Talk:Natural satellite

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[edit] Focused on Moons

Perhaps I should just share my ideas and let them be debated. What I want to do is move the move the moon information to be a subcategory to a category labeled "Types of Natural Satellites" and also add information on comets, asteroids, meterors, planets, etc. I am looking for either support or objections. Thank you :)
kf4yfd 04:49, 14 September 2006 (UTC)

No, that would be the solar system article. We already have it. Rmhermen 05:28, 14 September 2006 (UTC)
I agree with Rmhermen there. We already have it. Sorry. Deuar 14:48, 14 September 2006 (UTC)

I have noticed that this page focuses mostly on the moons of our solar system. Natural satellites, however consist of more than moons and tends to be a very broad subject. Natural satellites include earth's moon, the earth itself, the sun, meteors, comets, and even galaxies. In short, any celestial object can be a satellite and natural satellites are celestial objects . kf4yfd 01:32, 12 September 2006 (UTC)

Well that's a fair point it seems, although commonly more cumbersome expressions like "body orbiting so-and-so" seem to be used when discussing the non-moon cases (apart from satellite galaxies). A name change might be desirable to keep in line with what the article actually discusses, but I can't think of a good one (Moons in the plural?). The thought of how many articles link to this one is enough to make me cringe at the very thought. An article for the broader grouping could be called orbiting body or something similar. Not sure. Deuar 10:59, 12 September 2006 (UTC)

I believe extending the household notion of a moon is not helpful. The different ‘orbiting’ bodies do not have much in common except for being ‘bodies affected by gravity’. But orbits of planets' satellites are special: described by 2-body perturbed solutions or 3-bodies special cases. Little to do with other objects. The household moons have a lot in common (even if split into two categories: regular (formed in situ) and irregular (to be elucidated but probably captured). Further, they split based on the physical characteristics etc.

My point is that being a ‘tertiary object (orbiting a secondary on orbit around the primary) from celestial mechanics point of view and being metal/silicate/ice composition from the physical point of view defines this category. Including other "orbiting" objects dilutes the meaning of the category in my opinion. If you look at the list of objects you quote one by one, you see that both (celestial) mechanics and physical characteristics put them aside from the ‘moons’ (commonalities of course exist). The category of ‘being affected by gravity’ would be of little value IMHO. Eurocommuter 13:10, 12 September 2006 (UTC)

[edit] (IAU clarification on Planet definition)

I made several changes to this page to reflect the change in status of Pluto to a dwarf planet. I included a mention of the 3 dwarf planets and their moons. Scottosborne

[edit] (Asteroids and KBOs)

Why are the asteroids included in a list of moons? They don't revolve around planets, if I recall, but around the Sun. --montrealais

I put them there merely for purpose of comparison. They're in the same general size class as moons, and so comparing them helps get a feel for them both. Bryan

If we are going to include some of the larger asteroides in this artcle, should we also include the larger KBOs? jeff8765

Sounds reasonable to me. Perhaps to save space, though, they should be combined into the asteroid column, which can then be renamed "minor planets" or somesuch and maybe moved to the right side of the table (rather than remaining between Mars and Jupiter)? I can do the work, if that sounds good to everyone. Bryan 02:45, 4 Mar 2004 (UTC)
Sounds good to me --- I think that putting the "minor planets" column off to the right partially answers Montrealais' objection & accounts for KBOs nicely. Btw, I like having the minor planets in there for comparison. -- hike395 05:38, 4 Mar 2004 (UTC)
All prepped and ready to go, but I'm just about to turn in for the night so I'm not going to add any KBOs myself just yet. I'll get to it tomorrow if nobody beats me to it. Bryan 06:17, 4 Mar 2004 (UTC)
Oh, this raises an interesting issue. Pluto itself has a diameter of only 2320 km, and Mercury 4879.4 km; both of these diameters fit into the range covered by the table. How about changing "minor planets" to "other objects" and including these two planets in with them as well? Bryan 06:27, 4 Mar 2004 (UTC)
While fewer people are considering Pluto a planet these days, Mercury's another story. I guess we'll have to wait for the IAU. - Jeandré, 2004-03-17t11:30z

