Talk:List of possible dwarf planets/Archive 1

Archive 1

Archive 2

Move

This page was moved without discussion. I am not sure I approve of the move. See Talk:Plutoid -- Kheider (talk) 20:26, 15 June 2008 (UTC)

I would rather move it back to List of dwarf planet candidates (from the current name: List of plutoid candidates) Bluap (talk) 11:56, 17 June 2008 (UTC)

New Candidates

My thought process when adding large candidates to this list:
1. Start class articles or better (20000 Varuna and above) should get top billing since we know the most about these objects.
2. Objects known well enough to numbered by the MPC or have peer-reviewed papers written about them (2002 MS4) should get listed next.
3. Objects that are not officially numbered by the MPC and do not have research papers written about them should get listed last. For example all the objects with generically assumed albedos of 0.09.
-- Kevin Heider

Charon

maybe we should add a paragraph about the still vacant position of charon regardin its satellite or "part of a double planet system" status --SquallLeonhart_ITA (talk) 17:01, 24 July 2008 (UTC)

The IAU has stated, "Satellites of plutoids are not plutoids themselves." Pluto is the dominant primary. Charon is simply a relatively large (but submissive) satellite. -- Kheider (talk) 14:47, 25 July 2008 (UTC)

Isn't it arguable whether or not Pluto is the primary? I believe that the centre of mass of the system lies outside the surface of Pluto, and that this is one of the definitions that people use for a double-planet system... Bluap (talk) 00:43, 26 July 2008 (UTC)

Pluto is obviously the more important object. It is larger and more massive, and thus is the primary. There is no official definition of "double planet" or "double dwarf planet". Besides a barycenter is a function of the distance from the primary. The IAU still has yet to define satellites. Currently a plutoid can not be a satellite. See Definition_of_planet#Double_planets_and_moons -- Kheider (talk) 01:12, 26 July 2008 (UTC)

Eeehrrmm! Isn't Charon a perfect example of a charonid? Or maybe at least a charonid candidate? Said: Rursus ☻ 22:57, 29 July 2008 (UTC)

Is there a candidate list out there

Or is that list invented here on WP? In the latter case, shouldn't we consider searching for external discussions on this "dwarf" "planet" stuff to avoid WP:OR? ("Dwarf planets" are neither "dwarfs" nor "planets" in essence, "but whattehecc", says IAU, "we have the rights to perpetuate linguistic errors and confusions, because somebody did so in the past") Said: Rursus ☻ 23:07, 29 July 2008 (UTC)

Any TNO with an absolute magnitude brighter than 4 is a good candidate for a dwarf planet. Michael Brown has already stated that "somewhere between 200 and 400 km an icy body becomes round". Most bodies under 1000km in diameter have an albedo less than 0.25. So if you use NASA's absolute magnitude table you can get a likely range for the diameter using an albedo range of 0.05 to 0.25. An object with an absolute magnitude of 4 will likely be 420 to 940km in diameter. Of course until you know the albedo of an object you will not know the correct size. But the candidates are easily verifiable. -- Kheider (talk) 02:47, 30 July 2008 (UTC)

I wonder why the NASA table uses 0.25 as an upper limit for the albedo, since e.g. Eris has albedo 0.86, and Venus 0.6.--Roentgenium111 (talk) 14:26, 4 August 2008 (UTC)

@ Rursus: There is a list of (probable) dwarf planets on Mike Brown's web site, containing about 40 objects. I haven't checked whether it is the same as this one, but it might be a good reference.--Roentgenium111 (talk) 14:26, 4 August 2008 (UTC)

one plutoid or four?

According to the naming section of this article, being named as a plutoid does not entail classification as a plutoid. However, the intro presumes that it does. Since we refused to classify Haumea and Makemake as plutoids based on their albedos before they were named, it doesn't make much sense to classify them as plutoids now either. Either that or the naming section is wrong. I'm putting a 'dubious' tag in the intro; someone who knows the bureaucracy fix it up, please. kwami (talk) 21:08, 11 October 2008 (UTC)

Change name to "List of dwarf planet candidates"?

and add Vesta, Pallas and Hygeia? Serendi^podous 16:31, 6 March 2009 (UTC)

"Lust of dwarf planet candidates"? This is, I think, a new word in astronomy! :-)

OK. There. Yes, I'm careless and thus open to creating unintentionally humourous typos. :-D Now that we've got that out in the air, what do you think of my proposal? Serendi^podous 17:20, 6 March 2009 (UTC)

I know I prefer "list of dwarf planet candidates", but I don't know if it is any better or worse than List of plutoid candidates. I do believe that in 20 years, if Pluto is still a dwarf planet/plutoid that the next generation will prefer the term "dwarf planet" over plutoid since it better describes, IMHO, what they really are. The concept of having two basically identical categories (where Ceres is currently the only exception) is pointless.-- Kheider (talk) 17:31, 6 March 2009 (UTC)

Since all plutoids are dwarf planets, it makes sense to rename this list. Additional reason is that the term dwarf planet is better known for an average reader than rather obscure plutoid. In other words the readers will be better served if the article is renamed. Ruslik (talk) 20:43, 6 March 2009 (UTC)

But that can be readily turned around: since all dwarf planet candidates are plutoid candidates, it makes sense to keep the name as-is. :)

Okay, brace yourselves, I got all essayish. Here we go:

As I was getting at below, I think arguments about the relative usage rates of the two terms are inappropriate. For starters, "dwarf planet" has been around for two years longer than "plutoid," so there's an element of apples and oranges there, and to that we add that "dwarf planet" generally got more general-interest press on the strength of the Pluto classification media circus, while "plutoid" kind of slid out under the radar as a bit of unfinished IAU business.

And while "dwarf planet" is probably getting more column inches these days in the popular media, it also boasts more emphatic dislike as a term. While "plutoid" isn't getting as much usage, at least nobody thinks there's anything wrong with it as a term for as a discrete class of objects. As several astronomers involved in the whole classification brou-ha-ha have noted, "dwarf planet" isn't a particularly well-loved term internally because of the way it has to be interpreted ex ante as a compound noun rather than a conventional adjective-noun pairing: because the category is emphatically for non-planets, it technically isn't really a setup where a noun ("planet") is modified by an adjective ("dwarf"). (This sort of irritant has long been also true of the term minor planet, of course, but does put if out of synch with dwarf star, dwarf galaxy and so on.)

But more than any of the above reasoning about linguistic resonance, I think the single most important factor is whether using it in this context provides added technical nuance. And I think that the case is pretty clear here.

Make no mistake, this is a technical article about a technical subject. It is of primary interest to individuals with some prior astronomical knowledge, and discusses concepts like albedo and hydrostatic forces which Ms. Frizzle didn't cover when The Magic School Bus travelled through the Solar System. That is not to say it should be left inaccessible to a new and curious reader, rather, as is noted within WP:MTAA and WP:MTTMP, it is of utmost importance to the utility of Wikipedia that the right balance is struck in these articles between allowing a general audience to get a good sense of what we're talking about while not taking any short cuts for the sake of popular appeal. Using "dwarf planet" rather than "plutoid" seems to be just such a short cut, particularly because "plutoid" isn't significantly harder to explain than "dwarf planet," and is something the article manages to do quite fine already IMHO.

On a scientific level, I will venture that "plutoid" is a considerably more useful clade than "dwarf planet." Members of the group have a homogeneity in terms of origin (low density planetisimal leftovers swept out by gas giants) and composition (ice and rock and tasty tasty tholins) and geological phenomena (e.g. atmospheric outgassing and freezing cycles related to changing distance from the sun affecting their albedo). On subjects such as the relative size of natural satellites or frequency of their occurrence, there is a distinct characteristic (much higher than inner-Solar System rocky bodies) that correlates very with membership in this group. At the end of the day scientific papers comparing Pluto to Makemake exist and will continue to be written. Scientific papers comparing Pluto, Makemake and Ceres? Not so much.

Indeed, much of this list's and these article's content refers back to our broader collection of material on topics common to all trans-Neptunian objects, and because plutoids are a clean subset of the TNO grouping, references to these bodies by that name "plugs into" those articles more neatly than references to "dwarf planets."

Sorry for running on and on. I hope at least somewhere in there I got a point across.  :) The Tom (talk) 02:39, 7 March 2009 (UTC)

If you want a comparison of Ceres with plutiods, you can read this. Ruslik (talk) 19:25, 8 March 2009 (UTC)

I'd like to voice my opposition. The evidence that further asteroids will be found to be in hydrostatic equilibrium is very weak. As such, it makes the most sense to keep the article title as specific as possible.

I also believe it is inappropriate to speculate as to what extent the names "plutoid" or "dwarf planet" will take hold in the public discourse and try to name articles accordingly. Arguments can be made both ways as to what is a more useful label--for instance, plutoids share compositional characteristics as well as a common history with the Kuiper belt's formation, while no such common characteristics exist across the entire "dwarf planet" class. The Tom (talk) 17:56, 6 March 2009 (UTC)

Keep in mind that Wikipedia:WikiProject Solar System/Popular pages seems to suggest that the term "dwarf planet" #24 is more common than "plutoid" #111, even if that is a partial result of one term coming out 2 years before the other. -- Kheider (talk) 18:47, 8 March 2009 (UTC)

The terms "dwarf planet" and "plutoid" are not interchangeable. Vesta, Pallas and Hygeia are all possible candidates but are not included here. Serendi^podous 17:02, 9 March 2009 (UTC)

I'd say, then, that "dwarf planet" would be better as it would allow the inclusion of all candidates, and thus prevent fragmentation of the list. --Ckatz^chat_spy 20:28, 9 March 2009 (UTC)

So is everybody cool on the move? Serendi^podous 18:05, 21 March 2009 (UTC)

The chances for Vesta are actually quite good, but would depend on the acceptance of a significantly deformed ex-equilibrium body as a DP. The chances for Pallas and Hygeia are low. By the time Dawn arrives at Vesta, there's a good chance we'll have better images of the others as well, as so may be able to answer candidacy questions for the asteroid belt before the Kuiper belt. In any case it will be an interesting conversation to cover here. kwami (talk) 18:06, 21 March 2009 (UTC)

So should we move it or not? Serendi^podous 12:08, 22 March 2009 (UTC)

Furthest Large Bodies from the Sun?

