Talk:List of Solar System objects by size

Graphical overview 1st diagram has wrong scale for the Sun

Diagram topmost values (left side) of 360000 and 400000 should be 1360000 and 1400000 respectively. Sorry not to have done it myself but I do not have the graphical tools for that.

Reduce 200-400 km section?

The section with sizes from 200km to 400km radius is overwhelmingly dominated by transneptunian objects, about which there might be some knowledge in some cases, but I think not enough to warrant listing volume, surface gravity and Earth comparison values. But there are values for a lot of TNOs, and often they don't even match the values they should have according to the radius given. I would prefer if the section columns were reduced to those of smaller sizes, plus density as that may be known in some cases.

On the other hand, I think the section should contain all known objects of the size, and not just a selection like with smaller sizes. Brown's list contains 72 TNOs in the ranges between 200km and 400km radius. If people think that's too much, then maybe move the lower limit to 250km; for that value there are just 37 TNOs in Brown's list, the other 35 are estimated between 200km and 250km radius. Ambi Valent (talk) 21:25, 8 April 2014 (UTC)

If people think it's OK, I could update the section (once there's an agreement about what I'm allowed to do). Ambi Valent (talk) 21:56, 8 April 2014 (UTC)

Another possibility, to cut down a bit, would be to list only named objects, or only cis-Neptunian, or only cis-Neptunian + satellites (for Pluto's moons). BTW, if we don't know the radius accurately, it's a bit meaningless to compute area or volume; if we do, we need to include the precision. — kwami (talk) 00:12, 9 April 2014 (UTC)

There's a greater problem, that nearly all of the data is wrong. For example, much comes from the JPL Small-Body Database Browser. They give all figures to a precision of ±10 meters. We only know the size of Vesta to ±100 meters, and that's after orbiting it for a year! Now, maybe JPL provides the uncertainties in another column, or if you're accessing it you're expected to know what to do with the data, but for us, simply regurgitating the figures is unacceptable. I'd be willing to bet my life savings that any one of these is wrong. For example, we give the radius of 1021 Flammario as 49,695 meters, when the margin of error according to our article is almost 2 kilometers: The chance of it actually being 49,695 meters is minute. We give 2003 AZ84R as 363.5 km, when the true error is almost a thousand times that. Any figures without error measurements should be deleted, or at least rounded off to the nearest 10km for smaller bodies and 100km for larger ones. — kwami (talk) 22:15, 8 April 2014 (UTC)

How about breaking it into two lists: one a selected list of objects with measured sizes, and another, overlapping list of those objects that are just assumed from magnitude. The magnitude list would contain only magnitude, size range (for some consistent, stated albedo range, like .05 to .25), and type of object. The selected list would stay as is. Tbayboy (talk) 03:51, 9 April 2014 (UTC)

I changed the assumed sizes to "unknown", and there weren't very many of them, so there's not much of a gap for a second list to fill in. (Though I was going off our articles, so there might be others I missed.) Maybe we could list them as "assumed X–Y", where X and Y are calculated from the albedo range? — kwami (talk) 05:40, 9 April 2014 (UTC)

I like the inclusion of uncertainties. There is one problem with just listing "unknown": there is then absolutely no reason why it should in a certain position in this list, or even subsection. With an estimate with huge bounds, at least we have a way determining where in the list we'd have to put the object. Maybe we could list H and known/assumed albedo in separate columns? --JorisvS (talk) 12:43, 9 April 2014 (UTC)

Note that there seem to be at least a dozen more that are assumed sizes, the "largest" being 2006 QH181. I agree with JorisvS re "unknown". Kwami's "assumed" sounds good to me, although maybe 300±100 is a better way to express it than 200-400, since it then makes the position in the list a bit easier to see. Tbayboy (talk) 13:18, 9 April 2014 (UTC)

Agreed that "±" is better. It is hard to handle such poorly constrained sizes well. What would you realistically take to be the minimum and maximum values? --JorisvS (talk) 13:43, 9 April 2014 (UTC)

Salacia is around .04, Orcus ~.25, Sedna ~.32, and the Haumeans much higher (maybe they can be handled separately). 2002 MS4 and 2002 XV93 are also dark, in the .05 ballpark. So I would guess that .04-.5 would capture almost all, and .05-.25 would still get most (since smaller ones <1000km are less likely to be bright). To find out, run down the list for (say) 6 > H > 3 that have good measurements (IR or occultation -- i.e., error bars within 10%) and see what the albedo range looks like. I think one of the TNOs are Cool" papers might have a nice table with this info (I'll look this evening). Tbayboy (talk) 16:50, 9 April 2014 (UTC)

Took a look around: Brown's DP list has the info (abs mag and albedo) right there. I just ignored the "estimated" entries, except I also dug out a few of those for which there are radiometric measurements from TNOs are Cool. Of the 46 I tallied in the H=3.0-5.9 domain, 5 were Haumea family (albedo ~70%), 4 have > 20%, 1 > 30%, none < 4% (although several = 4%). So an albedo range 4-30% seems reasonable. Excluding Haumeans, the overall average albedo is 12%, with 15% for H=3.x, 12% for H=4.x, 11% for H=5.x. So 12% looks like a good nominal albedo to use for sorting purposes if you want to get fancy. With albedo=12%, H=4.9 is 402km diameter, and H=3.4 is 802km. So TNOs in that H range (with no other size measurements) would be in the 200-400 radius table, lower Hs in the 400+ table, and higher Hs in the smaller-size tables (if at all). Tbayboy (talk) 00:50, 10 April 2014 (UTC)

