Talk:List of Solar System objects by size: Difference between revisions

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I'm not sure if I agree with the system of ranking objects that are irregularly shaped. Shouldn't we find the average radius of those objects and use that to rank them? Otherwise, small oblong objects could rank above generally larger but rounder objects. --Patteroast 14:48, 15 Jun 2004 (UTC)

I didn't really use a system when trying to compare and rank irregularly-shaped objects, just more or less did it "by eye". Perhaps there's a better way. -- Curps 17:43, 15 Jun 2004 (UTC)

You could compare for example the average radius - the radius of a sphere that will have the same volume as the moon. If a moon has a volume of V, then the average radius is

3V^{1 \over {3}} \over {4\pi }

Smartech 19:27, 11 July 2005 (UTC)[reply]

That's the same as comparing the volumes.

In my corresponding page, I just referred to it as Solar system by size, thereby sidestepping the whole "radius" issue. When one gets down to the irregular bodies, the ranking necessarily becomes somewhat arbitrary anyway. --P3d0 03:09, July 13, 2005 (UTC)

Radius/diameter

Thanks to User:TheTom for catching my goof. I had a suspicion something was wonky but didn't figure it out, even while changing half the numbers. This brings up an interesting question, though. Why are we charting by radius, when the planet infoboxes and most articles use diameters? I'll add a note inside, though, to future editors, so they don't make the same mistake I did! --Dhartung | Talk 18:42, 31 July 2005 (UTC)[reply]

Rename

I'd like to rename this article to the following: List of Solar System objects by size. Any objections? --P3d0 21:44, August 3, 2005 (UTC)

Since it's unlikely there would be a different corresponding article, e.. List of Solar System objects by diameter, I don't object. There will be a bunch of redirects to fix, though. --Dhartung | Talk 05:13, 5 August 2005 (UTC)[reply]

Keep the "radius" wording, but if you'd like to make a redirect from List of solar system objects by size to this article, go ahead. The problem with "size" is that it's too loosely defined. —Bkell 21:01, 9 August 2005 (UTC)[reply]

... or you could go with "volume", if irregularly shaped bodies are causing a problem. —Bkell 21:03, 9 August 2005 (UTC)[reply]

The looseness of "size" is why I prefer it. For smaller bodies, there's no easy way to rank them precisely by volume until we go take each body, dip it in a bathtub, and — eureka! — measure how much water it displaces. --P3d0 01:03, August 14, 2005 (UTC)

Rank is not a useful column

This list is not exhaustive, and so the Rank column is not useful, and may even be misleading. I would like to remove it. Any objections? --P3d0 01:04, August 14, 2005 (UTC)

I sorta like it, but I can't see keeping track past (say) Pluto. I agree it's potentially very misleading for the lower end of the list. Then I can't think of a good argument for only having it for part of the list. Primarily, it's going to be a pain to maintain as more TNOs are discovered and others, like 2003 UB313, have their diameter pinned down. --Dhartung | Talk 01:28, 14 August 2005 (UTC)[reply]

I'm not sure why the Rank column is 'not useful'... this is a list of objects by size, correct? Going from largest to smallest? In which case, the size-ranking is of interest. --Firsfron 03:46, 27 August 2005 (UTC)[reply]

As I said, it's not useful because the list is not exhaustive. The rank we present is meaningless, aside from listing where an item appears in our list. There's absolutely no reason to believe, for instance, that Mercury is the 11th-largest body in the solar system, since we could discover a larger TNO at any time. This problem becomes even more pronounced as one moves downward in the list, at which point there are even known bodies that are not in our list. I have started by removing the ranks after Europa, since the relative ordering of Triton and UB313 are not known. --P3d0 16:27, August 27, 2005 (UTC)

According to Dave Jewitt, we could discover something larger than Jupiter at any time, too: "a planet of Earth's mass could exist undetected if it were more than a few 100 AU away, and even a Jupiter (300 Earth mass planet) could exist at distances only slightly greater." (from the Kuiper Belt Page: http://www.ifa.hawaii.edu/faculty/jewitt/kb.html ) However, there is ample evidence that Jupiter is the 2nd largest body in the solar system, and that Mercury is the 11th-largest body in the solar system: in over three hundred years of telescopic astronomy, we haven't discovered anything larger.

