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Archive 5Archive 6Archive 7Archive 8

Mimas

Mimas is known not to be in hydrostatic equilibrium despite its roughly round shape.--Reciprocist (talk) 15:27, 9 October 2015 (UTC)

So? The article says it is not in hydrostatic equilibrium. By the way, why are moons of saturn being discussed in the dwarf planet article? Huritisho 17:13, 9 October 2015 (UTC)
I've just removed info related to moons of Saturn. The paragraph I removed was entirely about moons, and it added nothing of value since it contradicted itself (first, it was taking into account Mimas was in hydrostatic equilibrium, but later, it turns out it was not). That's just fluff. Huritisho 17:26, 9 October 2015 (UTC)
Saturn's moons are discussed because Saturn has 7 large spherical moons and we know them better than any other set of moons in the Solar System. I think deleting that content might be a bad idea. -- Kheider (talk) 17:28, 9 October 2015 (UTC)
Good. But discuss them in Moons of Saturn. That size and mass section (now called "hydrostatic equilibrium") is already long enough. Also, there is a "main article" link, so the section should be just a summary. Huritisho 17:42, 9 October 2015 (UTC)
The point of mentioning them is to sketch our knowledge about when objects can be expected to be round and which of those can be expected to be in hydrostatic equilibrium. The Saturn system is the only system that can provide us with examples relevant to the trans-Neptunian region. --JorisvS (talk) 12:48, 10 October 2015 (UTC)
Blanking the information about moons probably just makes it more difficult for the reader to know about examples of HE. Because of Cassini–Huygens we know a great deal about the Saturn system. I may revert you because other people do not agree that all of this belong at HE. See: Talk:Hydrostatic_equilibrium#Article_too_focused_on_astrophysics. -- Kheider (talk) 13:28, 10 October 2015 (UTC)
I've been thinking of re-writing the last couple of paragraphs. They confuse the idea of gravitational relaxation with having a particular shape (the shape is a consequence of the relaxation, and so a necessary condition, but not a sufficient condition), misunderstand Cole's work, and add in Lineweaver-Norman (which is a bit different from Cole and more directly relevant to DP-ness). Including the empirical evidence from the well-observed moons belongs here, too, since it's the closest data we have to what the transition might be like in the trans-Neptunian zone. And little Methone illustrates that even equilibrium is not sufficient, that DP-ness requires the equilibrium to be due to the breaking of the material bonds. Tbayboy (talk) 16:48, 10 October 2015 (UTC)
I strongly disagree with re-adding information about the moons of Saturn, but if that's a consensus, then what can I do. Huritisho 17:24, 10 October 2015 (UTC)
Since the page is "dwarf planet", not "moons of Saturn", I'd tend to disagree, too, but...I can see a need for explaining. I'm just not sure this is the place for it. Isn't hydrostatic equilibrium the place, if anywhere? There, the examples can be used without straying too far afield. TREKphiler any time you're ready, Uhura 18:03, 10 October 2015 (UTC)
Other than the potential for tidal forces acting on a moon, there is very little difference in the physical characteristics of a dwarf planet and a large spherical moon. -- Kheider (talk) 19:08, 10 October 2015 (UTC)
"there is very little difference in the physical characteristics" It's not the characteristics that are at issue, really. It's what's being discussed that is. The similarity seems better handled at a page designed for dealing with the common issue than at one intended for something quite different in objective. TREKphiler any time you're ready, Uhura 20:27, 10 October 2015 (UTC)
The problem is that it isn't hydrostatic equilibrium (the section is poorly named as well), it is having "sufficient mass for its self-gravity to overcome rigid body forces". Hydrostatic equilibrium (and the commensurate shape) is a consequence of that. The section is not about explaining HE, it's about explaining the requirements for how HE might be attained in this specific context. Also, it's not about the moons of Saturn, it's about the well observed objects that straddle the boundary between rigid and plastic; where they're from is coincidental, and Vesta, Pallas, and Proteus should be mentioned, as well, so not just moons of Saturn. Since this is specific to DP, and not used elsewhere, I think it is a better fit here than in the hydrostatic equilibrium page. A separate page might work, too, like with clearing the neighbourhood, but it might be small to be a page of its own, and I don't see an obvious name for it. Tbayboy (talk) 02:55, 11 October 2015 (UTC)
"A separate page might work" That makes sense to me, more than trying to shoehorn it in here. Let's not make this page more complicated than it needs to be. TREKphiler any time you're ready, Uhura 03:50, 11 October 2015 (UTC)

Alphabetization

I've been using {{DEFAULTSORT:}} to alphabetize dwarf planets and other minor planets by their given name (if they have one), rather than by their minor planet number (MPN); because in most contexts minor planets, at least the bigger, better known ones, are usually called by their given name only, e.g. “Vesta” rather than “4 Vesta”. Thus, {{DEFAULTSORT:Sedna}} or {{DEFAULTSORT:Salacia}} (see Sedna, Salacia). (Obviously, the articles “Ceres (dwarf planet)”, “Eris (dwarf planet)”, or “Pluto”, because of the article title, need no DEFAULTSORT.) Also, the given name can begin with any of 26 characters (discounting accented vowels, etc.), whereas the MPN can only begin with one of 10 characters (assuming MPN < 100,000 means that the first character is 0). Thus, alphabetizing by given name results in more possible initial characters, preventing clutter in the alphabetic lists. Okay?--Solomonfromfinland (talk) 23:35, 30 November 2015 (UTC)

RR245

Is 2015_RR245 sufficiently official to be listed on this page? JDAWiseman (talk) 19:17, 14 July 2016 (UTC)

