Talk:Moons of Pluto

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Inclined to its own equator?[edit]

The table indicates that Pluto is inclined 0.001° to its own equator. This is an error, I think... it does not seem possible. If anyone agrees with me, please go ahead and correct the table. (talk) 03:27, 16 May 2010 (UTC)

I think what is meant is its inclincation to the Pluto-Charon barycentre. Lanthanum-138 (talk) 14:13, 28 July 2011 (UTC)

Orbits and diameters of S/2005 P1 and P2[edit]

Orbital periods of 28.1 & 41.7 days calculated from orbital radii of 50 & 65 Mm, assumed to not vary significantly from the semimajor axes, and a Plutonian mass of 1.25 E22 kg. Radii are consistant with the Plutonian system diagram published by NASA (in fact I measured just those figures), but no other source was provided. kwami 01:47, 1 November 2005 (UTC)

According to the diameters of the two new moons are between 30 and 100 miles (45 and 160 kilometers). There orbits are 27,000 miles (44,000 km) from Pluto. Martinwilke1980 09:40, 1 November 2005 (UTC)

Yeah, that report didn't match the NASA diagrams. Anyway, now confirmed with IAU release ref'd on the orphaned duplicate article. kwami 10:07, 1 November 2005 (UTC)


forgive my ignorance, but could the 'images' be uploaded to wikipedia if the moons have been 'imaged'? 'In The News' currently mentions them after all. Or are the images unsuitable? -- 19:48, 1 November 2005 (UTC)

They're on the individual moon articles. kwami 01:17, 4 November 2005 (UTC)

Nix and Hydra can be seen here:


who says Charon should be pronounced "shair'-un"? For all I know, it should be pronounced [xa'ro:n], or [kha'ro:n], or, if you really cannot avoid giving it a Modern English tint, "kair'-un" would be acceptable (but should not be prescribed as superior to the former). 20:34, 1 November 2005 (UTC)

Sorry, [xa'ro:n] does not fit English phonotactics, and this is an English encyclopedia. If you'd read the article, you would have found out that the discoverer pronounced it shair'-un in honor of his wife, and that this is the common English pronunciation of the astronomical community. The alternate pronunciation is the standard English literary pronunciation of the mythological character, kair'-un. If you wish to pretend that we're speaking Greek (I enjoy doing this myself), then the Greek is right there for you to use. Other readers have objected to including the Greek, and I defended it because I thought people like you and me would be interested in the Greek pronunciation. But the assimilated English pronunciations are there because they are what people actually use in conversation. kwami 00:10, 2 November 2005 (UTC)
I realize that it doesn't fit English phonology. If it did, why would we give a pronunciation key at all? We can say "the discoverer pronounced it like Sharon", or "the common English pronunciation of the astronomical community is shairun", but not just "Charon ([ʃæ'rən])" as if that was somehow the 'correct' or 'prescribed' (by whom?) pronunciation. 11:07, 2 November 2005 (UTC)
The discoverer's preference is that it be pronounced like Sharon, and I haven't met an astronomical authority yet who has not done so. By some quirk of history, this is the accepted english pronounciation, so that's how we should report it. If some dispute appears, we of course are obliged to report on that but until then we should stick with reporting the facts as they currently stand.
Wellspring 16:12, 2 November 2005 (UTC)
But is it "Sharon", with the vowel of marry, or "shairun", with the vowel of Mary, to those of us for whom those aren't the same?--JHJ 21:07, 2 November 2005 (UTC)
I've only heard that it's like Sharon, after Char/Charlene. To me those have very different vowels, but I don't make the Mary-mary distinction, and don't know if Christy did. I've tried writing to some of Christy's colleagues to ask about this, but have never got an answer. If anyone knows, I'd be obliged as well! kwami 21:19, 2 November 2005 (UTC)
Googling for "Charon" and "pronounced" finds some suggestion that the intended pronunciation may really have had ar pronounced as in Charlene - shar-un in your system, I think - see [1] and [2]. It also seems that there are at least four different ways of pronouncing Charon suggested on different websites.--JHJ 17:13, 4 November 2005 (UTC)
Without a pronunciation key, the first site doesn't tell us anything. They could just mean 'like "Sharon"'. But they second is pretty unambiguous. The only question is whether they're getting this from an ambiguous website like the first one you gave, or if they're going from how astronomers . But it does make sense with his wife's name being Char(lene). How about we change it, but keep in mind that this is tentative, and we really need to confirm with one of the Pluto teams? kwami 22:37, 4 November 2005 (UTC)