Furthest Large Bodies from the Sun:

Object	Distance in (AU)	APmag
Eris	96	18.7
Sedna	88	21.1
2007 OR10	85	21.3
2006 QH181	82	23.0

Should we add this table to the article? Does it provide useful information that some readers may want or does it just add clutter? I originally created the table to add content to the 2006 QH181 article. -- Kheider (talk) 17:38, 21 March 2009 (UTC)

I'm not sure of the value of it, but if we do include it, it would be nice to include current distance, perihelion, aphelion, and semi-major axis as well. kwami (talk) 17:57, 21 March 2009 (UTC)

Hmm. Would something along these lines pass muster in terms of being comprehensible? The Tom (talk) 00:16, 30 December 2009 (UTC)

Furthest Large Bodies from the Sun:

Object	Distance (in AU)
	Perihelon						Average						Aphelion
Eris	37.77 ~2256	<		<		<	67.67 ~2162	<	96.70 1 Jan 2010	<	97.19 1 Jan 2000	<	97.56 ~1978
Sedna	76.15 ~2075	<	87.61 1 Jan 2010	<	90.88 1 Jan 2000	<	525.86	<		<		<	975.56 c. 4000 BC
2007 OR10	33.62 ~1857	>		>		>	67.33 ~1951	>	83.39 1 Jan 2000	>	85.99 1 Jan 2010	>	101.03 ~2133
2006 QH181	37.60 ~1860	>		>		>	67.3 ~1959	>	79.62 1 Jan 2000	>	82.13 1 Jan 2010	>	97.02 ~2137

Weak candidates

The following candidates were added by 89.41.195.201. I have moved them to the talk page since even assuming an albedo of 0.04, an object with a absolute magnitude of 6.4 would only be 350km in diameter. Does anyone know if I am missing something? -- Kheider (talk) 19:18, 29 December 2009 (UTC)

Above 6

Name	H	Category	Diameter (km)	Average distance from the Sun (AU)
2008 UB332	6.9			39.50
2008 SO266	6.9			39.64
2008 CS190	6.4			42.08

Above 7

Name	H	Category	Diameter (km)	Average distance from the Sun (AU)
2009 KL30	7.6			45.60

Above 8

Name	H	Category	Diameter (km)	Average distance from the Sun (AU)
2006 WS195	8.2			39.65

Above 9

Name	H	Category	Diameter (km)	Average distance from the Sun (AU)
2005 PH23	9.1			44.07

Above 10

Name	H	Category	Diameter (km)	Average distance from the Sun (AU)
2001 FB185	10.4			43.17

Should we include Charon?

It was initially considered for planet status, and may be reconsidered in future. Serendi^podous 20:42, 13 April 2009 (UTC)

My gut instinct is to not include Charon since it is submissive to Pluto (thus does not really directly orbit the Sun) and the IAU has not officially defined what a satellite is. If we listed Charon I would feel weird not speculating about possible future definitions that might include Triton (captured dwarf planet) and Earth's moon (kamikaze dwarf planet). Currently satellites can not be dwarf planets. -- Kheider (talk) 21:02, 13 April 2009 (UTC)

Is the barycenter within the Roche limit of Pluto, or outside it? If it is outside it, it seems that Charon should be considered. As Pluto and Charon do not orbit each other, as the barycenter is outside of Pluto, it's more like the two of them are moons, and there is no central (dwarf) planet that they orbit... 64.229.101.183 (talk) 00:28, 16 February 2011 (UTC)

IMHO, it really comes down to this: do we have a reliable source stating that the IAU/MPC are considering this designation for Charon? If not, we risk falling into speculation. --Ckatz^chat_spy 01:41, 16 February 2011 (UTC)

I agree with Ckatz: wait for the IAU to say, if it ever does. In Brown's "How I Killed Pluto ..." book, he was very much against the barycentre definition of a double planet (surface, not Roche), leading me to guess that there may have been others at the IAU conference of similar mind, hence Charon's exclusion. He points out that the Jupiter-Sol barycentre is outside the sun. So (my logic here, not necessarily Brown's), if Charon is not a satellite, then neither is Jupiter, hence Jupiter's not a planet because it doesn't orbit the sun! Tbayboy (talk) 18:08, 16 February 2011 (UTC)

Do we need the mass guestimates?

Several entries have masses which are estimated by assuming a density and assuming a diameter from the absolute magnitude. Given the wide range of values for both the diameter and density, the resulting mass estimates are lucky to be within a factor of ten (more like 2^3 * 3 = factor of 24). Do we need such wild guesses here?

The ones based on satellites (Orcus, Quaoar) or perturbations (Vesta, Pallas) are fine. So is 1999 TC36, but that shouldn't be on the list now that it's binary (or trinary, pair with the moon). Several others have satellites with undetermined orbits, so reasonable mass estimates for them will trickle in. So the mass column could stay. I just don't like filling it with innaccurate numbers.

Especially Sedna. Sedna has no accepted origin explanation, so we can't even say that it's likely to be icy (like KBOs, even if some of them are rocky, post-collision cores like Haumea). Tbayboy (talk) 17:55, 8 January 2010 (UTC)

Actually I am happy with the assumed masses now listed. I have only fixed the masses of the objects with Spitzer diameters. Since real dwarf planets will have densities of 1 to 2.3 (on average), I suspect the current single figure estimates are correct within a factor of 5. I do not suggest putting any more mass estimates that do not have a well-established diameters. The value for Sedna assumes a range of 8.3×10²⁰–7.0×10²¹ kg^{(Radius of 590 km and density of 0.97 = 8.3×1020 kg mass. Radius of 900 km and density of 2.3 = 7.0×1021 kg)(0.05–0.42 Eris)} The examples listed are good enough to at least give readers a ballpark figure. -- Kheider (talk) 18:22, 8 January 2010 (UTC)

I also think TC36 should stay because it demonstrates how little we know about these objects. Obviously not all candidates will qualify. -- Kheider (talk) 18:27, 8 January 2010 (UTC)

Ixion, for example, has a Spitzer diameter of 430-910, for a range factor of >2, and thus a volume factor of >8. Quaoar and Haumea both have densities that might be over 3. So densities might range from about 1 to about 3, for a factor of 3. That makes for a mass range of a factor of >24 (highest/lowest). Quaoar's Spitzer size (654 -- 1051) has high/low = 1.6, for a volume range of ~4. For a mass ballpark, you can just state one which would apply to all the objects in the table (e.g., .2 Yg - 2 Yg for H=3 to 4).

TC36 is not a candidate. As a demonstration of the problems, it could be put into the text (i.e., before or after the tables).

Anyway, I'm sure you understand the complaint, so I'm okay. Tbayboy (talk) 19:49, 8 January 2010 (UTC)

Ixion: 4×10¹⁹–9×10²⁰ kg^{(Radius of 215 km and density of 0.97 = 4×1019 kg mass. Radius of 455 km and density of 2.3 = 9×1020 kg mass)}

2004 GV9: 1.1–5.0×10²⁰ kg^{(Radius of 303.5 km and density of 0.97 = 1.1×1020 kg mass. Radius of 373.5 km and density of 2.3 = 5.0×1020 kg mass)}

It is good to debate the merits of this stuff. Ixion is still somewhat of an extreme given the error bar on the albedo. Most Spitzer dwarfs do have much tighter albedo ranges. The range on Haumea's density is a function of the imprecise dimensions, ie: a larger volume will result in a lower density. We still can not technically rule out dwarf planets with a density greater than 4, though I think for general purposes it is reasonable to use Eris (2.3) as a generic upper bound. I am open to suggestions -- Kheider (talk) 20:22, 8 January 2010 (UTC)

Should we comment on objects qualifying thru mass, as that determines the gravitational part of equilibrium? Mimas is the smallest known at 3.75×10¹⁹ kg, and Proteus the largest exception at ~4.4–5×10¹⁹ kg. Presumably any icy body on the order of ×10²⁰ kg would be a DP regardless of thermal history. And that's a lot easier to measure than size if there's a moon. Are there any refs for this approach? — kwami (talk) 18:07, 4 July 2011 (UTC)

No mass refs that I know of. I've always thought there should be, since there are many TNOs with moons, so mass is often likelier to sooner have a good measurement than diameter. Also keep in mind that there really is no official list (the oft-Wikipedia-cited list is not official, just informative -- Brown mentioned that aspect in one of his blogs, but I don't have the reference), so you could use any reputable source -- it doesn't have to be just the IAU.

I have to point out, though, that Mimas and other moons are not good yardsticks for TNOs, since the moons are often subject to tidal heating, so they round out much easier than a TNO would. Assuming iciness is dodgy, too (see above re Quaoar). So I think the threshold would have to be higher, say half a Yg (×10²¹ kg). Tbayboy (talk) 19:05, 4 July 2011 (UTC)

Really? Vesta completely melted at less than that. Agreed tidal heating could explain Mimas, but 1×10²⁰ is still twice the mass of Proteus. Maybe an ordered chart with Vesta, Pallas, and Proteus thrown in for comparison? — kwami (talk) 20:25, 4 July 2011 (UTC)

Well, Vesta apparently hasn't been able to melt again after its "great collision" millions of years ago - otherwise it would be spherical again. So its mass alone doesn't suffice for gravitational equilibrium. Maybe it had some other heat source in the distant past (perhaps another collision?) ... --Roentgenium111 (talk) 21:00, 4 July 2011 (UTC)

²⁶Al, but that only lasted a few million years. But Vesta is basalt. It's dubious that any TNOs are solid rock.

Okay, bodies I've been able to find w/ m > 0.5e20 and moons to enable a mass calculation rather than guestimate:

Eris 167e20
Pluto 130
Haumea 42
Quaoar 16
Charon 15
Ceres 9.5
Orcus 6.3
2003 AZ84 ~5.3 [spurious fig? not calc?]
2002 UX25 [not yet calculated; ~3 expected]
Vesta 2.7: rocky, melted (once regular)
Pallas 2.1: rocky irregular
Salacia 2.0
2002 WC19 ~0.7 [not calc?]
1995 TL8 ~0.5
Proteus ~0.5: icy irregular
1997 CS29 ~0.4 [calc?]