Most are not listed here. I don't see why it would be special enough to mention here. Note, though, that officialness is a non-reason. --JorisvS (talk) 19:29, 14 July 2016 (UTC)

a dwarf planet is not aplanet — Preceding unsigned comment added by 63.134.173.4 (talk) 18:23, 15 August 2016 (UTC)

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Language

This talk page now has the template, "This article is written in British English..." Previously, it had the template, "This article is written in British English with Oxford spelling..." Oxford spelling basically means that the spelling <-ize>, not <-ise>, is used in organize, realize, finalize, etc. (See American and British English spelling differences.) However, in the lead part of the article, Oxford spelling seems to be consistently used for said lexical set: (citations deleted)

"The term dwarf planet was adopted in 2006 as part of a three-way categorization of bodies orbiting the Sun..."

"The exclusion of dwarf planets from the roster of planets by the IAU has been both praised and criticized..."

"As of July 2008 the International Astronomical Union (IAU) recognizes five dwarf planets: Ceres in the asteroid belt, and Pluto, Haumea, Makemake, and Eris in the outer solar system. Brown criticizes this official recognition..."

"Five recognized dwarf planets" [caption]

Same in the rest of the article.

Did they actually agree to change the official language-variety? (Albeit only in removing the "Oxford" part.) (The language templates state, "According to the relevant style guide, this should not be changed without broad consensus.") Did they achieve such consensus? Or did someone change the language template without such consensus? Should we restore the Oxford-British template?

I myself would never, ever, in good conscience, be able to perform de-Oxfordizing edits on any Wikipedia article; i.e., change <realize> to <realise>, <organize> to <organise>, etc.; or equivalent with derived words like realization, organization; English spelling is already disgustingly irregular; de-Oxfordization means moving even further away from the idea of a transparent orthografy; the plight of millions of functionally illiterate English-speakers cries out to me too strongly. Handbook of Orthography and Literacy by R. Malatesha Joshi and P.G. Aaron documents clearly how un-transparent orthografies encourage poor literacy, and slow down the process of learning to read and write. That un-transparent orthografies encourage poor literacy and result in time needlessly wasted in the process of learning to read and write, is a fact, not an opinion. I beg you fellow Wikipedians to hav a conscience the way i do, and never de-Oxfordize.

Or, could the language template be removed altogether, and the language-variety be unspecified, like with the vast majority of Wikipedia articles? Honestly, it felt kind of odd that this article was in British English (Oxford or otherwise); given that the article Pluto is officially in American English, and i can see a reason for that: Pluto was discovered by an American, Clyde Tombaugh, at Lowell Observatory in Arizona, United States; and New Horizons, the first, and so far only, spacecraft to visit Pluto, was launched by the United States (NASA). Makes me think that the language-variety should be unspecified, particularly since the subject in question does not hav clear ties to any one part of the Anglosfere.--Solomonfromfinland (talk) 03:56, 18 June 2018 (UTC)

Note that this article does have some connection to Commonwealth spelling: the IAU spells it "neighbourhood" in their documents, which we're quoting here. Tbayboy (talk) 13:04, 18 June 2018 (UTC)
The article "Clearing the neighbourhood" currently uses the spelling <neighbourhood> (at least in the article title), tho' there hav, understandably, been proposals to change it to <neighborhood>; see the Talk page. On the other hand, the article Pluto is officially in American English, for which, as i pointed out, i can see justifications. Otherwise, does this article really hav any particular ties to one spelling convention or the other? Btw, for "relevant style guide", see Wikipedia:Manual of Style#National varieties of English.--Solomonfromfinland (talk) 13:53, 18 June 2018 (UTC)
Yes ... as mentioned; see the quote in the History section. Tbayboy (talk) 16:11, 18 June 2018 (UTC)

Definition

Unexpected by me, it looks to me that the definition of a "dwarf planet" is locational. So even Jupiter would be a "dwarf planet" if far enough from the sun, or as a rogue planet. There's a log-log mass vs semimajor axis graph here and here that perhaps would aid this article, with a Hill radius related threshold lines separating major planets from others. So even Jupiter would become a "dwarf planet" if further than ~60,000 AUs (1 lightyear), but within Oort cloud limits. Tom Ruen (talk) 13:45, 27 January 2019 (UTC)

Why? Jupiter is 218 Earth masses; the Oort cloud is about 5 earth masses. And very likely there wouldn't be an Oort cloud if a Jupiter-sized object were flying through it anyway. Serendipodous 16:15, 27 January 2019 (UTC)
See the Numerical Values table in Clearing the neighbourhood, the columns Π = 1 or Λ = 1. That's the distance where the body transitions from planet to dwarf. For Jupiter, it's about 64000 AU (about a light year) for Π. Mercury might not be a planet if it were out past Neptune. "planet" is mostly a dynamic category rather than a physical one, and always has been (since little was known about the physical bodies until relatively recently, historically speaking). Similarly, Earth would not be a planet if it were orbiting Jupiter. I think a lot of the controversy is driven by people not realising that they're trying to categorise two orthogonal concepts under one category. Tbayboy (talk) 17:20, 27 January 2019 (UTC)

Tidying of the intro

I've just cleared a lot out of the intro, and bunged some of it holus bolus into the body. A bit brutal perhaps, but the intro needs to be clean and readable. - Snori (talk) 04:57, 5 February 2019 (UTC)

Well done! — JFG talk 12:32, 5 February 2019 (UTC)

Mass chart

The pie chart showing the masses of the dwarf planets relative to the Moon should probably be a bar graph of some form. Samer (talk) 16:31, 6 April 2019 (UTC)

When did Ceres become a DP?

