Talk:Dwarf planet

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For the discussion on developing a strategy for naming dwarf planet articles, please see Talk:Dwarf planet/Naming

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)

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)

"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)

Featured article?

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)

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)