I only used ± when that was in the source. Otherwise I gave a typical range, so as to avoid OR as to what the median should be. (I don't mind converting, as long as there are more minds involved than just mine. I think differentiating assumed ranges from measured ranges is important, though.) "Unknown" was only meant to be temporary. One of them, BTW, is given as unknown because one of our sources appears to have a typo. — kwami (talk) 02:06, 10 April 2014 (UTC)

Good point. A note above the table could make clear that the ± is for measured sizes and the range is for assumed. What's bugging me is that the column is sortable, and X±Y doesn't sort well with X-Y. The "ca." also throws off sorting. On the other hand, the list is supposed to be sorted by radius, anyway, so maybe there's no need for that column to be sortable. Tbayboy (talk) 03:25, 10 April 2014 (UTC)

What's with all the "citation needed" for the mean radius numbers of the planets? I presume the numbers were taken from the planets' articles, and there is a citation for radius - except that the articles only use polar and equatorial radius from that source, but ignore the mean radius. Ambi Valent (talk) 21:30, 9 April 2014 (UTC)

Exactly that: The mean radius should be in the main article. 'Citation needed' was a reminder that we don't have a source for the figure. Also, "±?" for figures which are likely to be precise but which don't have their precision listed in the main article. — kwami (talk) 02:06, 10 April 2014 (UTC)

Then the main articles should be fixed. The source given for polar and equatorial radius numbers in these main articles also contains mean radius numbers, but they are missing in the main articles. But I notice now that whoever copied the numbers from that source made changes on his own to the last digits of those numbers instead of copying the actual numbers given. Ambi Valent (talk) 07:25, 10 April 2014 (UTC)

I added main radius data to the planet main articles, put in the numbers from the radius source, and put those numbers in into the table over here, removing the cn tags. Ambi Valent (talk) 19:16, 10 April 2014 (UTC)

Maybe we could update {{Listrow}} to accept Δ_r and Δ_m? — kwami (talk) 03:16, 10 April 2014 (UTC)

While we're on the subject Kwami, do you think you could reorder the Moons graph in order of size? I didn't want to bring this up, because you did such a good job on all those mass graphs, but it's always kinda triggered my geek order reflex. Serendi^podous 04:20, 10 April 2014 (UTC)

Note that they're in order of planet, so you can see the fraction of Saturn moons vs Uranus moons. Although those fractions aren't complete, they're pretty close. Tbayboy (talk) 13:14, 10 April 2014 (UTC)

Yes, that's what I was going for. The solid-bodies graph orders by mass, which I agree is also nice to have. — kwami (talk) 02:19, 11 April 2014 (UTC)

There was only one red link, so I created a stub at 2010 VK201. However, I can only access the IAU discovery announcement. I added a link to a more recent article, if s.o. here can access it and update the stub. Also, at List of possible dwarf planets there are several other objects in this H range, and one a bit brighter, so those should presumably also be listed here, if we want this list to be complete above r=200km. — kwami (talk) 03:47, 11 April 2014 (UTC)

The problem with that section is that there are 8 objects with "Unknown" as their radius. I don't think "Unknown" qualifies as 200-400 km. Though there are also sorting errors, for example 250 km between 350 and 340, and 170 above a "ca. 300". 85.217.44.90 (talk) 01:35, 8 August 2014 (UTC)

The standard approach to that seems to be to use the absolute magnitude (worked from apparent magnitude and best estimate of distance, where that's actually known well enough) and a default, quite high value (I guess something like second standard deviation/90th percentile amongst all the properly known values?) for the albedo to calculate a reasonably firm *minimum* figure for the possible size (as a very reflective object will be brighter for the same size, and smaller for the same brightness) as a backstop, then try to either directly measure it with submillimetre arrays or stellar occlusion observations for a better estimate of the true size, or try to make a better estimate of the true albedo (using spectrographic or even just gross colour dimension studies, particularly redness vs blue-ish-ness, as there seems to be a fairly reliable trendline connecting that relationship with overall reflectivity) and thus adjust the size - most likely upwards, by as much as 10x in some extreme cases, but sometimes downwards *a little* - based on that and the already known magnitude.

Therefore using those more modern techniques there shouldn't really be any "unknown" size objects any more, unless the observations of them are so limited that we don't even really know their current orbital radius and position, and thus distance from Earth... and in which case, we're likely to lose track of them completely in short order anyway. Just a whole bunch of them listed with diameter being "at least X kilometres". Which isn't a great basis for sorting the list, but it gives at least some scant ability to decide whether an object should fit into the list anyway (if there's a minimum size cutoff), and roughly how high up it should be, with the position further refined (likely moving upwards) as more information comes in. Additionally it could be argued that the more we know, and more accurately, about a particular object, then the more "interesting" it becomes, and the more it maybe deserves (from an anthropocentric, astronomical viewpoint) to get a more prominent position on the list. Until we know for certain, it can be stuffed in at the position equal to its likely minimum size, with that "this is a lowball estimate" caveat added on to it... 146.199.0.203 (talk) 01:48, 3 March 2018 (UTC)

Radius vs. Diameter

I thought it was odd that this table uses radius rather than diameter as the primary measurement. Apparently I'm not alone, as Nyth mentioned this above. I also noticed, while clarifying estimates for the size of Pluto's moons in the New Horizons article, that at least some of the figures given in this table are already diameter rather than radius. No doubt the editors who added them made the same intuitive leap. At the very least these need to be checked. Now, I don't precisely object to having radius as a measurement, if astronomers find it useful, but I think that the primary measurement should be diameter, since this is what most people expect. I also realize that many smaller objects aren't perfectly round, but this affects estimates of radius as much as it does diameter. I propose adding diameter to the table, alongside radius. I understand that it's a simple matter of multiplication, but readers shouldn't have to do figures in their heads, assuming they remember their geometry at all. P Aculeius (talk) 13:02, 27 May 2015 (UTC)

I've been noticing this, and the sometimes egregious errors in stated size, more and more whilst mooching through particularly the individual dwarf/potential dwarf/notable minor planet articles. Sometimes (far too often) there's even a kilometre figure listed simply as "size" without clarifying which it is, and when you check citations (or google for more info where the citations are lacking) it's a coin flip as to which one it is when you find more scientifically rigorous data.