This article gave the same date for Ceres that the name 'Eris' was approved, but I don't see anything about that in the Ceres article. I would think that Ceres, Eris and Pluto have been considered DP's since Resolution 5A was passed. They were the primary objects under consideration, weren't they? There was an official announcement for Pluto (Res 6A), but nothing in our Ceres article about anything similar for Ceres, so I removed the claimed date. — kwami (talk) 18:34, 11 September 2019 (UTC)

Also, no announcement dates for Orcus or Sedna in our articles. Was Quaoar really announced the day after it was discovered? (The dates in our article were off by a day, which makes me wonder if this was just a mix-up.) — kwami (talk) 19:06, 11 September 2019 (UTC)

Found the dates. Quaoar's was wrong. — kwami (talk) 22:06, 12 September 2019 (UTC)

time to update the 2008 list?

It's been over a decade since the IAU five were announced. The IAU is obviously not in the business of announcing whether something is or is not a DP, though if another bright object is discovered it will presumably be named under the assumption that it's a DP. So, is it time to abandon the five as "the" DPs, and go by consensus of astronomers, as we do for every other astronomy article? I think if Brown, Tancredi and Grundy et al. all agree that a body is likely to be a DP, we should go ahead and list it in the chart as a DP. We may not be sure of any but Pluto and Ceres until they're visited, but even the IAU five aren't certain, so requiring perfect confidence is a bit unreasonable. — kwami (talk) 06:53, 5 September 2019 (UTC)

I have no problem calling them "likely DPs", but there is no reason Wikipedia should declare what *is* or *is not* a DP. -- Kheider (talk) 08:02, 5 September 2019 (UTC)
There's nothing obvious about the IAU position, since there's been nothing for them to do: nothing new has met the naming criterion, and the whole question of when something becomes a DP has only become murkier. Brown's argument is premised upon Mimas and Enceladus meeting the physical criterion, and that has been shown false. Grundy counters some of Tancredi, casting doubt upon T's process. The changes since 2008 have been in the direction of less likely. Tbayboy (talk) 13:48, 5 September 2019 (UTC)
Exactly. So shouldn't Haumea and Makemake be listed as 'likely DPs'? The fact that their magnitude is greater than 1 doesn't make them DPs. That was just a bureaucratic decision to settle which committee gets to name them, not a scientific judgement, which is beyond their mandate. And even if it had been a judgement, it was over a decade ago and the field has moved on, as you've noted. So we have Eris, which is universally assumed to be a DP, Ceres and Pluto, which have actually been shown to be DPs, then a bunch that are believed likely to be DPs by various researchers, including conservatively Makemake, Haumea, OR10, Orcus, Quaoar, Sedna as a consensus list. That could change in the future, of course, but such is true for any science. Exoplanets have varying degrees of confidence too. But cutting off the list at an in-house bureaucratic decision is unscientific. We should be updating our coverage to follow developments in the field. — kwami (talk) 16:27, 5 September 2019 (UTC)
Once again, Kwami, the situation absolutely sucks, but it's not Wikipedia's job to fix it. Even Mike Brown's pissed off about it, and if he can't do anything, how can we? Serendipodous 17:00, 5 September 2019 (UTC)
From the announcement: "The International Astronomical Union (the IAU) today announced that the object previously known as 2003 EL61 is to be classified as the fifth dwarf planet in the Solar System and named Haumea". It (and similarly Makemake) is as much a DP as the others by IAU reckoning. A line in the sand is being drawn regardless: either we pick the IAU line, or we make our own line by deciding what constitutes "consensus" (especially since it seems few astronomers care, other than to pump up the importance of their discovery in the pop press). That said, I like your list (the first, shorter one) in list of possible dwarf planets with the columns showing the various evaluations. It shows the transition from near-universal acceptance (IAU DPs) to the uncertainty of Grundy's Xs paired with Tancredi's checks. Tbayboy (talk) 17:33, 5 September 2019 (UTC)
Of course we follow the astronomers! This is an astronomy article. A press release by the IAU is just a press release. They trump up things too, and dumb them down, so the popular press will pick up on them. If we took NASA press releases literally, we'd end up claiming all sorts of things that go against the scientific consensus. Instead, we look at the academic publications that those press releases are based on. We should do the same here, and in any scientific article.
There was never an official decision that DPs were defined by their magnitudes. That was always for naming purposes, just so they could decide which committee got to name them. If the IAU did make such pronouncements officially, it would be a pseudo-scientific organization and we would ignore them completely. But it doesn't. The official publications are all about HE and clearing the neighborhood and which committee is in charge of naming what.
During the first few years, I could see putting it on the back burner to see what the IAU would do next. But it's pretty obvious by now that they aren't doing anything. An "IAU dwarf planet" is not a scientific concept, and has no business in a scientific article except as a side-note for how DPs are named.
As for there not being a lot of people working on DPs, again, so what? There aren't many people working on any individual exoplanet either. We do the best we can with what is being published. Eris, Pluto and Ceres are (AFAIK) universally accepted as demonstrated. Therefore we can just say the "are" DPs. Makemake and Haumea are not. Who got to name them is irrelevant for determining their nature. Noting who had ID'd which body as a DP is important. But elevating the IAU above the scientific consensus, as if they actually determined such things, is silly. And IAU press releases written by who-knows-whom do not trump peer-reviewed articles in refereed journals. — kwami (talk) 01:23, 6 September 2019 (UTC)
Again, Kwami: THIS IS NOT OUR JOB!. We are not a recognised authority on anything, least of all astronomy. We report what others say; we do not draw our own conclusions. Wikipedia is a scrawl on a public bathroom linked to citations. Nothing else. Serendipodous 19:45, 6 September 2019 (UTC)

"We are not a recognised authority on anything, least of all astronomy. We report what others say; we do not draw our own conclusions" Exactly right. So let's do that! We don't get to dictate which object are DPs, and neither does the IAU. Substituting authority for research is pseudoscience. So, let's reflect the scientific literature rather than legalistically substituting a bureaucratic decision for science -- like we do with every other science article on WP.

