Talk:Irregular moon

Triton
Do you think Triton should be mentioned here? It is often said to be "irregular" - to distinguish it from the "regular" satellites that were formed around with the planets. On the other hand it's completely in a class of its own, sharing very little with these small outer bodies apart from having been captured. Deuar 22:40, 4 August 2006 (UTC)
 * Certainly, one just needs to write a balanced account from multiple sources. E.g. some authors do not hesitate to use the term of normal irregulars to avoid Nereid and Triton altogether. Others divide the natural satellites into regular, irregular and 'special'. Triton-TNO connection is exceptional as well. I hope someone interested specifically by Triton writes all this up; otherwise I’ll be back on this later. Another special subject is Uranus story given the massive kick it took (it should have lost its outer satellites(?!); what’s Margaret's story etc.). I just wanted to write up some core beliefs first and handle puzzling cases later. Eurocommuter 09:13, 6 August 2006 (UTC)
 * (Triton as a survivor from a binary). Happy to see you claim a rightful place for Triton I shamefully tried to hide. Triton (and Nereid) are so interesting that they origin deserves their own chapter! Funny, I was just thinking (and inserted some comments) about how interesting it would be to try and put together an article summarising current theories about… the binaries. Good stuff! Eurocommuter 20:55, 12 September 2006 (UTC)

Suggestions to implement
(from other talk pages) Eurocommuter 11:13, 9 September 2006 (UTC)
 * Consequences of the observed size distribution (from TheSingingBadger)
 * A section on highly perturbed non Keplerian orbits (from Deuar)

Move page?
Should this be moved to 'irregular satellite'? I mean, is there such a thing as an irregular artificial satellite? The Singing Badger 13:33, 11 September 2006 (UTC)
 * Agree! While creating the article, I followed ‘’natural satellite’’ pattern which I find pedantic (scientific papers use satellite or moon but not ‘’natural’’ satellite; never read about irregular natural satellite either). Technically, our probes were irregular artificial satellites during segments of their flights, but the move is logical. Remains a small question of more than a few links… Thanks Eurocommuter 15:39, 11 September 2006 (UTC)

Done. The Singing Badger 15:45, 11 September 2006 (UTC)

Leading picture
Well, I find it illustrates well the orbits! I hope we’ll keep Phoebe’s image(s) as well, as it is the only irregular we got close to. It would be good to have a brief exploration section, for example. Thanks Eurocommuter 15:46, 11 September 2006 (UTC)


 * Yeah, I didn't really want to delete Phoebe, I just couldn't find space for it right now. The Singing Badger 16:26, 11 September 2006 (UTC)
 * Seems to fit in here somewhat... Deuar 17:17, 11 September 2006 (UTC)

Overview
I believe that the lead should be followed by some overview section, regrouping core facts in flat English, before digging into details. (collecting ideas here). Feel free to give it a try. Eurocommuter 17:44, 11 September 2006 (UTC)
 * Updated the summary table there but have no idea where to put it unless we have this overview section. Other wide-public columns could be added as for example size distribution into large (>50km), medium (>10km) and small. Eurocommuter 16:34, 13 September 2006 (UTC)
 * Such a table is very desirable. It could go in overview or just the intro. Deuar 16:45, 13 September 2006 (UTC)

Exploration
A question. As far as I remember, one of the refs quoted mentions that Voyager 2(?) made a distant picture of Himalia. Did one of Voyagers come a few Gm from it? (I failed to find the picture) Eurocommuter 17:49, 12 September 2006 (UTC)
 * The spacecraft that made the distant picture of Himalia was Cassini. --Patteroast 18:34, 12 September 2006 (UTC)

Refs
As I was putting refs in a hurry in the early stages of the article, they require some cleaning. E.g. <ref name= should be in "", some authors are once wikilinked, another time they are not etc. I’ll clean it up once I finished their cleaning on my own page (the refs in the individual moons' articles I'm doing are cleaner). Eurocommuter 23:43, 12 September 2006 (UTC)
 * Done. Eurocommuter 10:34, 13 September 2006 (UTC)