I've changed the 750-1 000 row, to 900-1 000 to cut it off at 2002 TX300. Another option would be to include "(too many to list)" below 20000 Varuna (and then order everything by size!), and change the row name to 500-1 000, since it's kind of ill-proportioned at the moment. - Jeandré, 2004-03-17t11:30z

Another alternative (which is more balanced) is to give upon listing "other objects" less than 1000km, because more and more TNOs will be discovered in that size range... Also, I think Ceres & Varuna are both >1000km? (I've seen a 1003 km estimate for Ceres). -- hike395 15:11, 17 Mar 2004 (UTC)
I agree with the 1000km cut off. Some (good?) sources: Varuna 900km (+125/-145). Ceres 950 × 920, 930 and 970. - Jeandré, 2004-03-17t17:12z
Agree that Ceres is <1000km (took it out already) I did some research a while ago on Varuna's diameter. The latest paper from France & Spain[1] gives a thermal estimate above 1000km. Dr. Jewitt's web page does not reflect the latest work, because it was published in 2001. In fact, the Lellouch paper cites the Jewitt paper. I'd like to stick with the latest results. --- hike395 18:29, 17 Mar 2004 (UTC)
More, from Lellouch's paper (JAE01 being the 2001 Jewitt paper) ---
We find D = 1060+180−220 km. Although our central flux value, when rescaled to 850 �m, is 25–30% lower than JAE01's, our inferred nominal value is slightly higher than theirs; this is due to different assumptions on the millimeter emissivity, the distribution of temperature, and the fact that JAE01 adopted the Rayleigh-Jeans approximation (which is relatively inaccurate at 0.8 mm – about 20% error for T = 45 K). With our model, we would infer a 1220+175 −200 km diameter from JAE01's measurements. The two determinations nonetheless overlap within error bars.
So, shall we keep Varuna > 1000km? -- hike395
IANAA, but that looks good to me. I've found another link to Lellouch's 1060+180-220 data on the Johnston's Archive site which I've found useful. - Jeandré, 2004-03-17t22:01z

I really think Ceres should be on that table, at the very least; it's the largest asteroid and people will be curious about how the asteroids measure up. How about modifying that (too many to list) note to (and many others), and insert a couple of notable asteroids into the sub-1000km cells? Bryan 00:43, 18 Mar 2004 (UTC)

That's a good compromise. -- hike395

[edit] (Moons of Saturn, Uranus, Neptune)

I was curious as to why Saturn's newest moons have been listed under unknown, I've been able to find figures that generally agree on Scott Sheppard's page and a JPL page. Hope those are helpful, this is a very informative entry. - patteroast

Thanks! I incorporated the diameters from Scott Sheppard. -- hike395
I think there's some similar info for Uranus and Neptune's smaller moons on Scott Sheppard's site, also. It'd be nice to get rid of that unknown section. :) - patteroast
Done -- hike395

[edit] Method?

What is the ordering of moons and others in each box? It is not alphabetical, order of discovery or distance from sun. Is it random? Or are there just mistakes in the ordering? Rmhermen 04:58, Apr 3, 2004 (UTC)

It could be that several different editors each thought the ordering was based on a different characteristic, and so the combination of their additions has resulted in this confusion. :) How about we arrange the names in order of size, since the table is already ordered that way on a large scale? For the little tiny moons that are all about the same size (or as near as we can tell, anyway) we could resort to some other ordering. Bryan 19:33, 3 Apr 2004 (UTC)
Sounds good. We should mention that somewhere. Bound to more more moons discovered -but probably only small ones. Of course, the box with Sedna, Quaoar, etc. will be anyones guess as to size order. Rmhermen 20:00, Apr 3, 2004 (UTC)
I suppose a good method of arranging the smallest moons when they all have the same size is to go by discovery order. I'm cringing at the thought of seeing all those S/2003 Jx's every which way, though... patteroast