I'm not really sure how it can be fixed, without setting some fairly strict and draconian rules on how articles about and data regarding celestial objects should be entered, and launching a major whole-site initiative to pull together as many people as possible to exhaustively go through each and every one of the 450,000+ articles (many no more than stubs) checking and correcting the formatting and data within it. It's far greater a job than could ever be completed by a single editor, or a small group of maybe a couple dozen, and certainly not within any kind of reasonable timescale. It's a massive problem that needs a massive effort, maybe bolstered by some very cleverly programmed bots. 146.199.0.203 (talk) 01:28, 3 March 2018 (UTC)

I have often wondered why planet infoboxes like Earth show radius instead of diameter. For Joe Q. Public I have always thought diameter would be assumed by a casual reader. -- Kheider (talk) 13:58, 27 May 2015 (UTC)

I am guessing, that from a mathematical view, the equation for volume using the radius rather than diameter, has one less term in it (1/2), that that is used for calculations preferentially. Then you don't have to remember to convert. But radius is definitly less intuitive. You would never give the size of sports balls of any type by its radius. Nyth63 17:05, 27 May 2015 (UTC)

The annoying thing is that mathematically the radius is the primary useful value, but intuitively it's the diameter. And having both would be incredible overkill. Is something fancy where people could switch between the radius and diameter values in the same column possible to make? --JorisvS (talk) 18:47, 27 May 2015 (UTC)

I'm not an expert on wikipedia's programming languages, but I would say that with a more advanced language it would be fairly easy to do, but considering the simplified language wikipedia editing uses, such a thing would be possible, but not simple. exoplanetaryscience (talk) 18:55, 27 May 2015 (UTC)

If we could pull that off (with help from somewhere), it would solve the issue. --JorisvS (talk) 19:12, 27 May 2015 (UTC)

Anyone who knows how to calculate the volume of an object using its radius already knows that the radius is exactly half of the diameter. The goal of Wikipedia is to make information accessible, not to cut as many steps as possible out of technical calculations. Especially when the volume is already given in the table using two different measurements, obviating the need to calculate it. The radius may be more useful for calculating volume, but it's only marginally so. Diameter is far more useful for giving the reader a notion of scale. If we have to choose one or the other, it should be diameter. P Aculeius (talk) 03:29, 28 May 2015 (UTC)

The problem really is that there are an awful lot of celestial objects that have simply a "size" listed (literally that word), without it being defined as either radius or diameter, and there certainly doesn't seem to be any prevailing standard for which of them it is. You're about as likely to find one as the other. Seems like WP maybe needs a proper style guide for defining the characteristics of Things In Space, particularly on that recommends hitting anyone who just says "size" with a hefty cluebat. If it was simply a case of there being 50% that outright state "diameter", and another 50% that state "radius", it wouldn't be so bad, and although continually having to do mental arithmetic to convert half of them to your preferred standard (and occasionally forgetting to do that and getting it wrong), at least you could then be more sure what the correct figure (or estimate) actually is. (...worse, I'm pretty sure I've seen a few where it is stated, but the author has incorrectly assumed an unclear source is one or the other, so the figure is precisely defined, yet still inaccurate by a factor of 2 one way or the other) 80.194.203.132 (talk) 13:48, 1 August 2019 (UTC)

The confusion has corrupted this list as well: the erstwhile critical dimension for HE is 400km in diameter, and we separated the list at 400km in radius, making the sections meaningless. I did a half-assed job stitching them together, but they have different numbers of columns. I think we should break the list at r = 750km (separating Rhea in HE from Iapetus not in HE) and again at Brown's estimate of r = 200km. The third break should be at the point where we no longer try to list everything. — kwami (talk) 01:55, 24 July 2015 (UTC)

@Kwamikagami: Thank you for that very inconsidered crashing of the editing I've been doing now for several days. As of now, I cease any further amendments to the list, before I completely lose my temper and add to the confusion that obviously already exists. Rfassbind -talk 02:25, 24 July 2015 (UTC)

I didn't change any of your edits, so I have no idea what you're talking about. — kwami (talk) 02:37, 24 July 2015 (UTC)

Was this re-arrangement / repair job ever completed, or a fresh attempt made after this point? It's been 2 1/2 years since the last comment, after all, and the list still seems to break at 400km then 200km then 100km radius. And I'm sufficiently confused now that I don't know if that's correct or not. But I do know that neither 750 nor 375km appears there. 146.199.0.203 (talk) 01:31, 3 March 2018 (UTC)

cubic megameters

• I would suggest changing the SI units provided for volume in the first table to cubic megameters (Mm³) instead of billions of cubic kilometers (10⁹ km³). Otherwise you have the nonstandard usage "Jupiter is 1.4 million billion cubic kilometers (1.4 × 10⁶ × 10⁹ km³) in volume" as opposed to the standard usage "Jupiter is 1.4 million cubic megameters (1.4 × 10⁶ Mm³) in volume." Nicole Sharp (talk) 11:43, 17 October 2016 (UTC)
• Masses should also be in yottagrams (Yg) for the first table. Right now, there are badly mixed metric units being used. Metric units are presented in the first table using three different metric systems: centimeter-gram-second (CGS, with grams per cubic centimeter for density), meter-kilogram-second (MKS, the SI standard), and kilometer-tonne-second (KTS: if the kilometer is used as the standard unit of length, then the tonne [megagram or metric ton] should be the standard unit of mass, and density then in tonnes per cubic kilometer). Nicole Sharp (talk) 12:09, 17 October 2016 (UTC)

