|WikiProject Solar System||(Rated B-class, Mid-importance)|
|WikiProject Astronomy / Astronomical objects||(Rated B-class, Mid-importance)|
The OED has two adjectival forms, an obsolete 'Proteusian' (proe-tew'-zhun?), and 'Protean' (proe'-tee-un, proe-tee'-un). However, since Protean has strong connotation of its own (variability of form, playing more than one role, etc.), maybe it would be better to use Proteusian as the literal adjectival form for the moon? However, the form expected from the Greek is the current Protean. kwami 2005 June 30 08:14 (UTC)
Largest non-spherical moon??
>It is the largest known non-spherical moon in the solar system.
But Iapetus (moon) is bigger and also is a non-spherical moon (although apparently closer to spherical shape than Proteus). Should the above sentence thus be deleted?--Roentgenium111 (talk) 19:45, 10 March 2008 (UTC)
- Proteus is clearly not spherical, Iapetus is basically spherical. -- Kheider (talk) 02:45, 13 March 2008 (UTC)
updated data available
- Jacobson, R. A.; Owen, W. M., Jr. (2004). "The orbits of the inner Neptunian satellites from Voyager, Earthbased, and Hubble Space Telescope observations". Astronomical Journal. 128 (3): 1412–1417. Bibcode:2004AJ....128.1412J. doi:10.1086/423037.
has been superseded by:
- Jacobson, R. A. (3 April 2009). "The Orbits of the Neptunian Satellites and the Orientation of the Pole of Neptune". The Astronomical Journal. 137 (5): 4322–4329. Bibcode:2009AJ....137.4322J. doi:10.1088/0004-6256/137/5/4322.
Ok What is most important in Wikipedia? Factual information or "better grammar"?
"More than 400 km" or "420 km"
If ″better grammar″ is the most important factor, then fine, just tell us that the Sun diameter is greater than 1,000,000 km with better grammar than someone who says is is 1'392,000 km with somewhat imperfect grammar.
Because a 5% larger diameter is not inconsecuential in a moon size body. A 5% discrepancy in diameter gives a 15% more volume and all things being equal it diminishes the average density in about 15%. This in turn has important consequences as to the mix of Ice vs Rock and also the compactness of the body.
Proteus has a mean diameter of 420 km not just a diameter greater than 400 km. Why not just say it is greater than 240 miles instead? With marginally "better" grammar", of course! Also Pharos the crater is not just "larger than 200 km in diameter" it is actually an aproximate ellipse of 230 km by 260 km. Rudy235 (talk) 22:28, 20 September 2015 (UTC)
- As I already said in my edit summary, the point is that Proteus is larger than 400 km and yet is clearly not spherical. The 400-kilometer cut-off comes from Michael Brown's point that everything known above that size is round (and hence in the Kuiper belt). Yet Proteus is larger and not round. Its exact size is not interesting then. People specifically interested in its size will refer to the infobox anyway, where the best known value should (and is) listed. --JorisvS (talk) 07:40, 21 September 2015 (UTC)
- As for the crater, the only source that was on its article was Gazetteer, which does not list a size. What's your source? --JorisvS (talk) 07:40, 21 September 2015 (UTC)
- Also note the error bars on the size. In the context of the sentence and paragraph, there is no significant difference between "around 420" and "more than 400". I don't have an issue with rephrasing it to use 420 ("Despite being approximately 420 km in diameter..."), nor with saying the size of Pharos is 230, but you broke the rest of the paragraph with bad grammar. (Note to JorisvS: See the Physical Characteristics section for the size of Pharos.) Tbayboy (talk) 15:28, 21 September 2015 (UTC)
- Tbayboy. Better grammar is on the eye of the beholder. I consider myself a better person of science than a grammarian. You are welcome to improve my grammar anytime.
- As to the Size of Crater Pharos size I will gladly give you the source. Croft, S. (1992). "Proteus: Geology, shape, and catastrophic destruction". Icarus 99 (2): 402–408. In there it does not say that it is 230 x 260 km but that is " ..Pharos has a diameter from 230 to 260 km"
- As to the the point that everything above 400 is round I consider that it really depends on the composition of that "everything". Gravitational forces on an ideal body made out of almost pure ice and specific gravity close to 1 is somewhat different from forces in a body made out of rock -silicate and irons- and with specific gravity closer to 3 ~ 3.5. There are bodies a bit smaller than 400 km like Mimas that are round. And on the other hand there is some doubt still about a larger body –Enceladus– which is over 500 km in diameter- as to if it has reached hydrostatic equilibrium.
- As you seem to have more experience than myself on the mysterious ways of wikipedia editing, I suggest you incorporate the more actualized dimensions into a final editing. --Rudy235 (talk) 02:52, 23 September 2015 (UTC)
- Yes, there are rocky asteroids > 400 km in diameter that are not round, "everything" → "everything icy", which is what I really intended of course. Mimas is round, but not in hydrostatic equilibrium (HE). Enceladus is round, but not in HE; all the way up to Iapetus (~1500 km) is round, but not in HE. Phoebe (213 km) used to be round, but got battered out of a nicely round shape. Yet Proteus is noticeably not even round. The lead is supposed to summarize the most important points about the object, not provide details. --JorisvS (talk) 08:07, 23 September 2015 (UTC)
JorisvS: Well, first of all I believe that the text is now much improved. What I do not understand why should people understand what you intended to say if you do NOT say it. Rudy235 (talk) 10:59, 23 September 2015 (UTC)
- That's a good point. People can't, and that's why I rephrased it to "Despite being a predominantly icy body more than 400 km in diameter, Proteus's shape deviates significantly from an ellipsoid.". Maybe we can improve this further? --JorisvS (talk) 14:20, 23 September 2015 (UTC)
- I am satisfied. I now understand the 400 km parameter and agree that it need not be changed to 420. However, for the crater there is not an equivalent 200 km parameter, so I believe in could well say >230 instead of >200 Rudy235 (talk) 15:38, 23 September 2015 (UTC)
- It formed when when the original Neptunian moon system was disrupted by the capture of Triton, which likely happened after Neptune plunged into the proto-Kuiper belt. Couldn't it have formed from small debris that formed from fully disrupted moons instead of partially disrupted moons? --JorisvS (talk) 16:36, 23 September 2015 (UTC)