Talk:Hyperion (moon)

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English pronunciation [hy-PEER-ee-un]. Seeminly universal in astronomical sources; confirmed in Meridian/Crowell's Handbook of Classical Mythology (Tripp). *[hy-PUR-ee-un] does not seem to be a variant. kwami

It would seem from the Greek that the adjectival form would be Hyperionian (the first n is part of the root). Need to check if this is etymologically related to the musial term hyperionian. kwami 09:00, 2005 May 27 (UTC)

The etymologically 'correct' pronunciation would be hye'-pur-ree'-un, as the i is long, and thus takes the stress. However, since long i's are not written in Greek, only in Latin, this seems to have been missed, and hye-peer'-ee-un seems to be the universal pronunciation in English. kwami 2005 June 30 02:41 (UTC)
Verified further with Perseus at Tufts: the Greek is Huperîôn, gen. huperîonos, with a long iota. The forms in Latin are Hyperīon, -onis, with a derivative hyperīonius. No getting around it, the regular pronunciation in English would stress that i, for hye'-pur-ree'-un (or maybe hye'-pur-rye'-un, which to my ears sounds like "hyper ion"). Adjective hye'-pur-eye-oe'-nee-un. kwami 07:20, 3 October 2005 (UTC)
These comments about the "etymologically correct pronunciation" and so forth show some lack (unfortunately very common) of understanding about how Latin and Latinized Greek names are pronounced in English -- which is a very different matter from Latin or Greek. In English, the original quantities of the vowels are irrelevant for every purpose other than ascertaining the position of the stress accent in Latin -- and sometimes, as in this case, traditional pronunciations have arisen for which even the Latin forms are not a good guide. A quite different set of rules, based on stress position and syllable type (which is too detailed to elaborate here) governs the quality of the English vowels. To be brief, the traditional pronunciation of Hyperion has the 2nd syllable pronounced as "peer", not "per", although something like "hyper ion" might be historically warranted. In Hyperionian the 3rd syllable cannot be "rye", because it is an unstressed, non-initial vowel immediately adjacent to the primary stress. Cf. a similar alteration in the pronunciations of "mAniac" and "manIacal". [anon]
For 'Hyperion', that's what we have. For the 3rd syllable of 'Hyperionian', it may usually be the case that vowels are short in such possitions, but they're long when there is no consonant between them and the following stressed vowel. The semivowel at the end of the "long" vowel fills in almost as a consonant. E.g. in uncooperative there's still a [w] sound between the two o's, as in cooperate; or in cationic, which is [kætaɪˈɒnɪk] per the OED. kwami 12:11, 18 November 2005 (UTC)
Incorrect generalization. It's true that in general, in sequences of two vowels in hiatus, the first one is "long"; but it's not true of i, which has to be either 1) initial or 2) stressed in order to be pronounced [aɪ]. Maniacal has a "long i" because the i is stressed, but in words like "pronunciation" "enthusiastic", "histrionic", or "periodical", in which the i is unstressed pretonic, the i is not "long". Cationic is a word of recent coinage that simply breaks the rules (in all sorts of ways, not just that one), presumably because the coiners were unfamiliar with the rules of the language (which had already ceased to be productive) and simply added up cat-, ion, and -ic. But to go for a much closer model, I'll see your "cationic" and raise you an "Alcyonian" [ælsɪˈownɪən], which is exactly the same type of derivation as "Hyperionian". [anon]
I stand corrected. Ixionian, amphictyonian, sturionian do the same. Even closer are isethionic, polypiarian, and posterioric, where the i isn't bound by stressed syllables. The only cases where I find [ai] with the meter of Hyperionian are compounds like tetrathionic, or like uncooperative and cationic above, where the i is in the first syllable of its root. So the vowel is long, but takes its Latin rather than native English pronunciation.
How would you pronounce Hyperionian then? Would you still reduce the er? kwami 02:59, 19 November 2005 (UTC)
Those, my friend, are some damn fine words.  :) May I ask how you dug them up?
Oh, they're just whatever came to mind.
Yeah, right! I did a reverse search (for *ionian etc.) with the online OED. kwami 04:03, 20 November 2005 (UTC)
The pronunciation should be with the same meter and vowel sounds (for the first three syllables) as "superiority", i.e. [haɪˌpɪrɪˈoʊnɪən]. The [ɪ] is the result of rhotacization of the expected vowel [i], which in turn comes from e followed by any CiV sequence (as in mediocrity, heliograph, theriomorphic). However, there are likely some dialectal differences in English with respect to this rule, and if you happen to say [suˌpərɪˈɔnrəɾɪ] or [suˌpɛrɪˈɔnrəɾɪ] (or something different) then you'll probably pronounce "Hyperionian" in similar fashion. [anon]
With that stress pattern, I never would have even considered pronouncing the -ionian as "Ionian" with an [aɪ]. However, because the Greek genitive is huperîonos, with the epsilon becoming a short e in Latin, I would expect the second accent to be on the Hy-: [ˈhaɪpɪrɪˈoʊnɪən], with the stress pattern of isethionic. (When you go back two syllables from the primary stress, and the syllable is light, you go back one more for the second stress, as in isethionic, polypiarian - or so I thought.)
You are probably right. That rule is inactive in my dialect of English (at least in some types of derivation), so I didn't think of it; but a quick check shows stress patterns like [ˌsupɪrɪˈɔnrəɾɪ] are current in some dialects. I don't believe it affects the pronunciation of the "e", however.
That I could see having a reduced "schwer", as [ˈhaɪpəraɪˈoʊnɪən], but it only sounds right with that extra [aɪ], as in polyphyletic [ˈpɒlɪfaɪˈlitɪk]. Why would we have stress on the syllable [pɪr]? Is it because this is a derived adjective and the stress of Hyperion could be expected to stay put? I must admit it sounds better that way, but still, it can take a while to get used to adjectival forms when the stress shifts, so I don't want to go on that. kwami 04:03, 20 November 2005 (UTC)
No, it's just a dialectal idiosyncrasy. Either [haɪˌpɪrɪˈoʊnɪən] or [ˌhaɪpɪrɪˈoʊnɪən] are acceptable, to my ear (which can barely distinguish them, anyway).


