Talk:Moons of Uranus

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archive 1

One wrong word ...[edit]

OK, this is very much a personal bugbear, but Herschel's four spurious satellites were not "small" stars but "faint" stars! —Preceding unsigned comment added by 121.216.109.12 (talk) 11:48, 15 January 2011 (UTC)

Good point. :) Serendipodous 11:59, 15 January 2011 (UTC)
Herschel did describe them as "small", which was the word then used for "faint". Maybe we should mention both in the article? CielProfond (talk) 12:54, 15 January 2011 (UTC)

Mab diameter?[edit]

The table has Mab listed with a diameter of about 25km, but the article on Mab states a mean radius of 24km. Did someone put the radius in place of diameter (or vice versa) by mistake? -- 136.181.195.29 (talk) 23:34, 22 January 2011 (UTC) MikeS

I can not access the reference in Mab (moon). But Scott Sheppard shows Mab (S/2003 U1) at only 10km in diameter. Something may be wrong with the references. -- Kheider (talk) 01:53, 23 January 2011 (UTC)

Number of moons[edit]

In the first sentence, it says that "Uranus has 30 known moons." However, all the other statements indicate Uranus has 27 moons. I believe the number '30' is wrong. Would somebody care to edit this, for I am not sure if my thought is true? --Weatherlover819 (talk) 14:09, 17 May 2014 (UTC)

Discovery image of Margaret[edit]

http://home.dtm.ciw.edu/users/sheppard/satellites/ura2003movie.html — Preceding unsigned comment added by 8.2.215.33 (talk) 14:25, 22 August 2015 (UTC)

Inclination[edit]

The inclinations of the 4 largest moons are all below 1° according to a table in the article. Inclination is the angle between the plane defined by the moon's orbit around Uranus and the reference plane. What is the reference plane in here? Is it (i) the plane defined by Uranus' orbit around the sun, or (ii) the plane defined by Uranus' equator? In other words, are the moon orbits close to co-planar with the ecliptic (i) or rather perpendicular to it (ii)? Tomeasy T C 00:13, 4 September 2015 (UTC)