Does the possibility of something existing that is larger than Jupiter mean Wikipedians can never create a list including the rankings of known objects by size, because there might be something larger? Of course not. Many resources, including books and web-sites, refer to the size-ranking of various bodies: check here for Mercury , here for Jupiter, and here for Europa (official NASA site, BTW). If NASA's ranking planetary bodies by size, there's no reason Wikipedia can't. --Firsfron 22:27, 27 August 2005 (UTC)[reply]

The potential to find new objects is secondary; I'm sorry I focused on it in my remarks, because it was a spurious argument that seems to have utterly distracted you from my main point, which is that our list is not exhaustive. Even if it could be made exhaustive, which I doubt; even if we could find some means to include every known solar system object in the list, and keep it up to date with new findings; the sizes of most of them will never be known with enough precision to allow them to be ranked. The whole concept of the ranking is fundamentally futile beyond about 15th or so.

Having said all that, if you would like to use a ranking you find in another source, and cite it, be my guest. Wikipedia is all about collecting knowledge from credible sources. --P3d0 03:26, August 28, 2005 (UTC)

Hmmm. Yes. I believe you said that, once or twice. "You keep using that word. I do not think it means what you think it means." ;) Exhaustive: from Dictionary.com : very thorough; exhaustively complete. I'm not exactly sure how you think this list of objects could be more thorough or complete. If you think the list is incomplete, I wonder why you don't add the information you have (with suitable citation, of course). If it's just that you believe that more objects exist out there, yet undiscovered, I think I already addressed that: there's always the potential for larger objects (than Mercury or Jupiter) to exist, but we haven't found any, in the last three hundred years. And even if we do, it's really not too hard to update the list. Meanwhile, these are the largest objects known to exist, outside of fringe speculation and conjecture. If you're basing your objection to rank based on speculation, I don't know what to tell you: I've taken a look at your edits on other pages, and they seemed really sound, so your argument here seems quite puzzling.--Firsfron 13:05, 28 August 2005 (UTC)[reply]

Please, just for one moment, consider the possibility that I'm not an idiot. Maybe, just maybe, I have a point, and that is this: 1) there are upwards of 5000 bodies currently known in the solar system; 2) most of them are very small and their sizes are only known to one significant figure, and 3) this makes a ranking of 90% of the bodies impossible and meaningless. --P3d0 16:09, August 28, 2005 (UTC)

I don't think you're an idiot, P3. In fact, I thought I pretty much said that above, when I said I liked your earlier articles. I'm not sure why you thought I didn't think you weren't intelligent, as my post tried to indicate something else entirely.

I'd like to address these new points, P3, but I wish you would have mentioned them earlier. Anyway, back to your new points, which weren't mentioned earlier.

And I wish you had asked, or found out for yourself, rather than assume I was mistaken. ;-)

1) there are upwards of 5000 bodies currently known in the solar system; 2) most of them are very small and their sizes are only known to one significant figure, and 3) this makes a ranking of 90% of the bodies impossible and meaningless.

There are certainly 5000 bodies currently known in the solar system. Most of them are very small and their sizes are not all certain, true. However, you're off on point three: the list we are discussing doesn't contain 5,000 bodies. It contains the largest bodies known. You say this makes a ranking of 90% of the bodies impossible and meaningless, but in point of fact, the 90% of the bodies were never on this list. Only the largest bodies were on this list, and their ranking according what's currently known. Astronomy is an ever-evolving field, and our knowledge of heavenly bodies is always expanding; that doesn't mean that a list of solar system bodies, or even a ranking of known solar system bodies, is meaningless: as I said earlier, more than one resource, even NASA sites, cite size ranking, so obviously it's important to some people. Certainly the high school student who is writing a report on Saturn might find it useful to mention that Saturn is the third-largest body (known) in our solar system, and that's where a ranking might be useful, and not at all meaningless. Cheers! --Firsfron 16:42, 28 August 2005 (UTC)[reply]

First, the 35 or so bodies we have listed are not the 35 largest known bodies. They are the 35 bodies that people felt like adding to the list. That is why I keep saying the list is not exhaustive (though that could be fixed). Second, out of just these 35 bodies, the rankings of more than half of them are uncertain. Thus, even if you don't want to consider all 5000+ bodies, my points still stand with just these 35. Our rankings for most of them are meaningless. --P3d0 21:44, August 29, 2005 (UTC)

First, the 35 or so bodies we have listed are not the 35 largest known bodies. Not true. According to [[1]] the KBO on our list are the largest objects. Also compare with [2]. Neither site lists any KBOs that are larger than any on our list, so this isn't a case of the list here being inaccurate because people 'felt like adding bodies to the list'. As far as I can tell, Wikipedia's list here agrees with the findings on both of these sites, which I might add are run by professional astronomers. See also my talk page or yours for further comments. --Firsfron 04:37, 30 August 2005 (UTC)[reply]

I concur with the elimination of a ranking number past 15, and I've added an editorial note to that effect inside the article (with a see talk). I think it's OK to have it there, at least partially, because it's something that a casual reader might expect.

