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--JeffGBot (talk) 03:27, 1 June 2011 (UTC)[reply]

So-called spheroid inside Haumea family

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Revision as of 21:09, 29 April 2013 (edit) (undo) Roentgenium111 (talk | contribs) (Undid revision 551919929 by ONaNcle (talk)(IAU explicitly classified Haumea to be a dwarf planet; it's not "potato-shaped" but a triaxial ellipsoid in hydrostatic equilibrium))
Ok Roentgen, I give you the last word inside Main but I prefer to let future contributors know about our controversy: you keep on thinking the balls used in soccer and football are both spheroid and myself I disagree with you. ONaNcle (talk) 07:02, 30 April 2013 (UTC)[reply]
Haumea is a scalene ellipsoid. No one seriously disputes that. Potatoes are irregular, not ellipsoids. --JorisvS (talk) 08:38, 2 May 2013 (UTC)[reply]
Ok about no disputes with you too ;-))) and, as soon as I've said earlier that I'll involve myself in no edit war about this funny legend, you can try by yourself to see if a specialist reacts if you edit http://en.wiki.x.io/w/index.php?title=Ellipsoid&action=edit&section=9 and replace ellipsoid by spheroid over there. — Preceding unsigned comment added by ONaNcle (talk • contribs) 11:22, 2 May 2013 (UTC)[reply]
What do you mean to say exactly? --JorisvS (talk) 13:48, 2 May 2013 (UTC)[reply]
It's a bit perplexing how come Haumea is widely considered dwarf planet, while most other large TNO's can't be confirmed as such until visited because it's difficult relying just on telescopic observations to prove whether or not a given TNO is spheroid/ellipsoid/in hydrostatic equilibrium. Ceres is much closer than any of them (more than make up for its small size, if you think in term of angular size) and it was only confirmed thanks to spacecraft info not telescope info. Iapetus moon of Saturn is almost same size as Haumea and is not in hydrostatic equilibrium. احمد الليبي (talk) 03:18, 21 December 2020 (UTC)[reply]

Did the 2006 IAU vote apply to Haumea-like objects ?

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The relevent criterium to being a dwarf planet is being in hydrostatic equilibrium (HE), not whether or not it's a spheroid. Haumea is not a spheroid, and nobody claimed it was, but it is in hydrostatic equilibrium. Tbayboy (talk) 18:35, 2 May 2013 (UTC)[reply]

Such as said above, ellipsoid objects are different from pure spheroid ones and I keep on believing Haumea doesn't show a nearly spherical shape ONaNcle (talk)
That's what everybody else believes, too. What of it? The actual criterium from the link you provided is "(b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape"; nothing about spherical. "Spherical" was only used in the Q&A, to try to describe the concept of hydrostatic equilibrium to casual readers, not in the actual definition/resolution. Tbayboy (talk) 13:55, 3 May 2013 (UTC)[reply]
When you say about Haumea it looks nearly round it means imho something quite different from the actual shape of Haumea... Too bad... I'll die idiot... Never knowing how Haumea became a planet while Haumea was not on those dwarf planets initial list... ONaNcle (talk) 07:38, 10 September 2013 (UTC)[reply]
The definition is HE. "Nearly round" is an attempt to avoid jargon. The only problem is that Iapetus, at 1,470 km, turns out not to be in HE after all, though it's quite nicely ellipsoidal, so we can't be sure Haumea and Makemake are really DPs. It's not a practicable definition. — kwami (talk) 10:39, 10 September 2013 (UTC)[reply]
Recent & different answers can be read here : Talk:Iapetus_(moon)#2001 ONaNcle (talk) 15:20, 10 September 2013 (UTC)[reply]
No, it's the same answer there. Just any old round is not sufficient; it must be correctly round. E.g., Haumea's roundedness is correct for Haumea, but not for Ceres, because of different spins. Tbayboy (talk) 20:06, 10 September 2013 (UTC)[reply]

Haumea was being considered by the IAU as a DP candidate since before DPs were defined to not be planets. See it here (back then it was still 2003 EL61). Double sharp (talk) 08:47, 28 September 2021 (UTC)[reply]

Failed attempt to save Pluto

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The category of DP is a historical accident, born of a failed attempt to save Pluto's planethood. Since we can't tell which objects are DPs, it would be more professional to just call all the big ones "planetoids". — kwami (talk) 04:36, 11 September 2013 (UTC)[reply]