There's a bit of a problem with the MKS system, even though it should be the universal standard, in that it pretty much mandates slipping into some other variant, because of the messiness of constructions like giga-kilogrammes, so any practical notation is forced into being some kind of non-SI amalgam of more easily written and spoken units... unless of course you stick strictly to standard form and ten-to-the-power-whatever kg, which obviates the issue completely, but isn't the fastest to write with a regular keyboard.

Personally, when drawing up a table of objects using WP derived info, I've used Tonnes as the basis, with Giga- thru Zetta- (and Yotta, for the sun only) prefixes as appropriate, because that's the neatest and easiest to mentally visualise, but your suggestion of basing on grammes could also work, with a 10^6 adjustment in magnitude... the only issue with that is that we hit the largest currently available prefix, ie Yotta-, rather too early and have numbers growing into tens of thousands or even millions of yottagrammes when the idea of magnitude prefixes is to constrain figures within the 1.0 to 999.99 range (1.21 gigawatts in place of 1,210,000 kilowatts, for example). Whereas tonnes (ie, kkg, or Mg) fit the range of trackable objects hurtling around the solar system quite nicely... the smallest in Earth orbit being around 0.01t, and the sun being roughly 2000Yt.

However, there's no equivalent single-word, single-letter unit equal to 1000 km, so for physical dimensions and distances, Megametres (and for larger distances, AU) have had to serve, and terrestrial Years for orbital periods (seconds would be ungainly and basically useless in terms of making any sense, though I've seen spacey sci-fi settings where they use SI prefixes with seconds to define non-Earth-centric time units, like kiloseconds instead of hours and megaseconds instead of weeks; days might work rather better, but are still arbitrary and terrestrial anyway, and ultimately themselves rack up indecipherable figures pushing into the hundreds of thousands once we pass beyond the Plutoids). So the system is a sort of weird (mega)Metre-Tonne-Year setup. As it's designed for human reading, rather than calculating things inside a database that would reformat for display anyway, it serves alright. If you were intending to use the data for actual scientific purposes, rather than encyclopaedic reference, you'd of course convert it back into MKS first, and probably use a better, preconverted/preformatted source for it anyway. 146.199.0.203 (talk) 00:53, 3 March 2018 (UTC)

Without commenting on Yg or the other units, CGS is commonly used in describing electromagnetic units. Density is commonly in g/cm³, or relative to the density of water, at least for ordinary solids and liquids. Not so obvious for things like neutron stars, where it might make more sense to compare to the density of the sun. (Since mass and distance have their own standard, the density of water might be slightly different from 1, but should be close enough for this discussion.) Gah4 (talk) 21:18, 23 February 2017 (UTC)

Just as a further postscript to this, I find myself wondering at why only the largest objects - no smaller than maybe Iapetus - have a volume figure given, even though that figure is actually more useful for sorting the *smaller* objects, whose sizes might not be easily expressible in terms of a single radius (or diameter) and hard to come up with a consistent average for (particularly, do you use arithmetic or geometric mean of the dimensions? some other method?), but having a fair estimate of the total material volume enclosed by the surface ... a certain "amount" of celestial play-dough, if you like, which may be of some arbitrary type with variable density, but can only be squashed into a particular volume, though that may be represented by any kind of weird irregular shape, or a more-or-less-spherical potato. But still made of the same particular amount of play-dough, which gives us a nice easily handled single number that the blobbier objects can be sorted by quite simply, instead of fussing over whether to go by average radius, or dimensions (which can be just one, two, or three figures, all of which can be very different), etc.

Most of the individual article pages for at least the midsize objects seem to include a volume figure (estimated to lesser or greater degrees of precision), so would it be worth adding this in for the end of the above-400km section and at least some of the sub-400km ones? 146.199.0.203 (talk) 02:28, 3 March 2018 (UTC)

Missing bodies

• trinary Lempo / 1999 TC36
• Farthest Object in the Solar System - V774104 — Preceding unsigned comment added by Gann123 (talk • contribs) 19:36, 13 December 2018 (UTC)
• others? — Preceding unsigned comment added by MistySpock (talk • contribs) 18:37, 17 October 2017 (UTC)

Density of 20000 Varuna

With radius of 310 km, mass of 0.37x10²¹kg, Varuna has density of 2.965g/cm³, but the source here (abstract / PDF) tell me that it has density of 0.992g/cm³. Newone (talk) 03:37, 4 August 2010 (UTC)

Ok, changed the values for Varuna and Haumea to that source. Fotaun (talk) 16:05, 3 March 2011 (UTC)

But has that made the mass incorrect, now? 146.199.0.203 (talk) 01:58, 3 March 2018 (UTC)

I recently did a lot of work on the Varuna article, as it had ... considerable problems. I'm not 100% sure where the "3.7 x 10^21 kg" estimate came from, but there's now a much more realistic one on there (added independently of seeing this complaint, which I literally only just ran across now), more in the region of 1.6 x 10^21 kg instead.