— kwami (talk) 21:25, 4 July 2011 (UTC)

(Backing up the indent) See Dwarf Planets Are Crazy: Brown disagrees with your assessment of the rockiness of TNOs :-). At least, it's not too rare for a TNOs to be rocky, so any threshold should accomodate the possibility. I picked .5 Yg just because it's the next round number up from Vesta, who clearly struggles with her shape. See also Cole, who calculates the minimum mass for equilibrium of a rocky body (density of 3, like Quaoar and Haumea) to be around .35 Yg, and down to .01 for a completely water ice body (well under your .1 proposal). The low end could be a threshold for candidate dwarfs, if only mass is known. Anyway, we would still need a good reference for any thresholds. Tbayboy (talk) 23:59, 4 July 2011 (UTC)

Error in image?

Colours of the Transneptunians

Am I reading this wrong? That tiny body on the right is supposed to be Mars? — kwami (talk) 16:35, 17 August 2011 (UTC)

Right-hand-most, topmost is Mars. TREKphiler ^{any time you're ready, Uhura} 18:48, 17 August 2011 (UTC)

Suggesting Mars is the size or magnitude of a small TNO. I don't get it. — kwami (talk) 19:01, 17 August 2011 (UTC)

Think what it would look like if it showed Mars at actual size. You would have a hard time seeing the actual Martian values, since the disc wouldn't fit in the picture. Tbayboy (talk) 20:38, 17 August 2011 (UTC)

So why have different sized icons for different sized bodies if the size is not representative? How is someone supposed to know which data point is real and which is fake? And why are we posting fake data in an encyclopedia? — kwami (talk) 20:54, 17 August 2011 (UTC)

The sizes are representative, for eveything except Mars, and that exception is for obvious reasons. Give the readers some credit for intelligence! Tbayboy (talk) 22:52, 17 August 2011 (UTC)

I couldn't figure out what it meant! I thought maybe there were two different scales, and Mars was on the magnitude scale while Orcus was on the diameter scale. And who knows about all the other things in there: they aren't labeled. If we want Mars not to scale, we need to label Mars as not to scale. Or better yet, mark it with an X and don't pretend that it's this tiny little body. This is false, and therefore either needs to be fixed, deleted, or reverted to the original version before the falsehood was added. I'll do the latter; if someone wants to fix it, great. As it currently is, it has no business in an encyclopedia. — kwami (talk) 22:59, 17 August 2011 (UTC)

Triton is off, too, if you're in the mood for a crusade. :-) Tbayboy (talk) 22:55, 17 August 2011 (UTC)

It's a crusade to expect accuracy of a scientific article? I suppose in Saturn's info box we could list its surface temperature as 6000°, and expect everyone to know that it's not the same scale of degrees as the rest of the Solar System. — kwami (talk) 22:59, 17 August 2011 (UTC)

This thread does explain some of the dp-issues currently taking place. If you always expect "exact perfection" you should not expect any result to be listed on Wikipedia until it has been accepted as fact for 50+ years. You could have placed a disclaimer for Mars and Triton in the text description below the image. PS: I reverted your edit, since there is a text disclaimer in the description. -- Kheider (talk) 09:28, 21 January 2012 (UTC)

By your standard, we don't need to accept the Earth as a planet. No, without warning that this is purposefully in gross error, it's simply in gross error. And the warning needs to either go in every article that transcludes the image, or be hard-coded in the image. — kwami (talk) 09:42, 21 January 2012 (UTC)

Mike Brown teaches his students that there are only 4 planets: Jupiter, Saturn, Uranus, and Neptune. -- Kheider (talk) 15:55, 21 January 2012 (UTC)

Source? From what I've heard, he teaches that they are a very different kind of object that the terrestrials, and that if we were to come of with a word for them today we probably wouldn't use the same word for both, but he's not teaching that Earth is not a planet. — kwami (talk) 21:57, 22 May 2012 (UTC)

Phoebe as a captured DP

The new Icarus article would seem to be relevant to this article. Although summaries of it do not use the word DP, they do say that Phoebe, at only 200km in diameter, appears to have once been a hot, equilibrium body, battered out of shape since it solidified. Which brings us back to the question of whether a body can be an ex-DP, and suggests that the 400-km lower limit may depend not just on composition but on DOB. — kwami (talk) 20:42, 27 April 2012 (UTC)

If Charon can't be on this list, I don't think Phoebe can. Besides, I don't see Deimos and Phobos on any asteroid lists. Serendi^podous 21:02, 27 April 2012 (UTC)

Of course Phoebe can't be on the list because it is (now) a moon. But it is interesting, and relevant to this article, to consider an object only slightly larger than 200 km that is approximately spherical (and may once have actually been that, but has since gotten too battered up). It means that in the mentioned range of 200–400 km the actual size at which bodies could (sometimes) become spherical is at the lower end. And this is in turn relevant for the weaker candidates. --JorisvS (talk) 23:10, 27 April 2012 (UTC)

I laughed when I read Cassini Finds Saturn Moon has Planet-Like Qualities (04.26.12). At some point you just need to draw a line. This is why the terms asteroid, protoplanet, dwarf-planet, and planet exist. Phoebe is physically borderline much as Vesta and Pallas are. -- Kheider (talk) 21:53, 27 April 2012 (UTC)

Why would you laugh (except for maybe the title)? What would you call an object that is roughly spherical and might once have been a true equilibrium body (these borderline cases)? --JorisvS (talk) 23:10, 27 April 2012 (UTC)

I would have no problem calling it a failed protoplanet. -- Kheider (talk) 03:53, 28 April 2012 (UTC)

How would it be a failed protoplanet? --JorisvS (talk) 13:41, 28 April 2012 (UTC)

It failed to mature into a dominant body. Claiming it "might once have been a true equilibrium body" relies on semantics too much for me. -- Kheider (talk) 15:14, 29 April 2012 (UTC)

But why wouldn't it simply be a protoplanet, why would it be a failed one? --JorisvS (talk) 16:02, 29 April 2012 (UTC)

Yes, that was my point. When an object is estimated to be 400km in diam, we have been considering it a weak candidate, because if the size has been overestimated it couldn't be a DP. But now it appears that the size could be overestimated twofold and it could still be a DP; also, there are hundreds of other bodies in the 200–400km range which no-one has been considering. Of course, many of these would presumably be like Phoebe, and so maybe ex-DPs rather than current DPs.

I'd be happy to call these things planetoids, and Pluto too. Better name than DP IMO. Or perhaps we could 'planetesimal' for borderline PMOs: massive enough to achieve equilibrium before ²⁶Al ran out, but not enough to maintain it. Anyway, it does make us reconsider what would qualify. — kwami (talk) 01:43, 28 April 2012 (UTC)

In that respect Brown's list is quite good, considering bodies with an estimated diameter between 200 and 400 km to be 'possibly' DPs. Using 'planetesimal' for such borderline objects is not in line with the current definition of the word. --JorisvS (talk) 13:41, 28 April 2012 (UTC)

I see your point, but then Phoebe's current shape speaks against the 200 km limit of becoming round for present-day objects - unless Phoebe was exceptionally unlucky being "battered up". And there is also the presumably icy Hyperion which has an average diameter of almost 300 km, but is far from spherical, which makes me doubt the limit for icy objects to be close to 200 km - unless, as you said, the shape does indeed depend primarily on the object's history in this size range... --Roentgenium111 (talk) 21:04, 29 April 2012 (UTC)

Since it probably coalesced from Saturn's accretion disk, Hyperion may have formed several million years later, and so missed out on differentiation from the decay of 26-Al. Proteus, at 400 km, presumably accreted even later, after the capture of Triton disrupted the original Neptunian system, and Mimas may only have achieved equilibrium through tidal heating. Thermal history is clearly important, but it's surprising to find s.t. at 200 km that looks like it was once in equilibrium, even if it isn't any longer. — kwami (talk) 05:24, 30 April 2012 (UTC)

Methone, moon of Saturn

Thanks for the explanations. I didn't find it that surprising since of course any object, no matter how small, achieves equilibrium if it is heated enough such that it melts all over. But today I was really surprised when I read that the tiny Saturn moon Methone has been found to be an almost perfect ellipsoid [1] - it's only 3 km in diameter! --Roentgenium111 (talk) 15:19, 22 May 2012 (UTC)

If it truly is in equilibrium (it sure looks like it, assuming the elongation is due to tides), then there may be things like this in direct orbit about the sun, and the IAU might need to modify its definition of dwarf planet to a solid body in HE. — kwami (talk) 22:00, 22 May 2012 (UTC)

I suspect the Methone equilibrium is a simple result of the resonance with the moon Mimas. This is in part why moons can achieve equilibrium more easily than objects in direct orbit of the Sun. -- Kheider (talk) 22:37, 22 May 2012 (UTC)

You mean from tidal heating from the resonance? Would that affect a body so small? — kwami (talk) 02:22, 23 May 2012 (UTC)

*IF* Methone is a fragment that was created as a result of a high-energy collision between larger bodies, I do not see why the resonance could not smooth the object out before it solidified. -- Kheider (talk) 12:52, 23 May 2012 (UTC)

Methone is just a pile of unconsolidated debris—a rubble pile, like all inner Cronian satellites. When Methone is shaken by tides these debris flow like a liquid. So, nothing surprising. Ruslik_Zero 19:11, 23 May 2012 (UTC)

Which would mean that it is hydrostatic equilibrium... --JorisvS (talk) 19:27, 23 May 2012 (UTC)

Which would mean, according to the defs I've seen, that it's a PMO. Which it obviously shouldn't be. — kwami (talk) 20:10, 23 May 2012 (UTC)

Note that the IAU dwarf planet definition also specifies that the graivity must overcome the rigid body forces. Is the RBF of a rubble pile that of the gravitation between the rocks, or the checmical bonds within each rock? Can we agree that the latter is intended? Otherwise, any old comet might periodically become a temporary DP. Tbayboy (talk) 15:46, 24 May 2012 (UTC)

They meant that the internal pressure must signification exceed the bulk material strength of the constituent materials, so they are crushed and all voids are closed. If an object is a rubble pile it means that it is, in fact, very far from the hydrostatic equilibrium. So, not everything that is round is in the hydrostatic equilibrium. Ruslik_Zero 18:22, 24 May 2012 (UTC)

Yes, if it's a rubble pile. But if it's a solid body covered in dust that's in HE, that's another matter. Though the RBF criterion would exclude dust balls, as well as liquid bodies. For Phoebe, it's a difficult question: did it only heat up enough to become plastic? Then it was presumably a DP. But it doesn't exceed RBF's currently, so would no longer be a DP even if in orbit about the sun. Vesta is presumably the same: an ex-DP. People speculated that it might be a DP before the DAWN mission, but I haven't seen anything like that since. — kwami (talk) 20:36, 24 May 2012 (UTC)

