to be spherical? You would need a reliable reference for that statement. As far as I am aware most asteroids when viewed up close are irregular in shape. Needless to say, even if some asteroids are spherical, very few are massive enough to be in hydrostatic equilibrium. -- Kheider (talk) 23:08, 14 November 2010 (UTC)

Actually only Ceres is spherical. Vesta and Pallas are nearly spherical but not completely. All other asteroids are highly irregular. Ruslik_Zero 19:05, 2 December 2010 (UTC)

Vesta was almost certainly once in equilibrium, given that it has a basaltic surface. The question is whether that's enough to qualify it as a DP today. — kwami (talk) 21:14, 2 December 2010 (UTC)

wait, what?

"The classification of bodies in other planetary systems with the characteristics of dwarf planets has not been addressed,[10] although if they were detectable they would not be considered planets." If a body in another planetary system is detectable, it would not be considered a planet? 66.41.250.223 (talk) 06:38, 11 December 2010 (UTC)

It means a "dwarf-planet-like body" in another system would not be considered an (exo)planet, not any body.--Roentgenium111 (talk) 15:33, 11 December 2010 (UTC)

Reference list

I suggest the implementation of {{Reflist|colwidth=45em}} on this article, because of the length of the reference list. Opinions, rejections? —bender235 (talk) 10:51, 16 December 2010 (UTC)

Would you prefer me to take it back? I can if you want, it just wasn't registering as double-columned. :) -That Ol' Cheesy Dude (talk)

Whether {{Reflist|colwidth=45em}} produces double-columns depends on your screen size.

Given the fact, that most of the references are very long, {{Reflist|2}} should not be used because a smaller screen resolution (1024x768 and smaller) would produce too many line breaks. —bender235 (talk) 18:08, 1 January 2011 (UTC)

Definition: Orbiting the sun, or a sun/star?

The article begins with A dwarf planet, as defined by the International Astronomical Union (IAU), is a celestial body orbiting the Sun. Is that the precise wording? If so, similar objects in other solar systems would be excluded. Is that correct? samwaltz (talk) 18:39, 16 December 2010 (UTC)

Technically, there is only one Sun (the star at the center of the Solar System). For other planetary systems there are currently only planet-like bodies and asteroid-like bodies. Heck even now masters and apprentices do not agree on the exact definition of a comet. :) -- Kheider (talk) 19:01, 16 December 2010 (UTC)

I'm pretty sure that was the wording used. At the time, I don't think anyone was really thinking about other solar systems. Given the problems we have detecting larger bodies around other stars, it doesn't seem likely that the question would be relevant. If/when such bodies are found the definition would probably be amended as your title suggests. --Khajidha (talk) 19:03, 16 December 2010 (UTC)

No new dwarf planets?

Eris was discovered five years ago and there have been no other dwarf planets since then? Does this call the definition into question again? Algr (talk) 16:55, 1 November 2010 (UTC)

Astronomers are basically finished searching from the Northern hemisphere, and are just now getting started with a Southern hemisphere search. There is no scientific need for non-dominant bodies like Eris, Pluto, or for that matter our moon to be full fledged planets. -- Kheider (talk) 17:07, 1 November 2010 (UTC)

And don't forget there are dwarf planet candidates. Rothorpe (talk) 18:31, 1 November 2010 (UTC)

Why would the number of dwarf planets call the definition into question? Since there is a fairly small window into which an object can fall to be called a dwarf planet, I would expect a fairly low number of them to exist. --Khajidha (talk) 18:48, 1 November 2010 (UTC)

Under the current definition, Jupiter would be classified as a dwarf planet if something larger drifted into it's orbit. One of the main arguments for demoting Pluto was that not doing it could result in 100 planets in our solar system. But it seems that that isn't going to happen. And in any case, there used to be 4 natural elements, and now there are over 100, but no one started insisting that atoms have to clear there outer orbits of electrons to be elements. Algr (talk) 17:39, 2 December 2010 (UTC)

There are many dwarf planet candidates and we will probably never know exactly how many of them are ~600km in diameter and in hydrostatic equilibrium. We will probably NEVER discover all of them since some of them will be near their farthest point from the Sun and will be very difficult to detect, much less study in detail. Dwarf planet candidate 2010 EK139 with an absolute magnitude of 3.8 would be the most notable discovery this year and might be a dwarf planet. Anything larger than Jupiter crossing Jupiters orbit would make the Nibiru collision look like nothing. -- Kheider (talk) 18:34, 2 December 2010 (UTC)

What he said. Also, the example of the natural elements doesn't really apply here. Individual elements are discrete things while planets, dwarf planets, small solar system bodies, etc are terms. They exist only as divisions along a continuum of objects. You may not like where the IAU has drawn those lines but they at least give reasons for those definitions. The "Pluto is a Planet" movement has not come up with any rationale that would keep Pluto on the list but exclude the other dwarf planets (which the Pluto boosters don't consider planets). --Khajidha (talk) 16:14, 16 December 2010 (UTC)

If something did come along and eclipse Jupiter and do as you propose, then of course you'd have to rethink things. However there isn't any evidence of that sort of occurrence happening. You can only classify what you have seen. 90.219.201.36 (talk) 16:57, 19 May 2011 (UTC)

PLuto I've been told is a dwarf planet. Unfortunelty cause I have to learn the order of planets again. Now Has anyone heard of Planet X and is that a dwarf planet? 76.229.230.146 (talk) 22:57, 16 December 2010 (UTC)

Planet X is indeed a Dwarf Planet. It was officially named Eris 90.219.201.36 (talk) 16:57, 19 May 2011 (UTC)

I should add that by Planet X, i assumed you meant the Tenth Planet found as reported in the mid 90s as opposed to the object that astronomers were searching for for over a century earlier, which they now believe doesn't exist 90.219.201.36 (talk) 16:40, 20 May 2011 (UTC)

Equilibrium vs. differentiated interior

I was wondering, is there, from a theoretical perspective, a link between achieving hydrostatic equilibrium and the formation of a differentiated interior? The section on Size and mass suggests there is, but it isn't spelled out anywhere. --JorisvS (talk) 20:22, 24 June 2011 (UTC)

There's a link, but I'm not sure we know how robust it is. Pallas is partially differentiated, or so we think. Vesta should be; maybe we'll have better answers in a couple months. — kwami (talk) 18:03, 4 July 2011 (UTC)

Table "Physical attributes of dwarf planets"

The entry for Haumea seems a bit problematic. The issue probably has to do with its ellipsoidal shape. If you plug in 1150 km as the diameter of the dwarf planet, and use a density of 2.6-3.3 g/cm^3, you get a mass of 2.8-3.5% of the Moon's mass -- not 5.7%.

Incidentally, what does "diameter" even mean for an oblong body like Haumea? Does it mean the diameter that a spherical body would need to have, given its suspected albedo, in order to be as bright as it is? Would it not make sense to give the dimensions 1,960 × 1,518 × 996 km, or at least take their average in some way? Maybe there's a way to briefly explain this, as a footnote to the table. Kier07 (talk) 17:03, 3 August 2011 (UTC)