Who do we have to work with? The IAU press releases, since even if they're not scientific are followed in a lot of 2ary sources. Tancredi. Brown. Grundy et al. Maybe a couple others. That's enough for an article like this. — kwami (talk) 21:39, 6 September 2019 (UTC)

If you really think that the IAU has declared those five to be DPs, then please share the resolutions which declared them to be so. I know they declared Pluto to be a DP is their resolution for Plutoid, but I can't find anything else but press releases. And, as you noted above, organizations tend to "pump up the importance of their discovery in the pop press". — kwami (talk) 22:55, 6 September 2019 (UTC)

Proposed table (top half)

All I'm proposing is that we merge the two tables. Rather than a "Bureaucratic List" from 2008 and a "Scientific List" from 2019, we should have just one list reflecting RS's in 2019. We say multiple times which bodies were named or accepted -- or, in the case of Pluto, declared -- to be DPs by the IAU. We don't need to repeat that with every section. A list of '(possible) dwarf planets' considered most likely by RSs, which are Tancredi, Brown and Grundy et al. I'd remove MS4 and Salacia from the list because of the latter. So this is what we'd have. It's much handier to have them all together. Is there any way is which this doesn't reflect the scientific consensus? (We could add an 'acceptance' column if you think that's needed.) — kwami (talk) 22:46, 6 September 2019 (UTC)

Objects most likely to be dwarf planets
Name Region of the
Solar System 		Orbital
radius (AU) 		Orbital period
(years) 		Mean orbital
speed (km/s) 		Inclination
to ecliptic 		Orbital
eccentricity 		Planetary
discriminant
Ceres Asteroid belt 2.768 4.604 17.90 10.59° 0.079 0.33
Orcus Kuiper belt (plutino) 39.40 247.3 4.75 20.57° 0.227 0.003
Pluto Kuiper belt (plutino) 39.48 247.9 4.74 17.14° 0.249 0.077
Haumea Kuiper belt (12:7) 43.22 284.1 4.53 28.22° 0.195 0.020
Quaoar Kuiper belt (cubewano) 43.69 288.8 4.51 8.00° 0.039 0.007–0.010
Makemake Kuiper belt (cubewano) 45.56 307.5 4.41 28.96° 0.159 0.02
2007 OR10 Scattered disc (10:3) 67.38 553.1 3.63 30.70° 0.500
Eris Scattered disc 67.78 558.0 3.62 44.19° 0.442 0.10
Sedna Detached 506.8 ≈ 11,400 ≈ 1.3 11.93° 0.853 < 0.07

Kwami, no matter how many individual sources we cite, unless we can account for the entire astronomical community, we are taking sides. We cannot take sides. Serendipodous 09:14, 7 September 2019 (UTC)

But you're the one advocating taking sides. I'm advocating we follow the scientific consensus. Which is what we need to do in any scientific article. — kwami (talk) 19:51, 7 September 2019 (UTC)
There is no problem with having TWO lists. The largest dwarf planets will in general be more significant. -- Kheider (talk) 15:16, 7 September 2019 (UTC)
The problem is not having two lists. The problem is presenting a naming decision from 2008 as if it were the scientific consensus. There's no question that in a scientific article we follow the scientific consensus. Anything else is pseudoscience.
Given that so many people unthinkingly follow the IAU press releases as if they were eternal scientific verities, I suppose it's useful to have a separate list for the IAU five. But we should have a full list for the scientific consensus. The first list won't change unless we discover something else with a magnitude greater than +1. The second could potentially change with every new publication, but that's the way a scientific article should be. — kwami (talk) 19:51, 7 September 2019 (UTC)
Since the IAU five are a subset of the current scientific consensus of nine (not counting Charon), why not just have one table and specially highlight and mark the rows for the IAU five? Double sharp (talk) 05:35, 16 September 2019 (UTC)
That works for me. Done. — kwami (talk) 02:23, 17 September 2019 (UTC)

10 Hygiea

Some scientists say that 10 Hygiea meets the conditions to be a Dwarf Planet.

https://www.eso.org/public/news/eso1918/

https://www.space.com/asteroid-hygiea-may-be-smallest-dwarf-planet.html

https://www.usnews.com/news/world-report/articles/2019-10-28/scientists-say-asteroid-could-be-smallest-dwarf-planet-in-earths-solar-system

https://www.cnet.com/news/tiny-mysterious-asteroid-is-likely-the-solar-systems-smallest-dwarf-planet/

https://news.yahoo.com/unknown-dwarf-planet-solar-system-153700978.html

https://news.yahoo.com/solar-system-family-five-dwarf-202500501.html

184.176.152.135 (talk) 04:54, 29 October 2019 (UTC)

"Surface properties of large TNOs"

I removed the rather lengthy para on the following article as nearly unintelligible (and not much point to what was intelligible):