If one excluded liquid bodies from qualifying for hydrostatic equilibrium, Jupiter and Saturn would not be planets, since they're for the most part liquid or even gaseous. This can't have been the IAU's intention; and logically, in a liquid body, gravity automatically overcomes the rigid body forces, because there are no rigid body forces! So technically, any liquid body in Solar orbit that is round because of its gravity (and not, as a water drop, because of surface tension) should be considered a dwarf planet... Humanity could create a (very short-lived) dwarf planet themselves by putting a one-meter-large water ball into Solar orbit. :-) --Roentgenium111 (talk) 13:22, 11 July 2012 (UTC)

Jupiter and Saturn are assumed to fit the def because their expected solid cores are large enough to qualify. They're also well past the qualifying mass. A 1-m blob of water would not qualify. — kwami (talk) 18:28, 11 July 2012 (UTC)

By your claims, Jupiter and Saturn would not be confirmed as planets until their solid cores are confirmed (and large enough); that seems absurd to me, and is not what the IAU resolution (listing them as planets) says. The point is that there is no fixed "qualifying mass" in the IAU definition (e.g. non-DP Vesta is more massive than many TNO dwarf planet candidates), the necessary mass depends on the rigidity of the object... --Roentgenium111 (talk) 17:38, 10 August 2012 (UTC)

I never said there was a fixed mass, and I just said the opposite of what you understood me to say. The IAU definition ("has sufficient mass for its self-gravity to overcome rigid body forces") is ambiguous—is that a hypothetical or is it meant as a descriptive statement?—but the acceptance of the gas giants means that they must be applying it in a hypothetical sense: if there were a solid core, rigid-body forces would be overcome. — kwami (talk) 17:49, 10 August 2012 (UTC)

Absolute magnitude

The absolute magnitude in the article can't be the same as the absolute magnitude for a star 10 parsecs away, can it? Bubba73 ^{You talkin' to me?} 14:47, 26 May 2012 (UTC)

No, it isn't: Absolute magnitude#Solar System bodies (H). --JorisvS (talk) 14:51, 26 May 2012 (UTC)

"others are thought likely to be classified as such in the future"

This wording was added years ago when we had a recent ref to that this might happen "soon". Half a decade later, there's no word on the IAU addressing this issue. Since the ref hasn't panned out, we shouldn't keep this wording, which suggests that more recognition is in the works. (All we have are Tancredi's recs, which AFAIK the IAU has never responded to.) Also, whether objects are classified as DPs or not is rather beside the point, since the article is about which bodies may be DPs, with any recognition being incidental. — kwami (talk) 06:33, 4 January 2013 (UTC)

What reference ever said "soon"? Only the IAU (or one of its people, speaking unofficially) can reliably say something like that. And recognition is not incidental if the list is official: these possible dwarfs should not include the official ones. The half-decade is irrelevent: a body should get listed when the IAU is satisfied with the evidence that it is a dwarf. Tbayboy (talk) 17:36, 4 January 2013 (UTC)

But we can't use what we think "should" be, only what we can reference. We have no evidence the IAU is active in this area, so any statements about what they might do in the future violates WP:crystal ball. As you say, only the IAU (or s.o. w knowledge of the workings of the IAU) is acceptable as a ref for the intentions of the IAU. Personally, I would welcome clarification on their part. — kwami (talk) 18:14, 4 January 2013 (UTC)

Reorganizing the lead

There's a lot of cruft that's been restored to the lead after I cleaned it up:

• technical details
• definition of 'plutoid', which is irrelevant and which no-one uses anyway
• the first likely DP since Pluto, which according to the article is incorrect

The topic of the article, the possible DPs, comes nearly last, after bodies which do not appear in the list and the cruft above.

Any reason the lead should start off-topic, be full of technical details, and have the actual topic last? — kwami (talk) 09:23, 4 January 2013 (UTC)

I like the shortened lead. However, I think "The PI's Perspective" ref should be dropped: it refers to dwarf planets as a class of planet, so it's not very reliable, more Alan Stern grinding his axe. Tbayboy (talk) 18:10, 4 January 2013 (UTC)

A scientific disagreement – which in this case is not even over facts, but over a definition – does not make a ref unreliable. Stern's concept of "planet" is a minority view, but no less scientific for that. (And remember, the whole reason for calling these "dwarf planets" was to reinforce the position of the IAU board that they were planets! Stern is only out on a limb for adding "satellite planets" as well.) In any case, the definition of "planet" does not change the definition of "dwarf planet" (the IAU def is just an attempt to word Stern's def more rigorously), and thus does not impact his estimate for the number of DPs, which is the latest referenced estimate we have. — kwami (talk) 18:22, 4 January 2013 (UTC)

I've reorganized it for a better flow, as we should move from the current state - five designated to the possibilities (second sentence), not the other way. --Ckatz^chat_spy 20:48, 4 January 2013 (UTC)

I disagree. The article is about possible DPs, and so should start out with possible DPs. That is the current state, according to the latest ref we have. How many of these are recognized and by who is secondary, because the article is not primarily about recognition. And we certainly shouldn't start by singling out five bodies that we don't even include in the article! — kwami (talk) 21:08, 4 January 2013 (UTC)

Well, I've had to revert you yet again as we should resolve this first before changing the pre-existing order. If the discussion leads to such a change, fine, but please don't keep reverting. --Ckatz^chat_spy 21:28, 4 January 2013 (UTC)

I think both read well enough, and both flow logically. It is sometimes conceptually easier to describe something in terms of its complement. Tbayboy (talk) 01:46, 5 January 2013 (UTC)

Except that the article is not about the IAU, and not about the five bodies which do not appear in the tables, as the opening line implies. I suppose we could add them to the H & Spitzer tables, but even so I don't see what could be conceptually easier than "it is estimated that there are X dwarf planets". — kwami (talk) 03:43, 5 January 2013 (UTC)

Minimum diameters

Minimum diameters should presumably be calculated from maximum magnitudes, or at least +1σ. Any other convention that would work better? We have a problem with Pluto and OR10, where we have no ref for σ. — kwami (talk) 22:21, 14 January 2013 (UTC)

Sounds right to me. I don't think it matters for Pluto, since the occultations have pretty good error bars, and they're way above the threshold. On the other hand, I just read [2] which says Iapetus might not be H-E. Tbayboy (talk) 02:37, 15 January 2013 (UTC)

But is that just an effect of the equatorial ridge?

If Iapetus is no longer in HE, then there's no reason to think that Haumea or Makemake are either.

— kwami (talk) 03:11, 15 January 2013 (UTC)

Not because of the ridge. It's too oblate for its current spin. One of their conclusions is that Rhea is H-E. But there's no sharp line from H-E to not, so it's really a question of how close you want to be before calling it H-E. It also depends on the interior model (differentiated or not). All but Rhea were a off H-E, but Iapetus was way off. Note, however, that "off" is only a few km. Tbayboy (talk) 04:31, 15 January 2013 (UTC)

That could simply mean that Rhea solidified at its current spin, not that it's still actually in HE. If that's the case, we have no known lower diameter or mass for HE beside the largest moons, in which case we can't conclude that there are any DPs. All are still only possibilities. — kwami (talk) 05:14, 15 January 2013 (UTC)

Or, they are in H-E, but it will just take a few more billion years to get there. The theory (Lineweaver, Cole) makes them well past H-E, but it doesn't address how quickly they flow to it. I think the real point is that there is no natural separation between H-E and non-H-E (unlike with planets vs DPs, or even the brown dwarf desert). At some point, an arbitrary line has to be drawn. I wonder if the planets are exactly in H-E. Tbayboy (talk) 14:19, 15 January 2013 (UTC)

Agreed. At at this distance all we can really say is that Pluto and Charon are pretty round.

Depends on what you mean by "exactly". There's always going to be a lag time to disturbances. But if there's a liquid layer and the overlying crust is not strong enough to support itself, as on Earth, then I think that would meet any common-sense understanding. The Galileans and Titan fit that, though it might be difficult to prove they fit the IAU def. And we don't (yet) know if Ceres, Pluto, and Eris actually qualify. If they don't, do you think they'll accept that DP is an empty category, or will they redefine it to include them? — kwami (talk) 20:49, 15 January 2013 (UTC)

Realistically, Pluto and Eris are DP by definition, since they're the whole point of the category. Any proposed metric for Dp-ness (for roundness and orbital clearing) must categorise the IAU planets and DPs as they are. The Saturn moons paper (mentioned above) just highlights the distinction as arbitrary. I think that differentiated Vesta shows that the category is not very useful scientifically. Tbayboy (talk) 04:10, 16 January 2013 (UTC)

Yeah, but the ultimate point of the definition was to get Pluto reinstated as a planet. Since that part of the resolution failed, the motivation for the category no longer exists. — kwami (talk) 04:15, 16 January 2013 (UTC)

Their alternative would be to also consider Vesta a DP, which makes sense scientifically, as Tbayboy has pointed out. --JorisvS (talk) 11:30, 16 January 2013 (UTC)

Brightness table

Would a table showing the brightest object discovered each year be useful to the article? (If nothing else it does show trends.)

Brightest absolute magnitude discovered each year:

Year	Trans-Neptunian object	(H)
2012	2012 BX85	5.5
2011	2011 FW62	5.0
2010	2010 EK139	3.8
2009	2009 YE7	4.4
2008	2008 ST291	4.3
2007	(225088) 2007 OR10	2.0
2006	2006 QH181	3.8
2005	136199 Eris	-1.2
2004	90482 Orcus (2004 DW)	2.3
2003	90377 Sedna (2003 VB12)	1.5
2002	50000 Quaoar (2002 LM60)	2.5
2001	28978 Ixion (2001 KX76)	3.2
2000	20000 Varuna (2000 WR106)	3.7
1999	(26375) 1999 DE9	4.7
1998	19521 Chaos (1998 WH24)	4.9
1997	(119979) 2002 WC19	4.9
1996	(19308) 1996 TO66	4.5
1995	(24835) 1995 SM55	4.8

-- Kheider (talk) 18:56, 22 January 2013 (UTC)

Maybe plotted as a graph?

1992: H.max = 7.2.