I do wonder if whoever worked the 3.7 figure out made the same daft mistake I did at first, figuring out the mass of a cube with sides the same length as the object diameter, instead of using the radius and the usual volume-of-a-sphere calculation, which means you overestimate by almost 2x. Bearing in mind that using the equivalent-area spherical size estimate (which is what seems to be used by most professional astronomers publishing papers about minor planets / TNOs) would still get the volume (and thus mass estimated from density) wrong; instead, for any object that's not wholly or near-as-dammit spherical, you have to use the dimensions to get the volumetric mean (...which itself is no good for giving an equivalent diameter estimate because it gives a different surface area vs a sphere of the same volume, and it's the area we're actually interested in for astronomic measurements, as it's that which reflects the light that most of the estimates are based on).

...which is a realisation I only actually came to recently so I've got a load of edits to go back over, maybe including Varuna, to re-revise mathematically derived mean diameter and/or mass estimates on.

tl;dr, argh, my head 146.199.60.87 (talk) 13:56, 13 August 2019 (UTC)

Binary/trinary

Just curious, why are these listed as part of the descriptors for some of the dwarf planets? I was under the impression that the terms usually referred to a situation where the object and its moon are close in size. --Ckatz^chat_spy 20:23, 18 September 2011 (UTC)

Not for asteroids. E.g., see Johnston. It's probably just tradition, back to when they had little idea of the sizes. Tbayboy (talk) 21:57, 18 September 2011 (UTC)

Technically even Charon is only a satellite. (B=Binary companion / S=satellite) See also (90) Antiope and (93) Minerva on the list. -- Kheider (talk) 00:00, 19 September 2011 (UTC)

Thanks for the quick replies, and for clearing it up. --Ckatz^chat_spy 08:46, 19 September 2011 (UTC)

The impression I get from relevant articles, particularly that for Pluto and some similar ones, the determinant is now more where the system barycentre sits, ie the "centre of gravity" which all of the objects in a particular system orbit around. If it's inside the primary object of a system, then it's traditional sun-planet, planet-moon, etc. If it's outside of the primary (above its surface, like), then it's a binary. So technically Pluto-Charon is binary, though that's a recent enough discovery that it's not really been made official and might take some time if it ever happens. Earth-Moon is *nearly* binary, but avoids qualifying by a couple dozen kilometres. Sila-Nunam is very definitely binary (having fairly close sizes and about a 2:1 mass ratio also helps with the decision). And in fact Sun-Jupiter would count as some kind of binary star system if only Jupiter was somewhat hotter and more radioactively active, to the point where it counts as a brown dwarf or other quasi-star, because the barycentre of the two actually sits outside of the Sun's nominal surface (and of course, outside that of Jupiter)... it's just we don't really yet have any technical way of categorising binary systems made of a smallish star (like our yellow dwarf) and a suitably supermassive planet orbiting it, or any other heterogenous binary (or trinary, etc) systems for that matter. 146.199.0.203 (talk) 01:57, 3 March 2018 (UTC)

How up to date / reliable is this list? (at time of asking, ie start of March 2018)

I only ask because I've been trying to work up some kind of manageable list of the top 100 or 200 things to put on a more comprehensive solar system map than the classic versions... and amongst them we have Haumea at #19 according to this list, and (145453) 2005_RR43 - another member of the Haumeid family - at #120... but nothing else from the Haumeids (or certainly, nothing else from the list of ten members estimated as largest after Haumea itself, on the Haumea Family article page) appears anywhere on the list. At all. By either their discovery serial code, or minor planet registration number.

That's at least eight TNOs sharing a similar orbit to Haumea and average radii of more than 85km, up to more than 160km, plus another of about 36km, that have been left off the list. At least two, maybe four of them occupying the ground in between the current #19 and current #120 off a list of roughly 300. Biiiiit of a glaring omission. And begs the question of whether there might be a lot of other objects of that size, maybe even greater, that have been omitted.

One or two might be understandable, but nine is a bit much, especially as none of them are recently discovered - the dates for these ones are all no later than 2005, and range back to 1995... so they've been known about for 13 to 23 years... and are members of a reasonably notable orbital family... how many others are out there that should also be on the list?

And really, how do we even properly keep track of such a sprawling list and verify its data in any kind of organised and usefully frequent manner, when there's about half a million potential entries to select the actual top 300 or so members from and keep the most recent astronomical data refreshed for? 146.199.0.203 (talk) 00:32, 3 March 2018 (UTC)

The line that Ceres is on does not have a darker background.

The other 3 Belt asteroids do. Will this be changed? — Preceding unsigned comment added by 2606:A000:1014:C2FC:0:5837:B088:A394 (talk) 03:31, 20 August 2018 (UTC)

Unlikely, as it's no longer considered a "belt asteroid" - it's a Dwarf Planet (the only one in the main belt, with even the largest "other" asteroids all being much smaller), and therefore should be, as it is, coloured the same white / light grey as the other four. Same way that the confirmed Kuiper Belt DPs aren't coloured the same as their asteroid and comet neighbours. 80.194.203.132 (talk) 13:40, 1 August 2019 (UTC)

Articles needed for objects

2001 QC298 and 2001 QC298 I (not sure about the spelling of the second object) are the only objects on the list without their own article. Both are very similar in name. I am glad to make the articles if anyone can give references to create them.--Wyn.junior (talk) 21:47, 5 February 2019 (UTC)

Seeing as the naming of the latter suggests it's the moon of the former, you probably only need one article, with the second one being a subsection within it... 146.199.60.87 (talk) 13:44, 13 August 2019 (UTC)