Whilest the discoverer may have named it 'Sharon' in honour of his wife, that means nothing. The discoverers of a certain large object named it 'Xena', that does not mean that is the official name for it. The official name for the main moon of Pluto is Charon pronounced in the Greek style, because it is from greek mythology. It may refer to the name of someone's wife in an astronomer's joke/pun, but the actual name is official because it is the greek ferryman to the underworld, matching the whole Pluto thing. It should no more be pronounced as the discoverer's wife's name than a certain planet should be called George.

Sorry, no astronomical body has an official pronunciation, so your point is baseless. There isn't even agreement on the Galilean moons. That's why we've included both the English literary pronunciations and the original Latin or Greek, so you can choose to pronounce Io as either eye'-oe or ee'-oe, as you see fit. However, the first pronunciation indicated should be the one that's most widely used when referring to the object in English. While for most that's the literary pronunciation, Charon is an exception. Sorry, that's just the way it is. Arguing otherwise is like correcting people's pronunciation of Paris from pair'-us to pa-ree'. kwami 00:49, 4 November 2005 (UTC)

At the time I commented, only the sharon version of pronunciation was given. Noting that astronomers tend to use one pronunciation, whilst the classical is another, is fine as it is. It simply hadn't been like this before. And I say Pa-ris, so there :-)

So do I (parr-is in the system as it now stands). I'd be amazed to hear it start like pair in a non-American accent.--JHJ 18:06, 10 November 2005 (UTC)

Well, I'm an astronomer, and I pronounce it in the Greek way. Whether the discoverer likes it or not, planets and moons are named for classical characters, and not for our loved ones. At professional meetings, both pronunciations are used approximately equally, so both should be given equal weight here.

Turns out that the pronunciation is shair'-ən, homophonous with "Sharon" rather than "Charlene". Refs cited on the Charon talk page. kwami 17:43, 19 February 2006 (UTC)

Animation link?[edit]

When I try to look at the animation link at the bottom (which is referenced in the article text), an AVI file is downloaded, and Windows Media Player gives me an error that it can't find the codec. What codec is needed to look at it? (And this should probably be referenced next to the link.) Tempshill 20:49, 1 November 2005 (UTC)

We can't give technical information for every media player that might be in use. You need to go to the support website for your software and look up which codex you need. Personally, I use WinAmp, and I chose the codecs when I downloaded the software so that I could play every kind of file that had support available. kwami 00:01, 2 November 2005 (UTC)
Tempshill, this appears to be IV50, Intel's ancient Indeo 5.0. Unfortunately. :( --Markzero 14:27, 4 November 2005 (UTC)

Cut from article[edit]

Naming notes

So far no asteroid shares the name of a Plutonian moon.

I just removed this short section. If the section can be expanded, put it back. It seems to be hinting at something, but currently detracts from the article.

Ummm, could you at least sign your comments? If you're familiar with the sections on each {Planet}'s natural satellites page, you would see that this is a "standard" comment made. The SWRI group has names forthcoming, I'm sure: but that's not the point. It's simply standard to note this since planetary satellite names and minor planet names can (unfortunately) overlap. --Sturmde 15:19, 3 November 2005 (UTC)


An anon added the statement that the proposed names for the new moons are Pluto's three-headed dog Cerberus and its two-headed brother Orthrus. Great names, and appropriate for medium moons, but I can't confirm, so I deleted. (One-headed Charon for Pluto I, two-headed Orthrus for Pluto II, and three-headed Cerberus for Pluto III - it's got a nice symmetry to it.) kwami 01:12, 4 November 2005 (UTC)