What source is being used for the moons' sizes? I was trying to do a little editting to put some of the ones in order when I noticed several weren't in the right box in the first place. I know it depends greatly on the source, but as an example, the only source cited on the page (Scott Sheppard's Site) and JPL's site gives Himalia's diameter as well over 100 km, in fact it gives a figure larger than Amalthea! I'd go on an edit spree, but I want to know if there's a different source being used - want to keep it self-consistent. If not, I'll be happy to do some re-arranging. Also, I think I'll add JPL's page as an addition source in the article now. --Patteroast 22:01, 20 Apr 2004 (UTC)

Looks like User:Bryan Derksen started the page about 2 years ago by moving the table from some other page. I am not sure we can track down a single source used for sizes. Probably best to find the most reliable source we can and make whatever changes are necessary. Rmhermen 13:53, Apr 21, 2004 (UTC)
I recall creating the table in the first place, but darned if I can remember what the specific source of the information was from. I believe (not certain, but fairly confident) that I took the information from existing Wikipedia pages. Some of that information would have been placed there by others, so I can't tell where it came from, but I recall that at the time I was expanding a lot of planet and moon pages with information gleaned from nineplanets.org. You might concievably find an earlier version of the table in the history of moon, since it was about that time when I split it into separate articles for Earth's moon and moons in general. Bryan 15:18, 21 Apr 2004 (UTC)
Well, if nobody minds, I'm going to update them. I'm using JPL's SSD information except where it's not available (a few of the most recent moons), in which case I'm using Scott Sheppard's data. --Patteroast 21:50, 21 Apr 2004 (UTC)
By all means. Just make sure to check the articles of the moons that need changing to avoid introducing inconsistencies that will confuse future editors all over again. :) Bryan 23:57, 21 Apr 2004 (UTC)
Okay, I went to try to do that, and.. I came up onto a few issues. 1) Some pages list the radius and some pages list the diameter. Not an unsurmountable problem, but it does cause some confusion. 2) With so many different references listing sometimes wildly different figures, which are to be trusted? For my own personal study, I've been using figures from JPL's Solar System Dynamics pages for the larger and mid-sized moons, and Scott Sheppard's page for best estimates of some other newly discovered moons. It just seems strange to change it to what I think is right without say. Perhaps there should be an agreed upon reference? 3) Finally, for irregular bodies, I've seen that the longest axis seems to be the favorite to be listed as the diameter or radius, instead of an average of all axes. I think this method's preferable, as it more accurately shows the volume of the object. Anyway, I could just start changing things, but I figured mentioning it somewhere would be a good bet, beforehand. Thoughts? :) --Patteroast 22:43, 24 May 2004 (UTC)
If you are going to be working on them, standardizing them all on either radius or diameter would be great. I don't care which but could we get them all to the same standard. Rmhermen 14:48, May 25, 2004 (UTC)
Right. I've started work on a new standard, using the mean diameter, using figures from JPL's SSD page where possible, and any info not available there being provided from Scott Sheppard's page. --Patteroast 15:23, 22 Jun 2004 (UTC)

I'd like to bring up a question.. would it be appropriate to create pages for unnamed moons? We have virtually the same amount of information about many of them as some recently discovered named moons.. and there are pages for un-numbered asteroids, which is sort of the same thing. I realize many would be named, but that may take years.. especially for objects like S/2000 J11 and S/1986 U10 which have been passed over for naming several times. I'd take up the task of creating the pages, and when they're named to change links and move them. How's that sound? --Patteroast 15:23, 22 Jun 2004 (UTC)

I'd say go for it, no reason not to. -- Curps 16:29, 22 Jun 2004 (UTC)
Seconded. That's what the "move this page" function is for. :) Bryan 00:29, 23 Jun 2004 (UTC)