Graphs
The graphs I’ve used for to the families (e.g. Pasiphae group) use polar coordinates (real space) as opposed to the graphs used here (Cartesian, phase-space). Both presentations have different qualities and drawbacks I believe; I’m unsure which are more suitable here for the brief review of the satellites of the individual giants. Suggestions, as always, welcome. Eurocommuter 23:53, 12 September 2006 (UTC)
 * Not sure. The cartesian "phase-space" plots have the advantage that they don't require radially spreading gridlines, which tend to clutter the plot a bit. Deuar 12:16, 13 September 2006 (UTC)

Origins
An alternative origin for irregular satellites is mentioned in this abstract

"Recent modeling work indicates they were dynamically captured during the Nice model, a violent reshuffling event of the giant planets ~3.9 billion years ago that led to the clearing of a ~35 Earth mass disk of comet-like objects. Close encounters between the giant planets allowed some comets scattered out of the disk to be captured via three-body reactions."

Martian moons
What about Martian moons? They are neither listed nor discussed in either Regular moons and Irregular moons. noychoH (talk) 15:17, 29 July 2014 (UTC)
 * Their orbits resemble those of regular satellites, but their likely origin by capture is more akin to those of irregular satellites, so they do not fit very well in either category. Earth's Moon also doesn't fit very well in either. Double sharp (talk) 15:17, 22 July 2017 (UTC)

Nonsense sentence
The sentence
 * Before 1997, when Uranian irregulars Caliban and Sycorax were discovered, including Triton, the largest irregular satellite of Neptune, Phoebe, the largest irregular satellite of Saturn, and Himalia, the largest irregular satellite of Jupiter.

seems nonsensical to me. Does anybody know what it is trying to say? JDAWiseman (talk) 21:50, 28 June 2015 (UTC)

Definition
According to the criteria given here, the Moon is an irregular satellite. I feel there's something missing somewhere... 79.73.145.112 (talk) 18:47, 27 July 2016 (UTC)
 * Yes, it is irregular in the current orbit. You are surprised? Ruslik_ Zero 19:56, 27 July 2016 (UTC)
 * The moon is not particularly inclined, nor particularly eccentric, nor retrograde. So not irregular. JDAWiseman (talk) 20:37, 27 July 2016 (UTC)
 * (Original poster here, checking up on some old edits) Well, that would seem to make sense. But those criteria are not the ones specified in the article, which is the point I was trying to make. 79.73.146.244 (talk) 01:05, 21 September 2016 (UTC)
 * The Moon's orbit is fact quite inclined to the equator, not "not particularly inclined". Ruslik_ Zero 21:00, 21 September 2016 (UTC)

So, which is it?
The article starts:
 * In astronomy, an irregular moon, irregular satellite or irregular natural satellite is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit. They have been captured by their parent planet, unlike regular satellites, which formed in orbit around them.

This seems contradictory to me. As the article also states that no universal definition has been agreed upon, that may be unavoidable, but still, I think it should be amended somehow, e.g. by inserting a "may" and a "usually" in the last period. The contradiction I am referring to is that the texts seems to assume "irregular orbit <=> captured". While most moons with irregular orbits may in fact be captured, and most with regular orbits may be formed from the same disk of material as the planet itself, that is hardly true in all cases. Of course, "irregular orbit" can be defined in more ways than one, and moons are not strictly either captured or formed with the planet (e.g., collisions may be involved, blurring this distinction).--Nø (talk) 08:44, 3 December 2019 (UTC)

Does anyone still think Iapetus is irregular?
Interestingly, the Minor Planet Center's Natural Satellites Ephemeris Service includes Saturn VIII Iapetus among the outer irregular satellites. (You can't select it in the checkboxes, but if you request all or all numbered outer irregular satellites of Saturn, you'll get it.)

According to Denk et al., Iapetus is not considered irregular, although it orbits close to $$0.05 r_H$$ and has a rather inclined orbit.

It does appear to have been sometimes considered irregular in the past. (Although that link considers Triton and Nereid regular satellites.) I wonder why the MPC includes it. If it is irregular, it would be a rather weird one among the bunch, about as exceptional as Triton and Nereid. Double sharp (talk) 14:06, 30 September 2021 (UTC)