I've only seen those names suggested in comments at Phil Plait's Bad Astronomy blog pages... Here's hoping the discovery gang picks up on the mnemonic value you've pointed out! one head, moon one... two heads, moon two... etc. Superb observation! --Sturmde 03:18, 4 November 2005 (UTC)
I'd think it'd go that way regardless, with Cerberus being the name of the brighter moon; also, the order 'Cerberus & Orthrus' correlating with P1 & P2, but it would be annoying if they ended up getting chosen but the other way around! kwami 04:29, 4 November 2005 (UTC)
Does anyone happen to know how to contact the discoverers or the IAU and propose this? --Doradus 03:15, 5 November 2005 (UTC)
I emailed several of the discoverers (at least one from each participating institution) but unsurprisingly haven't received any replies. They must be swamped in email about this. Anyway, hopefully one of them will have at least read it, in case these names are actually considered. kwami 02:13, 29 November 2005 (UTC)
Pluto and its satellites (2005).jpg
I like those names. I put them to the test. — Hurricane Devon (Talk) 18:02, 4 December 2005 (UTC)
  • Very good and interesting names. o.o i'm impressed. --Pedro 16:03, 7 February 2006 (UTC)

Now there's a change to suggest those names to Alan Stern. See this Planetary Society Weblog entry:

"Here are some ground rules: the names must come from Roman mythology and they must have a logical connection to one another and to either Pluto or Charon (or both)."

Well, I guess Greek names are ok.--Jyril 14:17, 19 February 2006 (UTC)

Damn! Cerberus is already reserved for asteroid 1865 Cerberus.--Jyril 14:20, 19 February 2006 (UTC)
That dosn't mater. There're are asteroids named after moons and moons named after asteroids. Cupid is the names of an asteroid, but Uranus now has a moon with this name. — Hurricane Devon ( Talk ) 17:00, 19 February 2006 (UTC)
When the discovery of P1 & P2 came out, they said that they'll study them in February 2006. And they said that they would name them once the're confirmed. It's only a matter of time now.
Hurricane Devon ( Talk ) 02:08, 23 February 2006 (UTC)


I'm a bit uncomfortable that we claim the Pluto+Charon system is a double planet just because the barycenter is not inside Pluto. I raised the same objection in Talk:Jupiter#Barycenter. The problem is, there are planet+satellite configurations where the barycenter is outside the planet, yet the pair is clearly not a double planet. For instance, if Neptune had a satellite at a distance of 50 Gm — well within its Hill sphere — with a mass of just 1/500 of Neptune, then the barycenter of this system would be well outside of Neptune, but I think this is clearly not a double planet system. --Doradus 14:34, 4 November 2005 (UTC)

Yes, 'often called a double planet' or 'the closest thing in the Solar system to a double planet' would be less misleading. kwami 22:26, 4 November 2005 (UTC)
I'd be happier if we were to claim the reason was Charon's large size relative to Pluto, rather than the system's barycenter; or equally good, if we were to cite an authoratative source that also claimed the barycenter as the reason. --Doradus 02:55, 5 November 2005 (UTC)

Never mind. Someone has reworded it now and I like it the way it is. --Doradus 00:01, 11 November 2005 (UTC)

Boulder and Baltimore?[edit]

Are these the nicknames of the moons? — Hurricane Devon ( Talk ) 20:27, 1 March 2006 (UTC)

Yes, they were used by the discovery team.--Jyril 20:41, 1 March 2006 (UTC)

Are the nicknames really important enough to be listed in the table?--Jyril 18:45, 2 March 2006 (UTC)

Your call. Take them out if you like. kwami 00:29, 3 March 2006 (UTC)

Common origin of the satellites[edit]

Recent Hubble images show the moons of Pluto have all similar color after all.[3] Schematic view of the Pluto system shows S/2005 P 1 to be slightly larger.[4] Unfortunately, no diameter values for the moons are provided in the news release.--Jyril 16:17, 10 March 2006 (UTC)

Thanks for that. Will incorporate. P1-P2 size difference and size relative to Charon may simply be diff in brightness assuming same albedo, since we don't have much else to go on. kwami 20:02, 10 March 2006 (UTC)
The sizes in the image suggest 44km for P2 and 58km for P1. kwami 21:17, 10 March 2006 (UTC)

Seen from the ecliptic?[edit]

The phrase "as seen from the ecliptic" makes no sense. Depending on where on the ecliptic plane one is located, the moons' orbits could look completely different. Does this actually mean "as seen from the Sun"? If so, why is it so different from the view from the Earth? --Doradus 16:36, 27 April 2006 (UTC)