I moved Charon to be a moon of Pluto. I know all about the controversy over whether or not Pluto is a planet, but I think it is still usually accepted as one. In addition, given that Charon is its moon (whether or not it is a planet) Charon should still be considered a moon. If the consensus is that this is wrong and that Charon really should be under "Other Objects" then it should be footnoted to explain why this is the case for the reader. Mfriedma 15:45, 25 Dec 2004 (UTC)

[edit] Jupiter's less-than-10km-diameter satellites

Back when I first implemented this table layout there were a whole lot fewer of these, but now that one cell is stretching the table hugely. Anyone object if I collapse it down to "too many to list, see Jupiter's natural satellites?" The downside is that there would no longer be a link for every moon in the solar system here, but I'm not so greatly worried about that now that there are categories and navigation footers and whatnot to keep track of them with. Bryan 00:58, 26 Jan 2005 (UTC)

Sounds fine to me. -- Patteroast 02:11, 26 Jan 2005 (UTC)
Ok with me. -- hike395
Make that "at least XX, see Jupiter's natural satellites" and I'll be happy.
Urhixidur 04:36, 2005 Jan 26 (UTC)

[edit] Templating the table

David Kernow moved the table over to a template and transcluded it, but I can't see any good reason to do so - it's not overly large, it's not located in a confusing spot for new editors like infoboxes are (and indeed it makes it harder to find in the source), and it's only used in this one individual article. Furthermore, it makes footnoting problematic. I'm going to subst it back. Bryan 18:55, 2 July 2006 (UTC)

I thought it might be (adapted for) use in individual moons' articles, e.g. made (semi-)hideable via <div class="Nav*">s. Regards, David Kernow (talk) 04:05, 9 October 2006 (UTC)

[edit] Other topics

I'd like to see this article cover the topic of the Hill sphere with respect to the stability of satellite orbits. Also some discussion of "regular" versions "irregular" satellites would be much appreciated.[2][3][4] Thanks! — RJH (talk) 21:34, 24 July 2006 (UTC)

Just discovered your post (and read this article for the first time). I’ve covered some of it in the irregular satellite since. This article could benefit I believe by making clear regular/irregular distinctions, referring for more details to irregular sat article (started with a few remarks). Eurocommuter 15:55, 12 September 2006 (UTC)

[edit] Origin?

Under origin it mentions that the Earth's moon is a fragment from the Earth blasted into orbit.

"others may be fragments of larger moons shattered by impacts, or (in the case of Earth's Moon) a portion of the planet itself blasted into orbit by a large impact."

I know this is a theory but not that it is accepted as fact. Should (in the case of the Earth's Moon) be removed? At this point, no one knows where the Moon came from.

[edit] Minor and others

Why are some objects listed in the others for comparison column while others in the same class are in the Minor planets column. Seems confusing. Rmhermen 15:55, 17 August 2006 (UTC)

Yep, this column seems to cause confusion every so often. I've attempted a new label. Perhaps it is better (?). Deuar 15:01, 23 August 2006 (UTC)
Following the footnote makes it clear. But is the "many more TNOs" really correct for moons of minor planets? Are there that many known? Couldn't it say, if true, "many more moons of TNOs"? Rmhermen 16:28, 23 August 2006 (UTC)
It is often estimated that 10% or even as much of 20% of TNO could have satellites. The theories are intriguing (once I’ve done with the irregulars I hope to write something about the binaries). A half-cooked but intuitive explanation for large population of the multiples is the large Hill sphere compared with the asteroids. In flat English, given the distance to the Sun the zone of gravitational influence of any sizable rock is quite large. However, there’re problems including the available initial density of the primordial disk for example. Eurocommuter 16:07, 12 September 2006 (UTC)

[edit] moons having moons

I don't understand. If a moon can't have moons of its own, how is it possible for spacecraft and satellites to orbit moons? In that case, they're just behaving the way in which moons and satellites behave with planets. You could look at it this way: Pretend that the Sun is a planet and that there are 8 moons orbiting it (Mercury --> Neptune). 6 of these 'moons' have their own 'moons' orbiting them. The principle is the same: A primary being orbited by a secondary which is being orbited by a tertiary.

