Talk:Open cluster

relation between open and globular clusters?

The article treats open and globular clusters as completely separate types, yet according to one of the external links, "some researchers have recently suggested that both types of clusters could be better described as a single continuum of objects". By implication this isn't yet an accepted theory so doesn't need a strong mention, but shouldn't some comment be made about it? The reference given strongly suggests that the only difference may be age (I guess older clusters have to be bigger to stay together and to be seen?). Mozzerati 15:49, 2005 May 8 (UTC)

I've added a bit about the relationship between opens and globulars, which I hope addresses this point. Worldtraveller 20:21, 8 May 2005 (UTC)

There's a general article on star clusters that also covers stellar associations. I think that page addresses the issue. Thanks. — RJH (talk) 17:10, 11 January 2007 (UTC)

star formation and other statements

This article states that "All stars are originally formed in multiple systems." and yet the star formation article doesn't mention that and also papers that I have (just) read instead state that "truly isolated star formation may therefore be a rare phenomenon, and even in low-density regions, most stars may form in groups [...]" (Larson). What rules out the possibility of a single star forming and the rest of the gas present failing to form another object? Possibly in the presence of gravitationally attrictive non star forming mass (dark matter??)? Or would that count as a "multiple system"?

I might have been a bit strong with the wording there. I guess as a scientist I should occasionally stick with a vague wording, like virtually all. It's my understanding, though, that only a cloud of gas with several hundred solar masses or more will ever collapse under its own gravity, but the mechanics of star formation mean it will always fragment into smaller chunks. A cloud of gas small enough to form just one star would not collapse under gravity; a cloud of gas large enough to collapse would always fragment into many chunks, ranging in mass from brown dwarf size to up to 100 solar masses, but I think it would be impossible to form one stellar object and thousands of non-stellar ones. I'll try and expand that section of the article to explain it fully. Worldtraveller 20:21, 8 May 2005 (UTC)

You are correct that a cloud of gas must be much much larger in mass than the resulting star(s) it forms. But the "multiple systems" wording could be confusing. Nearly all stars are formed from a could of gas which forms multiple stars, but only about half of those stars formed are multiples--binaries, triples, etc. —Preceding unsigned comment added by 68.232.114.99 (talk) 15:55, 14 September 2009 (UTC)

"the stellar density in open clusters is much lower than that in open clusters" - I guess that my italics should read "globular" Mozzerati 16:28, 2005 May 8 (UTC)

Indeed - corrected it now :) Worldtraveller 20:21, 8 May 2005 (UTC)

potential additions to the article

A nice thing to add to the article would be a bit more history of research on open clusters. Who named them? At what point was their importance in measuring distance suggested?

I have an excellent book about the history of the study of 'nebulous' objects, but I lent it to someone about four years ago and haven't seen it since. If I ever get it back off them I could probably flesh out the history a lot more, but in the meantime, if anyone else has a copy of The Search For The Nebulae by Kenneth Glyn Jones... :)Worldtraveller

TOC layout

I'm not sure I like the right-aligned TOC - I think it makes the top of the article look very cluttered, with the different-sized boxes for the image and TOC somewhat jarring on the eye. Default TOC gives a lot of whitespace but on balance I prefer it - what does anyone else think? Worldtraveller 14:35, 29 July 2005 (UTC)

I do not like {{TOCright}} - the TOC is something that should be standardised by default and fixed in CSS or whatever. I have filled the whitespace with the lead Pleiades image (but another one could be added, if you like).-- ALoan (Talk) 19:08, 29 July 2005 (UTC)

Is this for real?

Italics are mine:

"Another view to cluster formation is that they form rapidly out of a contracting molecular cloud core and once the massive stars begin to shine they expel the residual gas with the sound speed of the hot ionised gas. From the time of start of cloud-core contraction to gas expulsion takes typically not more than one to three million years. As only 30 to 40 per cent of the gas in the cloud core forms stars, the process of residual gas expulsion is highly damaging to the cluster which loses many and perhaps all of its stars [6]. All clusters thus suffer significant infant weight loss, while a large fraction undergo infant mortality. The young stars so released from their natal cluster become part of the Galactic field population. Because most if not all stars form clustered, star clusters are to be viewed the fundamental building blocks of galaxies. The violent gas-expulsion events that shape and destroy many star clusters at birth leave their imprint in the morphological and kinematical structures of galaxies [7]."

Is this simply poor English or the goofy work of a vandal? I've never read anything like this in an astronomy textbook. 68Kustom (talk) 07:03, 5 May 2008 (UTC)

Units

I notice the use of both light years and parsecs in this article (as well as many other astronomy-related articles). I think one or the other should be used, but not both. Astronomers typically use parsecs to measure large distances, whereas the public and media use light years. If anyone feels like fixing this, a parsec is ~3.26 light years. —Preceding unsigned comment added by 68.232.114.99 (talk) 15:50, 14 September 2009 (UTC)

Lead

No offense intended, but I think the first paragraph of the lead could be clearer. First of all, the second sentence immediately makes a statement about globular clusters, but does not explain what they are. It seems distracting, and the sentence could easily be removed without losing anything. Also the terms "loosely" and "tightly" are vague here. Are they meant to indicate compactness, longevity, or both? Globular also loose much of their stars through interactions and internal dynamics. They're just more massive and so tend to last longer.

For comparison, see the open cluster article by David Darling. It relates the gravitational strength directly to the expected lifespan of the cluster.—RJH (talk) 23:11, 30 April 2010 (UTC)

I was "bold" and modified the lead. Hope it looks okay.—RJH (talk) 16:11, 1 May 2010 (UTC)

First use of "open cluster"

I've been trying to determine who coined the term "open cluster", but thus far I haven't had much success. It wasn't in use during the 1790s when William Herschel put out his first catalogue of clusters in use; Herschel himself used the expression "irregular cluster". The oldest confirmed use I could locate for "open cluster" was from an 1844 publication.[1] That range would fit the time frame when John Herschel performed his early astronomy work. However, his General Catalogue of Nebulae and Clusters wasn't published until 1864.—RJH (talk) 21:31, 21 May 2010 (UTC)

where to put stuff...

I have Kaler's Cambridge Encyclopedia of the Stars at present. It notes on p. 167 that many clusters have abbreviations of discoverers' names - "Mel" for Philibert Jacques Melotte, and "Tr" for Trumpler are among the most common. I wasn't exactly sure of the best place to insert it however. Casliber (talk · contribs) 03:31, 26 May 2010 (UTC)

• It would be nice to add how many have been discovered in the LMC and SMCs, or even Andromeda. Casliber (talk · contribs) 03:32, 26 May 2010 (UTC)

Trumpler classification of the Pleiades

Regarding the statement that "Trumpler scheme, the Pleiades are classified as I3rn", it is curious that in 1930 Trumpler himself classified the Pleiades as II 3r N.[2] Regards, RJH (talk) 22:47, 27 October 2011 (UTC)

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