Yes, my apologies. The view is from near Charon’s orbit pole, i.e. declination 0°, RA 133° following Buie. The 96° inclination can be tough to explain, and the inclinations to Pluto’s equator and Pluto’s orbit even tougher so I abandoned them as long as I do not have the diagram showing it. In fact, this is not so dramatically different from Uranus moons (except to Pluto’s orbit inclination, of course). I hope my update clears it up. BTW, the orbits have been assumed circular from the discovery images; now this is confirmed by calculation based on more images going back to 2002. PS. Relatively new to wikipedia, I've seen your feeling ‘makes no sense’ (indeed, I forgot longitude or RA) expressed by more polite statements. Regards Eurocommuter 18:53, 27 April 2006 (UTC)


The paper I cited is Lithwick & Wu, On the Origin of Pluto's Minor Moons, Nix and Hydra, American Astronomical Society, DDA meeting #38, #3.05, July 2007. I have only seen the abstract, and suspect I got the second eccentricity wrong, or that there's a typo. kwami 16:20, 2 October 2007 (UTC)

It's a bit confusing, but they write 0.8(R_Pluto/a_Charon) - who knows why they use this weird notation - which must mean 0.8 times the ratio. The ratio is 0.061, so they must be meaning an eccentricity of at least 0.049 (let's say 0.05, since 0.8 is only to one significant digit). Sounds like a reasonable number Deuar 10:16, 3 October 2007 (UTC)

"Moons of Pluto"[edit]

There has been consensus to change the name of the Uranus' natural satellites article to "Moons of Uranus" here. This fits the footer, is less jargony, and avoids the apostrophe issue some people complain about with Uranus and Mars. However, this article should have the same format. Anyone here wish to comment, support, or object? kwami 19:40, 13 October 2007 (UTC)

Eccentricities of Pluto vs. Charon[edit]

Why are there two different values for the orbital eccentricity of their circum-barycentric orbit (0 vs. 0.0022)? As long as you can neglect the influences of Nix and Hydra (together less than 3 permille of Charon's mass) the Newtonian laws of motion require the eccentriciues to be equal. The JPL page does not mention a separate eccentricity for Pluto around P+C's barycenter, therefore we can assume them to be equal.--SiriusB (talk) 13:09, 22 September 2008 (UTC)


Perhaps an image to consider:[5]kwami (talk) 19:17, 20 July 2011 (UTC)

Nix and Hydra can be seen here: — Preceding unsigned comment added by (talk) 16:19, 15 March 2015 (UTC)

Potential satellites[edit]

There are two more "potential" satellites that were discovered at the same time as P4, but they are smaller and are still only "potential" satellites. Is there a place in this article for those, or should we wait until the potential is realized (or rejected)? If this is included, can someone find an original source? The page I included above was linked to from the Twitter feed associated with, but it's written for the layman and lacks detail. (All it says about the potential satellites is "But P4 wasn’t the only body around Pluto discovered this year. Two more candidate satellites, smaller than P4, were also found. But they aren’t satellites yet. The team needs to do more research and make more observations before the new bodies can be confirmed or rejected as Plutonian satellites." Ben Hocking (talk|contribs) 11:48, 15 November 2011 (UTC)

I have mentioned it in the article and used [6] to source it. --JorisvS (talk) 12:14, 15 November 2011 (UTC)
That information seems to be outdated now, with the announcement of P5. Unless the second candidate is still being investigated, which would presumably have been stated along with P5's discovery... --Roentgenium111 (talk) 17:01, 20 July 2012 (UTC)

If our report of Showalter's email is accurate, and he expects them to be named within three months, and since he's stated in interviews that he's been waiting for confirmation of potential satellites before naming, then they've either disconfirmed P6 or expect to announce it soon. — kwami (talk) 17:27, 21 July 2012 (UTC)

Showalter's suggested names[edit]

I'm not sure how much we can trust this. And even if it is true, we can't guarantee this is what they will be named. Worth a mention or no? 134340Goat (talk) 21:25, 27 September 2012 (UTC)

P1 or (134340) 1[edit]

Why have we gone back to calling them S/2011 P1 and S/2012 P1? Although both are "official", I thought we'd decided to use Pluto's number rather than its letter. 134340Goat (talk) 01:57, 4 November 2012 (UTC)