Pinilla-Alonso, Noemi; Stansberry, John A.; Holler, Bryan J. (November 22, 2019). "Surface properties of large TNOs: Expanding the study to longer wavelengths with the James Webb Space Telescope". In Dina Prialnik, Maria Antonietta Barucci, & Leslie Young (ed.). The Transneptunian Solar System. Elsevier. {{cite book}}: External link in |chapterurl= (help); Unknown parameter |chapterurl= ignored (|chapter-url= suggested) (help)CS1 maint: multiple names: editors list (link)

Turns out it's accessible at Arxiv (changed the link in the ref). The "36 candidates" are merely anything with D >= 450km (to within 1 sigma), simply a population of potential objects so all likely candidates are included in the comparison, and pace the summary I deleted, the article is not an evaluation of how likely any of them are to be DPs that would be comparable to Tancredi et al., but rather a proposal that spectral imaging by the JWST should prove informative. The article summary says,

Surface compositions of TNOs appear to be correlated with size, with the largest TNOs, the dwarf planets, exhibiting dynamic, volatile-dominated surfaces. We refer to the next lowest size tier as candidate dwarf planets. These objects appear to be vastly different from the dwarf planets in terms of color, albedo, and surface composition, even though they are closer in size to the dwarf planets than the small TNOs.

Since they never mention JWST results for any of the bodies, referring instead to previous studies for their conclusions, they don't really say anything new at all. So I don't see any point in mentioning this article, certainly not elevating it to the status of a new study. Unless I missed something in skimming it over? — kwami (talk) 10:01, 19 December 2019 (UTC)

Hm, the only thing they list that was numbered since 2005 is 2007 UK126. Whereas they list thirty bodies smaller than 900km but D + sigma > 450, we list a hundred. So these 30 weren't selected just for size, but for whether they have size estimates from Spitzer or Herschel observations. — kwami (talk) 21:00, 19 December 2019 (UTC)

Still appears to be bullshit

well, what can I say, appearances are deceiving. user:IcesAreCool

Our edit-warrior, user:IcesAreCool, is back, still without justification. The first claim was, In 2016, Pinilla-Alonso updated the list in Tancredi and Favre incorporating geometric albedos from thermal measurements of the Herschel Key Program “TNOs Are Cool”. I can't access the paper (which dates to 2015, not 2016) to verify, but the abstract doesn't mention anything about this.

You can access the proceeding PinillaAlonso 2016, I downloaded it and read it from this Cambridge webpage where the article is accessible with a publication date in 2016, why you could not read the paper is something that I do not know.
DOI: https://doi.org/10.1017/S1743921316002970 Published online by Cambridge University Press: 27 October 2016
This work evaluates the different observable characteristics from the list of candidates e.g. albedo, color, etc. and studies if, according to them there are other indicators, apart from the size, that could be used to detect more dwarf planets. This is a good and needed exercise, and even a negative result is a result. Tancredi and Favre, not Tancredi et al., recognize in their publication the limited access to measures of sizes of TNOS " There is a limited number of TNOs with reliable size measurements." and they explain that they take a conservative approach that may not be ideal, but is the best they can do at that moment, this means using pv=10%. This value is known to not be accurate for most of these bodies nowadays, as can be seen in Muller et al. 2019, and that is why it is important to include that reference also. user:IcesAreCool
Their goal is to answer, "are these [four] the only objects in the TNb that, according the IAU definition, can be considered dwarf planets? And if not, which are their physical characteristics?"
There's a diff in albedo, with the IAU four high (+ one smaller object, presumably a haumeid), and Sedna intermediate, but Sedna's albedo isn't well constrained, so that might not mean anything. For the next two tables, not only are the CDPs not distinct from other TNOs, but neither are the IAU four, so I don't see how they tell us anything about HE. The IAU four are distinct in surface composition, which might mean that they are the only DPs, which would be at odds with your summary of Pinilla, or it could just mean that they're big, which we already know. But Pinilla doesn't draw either conclusion. He never answers his first question, and in his conclusion doesn't even address the second. It's a very odd paper when you set out to answer two key questions, and then conclude by ignoring those questions. Unless his conclusion is simply that his methodology can't answer those questions, in which case there's nothing for us to report. — kwami (talk) 08:01, 21 December 2019 (UTC)

From that moment, the key program TNOS Are Cool, which is called like that by the Herschel Observatory, not by me, has provided the most comprehensive study of the sizes of TNOs, only occultations can provide sizes of TNOs so reliable. Yes, the table in PinillaAlonso et al is only a compilation, but a compilation of the most updated results in Muller et al. 2019 reference that you insist on removing.

They just say that they review the previous decade's scholarship and will "entertain the idea of the science that can be done in the next 10 years". And the 2019 paper, which "was extended" from this one, doesn't update Tancredi & Favre's research. It only "updates the list" in the sense that it updates the list of large TNOs that might be considered, but that's trivial. Any child who can add and subtract up to a thousand could do that. We wouldn't even need to cite Pinilla-Alonso for their list. We could instead directly cite the public DB they used.

The second claim is This work was extended in 2019 using the final results of this key project. The final list contains 40 objects, the four dwarf planets already defined by the IAU in the trans-Neptunian belt, and 36 additional candidate dwarf planets (CDPs), six of them (2007 OR10, Quaoar, Orcus, 2002 MS4, Sedna, Salacia) with sizes above 900 km. Pinilla-Alonso et al. also show that the surface properties of these CDPs, typically used as a proxy of their surface composition, are not distinguishable from those of TNOs with sizes below 450km, which suggests that the physical properties of the dwarf planets in the TNb are unique.