— kwami (talk) 21:35, 22 January 2013 (UTC)

Well, that's certainly interesting in a geek-beard-stroking dataporn kind of way, but what is it actually useful for? Other than showing there was some kind of global problem around the mid noughties where no-one could see anything very well? Possibly side effects of that unpronounceable, untypeable Icelandic volcano that shoved loads of ash into the air? 209.93.141.17 (talk) 06:29, 25 September 2017 (UTC)

Since this simply charts the brightest object in each year, it just means that a good deal of bright KBOs (Haumea, Makemake, Eris) were discovered in the middle of the 2000s. Presumably the less bright KBOs continued to be discovered at a similar rate, but are simply not reflected in the graph simply because a few really bright objects swamp them for those years. Eyjafjallajökull erupted in 2010, and given that it was not erupting for the entire year, and not all observatories would have been affected by it, it is difficult to see why it should have had any sizeable effect at all. Double sharp (talk) 07:28, 25 September 2017 (UTC)

Diameters in H section

The diameters in the H section vary widely in their exactness. Most are just given as values with +- uncertainties. But a few have longer lines which I don't think are needed - they just make the column wider than it needs to be.

For example Vesta. Sure, it has different values on its axes. But Haumea is much more extreme in that regard and is given with the mean (which I think is correct here - people who want more info on specific objects can follow the links). Varuna is another "offender" with not one but two ranges given. Both are years old and don't take the new chord value from an occultation into account. Also, the "(assumed)" part for some objects could just go into a footnote, which could also be longer (to give the base of the assumption).

While I'm at it, maybe "average distance to the Sun" could be replaced by the much shorter "semimajor axis" which is also more exact. In a footnote it could be explained that the semimajor axis is the average between minimum and maximum distance to the Sun (it is *not* the average distance of that object to the Sun over time; that value is greater). Ambi Valent (talk) 05:51, 10 May 2013 (UTC)

Pallas and Vesta

Are they dwarf planet candidates? Should they be listed in {{Dwarf planets}} as "likely" candidates? "Possible" candidates? Double sharp (talk) 03:46, 2 June 2014 (UTC)

Pallas is not thought to have been in HE. Vesta was, but no-one seems to be calling it a DP because of that. — kwami (talk) 06:38, 2 June 2014 (UTC)

DP requires current HE. Vesta clearly isn't, and the images of Pallas, fuzzy as they are, clearly show that it is too lumpy. Tbayboy (talk) 12:35, 2 June 2014 (UTC)

OK, so why are they on this list? Double sharp (talk) 13:20, 2 June 2014 (UTC)

Because their H values are in the candidate range. Also, this list is out of date, especially regarding Vesta (it's pre-Dawn). Note that 1999 TC36 is also listed here because of it's H, even though it, too, is extremely unlikely to be a DP: it has since been found to be a trinary object. Tbayboy (talk) 16:48, 2 June 2014 (UTC)

Is there actually a (non-OR) rationale for H<5 being the "candidate range"? I couldn't find one in the article. (The explanation "as for H=5 the minimum diameter is only a third of the 400 kilometres (250 mi) limit." makes no sense to me - why a third, and not any other value?) If the limit H=5 is just an editors' guesstimate, there's no reason to keep entries below H=5 that are clearly not dwarf planets. --Roentgenium111 (talk) 17:53, 13 June 2014 (UTC)

I think it's hysterical: the H list predates Brown's site, and probably Tancredi's results, too. There were no references, so a relatively simple, arbitrary line was drawn. I don't object to removing those tables and just using Brown and Tancredi, since they mostly cover the same objects, anyway. Note, however, that Brown's list has some problems: it also includes 1999 TC36, and some other suspect numbers. Also, Brown's list is over a thousand TNOs long (348 to the end of "possible"), so we would want to cut it off at some point, which is also arbitrary. And Tancredi is out of date, not considering the Herschel observations and various occultations. There are no good references for this list. Tbayboy (talk) 23:03, 13 June 2014 (UTC)

If this article is reduced to nothing but a copy of Brown's list (not to mention Brown's bad values for the abs mag), then I would see no reason to even have a Wikipedia list. -- Kheider (talk) 23:21, 13 June 2014 (UTC)

The place where we currently cut off Brown's list (the end of "likely") seems, based on Brown's listed H values (which I gather are questionable?), to conform to our current arbitrary limit of H ≤ 5, although I think that it would also make sense to cut off earlier at the end of "highly likely" instead because some of the "likely" ones may very well be significantly smaller (in the range of 100 km smaller, perhaps, from looking at the article on (84522) 2002 TC302?) than the figures he gives due to measurement uncertainties, and thus stand much less chances of being DPs. (Brown's basing his list on size, while we're basing our list on H.)

I think we should absolutely keep our own list alongside those of authorities such as Brown's and Tancredi's, because it includes the uncertainties and (for some objects) different figures from different observations for the same body. Double sharp (talk) 15:24, 14 June 2014 (UTC)

Take 2012 VP113: MPC = 4.0, JPL = 4.05, Brown = 4.3. Mike Brown is often 0.3 mags too dim. This also throws off his diameter estimates. -- Kheider (talk) 19:34, 14 June 2014 (UTC)

I agree with Kheider here, that the list has little point if it's just a clone of Brown. On the other hand, Roentgenium111 has a fair point re OR. I think we should have a list, since it's a very natural question, and if the page were removed then I think somebody would just re-add it (in good faith). Given that most TNOs don't have solid sizes, I don't think we can do better than using H as a cutoff, either H < 5 or top 100 H. Whatever we do, the cutoff will be arbitrary. Even if there were solid sources, we would have the same problem, since it's unlikely that multiple sources would choose the same arbitrary cut-off themselves. Also, there are other lists that have the same problem: highest selling xxx, most popular yyy, largest cities of zzz -- you have to pick some arbitrary threshold.

In summary, I prefer keeping the list with H as the primary criteria, since it involves the least OR. However, I would like to see the lists folded into one. Rather than a separate table for Brown and Tancredi, just make them columns of their determinations. For sizes, there could be separate columns for various size determinations: measured (radiogenic and/or occultation), and several for albedo (.04, 0.9, .25, .7). Then make it sortable and leave it to the reader to decide. Tbayboy (talk) 22:00, 14 June 2014 (UTC)

I like this idea. Double sharp (talk) 04:04, 15 June 2014 (UTC)

Certainly a copy of Brown's list would be less OR than the existing H list (both the cut-off value and the use of H as the sole criterium are (mild) OR without a published list doing the same). Such a copy would actually have some advantages over just linking to Brown's original: we'd have wikilinks to all objects incorporated, the ability to sort by name, magnitude etc. and (via the article history) an archive of Brown's earlier versions (as he updates his list irregularly). The natural cut-off, given this article's title, would be to stop at Brown's "possible" dwarf planets, i.e. ~348, which seems an okay size. (FWIW, exact copying of external lists to Wikipedia is common, see e.g. the much longer (>100,000!) List of minor planets, an exact copy of the MPC's list.) Adapting your "merge" suggestion, we could keep our "best RS values" for the magnitude in an additional, separate column (if Brown's magnitude estimates do often differ from them), and have another column for Tancredi's results. Via the sortability by magnitude, we'd then essentially keep a copy of the current list at the same time, minus the obvious non-DPs like Pallas and Vesta. Any "problems" with Brown's list could also be added as footnotes. --Roentgenium111 (talk) 15:56, 16 June 2014 (UTC)

Deciding "obvious" can be more OR that picking a list cut-off or other simple inclusion criteria, like H or diameter. I would rather see them on the list (or in a separate list) with a reference saying that they're not. Tbayboy (talk) 12:42, 23 June 2014 (UTC)

In principle, I agree with your first sentence. But it's well-established that the HE limit is larger for asteroids than for TNOs, so it makes no sense to judge Vesta and Pallas by the TNOs' 400km limit (which is also used as a "justification" for the H=5 limit in the article). And since we do have RS'es noting this difference, it would be OR to include them nevertheless. (E.g. Brown explicitly writes, "In the asteroid belt Ceres, with a diameter of 900 km, is the only object large enough to be round.") I wouldn't mind a remark or footnote in the article clarifying why they're not included. --Roentgenium111 (talk) 14:07, 23 June 2014 (UTC)

Just to be clear, the reason I think they should be mentioned (whether in the list, or in a separate section) is that various refs suggested them as possible DPs when the DP category was created. So we need refs stating that they're now not DPs, else excluding them is OR. Post-Dawn Vesta is easy (I think I have one lying around), but we'll need a ref for Pallas. Similarly, Brown still has 1999 TC66 as >400 km, even though it's now known to be a triple, with the largest of ~270 -- its absence should be explained. Tbayboy (talk) 04:03, 24 June 2014 (UTC)

I gave a (slightly indirect) reference for both Pallas and Vesta not being DP's in my above post, directly from Brown's commentary to his list (fourth paragraph of text) ;-). I wouldn't remove 1999 TC66 from the list unless Brown does the same. (Or do we actually have other "more reliable" sources stating that it's probably no DP due to being triple? With Brown's method, it would still be "possibly DP" even with 270 km.) --Roentgenium111 (talk) 18:48, 25 June 2014 (UTC)

Brown only says that Ceres is the only one known to be round. Pallas is not known (nor was Vesta, when he wrote it). And why does he pick 200 as a lower bound? Why not 100 or 300? See 1999 TC36: the point of mentioning it here is just to show that Brown's numbers aren't always up to par. See also 2013 FY27, for which he mysteriously uses H=3.3. Tbayboy (talk) 00:39, 26 June 2014 (UTC)

There's no "known" qualifier in the Brown sentence that I quoted. And Pallas is known not to be round e.g. by Hubble's 2007 image given in 2 Pallas' infobox; similarly, [3] showed Vesta to be non-round in 2007. No-one is claiming Brown's list to be perfectly right (I already said below that I don't understand Brown's 200 km lower bound either, and we've essentially agreed not to use it below), but we need other "more reliable" sources to be "allowed" (via WP:OR) to make "corrections" to his list. --Roentgenium111 (talk) 12:30, 26 June 2014 (UTC)

The minor planets list is an official list. This is a list of candidates that are not officially recognized by anyone, not the threshold is officially suggested by someone. So the longer the list the more OR it is IMO. Nergaal (talk) 19:50, 16 June 2014 (UTC)