Dunno. Fits the table better, though. — kwami (talk) 23:44, 4 November 2012 (UTC)
The "P" names are correct for the 3 first discovered companions of Pluton (Charon = S/1978 P 1 = Pluto I, Nix = S/2005 P 2 = Pluto II, Hydra = S/2005 P 1 = Pluto III) because Pluto was still a planet by this time. However, it is not considered as such since 2006 then any satellite orbiting around Pluto discovered after this date shouldn't be named with "P" but with the "(134340)" name, hence the correct S/2011 (134340) P 1 (aka P4) and S/2012 (134340) P 1 (aka P5). SenseiAC (talk) 08:44, 7 November 2012 (UTC)
Without a ref, that's OR. The latter is (almost) the standard format for minor planets, but "P" is the established abbreviation for Pluto. — kwami (talk) 09:29, 7 November 2012 (UTC)
The problem is that here, we use P, but on the articles for the moons themselves, we use (134340). Should we not make it consistent in all areas? Meaning, we should either change the P here to the number, or vice-versa. 134340Goat (talk) 22:02, 7 November 2012 (UTC)
I don't think its a problem to use a shorter alt name in a table. We do that all the time with countries such as "America" and "China", for example. — kwami (talk) 22:14, 7 November 2012 (UTC)
Fair enough. After all, the names using the P are used in official sources, anyway. 134340Goat (talk) 22:47, 7 November 2012 (UTC)

Active versus passive[edit]

I'm a bit bemused by the reversions of my copyedits of the History section. We prefer the active over the passive voice and we prefer sentences which don't contain ambiguity. --John (talk) 23:52, 25 December 2012 (UTC)

Not true. The passive voice is used where the patient of the verb is the topic of the clause. You're making the section about Christy, which is ungrammatical as it is not about Christy. — kwami (talk) 23:58, 25 December 2012 (UTC)
It's very poor semantics, it is not poor grammar. Kevin McE (talk) 11:01, 26 December 2012 (UTC)
Alignment of the subject with the topic is grammar at the discourse level. — kwami (talk) 11:14, 26 December 2012 (UTC)
Obviously I disagree, and so would most style guides and I think our own peer review processes.--John (talk) 00:10, 26 December 2012 (UTC)
I provided a couple links on your talk page. Yes, there are several such style guides in the US, but they've been roundly excoriated for being idiotic, as demonstrated for example by their inability to identify a passive construction (in Strunk and White, most of the examples they give of the passive are actually active), and by the fact that they use more passive constructions than is normal for English in the section condemning the passive. Passive-avoidance ranks with other silly shibboleths such as not splitting infinitives and not ending clauses with a preposition. — kwami (talk) 00:41, 26 December 2012 (UTC)
I have to agree with kwami here. I see wholesale elimination of the passive voice as hypercorrection, and many style guides in the sciences (sorry, none at hand, but the old CBE manual mentioned this) make the same point that kwami does.--Curtis Clark (talk) 01:01, 26 December 2012 (UTC)
So you guys know better than me, know better than respected style guides, and know better than Wikipedia's own quality control processes. That's a lot of arrogance to be carrying around in two little heads. --John (talk) 10:01, 26 December 2012 (UTC)
Could you refer us to the Wiki policy that you refer to here? Kevin McE (talk) 11:01, 26 December 2012 (UTC)
That's four little heads. This is WP's quality control process. — kwami (talk) 10:39, 26 December 2012 (UTC)
But in this case it consists of keeping the article in a shit state through ignorance of basic English. Would this article pass GA? --John (talk) 10:51, 26 December 2012 (UTC)
I've been watching this from aside, but I'd like my little head to be counted as well in approval of the passive voice in this sentence. The big difference between the two is focus and for the John's version, it is simply wrong shit in the context. I'd also like to help carrying some of the burden of arrogance, by asserting that style guides that advocate elimination of passive voice are bullshit. No such user (talk) 10:55, 26 December 2012 (UTC)
A very obvious case of a sentence that cries out for the passive voice. Kevin McE (talk) 11:01, 26 December 2012 (UTC)
So, counting isn't a strength either. It's not a sentence, but actually six sentences in a row which use the passive voice. It makes the article read like a 12-year-old's first science report. I suppose if we leave it like this I can use it as a benchmark of poor writing, so it isn't a complete loss. --John (talk) 11:34, 26 December 2012 (UTC)
Hey, that's a great idea. Consensus is clearly against you, so instead of gracefully conceding the point, nit-pick and personalise the issue instead. Grow up, or go away. Kevin McE (talk) 12:55, 26 December 2012 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── John:

You're an admin? Then you should know better than to personalise an editing issue on an article's talkpage. Your superannuated prejudice concerning the passive voice is not supported by modern guides to style – certainly not Wikipedia's own WP:MOS. There are often advantages in using it, as we see in the case of this article and many like it. You might yourself be censured for using which rather than that here: "but actually six sentences in a row which use the passive voice". In fact, I support consistent and principled distinction of the relatives which and that; but I do not present my preference as a matter of strict propriety. Nor should you, when you inveigh against the passive voice.