Original research is forbidden on this wiki but some of you may fill or even translate this entry : http://fr.aleatexte.wikia.com/wiki/plutinorb Jacques Ovion aka ONaNcle (talk) 21:02, 12 September 2013 (UTC) [reply]
The word planetoid already exists and conveys a more general meaning including many different Solar objects. Derived from the latin word orbis (meaning circle) plutinorb could be used imho as a better specific term excluding ipso facto the too eccentric Haumea. ONaNcle (talk) 17:25, 11 September 2013 (UTC)[reply]
As far as Haumea is known, it can be well approximated by a scalene ellipsoid. It can therefore be said to be "round". --JorisvS (talk) 08:04, 12 September 2013 (UTC)[reply]
To be clear, "round" is being used in the sense of "continuously convex", not just "ball-shaped". Tbayboy (talk) 12:40, 12 September 2013 (UTC)[reply]
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This link is not dead. The URL http://www.gps.caltech.edu/~mbrown/dps.html redirects to http://web.gps.caltech.edu/~mbrown/dps.html . I've updated the use of this URL in the article. —RP88 (talk) 02:49, 30 November 2016 (UTC)[reply]

Dwarf Planet

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Will Salacia be considered a dwarf planet? Because it has a moon. Zachbarbo (talk) 18:36, 11 November 2021 (UTC)[reply]

That's not what makes something a dwarf planet, it only allows us to determine its mass. In theory, a DP is s.t. massive enough so that the mantle becomes plastic under its own weight, and so subsides into the shape that water would have. In practice, it's more of a guessing game, because it's essentially impossible to determine this from a distance. (We're still not even sure that Ceres is a DP.) So we call an object a DP if the astronomers working on it or similar objects call it a DP. And the practical definition seems to be that if a body we haven't visited by spacecraft is dense enough to be a fully solid body (no pockets of vacuum inside it), or bright enough to suggest a geologically active surface, then it's called a DP. Currently, Salacia is ambiguous: it was thought to be too light to be a solid body, so the (tentative) dividing line was between Orcus and Salacia. Salacia's density was then recalculated to be greater than thought. It might be as dense as Orcus -- but then it might not. (And, personally, I have my doubts about Orcus as well.) Latest RS we have says that Salacia is "DP-sized", which seems to be a way of saying "we don't know". It may be dense enough, but it's very dark, which suggests that it's never been resurfaced, which suggests it never had active geology.
The whole point of the category of DP is that they're geologically active worlds, not just dead balls of rock and ice. That's hard to know without a spacecraft. — kwami (talk) 20:45, 11 November 2021 (UTC)[reply]
I'm not so sure that that's the point of the DP category in practice, although people might say it is. Because the scientists who say that dwarf planets are planets are also pretty likely to say that all the round moons are planets, never mind that Callisto at almost Mercury's size is geologically dead. So it seems that geological activity is something that is conveniently forgotten about in favour of roundness when it comes to planemo moons. And since Tethys is pretty universally accepted as a "satellite planet" among this crowd, with a density so astonishingly low that it might indeed have non-negligible internal porosity even if it is mostly ice, I suspect that this will eventually turn into a simple "is it at least the size of Mimas" threshold like one paper by Runyon et al. already gives (yes, including non-round Proteus and Vesta). Of course, once this is the fallback position, one does start to wonder if a simple 2000-km threshold to save Pluto would not have just as much sense behind it.
But for now, Kwami's right: the line Grundy et al. use, and that seems to dictate whether or not an object is commonly called a DP in the literature, coincides well with "is it solid"? Although people seem quite ready to accept Orcus despite not knowing its density that well.
As for what I suspect: the data points of Triton and Pluto suggest that Eris might be active. Haumea and Makemake are smaller, but without geological activity it is difficult to explain why Makemake has nitrogen on its surface like Pluto and Triton, so maybe that's the regime there. If so Haumea likely has good hopes as well given its violent history. However, Charon seems to be inactive, and it's about Gonggong's size, so I suspect that the 5 "IAU dwarfs" are the only ones that have chances to be active. I would at least accept Gonggong and Quaoar as likely "dwarfs" in the sense of fully collapsing out, while not being entirely sure about Sedna and Orcus, and doubting Salacia, Varda, and some other 700-to-800 km ones a lot but leaving the door ajar. Double sharp (talk) 00:54, 12 November 2021 (UTC)[reply]

SALACIA MAP???

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I was just searching up fake planet maps for objects we haven’t visited. And the craziest thing just happened y’all… look

https://www.researchgate.net/figure/Individual-maps-of-120347-Salacia-Each-map-is-the-product-of-one-observation-AOR-The_fig1_45196253

i have no idea if this is official 2603:8001:C401:3D45:B195:5F5B:B619:622F (talk) 08:55, 31 January 2024 (UTC)[reply]

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