I'm not sure what this is supposed to mean. Yes, the list contains 40 objects, but that's just a blind copy of the Herschel & Spitzer results at the "TNOs Are Cool" public DB, a raw list of objects > 450km for possible evaluation. There is no actual evaluation of those objects the way Tancredi et al. evaluated their raw list, and concluded that some are likely to be DPs. [...]

It means that, if we exclude the actual five DP, the surface properties, that are studied in that chapter, are similar for CDPs and regular TNOs. Surface properties that we can measure at this point are e.g. color, presence of ices, geometric albedo. This means that, until JWST can give us more details on what is on the surface of the TNOs, we cannot say that those TNOs in hydrostatic equilibrium are really different (as per surface properties) to those that are not. Except, for Eris, Haumea, Pluto, and Makemake, which are really peculiar among the TNO population.
And what does that mean? How did they determine which TNOs are in HE and which are not, that they could say that their surface properties aren't different? I don't see how you draw your conclusions from the papers.
"which are really peculiar among the TNO population" -- and this is key, the only point that they seem to make. The only conclusion, if you had to draw one, is that only the IAU four can be DPs. There's certainly nothing in Pinilla to suggest that he agrees with Tancredi or Grundy on Orcus etc. being likely to be DPs, as you stated -- if anything, he says the opposite. — kwami (talk) 07:45, 21 December 2019 (UTC)

[...] What Pinilla-Alonso "shows" of the surface properties is also a review of previous research, and doesn't address individual objects, so this isn't research at all. Rather, it's a textbook-like summary. And if the physical properties of the DPs (= the IAU four) are unique, as Pinilla-Alonso says, wouldn't that countra-indicate the 36 CDPs, and thus contradict IcesAreCool's claim that Pinilla-Alonso agrees that the larger TNOs are likely to be DPs? Did Pinilla-Alonso find a single CDP that's compatible with being a DP? A literal reading is that they didn't, that none of the CDPs have similar spectra to the IAU four, and there is no evaluation of viable candidates in the raw list.

So, again, this edit appears to be bullshit. It's worded in a way (e.g. "final results of this key project") that suggests these articles contributed something to our knowledge of DPs, when it appears that they're just summarizing previous research and proposing future studies. And the one evaluative claim, that Pinilla-Alonso accepts Orcus, Sedna etc. as likely DPs, seems to be contradicted by at least the 2019 article. If there is something worthwhile here, perhaps IcesAreCool can point it out.

Those articles, Muller et al. 2019 and Pinilla-Alonso et al. 2019 are chapters in a book that compiles the actual knowledge on TNOs, they do not need to do new research but to be honest and knowledgable and honor research made by their colleagues. A book that is refereed and evaluated by peers, scientists before publications. "Key project", again, is the name that the Herschel Observatory gave to this program, it is rigorous referring to it like that. 2007 OR10, Quaoar, Orcus, 2002 MS4, Sedna, Salacia, are the six objects that are included in table 1 as the best candidates to be dwarf planets, not sure where you see the contradiction. user:IcesAreCool
All they are is TNOs estimated to have D > 900 km. That's trivial. We don't need a chapter to tell us that, we can use the same DB they did. — kwami (talk) 07:45, 21 December 2019 (UTC)

I wonder if there might be a COI here, as otherwise I don't know why anyone would push the trivial updating of a raw list and a recap of previous research on them as a "key project". Granted, Brown doesn't do any more than that with his list, but he's notable for having co-discovered many of them. Stern's comment doesn't have any detail to it, but he's notable as the coiner of the term 'dwarf planet' and the head of the NH mission. Tancredi, Ortiz, and Grundy all did actual research, which it would seem Pinilla-Alonso did not. — kwami (talk) 20:40, 20 December 2019 (UTC)

I am honored that you think I might be one of the coauthors of an Elsevier book chapter, but even if that is not the case, I am close to the field and I got to know and understand the job from Brown, Ortiz, Tancredi, Grundy et al... but also Pinilla-Alonso or Stansberry are serious researchers, known and respected in the field. The first did extensive characterization of the dwarf planets, back since 2005 and 2006. The latest is an expert in size estimation from thermal measurements of the geometric albedo, with Spitzer and with Herschel. They are recognized in the field and their work on this chapter is worth mentioning.
Finally, this article contains a description of the TNOs that are thought to be candidates to be called dwarf planets. There are different authors that have different criteria and opinions, I think this page makes a good job of including all of them but the best way to make an objective description is to do it in chronological order. Tancredi & Favre made the first list, and the first suggestion back in 2007-2008 using the standard channels in the community that are peer-review publications. There is no reason to start with Brown's web list. A chronological order should be preferred here. user:IcesAreCool
But it is not "a description of the TNOs that are thought to be candidates to be called dwarf planets". It's just a list of large TNOs. There's no evaluation to propose which of them are or are not in HE, the way Tancredi and Grundy et al have. It's more like Brown's list, and the only reason we use Brown's list is because he was one of the few sources we had when we started this article, and because he's notable for discovering and working on many of them. I suspect that eventually we'll drop the Brown list as not really contributing anything -- he's never addressed the issue of Dione & Iapetus not being in HE, for example, and how that would affect his estimates of how large an icy body would need to be to be "likely" to be in HE, so I don't really see much point to his list any longer. We certainly don't need more trivial lists of "TNOs > 900km", "TNOs > 600km", "TNOs > 450km" -- we can just link to our list of TNOs ranked by size.
This isn't a question of whether they are serious researchers, but of whether they say anything notable. The only thing I see of interest is the claim that there's a break in surface composition between the IAU four and the rest of the TNO population. But what that means, I don't know, because Pinilla doesn't draw any conclusions from it, doesn't do more than mention it in passing. He doesn't say that only the IAU four seem to be in HE, or that some of his >450km bodies are also in HE, or anything else that I can see. If I've missed where he said something worth reporting, please point it out to me. — kwami (talk) 07:45, 21 December 2019 (UTC)