As you must know, I have the highest respect for your competence in linguistics. But please do not let action at this page or your own talkpage spur you to impulsive changes at WP:MOS (see WT:MOS).


The whole article is poorly written, yes. I am no expert in the field, but I have rewritten the lead to make it less awkward. It is still awkward, of course; but I see that as a function of the strange choice of content to include there, which I hardly altered. At least vagueness and ambiguities are fixed. Now, how about focusing on a more trenchant cleanup of the whole, directed solely at clear communication of well-ordered content to the readers?

NoeticaTea? 12:03, 26 December 2012 (UTC)

Comment from a partial observer (I'm no fan of John's): I just looked at John's edits here, and, every single one was an improvement to the article. His edits should not have been reverted. -- (talk) 17:49, 27 December 2012 (UTC)
I see what's happening now: kwami, as the creator of and major contributor to this article, has OWNership problems. kwami, if you were smart, you'd back off for a while and let John improve the writing. (and tell your friends to back off, too). -- (talk) 18:01, 27 December 2012 (UTC)
You caught me: It's a grand conspiracy. I only ever get into style disputes in articles I created. My friends have set up WP accounts with fake edit histories to back me up in exchange for large sacks of unmarked bills. They would back off if I told them to, because, you know, conspiracy. — kwami (talk) 20:48, 27 December 2012 (UTC)
Uh, my sack must have been lost in the mail. Perhaps it was too large.--Curtis Clark (talk) 21:36, 27 December 2012 (UTC)
You don't have a chimney. How are you supposed to get your pay-off if you don't have a chimney? — kwami (talk) 21:41, 27 December 2012 (UTC)
I would not disclose my hat size to John, but I will disclose that I have a chimney. I shall check to see whether it lodged above the damper. At any rate, I agree with Noetica that the article needs more work that John addressed.--Curtis Clark (talk) 05:31, 28 December 2012 (UTC)
You're very sensitive, kwami. Do you agree with Noetica that the whole article is poorly written? Are you really making impulsive changes to the MOS? No matter, John's edits were improvements and they should have been left alone. What motivates you isn't important. What's important is writing a good article. -- (talk) 00:09, 28 December 2012 (UTC) (not my real name)
I'll have to toss my hat in on the side of Kwami if this is an issue of ever allowing passive voice. I only glanced at the edits in question, but it is true that "James Christy discovered the innermost moon, Charon" gives an inaccurate implication that the paragraph is about Christy. The sky doesn't fall either way, but this is an example that shows those unbending prescriptivists that the passive voice has its role. — Ƶ§œš¹ [ãːɱ ˈfɹ̠ˤʷɪ̃ə̃nlɪ] 22:20, 28 December 2012 (UTC)

Moons to be named "Vulcan" and "Cerberus"[edit]

See Seems S/2011 (134340) 1 and S/2012 (134340) 1 are supposed to be named Vulcan and Cerberus. The site says "It could take 1-2 months for the final names of P4 and P5 to be selected and approved." Does anybody know whether the approval already happened? -- Toshio Yamaguchi 09:45, 9 June 2013 (UTC)

"Vulcan" is a stupid name for an ice moon, and anyway it went together with "Romulus". Now that the latter is not being proposed, there's no good reason for the former. Don't know if it's going to be formally proposed, or if it would be approved if it were. — kwami (talk) 16:35, 9 June 2013 (UTC)

Good, they chose Styx, which fits. — kwami (talk) 00:38, 3 July 2013 (UTC)

Problem with a picture[edit]

You know that picture below the table that shows the scaled distances between the objects of the Plutonian system? Anyway, I see that it's been replaced to accommodate for the recently announced names of the moons, however upon clicking on it for the full picture, I simply get redirected here to the old one. Any way to fix this? 134340Goat (talk) 01:05, 3 July 2013 (UTC)

