Talk:Rings of Chariklo

Mesoplanet

Revision as of 22:22, 26 March 2014 (edit) (undo) (thank) JorisvS (talk | contribs)

(Undid revision 601415503 by ONaNcle (talk) ([[mesoplanet]]) not meaningful: many body smaller than Ceres are likely [[dwarf planet]]s) Next edit →

Chariklo qualifies indeed to become one day a __dwarf__ but will never nominated as a mesoplanet because Chariklo is far below the size of Ceres. ONaNcle (talk) 06:53, 27 March 2014 (UTC)

Units

Would it not make sense to use a more common notation like "km/s" or "km per second" instead of "km s^-1". Also, is The surface density of C1R is estimated at 30-100 g cm-2 correct? Density of matter is defined as mass per unit volume, but I don't see any unit of volume...-- Ohc ^¡digame! 04:21, 28 March 2014 (UTC)

The density is correct; it's a "column density." They get used all the time in astronomy where astronomers know 2 of the 3 dimensions. For rings, "height" is a somewhat arbitrary quantity which can be chosen fairly arbitrarily, whereas the inner and outer radii can be used to define a 2-d shape from which one can calculate a the column density. Sailsbystars (talk) 07:52, 28 March 2014 (UTC)

See column density. --JorisvS (talk) 09:34, 28 March 2014 (UTC)

OK thanks. -- Ohc ^¡digame! 14:02, 29 March 2014 (UTC)

Talk on the topic

I had the pleasure to listen to a areal nice talk on the topic from Colin Snodgrass. I liked best his suggestion to get Cassini by a close Titan flyby to leave Saturns orbit for Chariklo. --Stone (talk) 11:44, 7 April 2014 (UTC)

Is it online anywhere? — kwami (talk) 10:21, 13 April 2014 (UTC)

Cleanup section

We say, "With an orbital radius of 404.8 kilometres (251.5 mi) and an optical depth of 0.06, C2R is 40% narrower (less dense), and therefore more diffuse than C1R, containing approximately 12 times less mass than its companion."

This is gobbledegook. The radius does not make it narrower, it is not 40% narrower, width is not density, being narrower would make it less diffuse, not more, and the mass does not depend on its diffuseness – five logical inconsistencies in one sentence. — kwami (talk) 07:36, 13 April 2014 (UTC)

That's why you're here Kwami, to make it better, so let's change this section so it gets better. How would you rephrase it ? Krenakarore ^TK 08:51, 13 April 2014 (UTC)

I don't know. Is there a density calculation in there? It's not 40% narrower. Did they mean 40% less dense? (That can't be right either, it's not that massive.) — kwami (talk) 09:24, 13 April 2014 (UTC)

You're fast... and right :) ! C2R (width 3 km) is 40% narrower if compared to C1R (7 km), and also less dense (apparently there's no calculation involved, just what was reported by the news), therefore more diffuse (thinner in respect to being lighter) than C1R. Anyway, the sentence could be rephrased as you pointed. Is that what you mean ? Krenakarore ^TK 09:35, 13 April 2014 (UTC)

It's 60% narrower. But yes, if the 40% is just an arithmetical error. I didn't want to just assume s.o. got their figures backward, in case there were something going on here I didn't understand. — kwami (talk) 10:10, 13 April 2014 (UTC)

You have a vast knowledge of the subject matter Kwami. Your magic here is appreciatively needed. You are part of the team and we won't let you out. Change the article, whenever you see fit. We don't need to inspect your editing to know that it is correct :) ! Krenakarore ^TK 10:35, 13 April 2014 (UTC)

Thank you for cleaning this sentence up. I just want to add to the discussion to make absolutely sure what we are writing is correct. The nature paper states: "C2R is about 40% narrower than C1R, and contains about 12 times less material." They state that the radial width of C1R in the ring plane is 6.16km (+- 0.11) or 7.17km (+-0.14) from ingress and egress fits respectively. This variation is not an observational uncertainty, and is possibly related to resonant oscillations in the rings. The width of C2R is observed at 3.4km and 3.6km, not 3 as the table in the wikipedia article stated. A simple calculation using the former widths in the wikipedia article of 3 and 7km show that C2R is approximately 60% narrower (which the text reflected), however, using the more accurate values reported in the nature paper, C2R is between 40-50% narrower. I've updated the values in the table and the text to reflect the nature paper. I think the former values were settled upon after an agreement couldn't be reached on the number of significant figures to include in these values, which resulted in an improper representation of the actual widths.

The original nature paper does not mention the surface density of C2R, although it can rather crudely be calculated assuming a thin ring with the given radius and width of C2R and a total mass equivalent to an icy body (density of approx 1 g/cm^3) with a radius of 0.5km (as stated in the article). I suppose that whoever included the surface density of C2R in the wikipedia table may have calculated it in this way, but a surface density value for C2R is not explicitly mentioned in the nature article. I would therefore recommend that this column in the table be removed.

It appears that the authors assume both C1R and C2R are composed of ring particles that have an icy composition - I see no direct comparison of the density of these rings. I would suggest that we remove the phrase "markedly less dense" in this section. The article does not support this statement (unless I'm missing something). Feel free to revert these changes if you disagree with what I've said here.Apogalacticon (talk) 04:30, 15 April 2014 (UTC)

Thanks for the details. I will incorporate a bit more; also, a low optical depth doesn't make something narrow.

Do you have the precision for the narrower ring? — kwami (talk) 06:27, 15 April 2014 (UTC)

That's how I see it, although I'm not a "numbered" guy:

(C2R egress) 3.4 ÷ 7.17 (C1R egress) × 100 - 100 = 52.58019525 % (C2R is 3.77 km shorter than C1R)

(C2R ingress) 3.6 ÷ 6.16 (C1R ingress) × 100 − 100 = 41.5584415 % = (C2R is 2.56 km shorter than C1R)

I have emailed Felipe Braga-Ribas at the National Observatory in Rio de Janeiro asking for the density of C2R, just to know. Let's see if they reply. As I usually say, "who quarrels, loses reason" :) ! Krenakarore ^TK 13:41, 15 April 2014 (UTC)

Thanks again for fixing this up. I hadn't realized my revision implied that optical depth was related to radial width - I appreciate the grammar correction. The precision for C2R is 3.6 + 1.3 -2.0 and 3.4 +1.1 -1.4. I tried to include this in the article, but the formatting looks rather strange....Apogalacticon (talk) 14:47, 15 April 2014 (UTC)

Easy enough to remedy if you're familiar with the templates. — kwami (talk) 17:02, 15 April 2014 (UTC)