Proteus is described as "almost spherical". It isn't, unless bricks are considered spherical these days.

Hyperion's eccentricity[edit]

The eccentricity of Hyperion, stated above is only 0.0175. This is not high and is, in fact, only marginally higher than the earth's relatively low eccentricity of 0.0167. Whether the remaining conditions stated are still unique to Hyperion and sufficient to cause its chaotic rotation, I couldn't say.

The eccentricity is in fact 0.123, so it is indeed relatively high.
Urhixidur 14:41, 2005 May 11 (UTC)


The main image looks like the one shown on the main Cassini page. Some of the other raw images that were returned a little later have higher resolution, like [1] and [2]. Just a thought. kwami 01:10, 30 September 2005 (UTC)

You're right, those are better, thanks! (Man, this moon is weird-looking...) The Singing Badger 01:21, 30 September 2005 (UTC)
Your term 'sponge-like' captures it perfectly. It looks like what I'd expect a large comet nucleus to look like after large amounts had sublimated fast enough to cary any crust with them. Just bizarre. kwami 03:00, 30 September 2005 (UTC)
Now, technically I would disaprove of the present image as the 'main' one because it's false-colour. But in practice, it's so gorgeous I'll let it stand. Let's look out for a true-colour one though. The Singing Badger 20:32, 30 September 2005 (UTC)
Right here [3] is an approximatly true color photo, but you'll probably have to ask him for permission before we use it. (Photos from NASA press releases are in the public domain, but modification, manipulation and other such things on that forum are that particular author's work. See this note:[4]--Planetary 20:07, 9 July 2006 (UTC)
Alright, I added a photo from a NASA relase, which is ok to use.--Planetary 21:11, 10 August 2006 (UTC)
Nice. The Singing Badger 22:10, 10 August 2006 (UTC)
Hi. I'm the author of the approx. true-color composite in reference 3 and was wondering if you're interested in replacing the primary false color view with my version. Note that I've tweaked it a bit from the version found on UMSF, a more accurate version can be found here [5]. Ugo 09:14, 17 October 2006 (UTC)

Hat one looks nice as well. Go ahead and replace the current one.