Never mind, seems to have been fixed 134340Goat (talk) 14:31, 3 July 2013 (UTC)

"Ten Moons?"[edit]

Have there been any additional sightings of objects that might be further satellites than those already discovered that would substantiate this claim, since the discovery of Styx and Kerberos? (talk) 04:17, 3 July 2014 (UTC)User calibanu

I think Kwamikagami mentioned on Talk:Styx (moon) that a candidate sixth Plutonian satellite was found in the data that contained Kerberos and Styx, though it was never confirmed. Double sharp (talk) 12:22, 3 July 2014 (UTC)
Last Summer, I went down to Maryland/Washington DC to visit the New Horizons mission control center. I spoke to Alan Stern myself (he was kind enough to buy me lunch!) and I asked him about that. Apparently, Mark Showalter thought he'd found a P6, P7, AND P8, but it turned out just Kerberos and Styx were confirmed with certainty. We'll just have to wait for NH when it gains better than Hubble resolution.... 134340Goat (talk) 02:39, 17 March 2015 (UTC)

Pluto diameter[edit]

This article lists Pluto's diameter as about 2306 km, however Pluto's main article lists the radius as 1184 km (2368 km in diameter). As far as I know, the latter estimate is the most recent, so should this article be changed to reflect that? Or is there a reason it is listed differently here? 134340Goat (talk) 04:14, 18 May 2015 (UTC)

Pluto's diameter will really only be known for certain when New Horizons flies by it in July. However, even the cited source currently has different value from the one in the table (1195 km), but it is best to be consistent anyway. Good catch. --JorisvS (talk) 12:57, 18 May 2015 (UTC)

NASA-Audio (06/03/2015@1pm/edt/usa) - Moons of Pluto - "Surprising" Finds.[edit]

NASA-Audio (Wednesday, June 3, 2015@1pm/edt/usa) - Panel of experts to discuss latest "surprising" findings by the Hubble Space Telescope of the Moons of Pluto.[1] - Enjoy! :) Drbogdan (talk) 12:04, 29 May 2015 (UTC)


  1. ^ Chou, Felicia; Villard, Ray (May 28, 2015). "M15-085 - NASA to Hold Media Call to Discuss Surprising Observations of Pluto's Moons". NASA. Retrieved May 29, 2015. 

New info[edit]

This New York Times article quotes a new study published in the Nature magazine about Pluto's moon system. I hope info from that article can be incorporated into this article. I see lot's of news articles recently quoting the Nature article but it itself is behind a paywall. Published online 03 June 2015. (talk) 10:40, 4 June 2015 (UTC)

Things are going to change drastically in the upcoming month. We're going to get clear pictures of all the moons, especially Charon. We should get ready.Ericl (talk) 16:52, 23 June 2015 (UTC)
Certainly! That's what I've doing with this article and Pluto for the past two weeks or so, by standardizing and reordering content. You're welcome to help, of course. --JorisvS (talk) 17:04, 23 June 2015 (UTC)


Dimensions were not added to the individual articles. They were also overly precise. Do we know their precision other than by sig fig?

Do the masses correspond to the new diameters? They also contradict the articles, and do not have their source listed. — kwami (talk) 06:09, 2 July 2015 (UTC)

Measurement of Nix's and Hydra's size[edit]

In, it is said that Hydra's size has been measured to be 55x40 km, while Nix is 42x36 km. As these measurements differ from the one that was obtained by Hubble via indirect methods, I think they should be added as alternative values. As I'm technically not able to do this, can somebody help, please? Renerpho (talk) 16:48, 21 July 2015 (UTC)

The latest estimates should be used, IMO, though they suffer from each being based on a single image and therefor not fully covering all three dimensions. If anyone knows of a more reliable estimate, please chime in. — kwami (talk) 02:43, 22 July 2015 (UTC)

Pluto diameter[edit]

On the press conference today it has been said that Pluto's radius was estimated to be 1186 +-2 km, resulting in a diamter of 2372 +-4. That should be added to the article, though I don't know what I can give as a reference. Renerpho (talk) 20:45, 24 July 2015 (UTC)

Of course it should be added to the main Pluto article as well.Renerpho (talk) 20:46, 24 July 2015 (UTC)

Did they mention the density? Sometimes our calculations are a bit off. — kwami (talk) 21:03, 24 July 2015 (UTC)

No, they said "It's plus/minus 2, centered around 1186".Renerpho (talk) 21:44, 24 July 2015 (UTC)


Is this section accurate? I can't find the numbers given in the cites. The main papers are both available to read by anyone:


The resonance is summarized by the author of the main paper Mark Showalter as “If you lived in the Pluto system and were sitting on Nix, you would see Hydra go around three times every time Styx goes around twice,” which might be a good way to begin this section. (quote from that second Nature paper).