Regarding Jupiter: It's certainly possible for a Jupiter-sized object to exist on a very long orbit of the Sun, if hypotheses about a brown dwarf companion have any validity. --Dhartung | Talk 05:06, 28 August 2005 (UTC)[reply]

Hypotheses about brown dwarf companions to the sun are always interesting, of course, but doesn't that sort of fall into the category of speculation? --Firsfron 13:10, 28 August 2005 (UTC)[reply]

I was just responding to the over-certainty in the earlier comment. In fact, I think it's more certain that we will discover planetary bodies at least as large as Europa -- in other words, our Top 15 is by no means finished -- and remains possible that we will discover very distant gas giants at least as large as Neptune, so that the Top 5 might even change one day. That doesn't change my view that down past 1500km there are going to be objects too numerous (er, hyperbole) to count, let alone definitively rank. In fact, I think these are complementary views. --Dhartung | Talk 23:49, 28 August 2005 (UTC)[reply]

That doesn't change my view that down past 1500km there are going to be objects too numerous (er, hyperbole) to count, let alone definitively rank. While I agree there are still many bodies left to be discovered, some of which could be quite large, if the Main Asteroid Belt is any example, most of the larger objects in the Kuiper Belt have already been discovered (the first four asteroids discovered represent a majority of the mass of the entire main belt). In the past twelve years, we've discovered less than a dozen objects in the 1000 km range, which works out to less than one per year. That average doesn't really support claims of many large ("too numerous to count") objects in the range of 1500 km, and even if we discovered a large object every year for the next hundred years, we'd only have to update the list once a year.--Firsfron 18:30, 29 August 2005 (UTC)[reply]

David Jewitt, who discovered the first TNO, beleives that the Kuiper Belt contains some 70,000 objects larger than 100km, and is 300 times more massive in aggregate than the asteroid belt. [3] There are only 230 asteroids that large; and we're not necessarily counting objects in the Oort cloud (of which one is on our list already). Most of these are icy and dark. I don't think the history of asteroid belt astronomy is necessarily an excellent match; the first several TNos aren't even on our list, and it was only 1998 when we discovered the first of them (Ixion) and that's now the smallest listworthy object. So I still think there are a lot of them out there, and I don't think that 2003 UB313 is the upper bound; the odds are simply against it. Anyway, my argument has little to do with updating the list regularly; if anything, Wikipedia is in a better position to keep an updating ranking than NASA or anybody, because they publish static pages, while ours might be updated within minutes of an announcement. I'm just concerned that the ranking ceases to be useful after a certain point, because we simply don't know the mean radius value on which it is based to a reliable degree of accuracy. --Dhartung | Talk 19:54, 29 August 2005 (UTC)[reply]

@@ Line 57: / Line 57: @@
 :::::::: First, the 35 or so bodies we have listed are not the 35 largest known bodies.  They are the 35 bodies that people felt like adding to the list.  That is why I keep saying the list is not exhaustive (though that could be fixed).  Second, out of just these 35 bodies, the rankings of more than half of them are uncertain.  Thus, even if you don't want to consider all 5000+ bodies, my points still stand with just these 35.  Our rankings for most of them are meaningless.  --[[User:P3d0|P3d0]] 21:44, August 29, 2005 (UTC)
+:::::::::''First, the 35 or so bodies we have listed are not the 35 largest known bodies.'' Not true. According to [[http://www.ifa.hawaii.edu/faculty/jewitt/kb/big_kbo.html]] the KBO on our list ''are'' the largest objects. Also compare with [http://www.johnstonsarchive.net/astro/wrjs103ss.html]. Neither site lists ''any'' KBOs that are larger than any on our list, so this isn't a case of the list here being inaccurate because people 'felt like adding bodies to the list'. As far as I can tell, Wikipedia's list here agrees with the findings on both of these sites, which I might add are run by professional astronomers. See also my talk page or yours for further comments. --[[User:Firsfron|Firsfron]] 04:37, 30 August 2005 (UTC)
 :::::: I concur with the elimination of a ranking number past 15, and I've added an editorial note to that effect inside the article (with a ''see talk''). I think it's OK to have it there, at least partially, because it's something that a casual reader might expect.