I'd say keep the current infobox image and toss out the third image, which appears to be virtually identical, except rotated, smaller, and grayscale. "True color" is only so in a human-subjective sense, and I don't see any significant added value to justify the bandwidth of the other image; just let people go to the links if they want to see what it looks like in colors visible to the average human. --Scott McNay 05:31, 9 July 2007 (UTC)
P.S. Yes, I guess I am being a bit of a jerk, but that's why we have talk pages, so editors can express opinions without inflicting them upon readers. :) --Scott McNay 05:33, 9 July 2007 (UTC)


'that is, its axis of rotation zupalates so much'

Is this a real term? if so a ref to it's meaning would be useful. Google, Wikipedia and Wiktionary come up empty. --Shoka 20:42, 28 September 2007 (UTC)

Orbiting the Sun[edit]

If Hyperion was orbiting the Sun, it would be a failed dwarf planet candidate, demonstarting some of the issues with having an average diameter less than 300km. But I notice (ref 5) is showing it to be 410 km x 260 x 220 (geometric mean 286km) while the article shows it to be 360 × 280 km × 225 (geometric mean 283). Does someone know which dimensions are more current? -- Kheider (talk) 19:40, 1 January 2010 (UTC)

See [6], which gives dimensions (328 x 260 x 214) km and average radius 133 ± 8 km. See also [7], which gives for average radius 135 ± 4 km. Ruslik_Zero 17:50, 2 January 2010 (UTC)

Spoken Wikipedia recording[edit]

I've just uploaded an audio recording of the article. Please let me know if I've mispronounced anything. :-) --Mangst (talk) 23:43, 9 January 2010 (UTC)


"Hyperion is one of the largest highly irregular (non-spherical) bodies in the solar system (second to Proteus)." This doesn't sound right. Haumea is non-spherical, but much larger. Should probably say moons instead of bodies, but I don't know if that's true either. melikamp (talk) 00:10, 30 November 2010 (UTC)

Haumea is regular, it just bulges a lot. Would you call Vega an irregular star as well? (talk) 15:16, 5 December 2010 (UTC)


Good afternoon. I was looking at the Hyperion article and noticed it was out of date. There already is a reference that Hyperion was most likely a fragment of a larger body, and I wanted to add to that. Judging from the size of Hyperion, it is most likely a crustal fragment of the original moon which was probably the size of Dione or Rhea. The spongy terrain is the underside of Hyperion's crust. It is caused by the sudden decompression of the moon's core due to the impact event which destroyed the original Hyperion. The impactor was most likely a Phoebe-type centaur. Although Phoebe is smaller than Hyperion, it has almost twice its mass, and is believed be composed of almost 50% rock. An object the size of Phoebe,traveling at supersonic speed, could easily destroy a moon the size of Dione or Rhea. In November of 2010 the Cassini orbiter imaged the opposite side of Hyperion from a distance of 73000 km. This area contains many craters that are similar to those found on the other icy moons of Saturn. This terrain is not only most likely all that is left of the original surface of Hyperion, but may also contain the antipole of the impact event. The debris from Hyperion's destruction can easily explain the "equatorial ridge" found on Iapetus, and may also explain how Titan's surface and atmosphere came into existence. The latter can be explained by the combination of Hyperion's debris with the debris of the impactor, which if it was similar to Phoebe, would have had a large percentage of CO2 and other materials. All this would put Hyperion's orginal semi-major axis at 2 milliom km, with Iapetus orginally at 3 million km. The loss of Hyperion's mass would draw the fragment nearer to Titan, and cause Iapetus' orbit to change to its present dimensions. This is how NASA and the IAU are going to describe the creation of Hyperion eventually. They don't know it yet, but they are. Any feedback is welcome, thank you. And please, if they have not said it yet, someone give me credit when they do! Triton66 (talk) 20:02, 3 January 2011 (UTC)

Do you have any references for your statement, "Hyperion is most likely a fragment of a much larger, Dione-sized moon that once orbited between Titan and Iapetus early in the Saturn-Titan system formation"? You need to be careful when ruling out an oblique impact event on your proto-Hyperion. Claiming that proto-Hyperion may have been 1000km in diameter would be much more appropriate. Your statement would need a reliable reference that says proto-Hyperion was most likely Dione-sized (1100km). -- Kheider (talk) 20:49, 28 January 2011 (UTC)

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