Talk:List of trans-Neptunian objects
From Wikipedia, the free encyclopedia
What order is this list in? Size? Distance from the Sun? Date of discovery? It's not clear. The Singing Badger 17:36, 7 Feb 2005 (UTC)
Well, if some editors (such as The Tom) insist on splitting the number from the rest of the name, the table columns need to be correctly titled. For example, the "permanent designation" of (15760) 1992 QB1 is "(15760) 1992 QB1", not "15760". I don't see how to fix this without merging the columns back. Urhixidur 22:42, 2005 August 4 (UTC)
- "(15760) 1992 QB1" cannot by definition be considered a "permanent designation" because it is ultimately in line for replacement. The number is certainly locked in for eternity, but the year/letters/number part simply cannot be justifiably placed in a permanent column. mpl- is simply a cosmetic shortener so objects that have been assigned numbers but not yet names can be placed in a table row with no duplicate or inappropriately-placed information. Also, there's no ironclad reason year/letters/number designations have to mated-in-perpetuity with permanent numbers for every single occurrence: astronomers frequently shed the leading numbering on unnamed objects for convenience's sake (even within academic contexts) just as they'll often refer to the planetoid as "Sedna" instead of "90377 Sedna" --The Tom 23:07, 4 August 2005 (UTC)
[edit] Suggestions
How do people feel about re-arranging this in terms of mass? As far as usefulness goes, I think this makes the most sense. We list the mass and perhaps also list "Pluto masses" to provide a baseline comparison. Marskell 10:08, 13 March 2006 (UTC)
- Unfortunately, the masses are unknown, except for a few objects which are binaries or multiple systems (i.e. have at least one satellite), so the mass of the system could be calculated from Kepler's laws. The diameters are also unknown, except for large objects where the disk could be measured by HST or the albedo established via the thermal method and using the absolute magnitude (calculated from the apparent magnitude (the only thing really measured) with the distance known from the observed orbit and Kepler's laws). In other words, there’s not much to order this list. Even the discovery date is bit fishy because some objects had been observed earlier but not recognised as such, for instance 2003 UB313 has been actually discovered in 2005. Regards Eurocommuter 13:04, 13 March 2006 (UTC)
-
- For the larger bodies mass is not absolutely unknown. We can provide a range. We know how big Sedna is, more or less. We know that 2003 UB313 is bigger than Pluto... Mass stikes me as eminently more useful than (putative) discovery dates (think in the "school project" sense). Perhaps not rearranging this list but making another one. I think a placeholder listing, say, the top ten bodies relative to Pluto mass makes good sense. Marskell 22:19, 13 March 2006 (UTC)
- Well, I’m surprised that the mass is being put forward. Firstly, the size estimation from the albedo alone is to a factor of 3 or worse. Secondly, the densities (except the cases mentioned above) are not known, i.e. the density may easily represent another uncertainty of 2! Next; who remembers whether say (our) Moon is denser than Enceladus? As result, the comparison of the mass can easily mislead about the size. Finally, if told that the mass of a satellite is a bit more than 1% of the primary, how many people will think: 'wow, it is quite big!'? (well, it is big; it is again our Moon compared with Earth). Having said that, I’m, like you, unhappy about the discovery date. If asked, I would vote for the absolute magnitude. Given the differences in albedo it can mislead into overestimating a small-but-bright over a big-but-dim, but IMHO magnitude is more expressive than mass. The only problem with the magnitude is that it's logarithmic, so for a wide public, a TNO one magnitude dimmer or brighter than Pluto does not necessarily mean much. Regards Eurocommuter 19:23, 15 March 2006 (UTC)
- What about plain old (estimated) diameter? It's equivalent to the magnitude sorting for the majority of objects, apart from a few cases where we have more accurate data (which is even better). This seems the best compromise between wide applicability and understanding by readers. It gets used in e.g. List of solar system objects by radius, List of noteworthy asteroids. Deuar 14:43, 18 March 2006 (UTC)
- Well, I’m surprised that the mass is being put forward. Firstly, the size estimation from the albedo alone is to a factor of 3 or worse. Secondly, the densities (except the cases mentioned above) are not known, i.e. the density may easily represent another uncertainty of 2! Next; who remembers whether say (our) Moon is denser than Enceladus? As result, the comparison of the mass can easily mislead about the size. Finally, if told that the mass of a satellite is a bit more than 1% of the primary, how many people will think: 'wow, it is quite big!'? (well, it is big; it is again our Moon compared with Earth). Having said that, I’m, like you, unhappy about the discovery date. If asked, I would vote for the absolute magnitude. Given the differences in albedo it can mislead into overestimating a small-but-bright over a big-but-dim, but IMHO magnitude is more expressive than mass. The only problem with the magnitude is that it's logarithmic, so for a wide public, a TNO one magnitude dimmer or brighter than Pluto does not necessarily mean much. Regards Eurocommuter 19:23, 15 March 2006 (UTC)
- For the larger bodies mass is not absolutely unknown. We can provide a range. We know how big Sedna is, more or less. We know that 2003 UB313 is bigger than Pluto... Mass stikes me as eminently more useful than (putative) discovery dates (think in the "school project" sense). Perhaps not rearranging this list but making another one. I think a placeholder listing, say, the top ten bodies relative to Pluto mass makes good sense. Marskell 22:19, 13 March 2006 (UTC)
- The list is arranged by MPEC filing date because other minor planet lists are also sorted that way. A (rough) size-based list appears on trans-Neptunian object, Kuiper belt and scattered disc. The Tom 00:15, 16 March 2006 (UTC)