So, the point of the articles seems to be, "After the big four, none of the TNOs apart from the haumeids stand out spectrally. We should check them with the JWST, to see if there's any way to distinguish DPs at longer wavelengths. Here's a partial Herschel/Spitzer list of the bigger TNOs that we might want to start with." They don't even discuss how the big four stand out spectrally, though they do note that they don't all stand out for the same reason. Is there anything in that that's notable enough for us to cover? — kwami (talk) 20:08, 21 December 2019 (UTC)

if Venus isn't a planet ...

If the sources recently added to List of Solar System objects by size hold up, and Venus, Mars and Mercury are not planets by the IAU requirement for HE, is that requirement tenable? There's no way that astronomers are going to accept the other terrestrial planets being demoted to a Small Solar System Bodies. Unless they just ignore it, the IAU would be required to modify the HE requirement, which would affect DPs as well. How close to HE would they need to be, and how could we possibly determine that for TNOs without measurements from an orbiter, even for Pluto? At that point the definition is even more obviously impractical, and there is no effective difference between "dwarf planet" and "planetoid". We might as well go with Stern's definition and call them 'DP' if like Stern we accept them as planets and 'planetoid' if like Brown we don't. — kwami (talk) 21:34, 21 December 2019 (UTC)

I highly doubt that they do. I haven't been able to access the reference being used for Venus (and Mercury) but I am disinclined to trust a paper published in 1984 that has only 3 reference and 6 citations. The Gudkova reference was a presentation at the European Planetary Science Congress in 2008, that is not peer-reviewed and thus not suitable for a wikipedia reference and I've removed it at List of Solar System Objects. The Perry reference and the book reference for Mercury both seem to be talking about rather small deviations from hydrostatic equilibrium. Physdragon (talk) 22:00, 21 December 2019 (UTC)
Yeah, we should be able to find corroborative sources if they're correct.
A possibly similar 1977 paper on Venus is available here. — kwami (talk) 23:09, 21 December 2019 (UTC)

This article no longer meets the featured article criteria. There are unsourced statements, statements ascribed to sources that do not support the statement and material that has been tagged for attribution since October 2017. DrKay (talk) 09:49, 25 December 2019 (UTC)

704 Interamnia

An abstract of a new paper analyzing SPHERE data was posted on ARVIX here [1]. While its title states that Interamnia is a transistional object between a dwarf planet and an irregularly shaped body, the text of the abstract itself seems to state that Interamnia is in hydrostatic equilibrium, which therefore would make it a dwarf planet. Specifically it states, "Our observations reveal a shape that can be well approximated by an ellipsoid, and that is compatible with a fluid hydrostatic equilibrium at the 2 σ level. The rather regular shape of Interamnia implies that the size and mass limit, under which the shapes of minor bodies with a high amount of water ice in the subsurface become irregular, has to be searched among smaller (D ≲ 300km) less massive (m ≲ 3x1019 kg) bodies."XavierGreen (talk) 22:30, 3 December 2019 (UTC)

Their constructed image sure looks irregular. Could be a case like Phoebe. But is it really rotating fast enough to be scalene? — kwami (talk) 09:22, 19 December 2019 (UTC)
There are images of other angles in the journal article that look way more spherical than the one chosen for the infobox image, it may be that there is a big crater with a central peak like on Vesta. No way to know for sure until clearer images come out.XavierGreen (talk) 22:22, 30 December 2019 (UTC)

If one is interested in the surface gravity of spherical planets and dwarf planets

To make a quick estimate of the surface gravity in meters per second squared, multiply the radius in Kilometers by the density in kilograms per cubic meter, and then divide by 3,582,688. The 3,582,688 is the product of a Radius X Density that will give almost exactly 1.0 m/sec^2 surface gravity. Some Planets will have slightly higher surface gravity, a few will be slightly lower, and the Gas Giants will have slightly lower surface gravity (top of the clouds ). For example: Earth's Volumetric mean radius is about 6371.008 km, and its density is between 5514, and 5515. The GPS Gravity is taken as 9.80665 m/s^2. So 9.80665 X 3582688 = 35,134,167.28. Then divide by the radius of 6371.008 to get a non rounded density of 5514.695 206. Now you can round to 5514.7 kg/m^3. This is between the 5514 that NASA currently uses, and the 5515 they used previously.

You can estimate the surface gravity of every Planet, Dwarf Planet, Moon, or any other spherical, or semi-spherical object by: Radius X Density / 3,582,688 = __________ m/s^2. 98.245.216.62 (talk) 20:55, 23 October 2020 (UTC)

Removed text

I removed the following:

In 2012, Stern stated that there are more than a dozen known dwarf planets.[1]

  1. ^ Stern, Alan (August 24, 2012). The PI's Perspective. Archived November 13, 2014, at the Wayback Machine, August 24, 2012. Retrieved from http://pluto.jhuapl.edu/overview/piPerspective.php?page=piPerspective_08_24_2012.