I don't think using Brown's 200 km threshold for "possible" dwarf planets would be OR. Roentgenium111's idea seems very good, basing the table on a reliable source (Brown) while correcting any inaccuracies in the list with other reliable sources, instead of providing lots of lists with no easy way to compare (some of which are even cut off at a somewhat OR threshold). Double sharp (talk) 08:18, 17 June 2014 (UTC)

Nevertheless, it may be somewhat difficult to keep the list in sync with Brown's if we extend all the way down to 200 km diameter. Now, with only the top 47 objects (going to the end of "likely" dwarf planets), it can be done; but extrapolating, I think there may well probably be a lot more such shifts in the lower regions. Perhaps "probably" is really the best place to end, at 400 km diameter: in comparison, the smallest body known to be nearly in HE is Saturn I Mimas at 396.60 km in diameter, which is an icy moon. So maybe that is a surer place to cut off Brown's list, and yet keep it manageable? (Currently, ending there would give 84 objects, down to (47171) 1999 TC36: the sole named object that would be added is 38628 Huya.) Double sharp (talk) 15:38, 18 June 2014 (UTC)

I wouldn't oppose cutting the list off at "probable"; as you say, 400 km is the approximate HE limit among known-form icy objects. (Brown claims the limit is "somewhere between 200 km and 400 km" for icy moons, but all moons in the 200km-380km size range are known not to be in HE, AFAIK. Still, some objects estimated to be slightly <400km will likely turn out to be >400km in the end.) But maybe we should then replace "possible dwarf planets" by "probable dwarf planets" in the article title. --Roentgenium111 (talk) 16:13, 18 June 2014 (UTC)

Yes, I think that name change may well be a good idea; Brown even says that a few objects estimated to be in the 100km–200km range may well be large enough to round themselves, simply because of measurement uncertainties. So currently, strictly speaking we would have to copy in Brown's entire list of (currently) 1137 objects! Double sharp (talk) 01:04, 19 June 2014 (UTC)

Note that other authors have put the minimum at about 350 km, based on theoretical calculations. Unlike Brown's blog comments, these were actually published, peer-reviewed papers. Lineweaver and Norman did it a few years ago, and Cole way back in the 80s. I don't have the refs handy, but they're used on a some Wiki-pages. Tbayboy (talk) 12:42, 23 June 2014 (UTC)

Then we can cut off at 350 km, which would be even better as it is referenced by RSes. Double sharp (talk) 15:09, 23 June 2014 (UTC)

I'd like this cut-off, if we can find these sources for 350 km. But the Cole and Lineweaver-Norman sources discussed in Talk:Iapetus_(moon) don't give a value of 350 km; one gives 320 km and the other 400 km (with the latter NOT based on a theoretical calculation AFAICS).

If we do agree on the cut-off,could someone easily copy the top part of Brown's list to the article (using a bot?), or do we have to extend it by hand? --Roentgenium111 (talk) 18:48, 25 June 2014 (UTC)

Yes, it's 320 per Cole (600 for rocky), I just misremembered it. See the Iapetus talk for my Lineweaver reply: they don't actually give a number for current icy bodies, only rocky, and they use a liberal definition of round. Still, their 400-600 is close to Cole.

I'm hoping to get around to making a little sample table to show here, but it's currently fighting with the world cup for my time. Tbayboy (talk) 00:56, 26 June 2014 (UTC)

citation for H

Can someone who keeps this updated give refs for the H values? It is the main criteria used for this list and there are no obvious refs for its values. Nergaal (talk) 09:29, 13 June 2014 (UTC)

For the record the MPC is the better source for absolute magnitudes (H) as sometimes the JPL SBDB does not properly catch abs mag changes. Mike Brown's website is buggy and unreliable for abs mags. -- Kheider (talk) 19:16, 13 June 2014 (UTC)

I added in refs to the MPC for the first 3 tables. There was already a JPL ref for the H=4-5 table. Tbayboy (talk) 22:33, 13 June 2014 (UTC)

New List Format

Following the previous discussion (in Pallas and Vesta, above)... I prefer having a single, sortable table, combining most of the data currently presented.

Brown's list is ordered strictly by size. As such, I don't see any point to using his classes in the table. There is already a section on the limiting values to explain the lower bound (as poorly as that is known). His classes don't account for the strength of the evidence. For example, a well studied object like Quaoar, with multi-band IR reading and occultation results, should have a stronger classification than an object of similar H but no other measurements.

Brown's real contribution is the size estimates, but they are not sourced, and not well explained at the individual object level. His H values are sometimes different from MPC and JPL. The wiki pages for the candidates have the sourced estimates. However, Brown's estimates are better than H-only guestimates, since he sometimes uses albedo estimates based on other analysis (e.g., haumeids).

So I suggest a sortable table that is a top N list by size. N=50? 100? 200? Columns include a "measured" size (radiometric, occultation, soon direct images), Brown's estimate, and H-based sizes for max (albedo=0.04), typical (0.09), and min (1). The objects are then ranked (i.e., the table order) first by measured size, then by Brown's size (where there isn't a measured size), then by typical albedo size (if it isn't in Brown's list). Other columns should include H, mass where it's known, and Tancredi's result. Something like:

Rank	Body	H	Diameter Measured (km)	Albedo per Measured %	Diameter per Brown (km)	Albedo per Brown %	Typical Diameter albedo=0.09 (km)	Small Diameter albedo=0.8 (km)	Large Diameter albedo=0.04 (km)	Tancredi Result	Mass (Zg)	Category
	Quaoar	2.5	1074	20	1092	13	1400	470	2100	accepted	1400	cubewano
	2013 FY27	3.0			764	15	1113	373	1670			SDO
	Varda	4.4	705	10	694	13	584	196	876		265	SDO

(Note: This example table uses albedo=0.8 instead of the 1 mentioned above. It's the approximate observed max (haumeids) of non-huge DPs versus the theoretical max. I'm not sure which is better, but both would be unnecessary clutter.)

It would be preceeded by separate sections (mostly already there) describing: DP diameter threshold; Brown's classes and what he uses for his size estimates; Tancredi's work. In the table section itself, just above the table, the H+albedo sizes would be explained.

I would also like row colouring for IAU DPs, and also non-DPs so we could include a few moons and asteroids for comparison (e.g., Charon, Proteus, Mimas, Vesta, Phoebe).

It would be really nice to have a template that could do astro calculations. E.g., { {astro|h-albedo-diameter|3.3|27} } to generate a diameter given H and albedo, and other functions like { {astro|volume|1400|1300|1200} } to generate the volume of a tri-axial ellipsoid. Anybody got the wiki fu? Tbayboy (talk) 03:25, 17 July 2014 (UTC)

Rank	Body	H	Measured		Per Brown		Diameter			Result per Tancredi	Mass (Zg)	Category
			Diameter (km)	Albedo %	Diameter (km)	Albedo %	Typical albedo=0.09 (km)	Small albedo=0.8 (km)	Large albedo=0.04 (km)

Nergaal (talk) 10:34, 17 July 2014 (UTC)

Thanks for the improvements. See User:Tbayboy/sandbox for the under-construction table. Currently, it's just a re-order of Brown's list (down to 200 km), with no added or improved data. I removed the Rank column and added a Ranked diameter column to the far right. The list would be too hard to maintain with the rank explicit, but I still like to be able to sort it as mentioned above (after doing some other sort), so the ranked diameter is a copy of the diameter used in the ranking. Also, albedo is always %. Obviously still lots to do. Tbayboy (talk) 02:27, 24 July 2014 (UTC)

Progress report: I worked out a way to grab the data off MPC and Brown pages, massage them, and spit them out in wiki format, using vi and sql. The goal is to make the page easier to maintain, so I (or anybody else who wants the code) can regularly update the table from MPC and Brown.

I moved the mass under the Measured column group. Measured albedo is calculated from H and measured diameter. That generally works fine, but results in Makemake having an albedo of 125%. Haumea's is also high, but that probably has something to do with the shape (the formula assumes a sphere). Tbayboy (talk) 19:23, 26 July 2014 (UTC)

The sandbox table looks good to me in principle. I would prefer to generically sort by Brown's diameter value instead of the "measured" one (and put "Per Brown" values to the left of the measured ones), especially if the latter column has to remain half-empty. I think Brown's categories should be kept since they're what makes it a list of DP candidates rather than just a list of the largest TNOs, and they make the information readily understandable to laypeople. I don't see much point in adding the "typical-minimum-large albedo" diameter estimates since we have much more specific albedo estimates for all objects; the extra columns also make the table too wide for smaller screens (like mine). Anyway, thanks for the nice work! --Roentgenium111 (talk) 16:13, 30 July 2014 (UTC)

There are only a few specific albedo estimates (to a specific TNO, that is) -- the haumeids. Otherwise, the albedos Brown uses are mostly based on a statistical analysis of know albedos, from which he gets an albedo function based on magnitude (H). He also has adjustments for dynamic category and haumeids. That's fine for a general trend, but not always good for specific bodies. One standout is Salacia, which has an albedo much lower than Brown's formula would estimate (4% vs 10%, which would result in a difference of about 350km diameter). Also, Brown's Hs are usually off from those of the MPC -- only 14 of 1137 in his list match the MPC. (For the dozen of so that I checked, JPL matched MPC.) So while his albedo function might be better than the "typical 9%", his faulty Hs sabotage his resulting diameter estimates. I could add the column for Brown's H, in case anybody gets upset about his diameter estimate not matching what you would calculate from the MPC H and Brown albedo.

Brown's data is not always up to date. The standout is 1999 TC36. It's a known triple system (see the page), with the largest body around 272 km (+/- 10 or so). Brown has it listed as 403 km, which is the equivalent system diameter, showing that he hasn't updated that entry for a couple years.

And that's why there's a "measured" diameter column (I'm not fond of that name). It represents the most recent, sourced diameter determination, and is more reliable (in a wiki sense) than Brown's unsourced diameters. So the "ranked" diameter column is the current best diameter estimate.

Brown's categories would still be explained above the table, as would Tancredi's. Those sections would just lose their separate tables. The categories go strictly by diameter, and are independent of Brown's diameter estimate. In general, for a particular body, the category depends on which diameter estimate column you sort by. So Brown's categories are nothing more than a list of largest TNOs! Unlike Tancredi's algorithm, which also considers the light curve. Check out his page, it's just a list of the largest TNOs down to 100 km, in order.