Numbering

This entire list should be numbered with 1 being the largest and the biggest number being the smallest.--Wyn.junior (talk) 17:53, 6 February 2019 (UTC)

It's not very useful (beyond the first 20 or so) since the sizes are not that well known for most of the minor planets. That is, the sizes listed are often very approximate. At the smaller end (less than 200), this is not a complete list, just a list of the interesting or well-studied objects. Tbayboy (talk) 21:50, 6 February 2019 (UTC)

I disagree. A numbered list would at least give us how many objects there are listed.--Wyn.junior (talk) 15:49, 7 February 2019 (UTC)

What use is that? It's a list of selected objects, not all objects (billions), not even all known objects (hundreds of thousands). That is, "the number of objects that some wikipedia editors thought might be interesting". Tbayboy (talk) 17:13, 7 February 2019 (UTC)

You are correct. Nevermind.--Wyn.junior (talk) 20:21, 7 February 2019 (UTC)

There is actually a numbered list elsewhere on WP of all the known MPs plus their moons (on top of the sun plus 8 major planets + THEIR moons), which runs to many, many thousands of pages. Trying to replicate it here would be insane. However, it is quite a nice thing to have for the (confirmed or at least strongly suspected) larger objects, allowing us to easily count how many bodies of reasonable note are in our neighbourhood, rank them, and compare where various familiar examples fall on the list relative to each other. 80.194.203.132 (talk) 13:38, 1 August 2019 (UTC)

Edit: many hundreds of pages (at least 524 so far), but each page has 1000 entries... and it's linked from this page, IIRC. 146.199.60.87 (talk) 13:43, 13 August 2019 (UTC)

Almanac needed

Does anyone know of a an Almanac with the full information for this article so each of the objects can have the full same info and possible one long continuous list sortable in any you want?--Wyn.junior (talk) 20:52, 6 February 2019 (UTC)

There is no such almanac. The missing fields are missing because they're not known. Even many of the filled-in fields are just guesses. Tbayboy (talk) 21:52, 6 February 2019 (UTC)

Yeah, I'm yet again trying to use the available information to put together a nice pop-sci "map" of the 100 largest objects in the system and being stymied by multiple heavily conflicted measurements, and having to manually average out the most likely accurate ones (not always the ones stated on this particular list and used for its own sorting...). Our astronomical ability has undergone revolutionary improvement over the last 25~30 years, but it's still far from perfect, and there's just too much stuff to re-survey and not enough available observatories - or decent observational opportunities - to keep the updates flowing at a sufficient speed to properly nail everything down within less than probably another 25~30... For now we just have to, as has been the case all along anyway, go with the best guess. And encounter endless arguments over which of the many guesses is actually the "best". 80.194.203.132 (talk) 13:35, 1 August 2019 (UTC)

(Update: at this point, I'm pretty much thinking that I'm gonna have to make an error-bar chart for almost everything smaller than Pluto, save for the most well-studied major-planet moons, and see what kind of range fits within all of the reasonable recent (=< 12 years maybe) estimates... the variability is just too much and too confusing to keep track of otherwise) 146.199.60.87 (talk) 13:41, 13 August 2019 (UTC)

contradiction

AW197's classification contains two different descriptions: cubewano, detached object. That is impossible. An object cannot be simultaneously detached and a cubewano. Any detached object would have a perihelion beyond the main belt. Serendi^podous 14:26, 11 May 2019 (UTC)

The erroneous detached object classification of 2002 AW₁₉₇ has been removed. This list is quite large, and there may be some errors that I have missed. Nrco0e (talk) 04:43, 12 May 2019 (UTC)

I'm not getting on your back or anything. I'm impressed you took this on at all. The time I spent on it pretty much broke me. Serendi^podous 15:38, 13 May 2019 (UTC)

Surface gravity

Should the Surface gravity section be removed? I don't think it is relevant to the list since the surface gravity of objects are only listed for those with radii over 400 km. Nrco0e (talk) 00:35, 12 June 2019 (UTC)

I'm ambivalent, but some comments: It's not meaningful for the smaller bodies, since the non-spheroidal shapes can lead to varying surface gravities depending where you stand on the equator. This is also applies to larger non-spheroidal bodies, like Haumea, but the smaller ones are much more likely to have that problem. We also don't have the mass for a lot of the small and mid-sized bodies. The numbers get too small to be "interesting". Thus the cut-off here. It's similar to the discontinuing of the volume column, and of the Earth-units for the other columns. The surface gravity is interesting for the larger bodies, as in "how much would I weigh on XXX", which is why it's here in the first place. It's in the tables in List of gravitationally rounded objects of the Solar System, but not sortable there. Tbayboy (talk) 02:34, 12 June 2019 (UTC)

Probably somewhere around the point where you can achieve escape velocity by walking, so even relatively slow moving objects wouldn't be captured into its gravity and pretty much all kicked-up dust would be permanently lost into space, seems a reasonable limit, as the object's hill sphere is likely to be pretty small and not have any significant influence on its neighbourhood or gather much additional material over a sub-million-year timescale (on top of which, exploration by humans, rovers that move at any kind of reasonable pace, or probes that need to orbit the object would become extremely difficult). Not sure what that would be, but maybe 0.1 milli-G? Below which it could be listed as "insignificant", or just not listed at all (the same as mass and density estimates aren't for most smaller, little-studied objects). 146.199.60.87 (talk) 13:38, 13 August 2019 (UTC)

Measurement of HE

We have some conflicting information on the list, in the first block; there's a statement made in its lede that Rhea is the "smallest object for which detailed measurements have been made and found to be in Hydrostatic Equilibrium", and that its size plus that of Iapetus bracket a transition point of about 750km radius (quite where that leaves Oberon is anyone's guess).