I should've removed this years ago, but was waiting for a better ref and forgot about it. The reason is that Stern was counting satellite planets as dwarf planets (p.c. 2012). So the quantity "dozen" here doesn't tell us anything about how many TNOs Stern considered to be DPs. — kwami (talk) 09:05, 15 February 2021 (UTC)

Several posters by Runyon, Stern et al. list many more, of both satellites and TNOs, but they ignore their own definition as they do so. Not clear how much input Stern had, or if he just signed on. — kwami (talk) 09:45, 22 August 2021 (UTC)

Size

What is the maximum size of a dwarf planet? — Preceding unsigned comment added by Zachbarbo (talk • contribs) 02:06, 12 November 2021 (UTC)

No maximum. An object as large as Mars or even Earth could be a DP if it hasn't cleared its orbit. — kwami (talk) 23:40, 12 November 2021 (UTC)

What about giant planets like the gas giants and ice giants? — Preceding unsigned comment added by Zachbarbo (talk • contribs) 13:40, 13 November 2021 (UTC)

Sure. A Jupiter-sized object in the outer Oort cloud would be a dwarf planet. On the other hand, a Pluto-mass object in Mercury's orbit would be a full-fledged planet. (I say Pluto-mass because Pluto itself in Mercury's orbit would turn into the most spectacular comet ever seen.) The upper limit is about dominance, not size. Double sharp (talk) 14:36, 13 November 2021 (UTC)

The definition was created for the bodies we know about. There's an obvious division between the giant planets and the terrestrials, but Venus and Mars have to be planets, so the IAU couldn't draw the line there. The next obvious division is between the terrestrials and Eris/Pluto/Ceres, and that's what the IAU chose and what their definition is meant to enshrine. They could've just said "the big eight", but that wouldn't sound very scientific. It's doubtful the IAU definition will work well for other planetary systems, though, and it doesn't work for the early history of even our system.

The next obvious place to draw a line is between planemos and SSSB's, and that was the competing definition of "planet" that was considered by the IAU. And the one that's used by people like Stern and Grundy. But in practice that's a very difficult definition to apply, because we just don't have enough evidence to tell which bodies are planemos. So the IAU definition is practical, whether one agrees with it or not, as long as we don't discover an Earth-sized body in the outer Solar system that throws everything into chaos again the way the discovery of Eris did.

I suspect that if we find an Earth-sized body that is technically a DP, then the IAU will revisit their definition of "planet" and modify it so that the new body counts as a planet. After all, technically Mercury is a SSSB, but everyone ignores that and calls it a planet anyway. — kwami (talk) 21:07, 13 November 2021 (UTC)

And presumably dynamicists would ignore such a definition or pay lip-service to it the way they used to do to Pluto: call it a planet and then exclude it from their integrations.
I really wonder what would happen if even a Mercury-sized TNO was discovered, though. Double sharp (talk) 22:39, 13 November 2021 (UTC)

Dwarves are supposed to be small. — Preceding unsigned comment added by Zachbarbo (talk • contribs) 01:15, 14 November 2021 (UTC)

Yes, the terminology is a little unfortunate and makes it look like the distinction is about size, when it's really about dominance. But you could always use the old term "planetoid": something that's like a planet but isn't a planet. Double sharp (talk) 11:01, 14 November 2021 (UTC)
Actually, I think Zach may be right. They are supposed to be small. But the IAU rejected a size limit to define planets (e.g. "Pluto or larger") as arbitrary, so they needed some other way to say the same thing that looked more scientific. They chose orbital dominance. But I wonder how important the dynamic aspect really was, or if it was just convenient. Though it makes sense of course if you're working on the Nice Model.
As long as we don't discover anything significantly larger than Pluto, I think we're fine. But if we find things that start filling in the planet-DP gap, it might become an issue again. — kwami (talk) 13:34, 14 November 2021 (UTC)
Mike Brown talked about this in this 2011 talk from about 62 minutes onwards. He thought then that some of the largest inner Oort cloud objects (Sedna's population) would be Mercury- or Mars-sized, though he used a power-law argument and based it on a size of Sedna that we now know to be too big. He thought that the debate would reopen again when something like that was discovered, and that he didn't care if people widened the definition of "planet", but also said that he thought it was important to make it really clear that there's a difference between dominant and non-dominant objects and that a Mars-sized inner Oort cloud object would not be dominant. I agree wholeheartedly with his position. :D
So maybe the best answer to the OP's questions is: "The current definition of a dwarf planet focuses only on dominance. Consequently there is no upper size limit, and if we take it by the letter, Jupiter would be a dwarf planet if it were orbiting in the outer Oort cloud. However, we agree with Mike Brown that the definition would be reexamined if anything like that were ever discovered, so we should not take that too seriously at the moment." Double sharp (talk) 14:32, 14 November 2021 (UTC)

IAU Division F report refers to Quaoar as a "dwarf planet"

Quote from the 2022 IAU Division F report [2]:

Unexpected ring discovered around dwarf planet Quaoar. A kind of revolution has recently appeared in the field: another Kuiper belt object, Quaoar, hosts also a dense arc embedded in a continuous thinner ring, but that system lies outside Quaoar’s Roche lobe and thus should theoretically not exist. (p 2)

An unexpected ring was discovered around dwarf planet Quaoar (p 5)

Nrco0e (talk) 23:23, 6 December 2023 (UTC)

Cool! I've added mention of this in some places. Double sharp (talk) 11:25, 8 December 2023 (UTC)
@Kwamikagami: This might interest you. :) Double sharp (talk) 11:42, 8 December 2023 (UTC)
Thanks. The fact that the IAU itself is using that wording should put to rest the idea of "official" dwarf planets. — kwami (talk) 21:18, 8 December 2023 (UTC)
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