I also want to add to the limiting values section the theoretical minimums from Lineweaver/Norman and Cole. They provide a reason to end the list at 300 km, so it's not just a list of most TNOs, like Brown's page is (~1100 in Brown vs ~1700 in MPC list).

The "typical-min-large" diameters match the MPC H, and give a possible size range when there's no "measured" size (which is the common case). So you can sort on "large" to get a liberal idea of possible DPs, or on "min" to get a conservative one. Also, entries appear on MPC and not Brown -- there are some below the 300 km cut-off on the sandbox list, but above Brown's 100 km cut-off. Tbayboy (talk) 03:00, 31 July 2014 (UTC)

Adding the theoretical minimum estimates is a very good idea. I also agree that the "measured" column is useful (though I'd rather call it "most recent/reliable estimate" or something like that), since Brown's data are far from perfect. But since Brown's list is the only (non-OR) exhaustive list of DP candidates we have, I'd prefer to use it as the primary source and the primary criterion for the list's sorting. It's surprising that most of Brown's H values are different from the MPC; do you have any idea where his values come from? Can we be certain that they are "faulty" if they (presumably) only differ slightly from the MPC?

Brown's categories do not quite always "go strictly by diameter" - in the past he had categorized 2002TC302 as only "highly likely", not "near certainty", in spite of estimating its diameter at 1150 km, while giving the smaller Quaoar the higher category. (See the "archived" table at the top of this talk page; 2002TC302 has turned out to be far smaller in the meantime, as Brown expected). So he does "account for the strength of the evidence", at least marginally. Presumably he'd do the same if he considered there to be similar cases in the current list; therefore I think his categories do provide extra value. (But there's no need to add an extra column for them; I'd be content with just a background colouring of Brown's entries to provide the category, similar to the current Brown table in the article.)

I don't think the "typical-min-large" columns are necessary or very useful; we could just link to an albedo conversion site for those few readers who really want to know "conservative" and "liberal" estimates instead of just the "best" estimates that the "measured" column (and Brown's diameter estimate) provides. And unless you have a reference for the assumption of 9%/100%/4% being "typical/minimum/large", those columns would be OR-ish anyway. The MPC seems to assume a much smaller albedo range of 5% to 50% for "icy bodies" (and only 5%-25% for rocky bodies),[4] and doesn't give any "typical" albedo value AFAICS. Note that an albedo of 100% does NOT actually give a "minimum" diameter - theoretically, albedo can be far above 1.

--Roentgenium111 (talk) 19:03, 6 August 2014 (UTC)

I'll shift Brown's block to the left (right after the name) and make that the default sort, and colour per Brown. It will include Brown's H. Then will follow the "measured" group, including the MPC H value, then the rest. (about 20 hours after this reply, that is)

Most of the list items are just diameters derived from H and assumed albedo, so I want the high/low albedo derived diameters to give a range estimate. 3.5% was the lowest measured TNO albedo when I looked into it a few weeks ago (I forget the TNO), and the lowest value on Brown's list is 4%. The 100% is the commonly used "theoretical minimum" you mention above, even though, as you point out, it's not really the minimum. Brown has the haumeids at 70%, so 50 is definitely too low. What did you think the minimum should be?

As mentioned above, something is needed (for sorting the list) if an object is not on Brown's list and hasn't been otherwise measured -- there are currently several in the 200-300 km range, and it's not a stretch to think some might appear above 300 (and we might yet decide to go down to 200). Bear in mind that this list is to be semi-mechanically updated from MPC lists and Brown. Brown is using 8% for the default albedo in the small size range, so I could use that for the "typical". Tbayboy (talk) 04:27, 7 August 2014 (UTC)

I made those changes, using Brown's colouring scheme. I removed the "typical" albedo size: if Brown doesn't have it and there's no measured diameter, then I made the ranked diameter display the 8% albedo figure.

I don't like the Brown-first sort. If you sort by measured, you'll see a few that jump out, especially 2004 XA192. For the few I checked, Brown is using an assumed albedo, but there are newer Herschel measurements. (Except ignore 2002 KX14; that's an error by me, to be cleaned up next iteration -- there's no measured value, that's just the upper bound.) It seems that where Brown actually reports a measured value, it's very close to the most recent value from the wiki-page, but in some cases he's behind wikipedia when it comes to following the literature. Tbayboy (talk) 02:06, 8 August 2014 (UTC)

Thanks for implementing many of my suggestions. Actually I'd prefer the background colours to only be used for the first four columns (or even just for the three columns which give Brown's values), if that's possible without too much work. This would make it "doubly" clear which data these categorizations are based on (also, wide-area non-grey background colours are an eyesore for me, personally). Using Brown's 8% as a default albedo for sorting potential non-listed objects seems reasonable, unless there's a "measured" value for sorting in these cases.

I'd rather not give minimum and maximum diameters at all; I think they're not really needed, and inflate the table. But if you want to keep them, using the MPC's 50% for the non-haumeids seems reasonable to me. (You could use either Brown's 70% or the more conservative 100% only for the known haumeids instead, or just leave the column empty for haumeids.) Using 4% as an "empirical" lower limit is also reasonable, thanks for explaining your rationale behind it.

Are you intending to fill the "Category" column with TNO subcategories like KBO, plutoid etc.? Otherwise the column is unnecessary IMO, as is the (currently also incorrect) "Ranked diameter". Also, the "Measured" wording should still be replaced IMO - Brown's values for the largest objects are also based on measurements, after all. Other than that, feel free to go ahead with adding the list to the article. --Roentgenium111 (talk) 19:51, 8 August 2014 (UTC)

I don't know how to do just columns, but I'll look into it. Do you know any wiki-page that does it? The colours are just what Brown has on his page, and I find them garish. I'll tone them down, maybe try a more ordered scheme. It would also be nice to have some colour-blind advice: anybody out there? I modified the old little example table at the top of this section to show row colours, so play with that if you like.

The 8% thing only happens when there is no Brown entry and no measured value. I'll change the "ranked" to "best estimate" or something. It's not just the haumeids that need the high albedo: they show that albedos can get that high, so there might be other similarly formed TNOs with such albedos.

The "category" column is intended for "plutino" etc., as you thought. I wasn't intending to fill it in myself, at least not right away. The table is built semi-mechanically. I get the names and H's from MPC, Brown's data from his page, and fill in Tancredi manually (only needs to be done once). Once the table is up on the page, I will gather the measured diameter, mass, and category from the table as edited by others. I hope to get everything working in just SQL (using freely available MS SQL Server Express), the code and usage docs for which can be stored in some wiki-place for others to use (where's a good spot?). I.e., the semi-mechanical update process would (in effect) simply refresh the table with new data from MPC and Brown.

I'm away this weekend, so I won't be able to get to it until Wednesday. Tbayboy (talk) 03:31, 9 August 2014 (UTC)

E.g. this uses different colours within a row; the code seems to define the colour of each box individually. Your colours seem a bit more garish to me than Brown's, so toning down would be great. According to their article, Haumeids are "probably the only trans-Neptunian collisional family", so I don't think any other objects would be expected to be as bright. (That's the problem with using a genuinely "conservative" value - if you want to use a strict upper limit for the albedo of all TNOs, it will likely be too large by a factor of ten for 99% of them.)

I'd gladly help filling the "category" column, but I can't do more than a few dozens manually... --Roentgenium111 (talk) 20:59, 10 August 2014 (UTC)

PS: Since the "measured" albedo values seem to be faulty for at least Makemake and Haumea, as you say (at least they strongly contradict our articles' albedo values), and not actually measured but calculated, if I understand you correctly, I would consider removing this column. --Roentgenium111 (talk) 21:24, 10 August 2014 (UTC)

There are no measured albedos: they're either assumed or calculated from H and the body (like, say, surface area from the axes). Makemake's is not necessarily wrong -- the article uses Brown's albedo, as calculated from his H (0.1) and diameter, but the article's H is -0.4 (from JPL, and matching MPC). Haumea's is high because of the size estimate I used (650 mean radius); it drops to 83% if you use the 718 mean radius. Tbayboy (talk) 02:49, 14 August 2014 (UTC)

What I mean is, since these albedos are not measured, it's very misleading to give them under the "Measured" header. And calculating the albedos from diameter and H values taken out of two different sources seems like unnecessary synthesis to me, which in Makemake's case leads to an extremely high value contradicting the available reliably sourced value of 0.81+0.01/-0.02 given in Makemake's article. --Roentgenium111 (talk) 17:48, 28 August 2014 (UTC)

(I've been away on vacation, just getting back to it...) I'll move it out of measured, to between the "measured" and the "per assumed" sections, with a note (something like "as calculated from measured H and diameter with the formula ..."). Note that the main Makemake page's diameter-H-albedo are inconsistent (like saying radius is 1000 and circumference is 7000). Tbayboy (talk) 01:47, 31 August 2014 (UTC)

Thanks for the column-colouring ref. There's another version up now, with only Brown's columns coloured. Colours are low saturation, running through the rainbow from blue (near certain) down to red (unlikely), although red doesn't show up at the current 300 cutoff. A few other little tweaks. I want to start working on the notes/refs in the header. I'm thinking of indicating which of Brown's diameters are from assumed albedos by colouring dark red the text of the Brown-diameter column. Tbayboy (talk) 02:49, 14 August 2014 (UTC)

break

The table at User:Tbayboy/sandbox is neat. I like the coloring, but I think it should only be used for diameters (i.e. the H magnitude has nothing to do with wether Brown sees them as dpc or not). Also, I suggest extending this coloring scheme to the other diameter columns, and use a key at the bottom of the table to list the thresholds that Brown (seems) to use. Nergaal (talk) 09:55, 31 August 2014 (UTC)

I made the big change. Sorry about the delay -- real life interrupted. Tbayboy (talk) 18:46, 27 September 2014 (UTC)

Makemake's albedo

is over 100 percent. Should it be subbed with its albedo from its own page? Serendipodous 13:29, 30 September 2014 (UTC)

Geometric albedo, absolute magnitude, and diameter (assuming spherical) are tied together by a formula (see the albedo column's note). Using 81% here would be like saying you have a 1cm cube of a material of 5g/cm3 density that weighs 3g (yes, that means the Makemake page is self-contradictory). Albedo can be greater than 100% -- see Enceladus, at 137%. The albedo % is relative to a standard ideal surface, but some surfaces, notably frost, can cause more light to be reflected back to the source than that standard. The principle is used in those bright-in-your-headlights traffic signs, bicycle reflectors, etc. Also note that Brown's H-diameter-albedo numbers are sometimes inconsistent: e.g., it should be 79 for Makemake, and 90 for Eris. Tbayboy (talk) 23:41, 30 September 2014 (UTC)

Playing around a little, if I take Brown's H (0.1) and the diameter from the main page (1430, also from Brown's paper, but not the one he uses in his table), I get an albedo of 79% -- right in line with everybody else. So the problem seems to be that MPC's/JPL's H is wrong. Tbayboy (talk) 04:19, 10 December 2014 (UTC)

I agree, the cited abs. mag value seems to be wrong. --JorisvS (talk) 12:30, 10 December 2014 (UTC)

H value in Brown's list

People keep commenting that the H value in Brown's dwarf planet candidate list is wrong. However it seems that the list used the normal H value until about 1 Nov 2013, when most bodies' sizes were changed, most of them downwards. Since also the albedo in the list remains below 100% for all bodies, when it actually rose above 100% for Makemake in measured values, I guess this is a compensation for the opposition effect. But I have no source, it's just my guess.