But there are many objects on the list smaller than Rhea which seem to be strongly considered in HE (e.g. Makemake, as that was a condition of it being confirmed as a dwarf planet), presumably from being observed, measured and confirmed as such, and the line in the table listing Ceres clearly states that it's in HE. How do we know that? Psychic moon-rays?

Possibly the information has been misstated or poorly explained, but the statement as it stands seems in conflict both with parts of the following list, and assertions made on the individual pages for many midsize minor planets below the size of Rhea/Oberon/Iapetus that they are considered to be in HE from measurements of their size and/or mass plus lightcurves, occlusions, etc. Particularly for Makemake and Ceres given the importance of that confirmation for their classification, but also the "dwarf planet candidate" status of several others (2007 OR10/Gonggong, Quaoar, Orcus, Salacia etc) which are essentially just waiting in a queue for the IAU to get round to confirming them, not to mention the remaining large moons of Saturn and Uranus (and Pluto...).

So which is it ... have they been properly measured and confirmed or not? Either that lede is massively out of date and needs corrected to match the current state of play (for one thing I find it hard to credit Ceres not being sufficiently measured, given that its own article shows multiple extremely detailed photographic and topographic maps of its entire surface, plus analyses of its likely internal structure etc, and we more than likely have gravitational strength maps for it as well - we almost certainly know more about it than we do Rhea), or a good number of dwarf/minor planet & (dwarf) planetary moon article pages will need altering... 80.194.203.132 (talk) 13:28, 1 August 2019 (UTC)

At the time Makemake and Haumea were declared DPs, it was thought that HE for icy bodies happened around 400 km. Since then, it was found that several of Saturn's round moons (notably Iapetus) had shapes incompatible with HE, and that 2002 UX25 has a non-HE-compatible low density. Ceres was since measured and found to be compatible with HE, and Vesta not HE. Going by memory, measurements from Cassini images found Mimas, Enceladus, and Iapetus did not have HE-compatible shapes, and Tethys and Dione were indeterminate (whether their shapes are HE-compatible depends on their unknown internal structures). What was thought to be a fairly clear and simple transition from non-HE to HE turns out to be complicated, and the details aren't known.

Nobody knows if the IAU is confirming DPness anymore (probably including the IAU :-)). They have a process such that sufficiently bright objects are named assuming (but not asserting) they are DPs; no currently known, un-named objects meet the criteria. Haumea and Makemake were named under that process, and called DPs in the IAU press releases, but that was when Marsden was the MPC director. Brown publicly objected to that, and Marsden has since died, so the current MPC director might be gun-shy about such declarations.

There is no easy way to determine HE, no measurement, so don't expect any positive confirmations soon. And yes, the lead is out of date on this, as well as many articles. Although all that has really changed is that the grey zone has gotten much larger; 400 km is still a possible starting size. Tbayboy (talk) 17:52, 1 August 2019 (UTC)

Thanks. Maybe the statements need to just show whether something has been confirmed either in or not in HE and leave it at that without comparisons, though I do notice that Rhea's article now says "second smallest" (...or did it say that originally and I had a massive brainfart?). Interestingly whilst going through further research, it seems that bodies even as large as Haumea now have their HE in question, due to low density suggesting lack of compaction and differentiation, and irregular shapes that might not even be proper Jacobi ellipsoids. So there could be quite a bit of confusion over whether to consider any new object not studied up close by an actual probe as DPs, given that the status of those few already accepted could be in doubt... (then again, I suppose "gravitationally rounded", which IIRC is the exact wording used, might not necessarily be absolutely the same as "in hydrostatic equilibrium")

I wonder what this all means for the potential acceptance of the proposed name for OR10, and whether MS4 might get one, along with the other nine objects currently considered over 600km diameter which would fill in the name gaps all the way down to Gǃkúnǁʼhòmdímà / Ixion / Chaos (the first of which was recently named and therefore was probably assumed to be a DP; after which we can probably leave it given the rapidly increasing number of objects in the less significant smaller size bins; NB assuming RF43 gets bumped up the list due to recent increase in estimated size)? Not to mention names for any of their moons (which even Makemake's doesn't look to be in line for any time soon)...

Incidentally by "bright" do you mean "large", or simply bright (and then, apparent or absolute magnitude)? It does seem to go up sort of exponentially given that larger objects are *usually* (though not always) higher albedo, and vice versa, but there are exceptions, and it also hinges on distance... 146.199.60.87 (talk) 13:28, 13 August 2019 (UTC)

The IAU's naming directive refers to absolute magnitude: if it's 1 or less, the name is confirmed by two committees (forget which) under the assumption that it's a DP (but not necessarily asserting DP). Above H=1, it's named under the usual SSSB procedure. There are no known un-named objects that require this. Actual DPness doesn't matter for naming. For the IAU DP criterion, see Dwarf planet: it's actually "has sufficient mass for its self-gravity to overcome rigid body forces" with HE and "round" as stated consequences of that (otherwise something similar to Methone could be a DP). Tbayboy (talk) 04:10, 14 August 2019 (UTC)

Can we get the logarithmic size histogram updated?