The equator. The plane of Uranus's moon system is just as tilted as Uranus's equator. --JorisvS (talk) 20:40, 4 September 2015 (UTC)
Thanks, I really did not know.
Looking at the article's table in the "List" section, do you think this is sufficiently clear. The column "Inclination" is only explained by a link to the article Orbital Inclination, which formally leaves open which plane the "reference plane" is. However, the table presented in that article would rather rather make the reader believe that the reference plane is that defined by Uranus' orbit around the sun or the ecliptic, but not that defined by its equator.
I would introduce a footnote explaining which two planes define the inclination angle. Any objections? Tomeasy T C 11:04, 5 September 2015 (UTC)
Of course not. I've added it. It seems clearer to readers to have it regardless of whether it is mentioned in the lead. --JorisvS (talk) 15:38, 5 September 2015 (UTC)
Thanks.
I just made a copy edit so the footnote explains directly what is measured by the inclination rather than requiring the reader to also check the corresponding/linked article to understand the term reference plane. I also removed mentioning of the inclination between Uranus' equator and the ecliptic. I think it is good to mention this in the lead, but the footnote to this column header should concentrate on the definition of the values presented in the column. Adding a third plane (ie. the ecliptic) at this point rather confuses the reader who is in need of the footnote (because the angle is defined by two planes, independent of the ecliptic) .
One question wrt the 97° figure mentioned in the lead. We know from reliable sources that the tilt of Uranus' axis is 97.77°. We also know that Uranus' orbit has an inclination of 0.77° wrt to the ecliptic. From this, I cannot straightforwardly deduce that Uranus' equator has an inclination of (97.77° - 0.77° =) 97° wrt the ecliptic. It could just as well be (97.77° + 0.77° =) 98.54°. Am I missing an obvious sign conventions? As far as I can see, all planet's orbital inclinations wrt the ecliptic are specified as positive numbers - so we would not know whether to add or deduct the 0.77°. I could not find a source that talks about the inclination of Uranus' equator - other than Wikipedia. May be you know more?
Once this is settled, we should revisit the 97° sentence in the lead. At present, it is formally wrong (because the moons' orbits are not in the very same plane) and unclear (because only the already informed reader may guess why 97° is appended in parenthesis). Tomeasy T C 21:50, 6 September 2015 (UTC)
As it seems there is no verified basis for the 97° claim, I am going to remove it for the time being. Would be happy to bring it back into the article, if such basis can be found. Tomeasy T C 11:30, 12 September 2015 (UTC)
Joris, I saw that you introduced a statement claiming that Uranus' equator is tilted 97.77° wrt the ecliptic. This is plainly wrong, and I changed your edit in a way that it becomes a correct statement, while the 97.77° figure you introduced stays in the article. Surprisingly, you reverted me. You say that my edition makes it too complicated - fair enough. But then we may also leave it out. Uranus' orbit is treated in the planet's article. There is no real need to repeat it here, but if we do, we should do it correctly.
Feel free to re-introduce the 97.77° figure again in the lead, but be careful to do this correctly. This value describes the planet's axial tilt. Equivalently, it describes the angle between the planet's equator and its solar orbit but NOT the ecliptic.
Perhaps a good idea to first solve matters here, before reverting the article again. Tomeasy T C 07:01, 13 September 2015 (UTC)
Tomeasy, first of all, we're talking about Uranus's equator, which *is* tilted by 97.77° (maybe not the ecliptic, but Uranus's orbital plane, that's why I removed that part when I reverted you the first time; I have yet to see a source that tells clearly which it is). Secondly, the sentence is about the plane of Uranus's moons, not Uranus's rotation, which is why this article would be missing a crucial piece of information if it were to be removed. --JorisvS (talk) 10:09, 13 September 2015 (UTC)
The version you reverted clearly speaks of Uranus's axial tilt, not its orbital inclination. Frankly, just read it. --JorisvS (talk) 10:09, 13 September 2015 (UTC)
I was not saying that we have to describe the geometry as I proposed (using the axis). If you find a better way, I am more than happy. I am just firm that we cannot describe it the way you did (with the ecliptic), because that would be wrong.
Now you reverted me again, before settling here. Well, you choose your behavior.
About your recent edition, I have to say that, again, I do not like it. Now you have removed any reference for the angle's definition. You only state "... Uranus's equator, which is tilted 97.77°." This is not precise enough. You leave it to the reader to figure out what the reference plane for this angle is. However, by your previous edit you have proofed yourself that this is not trivial, because you got it wrong by mentioning the ecliptic. Now, if you as an experienced editor get it wrong, certainly many readers may get it wrong, too.
I propose that we either explain which planes are intersecting by an angle of 97.77° - or we do not mention this number.
You mentioned above that you are actually not sure what the reference plane is and that you are lacking sources. Hm, then how can you be so bold to revert me again and again? The sources for the axial tilt of Uranus (see here) are in fact abundant. It is 97.77°. And the definition of axial tilt is given, e.g., here. Now the following piece may be missing as you try to put the puzzle together: The equator of a planet is always perpendicular to its axis. So far, I assumed this was common ground, but your latest comments made me wonder. Tomeasy T C 10:30, 13 September 2015 (UTC)
Yes, using the equator. As I said, I removed the ecliptic from being mentioned already the first time I reverted you. Please read what I write.
I would like to reinsert the reference frame very much! However, without a source that says so, we can't assume it's Uranus's orbital plane (yes, I originally assumed just the ecliptic, which is just as wrong). The value 97.77° is indeed consistently mentioned as Uranus's axial tilt in Uranus (which is why it can easily stay), but the reference plane is missing every time. We should fix this. In the meantime, keeping this value here without a reference plane is still better than removing it altogether, because it paints the same picture for the average reader regardless of which exact reference plane it is.
"The equator of a planet is always perpendicular to its axis": This simply says that a body's equator is perpendicular to its rotational axis, which is really by definition so. --JorisvS (talk) 10:41, 13 September 2015 (UTC)
I've found a good source for Uranus's axial tilt, including the reference plane. I've included it in the articles. --JorisvS (talk) 11:25, 13 September 2015 (UTC)
Looks good now. Tomeasy T C 17:22, 13 September 2015 (UTC)

Image discussion[edit]

Orbits of Uranus's five main moons (in green).

I am not very impressed by the figure shown in the section "Large Moons":

  • What is the red line? It's not mentioned in the file description and not in captions. So, why is it shown? Maybe it's Uranus' orbit, but why would that matter and what what it show? The angle of the red line would then be arbitrary and showing it thus misleading. Only it's curvature could be compared to that of the moon orbits but, to be honest, I see hardly any curvature at all. Maybe, I am just going in the wrong direction. As I said, I have no idea what the red line is. I can only see that it is the most distinct feature of the figure.
  • What is this figure trying to tell? Are the diameters of Urnaus, the moons, and the orbits to scale? If so, that may be something. But enough to justify the figure? All those dimensions are specified and, since they are near circles, easy to visualize. There are other geometries that would benefit more from an illustration.
  • "Main" moons. The section is called "Large" moons and starts with defining the 5 "major" moons. Perhaps a bit picky here, but why do we use so many words if we mean the same thing. I know this is easy to fix, and I will, once we know what to do with the figure.
  • The file description states that the other moons are not visible from the perspective taken. Why would that be? Tomeasy T C 22:26, 6 September 2015 (UTC)
I am going to remove this image from the article. Feel free to challenge this decision, if you see good reasons for its inclusion. Tomeasy T C 11:37, 12 September 2015 (UTC)