Someone please explain.

It is a matter of stability. Check out e.g. what happened to SMART-1, which impacted the Moon just recently because its orbit had decayed. The decay is mostly caused by perturbations from the primary (Earth in the above case) and non-uniformity of the Moon's gravitational field. For orbits around most moons of interest in our solar system, the decay time is very short (often a few years) because the moons orbit close to their primary where tidal forces are strong. Any natural "moons of moons" would have to be on orbits that are stable for times of the order of the Solar system's age, meaning they would have to be within at most about 1/3 of that moon's Hill sphere. There are also other perturbations which all serve to destabilise such an orbit over long timescales: the gravity of other moons; nonuniformity of the moon's or planet's gravitational field; radiation pressure; collisions with other bodies, etc. While moons of moons are not ruled out in principle, in our solar system the only viable candidate moons to have their own satellites would be the distant irregular satellites of the giant planets. No such cases are currently known. By the way, this is also related to why Mercury and Venus do not have any moons. Deuar 15:23, 7 September 2006 (UTC)
Ok that makes sense. So in the end, could our moon's orbit decay in much the same way as the orbit of a satellite around the moon decays? I wonder if Mercury used to orbit Venus and then its orbit decayed and it became a planet... —The preceding unsigned comment was added by Just James (talk • contribs).
You might want to check out tidal acceleration. As for Mercury and Venus it is ruled out because there is no mechanism for Mercury to have lost enough gravitational potential energy to end up halfway to the Sun inward of Venus. Being a lost satellite might have been plausible only if Mercury's orbit was very close to Venus's. Deuar 22:05, 10 September 2006 (UTC)
It would be interesting to pick up an example of say 10-50 km rock around Callisto at no more than a few radii and calculate (over an envelope) how long it could last. My bet (haven’t done any calculations) would be that it could last for a while. Even if a smaller rock could last for a while the real problem would be to explain its origin! Some seriously devious scenario should be devised to create it (or place and keep it) on such an orbit. As Callisto has been seriously bombarded one could some expect bits and pieces go high. We discovered none, so either they are really small chunk or the orbits decay ‘’quickly’’. Eurocommuter 16:20, 12 September 2006 (UTC)


[edit] Merge of Definition of moon

A suggestion has been made that this article should be merged with natural satellite. As long as you guys have no problem with it I'm willing to do the merger in the next few days. -- Nbound 14:17, 19 September 2006 (UTC)


Straw poll to gauge consensus-

Support:

  • Patteroast 19:24, 19 September 2006 (UTC)
  • Support RandomCritic 19:29, 19 September 2006 (UTC)
  • Me too. Definition of moon can just as well be a section of this article, and would only enrich it. Deuar 20:45, 19 September 2006 (UTC)
  • Looks ok. The only issue is the length of the article. Rmhermen 21:00, 19 September 2006 (UTC)

Oppose:

Comments:

Merge complete -- Nbound 09:46, 22 September 2006 (UTC)

[edit] Merge Moon moon

I suggest merging whatever can be saved of this strange little article about a population of objects whose ranks currently stand at zero. Support? Oppose? RandomCritic 11:08, 22 September 2006 (UTC)

Due to the lack of opposition, I went ahead with the merger. RandomCritic 23:35, 25 September 2006 (UTC)

[edit] Meaning of "satellite"

 Technically, the term could also refer to a planet orbiting a star, or even to a star orbiting a galactic center,

I cannot find any evidence that this is true, 'technically' or otherwise; I find no evidence of planets being called satellites, or of stars orbiting other stars being called satellites. If "satellite" is never used in such a sense, why are we told that it is 'technically' possible? RandomCritic 07:55, 28 October 2006 (UTC)

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