It maybe only needs minor revisions, but it is still out of date. EG, Chaos is no longer in the top 50, having been displaced by 2010 RF43 (which in fact may need moving up the main list to just under Dysnomia anyway, instead of sitting between Ixion and Chaos, as recent best estimate is more like 695km diameter / 347.5km radius), and 229762 has been renamed to Gǃkúnǁʼhòmdímà, with a new size estimate of 632km/316km. There's probably other value and position adjustments needed too, maybe as far up as Eris and Dysnomia... 146.199.60.87 (talk) 13:19, 13 August 2019 (UTC)

I could update the old non-logarithmic version since it's just text, but the log version is an embedded png that requires image processing chops that I don't have. What do people think? Tbayboy (talk) 04:14, 14 August 2019 (UTC)

When this can be done, would it be possible to add error bars, either brackets or a lighter color at top? That should give readers an idea of how much things could change as we learn more, which bodies are secure and which are guestimates. Currently the graph is misleadingly absolute.

There are also missing largish objects that might should be in the main list. Johnston's Archive estimates from an assumed low albedo, and generally has larger estimates than e.g. Brown, but 1995 SM55, 2015 KH162, 2001 KA77, 2017 FO161 are all listed as r > 300km on JA (the cut-off for the log graph), and there another 15 with r > 250km that we don't have. — kwami (talk) 18:33, 4 October 2019 (UTC)

(55636) 2002 TX 300

Missing this Kuiper belt object in the list. Radius: ~143 km ! — Preceding unsigned comment added by 141.20.50.39 (talk) 19:31, 11 December 2019 (UTC)

Hydrostatic equilibrium of planets

I have seen that in recent updates this article suggest that all the terrestrial planets (Earth,Venus,Mars and mercury) are not in hydrostatic equilibrium. But the defining criteria of planet insist that hydrostatic equilibrium is must to become a planet.This means that they are not planets ,then what are they "asteroids". And despite of this if they remain planets, then asteroid Vesta is also a planet .

       Also this article suggests that Pluto and Ceres are also not confirmed in hydrostatic equilibrium, then how they dwarf planets !?

Conclusion: if Earth, Venus, Mars , Mercury , Pluto and ceres are not in hydrostatic equilibrium then how they are Planets or Dwarf planets ? Then what are they at all? Ayush pushpkar (talk) 04:27, 25 December 2019 (UTC)

Trans-Neptunian moons

Mass,density and shape of many Trans-Neptunian moons expect those of Pluto's ( Dysnomia, Vanth, Hi'iaka, ll'mare, Namaka, weywot, Actaea and moons of Makemake and Gonggong ) needs to be determined more accurately and their sections need data from more resources. Ayush pushpkar (talk) 04:59, 25 December 2019 (UTC)

Hygiea and Interamania

Could really objects that small can be in hydrostatic equilibrium, and thus become dwarf planets, when the larger Vesta and Pallas are not? Ayush pushpkar (talk) 05:01, 25 December 2019 (UTC)

Hydrostatic equilibrium

Okay, this is confusing. Recently, there has been a bunch of edits regarding hydrostatic equilibrium in bodies and I think we are taking it way too seriously. This a list of Solar System objects by size after all, there shouldn't be any fussy edits that overcomplicate this list. Nrco0e (talk · contribs) 02:59, 2 January 2020 (UTC)

@Nrco0e: I agree. It's insane to push the view that Earth, Venus, Mars, and Mercury are not in hydrostatic equilibrium (HE), which under the IAU definition, would make them minor planets instead of planets. On the article on the IAU definition of planet, it reads

there is no precise point at which an object can be said to have reached hydrostatic equilibrium. As Soter noted in his article, "how are we to quantify the degree of roundness that distinguishes a planet? Does gravity dominate such a body if its shape deviates from a spheroid by 10 percent or by 1 percent?"

What is the point of going through a list article and pushing a very particular POV that uses a very specific definition of HE? I believe that to do this kind of thing is effectively POV pushing behavior. I'm not sure how the situation should be fixed, though. Perhaps all references to HE should simply be erased, since it reflects a particular POV and doesn't contribute to the article in any way. BirdValiant (talk) 20:01, 10 March 2020 (UTC)

@BirdValiant: So I figured it is best to boldly remove the HE nonsense from the article. Nrco0e (talk · contribs) 22:00, 10 March 2020 (UTC)

@Nrco0e: I support the change. BirdValiant (talk) 22:16, 10 March 2020 (UTC)

There's also a statement in the paragraph preceding the actual list that The Moon isn't in HE, but cites no source to support that claim. This also contradicts the article for Iapetus, which states it's the largest Solar System body not in HE, since the moon is quite a bit larger than that. Would we be clear to go ahead and remove that statement as well?184.186.197.37 (talk) 16:06, 29 July 2020 (UTC)

dubious tags

The figs for the smaller bodies need to be checked. Often the sig figs of the error bar don't match the measure. When I've checked discrepancies like this, it's generally do to a misreading, where someone messed up a decimal point. So the error bar could be 10x what we indicate here. I've marked those I've noticed with 'dubious' tags rather than checking them all, but this list might be too long too long to maintain effectively. — kwami (talk) 06:23, 8 January 2020 (UTC)

Missing objects

Just curious. I noticed today that 2023 Asaph and 323 Brucia are missing from the list. Is it just that this list is missing a lot of the minor planet bodies, and need editors to add them? Or something else related to scope of the list? N2e (talk) 21:02, 12 July 2020 (UTC)

Reduction of list size

This list has become far too large to navigate comfortably and this page noticably has a lower performance with all those references and images. This page exceeds 300,000 bytes, so I will be removing most, if not all non-notable objects that do not have accurate size estimatess. Nrco0e (talk · contribs) 18:06, 15 July 2020 (UTC)

While I agree the list could be trimmed (I wasn't a fan of it getting this big in the first place) 300k isn't actually that long for a Wikipedia list. Just look at the lists that are longer. Serendi^podous 19:47, 15 July 2020 (UTC)