In these papers, I can find no mention anywhere of the numbers in the introductory paragraph of the resonances section of this article:

"Styx, Nix, and Hydra are in a 3-body orbital resonance with orbital periods in a ratio of 18:22:33.[14] The ratios are exact when orbital precession is taken into account. This means that in a recurring cycle there are 11 orbits of Styx for every 9 of Nix and 6 of Hydra. Nix and Hydra are in a simple 2:3 resonance.[14][15] The ratios of synodic periods are such that there are 5 Styx–Hydra conjunctions and 3 Nix–Hydra conjunctions for every 2 conjunctions of Styx and Nix."

How are those figures 18:22:33 derived from the paper? Where do the numbers 11, 9 and 6 come from in the citation sources? I can't find any of this with a search for those numbers in the papers.

Am I missing something, can anyone see how those numbers relate to what the paper says?

This is my summary of the relevant section of the paper from a science blog post:

"Details of their findings about the resonant orbits: the resonance is phi = 180 degrees = (approx) 3 s - 5 n + 2 h where s is the angular position of Styx, n is the angular position of Nix and h is the angular position of Hydra, all as measured from the barycentre of the system. There the angle phi will librate back and forth but is almost exactly 180 degrees. From which you can deduce that every three times Nix laps Hydra, then Styx laps Nix twice. (Using analogy of runners lapping each other on a racetrack). Then there is another resonance involving Kerberos. 180 degrees = (approx) 42s - 85 n + 43 k. From which it follows that every 42 times Nx laps Kerberos, then Styx laps Nix 43 times. But unlike the Jupiter system resonances, where the pattern repeats exactly, they are in different positions relative to the barycenter when they lap each other, each time the resonance repeats. It was already known (since Nix was discovered in 2011) that they are all in a near 1:3:4:5:6 resonance with Charon - but this is not exact. It may have been an exact resonance in the past if Charon's orbit was originally more eccentric."

Robert Walker (talk) 13:31, 13 October 2015 (UTC)

 Comment: This info was added by @WolfmanSF: on 23 June. Stas (talk) 07:27, 19 November 2015 (UTC)
Here is the easiest way to get those ratios. Showalter & Hamilton give the ratios of the periods of Nix, Hydra and Styx as 4:6:36/11 (3rd page of article, right column). Multiply those values by 11/2 to get the period ratios 22:33:18. Then take the inverses of those values, and multiply them by 198 to get the ratios of orbits: 9:6:11. WolfmanSF (talk) 22:16, 26 November 2015 (UTC)


Merged article into section. Deleted obvious garbage, such as image showing Charon eclipsing Sputnik Planum. I don't know how much of the rest might be garbage. — kwami (talk) 20:07, 2 December 2015 (UTC)

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Scale model of the Pluto system - Distances wrong?[edit]

I was measuring the relative distances and sizes of the image under List ( and it seems to me that the distances in the picture don't match the distances noted in the list above it. For example if I scale the image so that Charon is 1200 pixels wide, in reality ~1208km in diameter, I would expect the distance to the barycenter to be around 17536 pixel (the same in km). But instead it is just around 11600 pixel? Only for Pluto it's correct (semi-major axis = 2035km --> distance in image ~2035 pixel). I'm measuring from the center of each body.

Now I found this image ( used on the German Pluto wiki-page (They have the same table with all the moons there). Which even by looking at it you can see it has very different distances. But this one also seems off as I found out that it measures the semi-major axis from each moon's center to Pluto's center (which is not correct, it should be the distance from moon center to barycenter, that is the semi-major axis distance given in the list).

So what I'm saying is, that either the data in the list is wrong, or the image (in which case it should probably be removed or replaced by a correct version), or am I not understanding something correctly? (talk) 01:11, 27 August 2016 (UTC)