Talk:Large Magellanic Cloud

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Will someone please check my figures and math on the apparent size of the LMC? —ZorkFox 02:02, 11 January 2006 (UTC)

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[edit] radius

The radius of the LMC was listed as 20,000 - 50,000. I changed that to 10,000 ly, a much more realistic estemate. I am sure that the old value is incorrect. I also thinks that 'radius' and 'diameter' are treated as the same in most galaxy articles, which is of course incorrect. Radius is half a diameter! DaMatriX 20:18, 24 January 2006 (UTC)

The Radius figure in the info box is indeed confusing. It currently says "Radius - 35,200 ly (tidal)", now I don't know what "tidal" means (if anything), but this seems like a crazy size, it would therefore have a diameter of 70,400 LYs, that's nearly as big as the Milky Way! How can this be an accurate estimate for "Dwarf Galaxy"?
Also it says in the opening paragraph that LMC is about 1/20 the diameter of the Milky Way "It has about 1/20 the diameter of our galaxy", so that is about 5,000 LYs in diameter and 2,500 LYs in Radius (which sounds like a much more reasonable estimate).
So does anyone know the actual size? Or whether any of these figures are correct? If nobody responds I'll just put in the Radius figure of 2,500 LYs which seems to be closest to the truth.--Hibernian 05:50, 27 September 2006 (UTC)

[edit] Could someone add a section about the future of this galaxy?

As I understand it, the Milky Way is tearing up all of its satellites by absorbing their stars. Could someone confirm that and mention it in the articles.--Will 05:55, 14 August 2006 (UTC)

[edit] Distance to the LMC: SN 1987A estimate

I've added data and a reference to the 1998 Harvard article that published a new distance estimate to the LMC based on the observations of SN 1987A. Could someone review my inclusion of that estimate within the estimates formed "within the last decade" that are said to provide a different estimate with a smaller error? Wdfarmer 20:19, 6 May 2007 (UTC)

[edit] doesn't orbit milky way?

i recently read this New Scientist article that calls into question whether the LMC orbits the milky way, by claiming that its speed is too high, and it simply passing by. hopefully this can be included in the article (as well as in SMC). Mlm42 09:33, 7 May 2007 (UTC)

[edit] Size, again

Ok I've just been trying to look into this again, and I recently got the Celestia program, and in that it states the LMC has a diameter of 4.9 Kiloparsecs. Which is about 16,000 light years, so this figure is quite different then what we've been talking about. This NASA page also mentions the LMC being "about 15,000 light-years" [1] , so both of these agree. Now this of-course contradicts the claim made in the article that it is "1/20th" the size of the Milky Way, that would make it only 5,000 LY in diameter, so I don't think that figure can not be maintained. It's more like 1/6th or 1/7th the size of our Galaxy. So I'm going to go ahead and add in these numbers. --Hibernian 17:15, 22 June 2007 (UTC)

The web site "www.answers.com" states that the apparent size of the LMC is 5 degrees, but that telescopic studies indicate that it is much larger. This agrees with the apparent size of 10.75 degrees in the information box. However, that, at a distance of 168,000 light years, equates to a diameter of 31,150 light years, substantially larger than the figures cited here. I have not posted to Wikipedia before, so I hope that I get the protocols right. If I don't, please excuse errors arising from ignorance. -- Gary Thomas 19 July 2007

I have also seen the comment in various places that the LMC has 1/10 the number of stars as the Milky Way. If the star density is the same in the two galaxies, that would lead to a diameter of 46,000 ly for the LMC (100,000 ly times the cube root of 0.1). The LMC is also admitted to be the fourth largest galaxy in the local cluster (after the Milky Way, M31 and M33). Personally I don't think it is a dwarf galaxy at all. Gary Thomas 20 July 2007

Hi Gary, yes actually I just came back here again because I'm still not satisfied with this thing. I've just discovered that I made a mistake in my previous post, the Celestia program gives the LMC's Radius(!) as 4.9 Kiloparsecs, meaning it's Diameter would be 9.8 Kiloparsecs, which is actually about 32,000 LYs. I've been searching through the Internet in an attempt to get a reliable figure and now think that NASA site must be wrong, as all the other estimates are above 30,000 LYs. As no one here seems to know with any real certainty, I'm going to try to ask some people who hopefully will, I'm going to post about this on the Wikipedia:WikiProject Astronomical objects Talk page, to get some attention to the issue (If you can contribute, please do so). (I made that same radius vs. diameter mistake on the SMC page also, so that will have to be addressed as well). --Hibernian 15:09, 24 July 2007 (UTC)

[edit] Updates and 'Size' discussion

Please note that I have begun the process of updating the scientific information on the LMC. I have updated the intro and distance sections so far, although when I am more awake, I will likely make further corrections to both. In the intro I removed the discussion of the number of stars, since it is relatively meaningless, and replaced it with the mass of the LMC. The distance section is updated with the most current LMC distance. Regarding the discussions of the size of the LMC... when quoting the size of the LMC, many people seem to be quoting an apparent size, which, I assume, is derived from how the LMC looks on the sky. This, like the number of stars, doesn't tell us much of anything about a galaxy. The important number for a galaxy is its tidal radius. This is the radius out to which a star will be bound to that galaxy. The LMC's tidal radius is around 15 kpc. Eventually, I hope to add a section on the structure of the LMC, and hopefully something more detailed about the 'features.' Grochol17 10:05, 16 September 2007 (UTC)

[edit] Not a satellite

it looks like the LMC is just at its first pass http://www.astronomy.com/asy/default.aspx?c=a&id=6019

[edit] Abbreviations

It seems that the Large Magellanic Cloud is abbreviated more than it should be. Also, someone had abbreviated Milky Way to MW, which I felt was unnecessary, and subsequently changed.

In astronomy literature, it is very common to abbreviate names of objects (and often authors) that are rather long and are repeated throughout a paper. The Milky Way, Small Magellanic Cloud and Large Magellanic Cloud are examples of this. The proper use of abbreviations is to give the abbreviation after the first usage of the name in the main body of the paper and then use ONLY the abbreviation throughout the rest of the paper. Thus, the abbreviation of 'Large Magellanic Cloud' is correct, and they way 'Milky Way' had been abbreviated (before you changed it) was also correct.