There were quite some changes in the values: Before 1 Nov 2013, 8 bodies were estimated "almost certainly" dwarf planets (estimated size >= 900km), while 22 were "highly likely" (>= 600km). Today, in Brown's list, the 8 "almost certain" bodies still are there, but of the 22 "highly likely" bodies two (Salacia and 2002 MS4) are now rated "almost certain", 10 remain as "highly likely", and the remaining 10 were put in lower size ranges. (Also, Varuna and Chaos are now "highly likely" when they weren't before). Even with this big change, the estimates in Brown's list are still higher than the ones from the "Measured" columns, where Salacia was estimated in the "highly likely" range again, and two more bodies from "highly likely" were put in lower ranges.

So I think that the values were modified to prevent size estimates that are too high. But if anyone has better info on that, I'd be grateful. Ambi Valent (talk) 23:53, 23 November 2014 (UTC)

I e-mailed him. It is a glitch. An autobot could adjust albedo estimates (and thus diameter assumptions) without generating H values that contradict the MPC and JPL. -- Kheider (talk) 00:15, 24 November 2014 (UTC)

2014 FC69

Could someone write a Wikipedia entry for this object? Wikipedia strives to have articles for all notable objects, and I would think a 512 Km likely dwarf planet is notable. — Preceding unsigned comment added by 107.9.178.102 (talk) 20:42, 17 August 2015 (UTC)

Table Update

As of Mon Aug 17 2015 there are: 10 objects which are nearly certainly dwarf planets, 23 objects which are highly likely to be dwarf planets, 49 objects which are likely to be dwarf planets, 90 objects which are probably dwarf planets, and 366 objects which are possibly dwarf planets. — Preceding unsigned comment added by 107.9.178.102 (talk) 20:50, 17 August 2015 (UTC)

I did come here to ask, actually - how often is the list updated? Brown's list allegedly "updates daily"... or at least, we can probably take that as meaning "is generally updated within 24 hours of any new discoveries". As this notification of an update is now more than 2 years old, and contrasts with said master copy reporting...:

As of Sun Sep 24 2017 there are:

10 objects which are nearly certainly dwarf planets,

30 objects which are highly likely to be dwarf planets,

70 objects which are likely to be dwarf planets,

149 objects which are probably dwarf planets, and

703 objects which are possibly dwarf planets.

...I'd say it's quite likely that all but the "nearly certainly" data needs to be refreshed. Not that, with potentially more than 400 objects that have to be added/checked (might hit 450 by the time you finish), I want to volunteer for that particular job. Hopefully its last actual update was more on the order of days or weeks, rather than 2+ years, so any residual edit job right now would be fairly minor? 209.93.141.17 (talk) 06:08, 25 September 2017 (UTC)

Brown's list is updated daily, but it appears to be done by a bot. My guess: it gets info from the MPC or JPL, and calculates the size based on H and the orbital elements according to Brown's heuristic algorithm. Objects with direct measurements (occultation, radiometric, etc.) are not updated. In particular, note that Brown still has Pluto listed at it's pre- New Horizons value of 2329.

The data in the table here is wholly updated every few months, from MPC and Brown source tables, using a program-assisted process. See the wiki-comment just before the table, and the SQL program at the top of this talk page. Tbayboy (talk) 15:37, 25 September 2017 (UTC)

Diameters determined by albedo are wrong?

The minimum size we calculate for Makemake, assuming an albedo of 1, is greater than its measured size, from which an albedo of 0.8 was calculated. It would seem our albedo–size calculation is off. And if it's off for Makemake, it may be off for all, since I assume the same formula was used. — kwami (talk) 23:17, 27 August 2015 (UTC)

It's not a minimum size, just the size at the 100% albedo point, and called "small". Note that the albedo calculated from the measured values is >100%. Enceladus has an albedo of 137%, so the "minimum" size would have to use an albedo something more than 137%. The 81% albedo is from Brown, who uses a different H than the MPC/JPL, and also uses a different size estimate than our sources (see main Makemake page). See kheider's comment above: Brown's Hs are not to be trusted. Tbayboy (talk) 23:40, 27 August 2015 (UTC)

Oh, it's geometric. I'm used to albedo being 0–1 by definition. Are all the albedos in the chart geometric? — kwami (talk) 23:46, 27 August 2015 (UTC)

Yes. Tbayboy (talk) 00:04, 28 August 2015 (UTC)

Could the heading 'Albedo' then link to Geometric albedo? Or, better, state that explicitly? I'm afraid if I do it it'll be reverted w the next data update. — kwami (talk) 02:30, 28 August 2015 (UTC)

See the comment just above the table (in the edit source). Local changes are fine, and I just update the program to match. So go ahead and change the column header until it is as you like it. Note that there is a link to geo/astro albedo in note C. Tbayboy (talk) 02:56, 28 August 2015 (UTC)

Done. Thanks. Good to specify that the albedos of the two columns are the same. — kwami (talk) 22:40, 28 August 2015 (UTC)

reorder by measured diameter?

and include error bars? — kwami (talk) 18:48, 2 September 2015 (UTC)

What about those that don't have a measured diameter? --JorisvS (talk) 19:49, 2 September 2015 (UTC)

Then they go at the bottom, as "unknown". Or at the top if you do a reverse sort. Not that hard, surely? 209.93.141.17 (talk) 06:27, 25 September 2017 (UTC)

See the note for the "Best" column. Tbayboy (talk) 15:55, 25 September 2017 (UTC)

The columns are sortable. The original default sort was the "best" column (measured -> brown -> assumed albedo), but somebody wanted Brown and nobody spoke against it.

I'll look into error bars, but I think it should be easy. Tbayboy (talk) 20:32, 2 September 2015 (UTC)

Error bars might be taken care of automatically by using the "val" autocalc tag thingy. Just put in the mean figure (or estimate) in one part, the variance in the second (demarcated by a pipe), and let the machines do the rest. It won't be graphical but it may help control the sorting better.209.93.141.17 (talk) 06:27, 25 September 2017 (UTC)

Already done. Tbayboy (talk) 15:55, 25 September 2017 (UTC)

Sortable Body column

@Rfassbind added sorting to the Body column. This sorts by simple lexical order of the display name, so, for example, "(150642) 2001 CZ31" sorts before "(15874) 1996 TL66". You can see that here and now.

Meanwhile, on the French page, they have a sort that goes first by the MPC number and then by the licence plate (if there is no MPC#). That works better there than it would here since the French templates used to show the named bodies also show the MPC#; also, it goes in numerical order rather than lexical.

Other possibilities include:

• name then licence plate (ignoring MPC)
• numerical by MPC then licence plate
• licence plate only, using made-up-but-compatible ones for Pluto (1930 DA) and Ceres (1801 AA), which is nearly chronological

Or something else. Any preferences? Tbayboy (talk) 23:58, 20 September 2016 (UTC)

Tbayboy, I happily noticed that this table (or code) has been adopted on the French wikipedia. As for the column "Body", I removed the "non-sortable" |class= attribute, because any type of sorting is better than none. Yes, this alphanumeric sorting leads to a rather odd aggregation of intermingled 5- and 6-digit numbered, unnumbered, and named-only bodies. This is not perfect, and the fact that the French table sorts these bodies with so much ease seems suggestive that this could also be done here. But the French (as well as the German) wikipedia kept the parenthetical notation on named bodies, contrary to the English and Italian wikipedia. (I think this is the "source of all evil" for sorting minor-planet tables on English wikipedia). There are several not-so-great workarounds, such as using a 2-column designation. To me, sorting should always correspond to displayed rather than to hidden values. Rfassbind – talk 13:33, 21 September 2016 (UTC)

I've looked at the dp template, and I could change the Body column to show the MPC# for the named bodies, so it would present as, e.g., "(1) Ceres". (Worth doing for its own sake.) Then it could sort numerically by MPC# else licence and match what's displayed. That's if you prefer a MPC# sort. I also like sort by name else licence (ignoring MPC#), which favours a sort-by-name perspective. It depends on the goal of the sort: what is the preferred goal? Tbayboy (talk) 16:30, 21 September 2016 (UTC)

I'd say, that the preferred goal is to sort numbered minor planets (MPs) by number, separated from the unnumbered MPs, which are sorted alphanumerically. Yes, I would definitely use a MPC# sortkey (sorting numbered minor planets by their provisional designation would be very odd). According to convention, and as mentioned above, (1) Ceres should appear without parenthesis as 1 Ceres. In addition, I don't think template {{dp}} is useful here (using [[120347 Salacia]] seems to be simpler than {{Dp|Salacia|120347 Salacia}}). Unfortunately, the resulting table won't look as good as the French version when sorted, since it displays numbers with and without parenthesis, but that's the standard, unless you opt for a 2-column layout, which in turn has the disadvantage to add another column to the already broad table. Rfassbind – talk 21:11, 21 September 2016 (UTC)

See the table in my sandbox. How's that? Tbayboy (talk) 23:16, 21 September 2016 (UTC)

Seems perfect to me. The column heading "Body" could now be replaced by [[Minor planet designation|Designation]]. Rfassbind – talk 00:01, 22 September 2016 (UTC)

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Cheers.—InternetArchiveBot (Report bug) 22:48, 22 May 2017 (UTC)