Talk:Variable star

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Our own Sun[edit]

Our own Sun is a good example which goes through practically no measurable variation in brightness.

This is untrue. At present, there is a 0.1% variation between solar max and solar min years in the solar cycle. There is some evidence of greater variation on longer time scale. This is small, and much smaller than stars that are classified as "variable". But it is easily measured even with fairly crude apparatus. I have somewhat changed the offending sentence that was stated on this site. Securiger 00:45, 13 Aug 2004 (UTC)

From Solar analog: "Non-variability is ideally defined as variability of less than 1%, but 3% is the practical limit due to limits in available data. " I'd point out too the need to demonstrate the periodicity/recurrence of variation, to rule out supernovas/other one time occurrences. To another question, Have they found any red dwarfes that have a large planet companion making it totally 'disappear', as the planetar(?) would be larger than the host star?85.77.97.18 (talk) 03:12, 29 June 2011 (UTC)

Spectrum Variables[edit]

Is there a good reason why spectrum variables are not included?

No good reason, just our ignorance. 16:16, 24 September 2008 (UTC)

Reasons[edit]

It would be nice if the article actually provided some explanations of the reasons that the stars change their luminosity. Paranoid 20:09, 17 August 2005 (UTC)

That would be suitable. I'll see with what I can contribute. Said: Rursus () 16:17, 24 September 2008 (UTC)
Now Eddington pulsations for instability strip stars and for miras, while unknown for β Cepheids. Cataclysmic variable mechanisms are also pretty well known, but not written yet. Said: Rursus () 19:00, 16 October 2008 (UTC)
I believe an article could be written for Eddington pulsations, maybe. Said: Rursus () 19:01, 16 October 2008 (UTC)
This one source. Said: Rursus () 19:25, 16 October 2008 (UTC)
Reading that, the article describes a so called κ mechanism, driven by temperature and opacity, while Eddington proposed an ε mechanism, driven by central temperature and energy production. I don't know hwois responsible for κ, yet. Said: Rursus () 21:25, 16 October 2008 (UTC)
Answer: Eddington. Although he rejected it later. Said: Rursus () 21:37, 16 October 2008 (UTC)
This needs to be very brief. All the variable star types have their own articles (SPBs to follow soon) and we don't want to just repeat all that information here. Each star needs only a summary of the key points, which could include an indication of the mechanism of variability. I've just hacked out a bunch of the detail about Cepheids. There is an overview article on Cepheid, plus detail articles on each of the sub-types. Also, as of 2013 we have a basic understanding of the mechanisms of pulsation for all the types, and detail articles for most of them (eg. G-mode pulsation). Lithopsian (talk) 23:58, 25 February 2013 (UTC)
Where this doesn't already exists, and when I know it, I'm adding a brief mention of the mechanism for variability. No more than a sentence or soin each class, maybe a sentence in the sub-headings. Plus a larger general explanation for the different mechanisms behind pulsating stars. Hopefully that will let people compare and contrast the mechanisms in different variable types in a way that I don't think is done anywhere else. Lithopsian (talk) 14:49, 26 February 2013 (UTC)

Naming of variable stars[edit]

This system of nomenclature was developed by Friedrich W. Argelander, who noted that many variable stars were red and so began the naming with the letter R for rot (Red).

Is this really so? As far as I know, Argelander chose letter R as the first letter because the last letter used in Bayer designation scheme was Q. Bayer designations start from α and continue to ω. After the Greek letters were exhausted, lower case letters were used, and finally came the upper case letters. Non-Greek letter designations have largely fallen out of use. Few expections remain, h Persei (open cluster), e Eridani (not ε/epsilon!), and P Cygni. The last one is not a variable star name, although P Cygni is about as variable as a star can be.--Jyril 14:31, 6 November 2005 (UTC)

That's what I thought too. Don't have a citation offhand but I'm pretty sure that you're correct. JYolkowski // talk 17:36, 6 November 2005 (UTC)
I found it! Argelander wrote:
" I name R the star in the Virgin whose periodic variability was discovered in 1809 by Harding... I hope I will be forgiven for taking the liberty of designating by a letter a star which does not appear in the Bayer catalogue but it seems to me that owing to their originality, variable stars are entitled to claim such a distinction. To my mind, a particular name seems to be almost unavoidable to allow an easy identification of stars that are frequently mentioned. But in order to avoid confusion with the alphabetic designation of Bayer, I chose to use the last letters of the alphabet only and to write them in capitals... "
Source: [1]
--Jyril 18:32, 6 November 2005 (UTC)

General structure of this article[edit]

I think the general structure of this article may be improved. What I expect the "general visitor" of this article to look for would be more of a general introduction to the subject, giving insight in the first place, and less of a comprehensive catalogue of variable types. The article in its new form may consist of two parts:

  1. General introduction, including broad distinction between intrinsic and eclipsing/rotating variables; discovery history; observational data (kinds of variability, light curve, spectrum, magnetism, etc., and what may be learned from them); theoretical tools (why do stars pulsate; Eddington's "wave equation"); nomenclature system;
  2. General classification scheme. The present catalogue largely reflects the General Catalogue of Variable Stars (GCVS) ordering, which is often alphabetical; instead a more illuminating ordering would be based on physical criteria (such as type of star--main sequence, giant, protostar, white dwarf; or radial vs non-radial pulsations). The list should not be too detailed (the GCVS has some 115 categories and subcategories); instead, links to (new) wikipedia articles such as "intrinsic variable"; "rotation variable"; "eclipsing variable" should refer those interested to a more comprehensive treatment.

I will try and make these amendments to the Dutch nl.wikipedia article first; if this is an improvement I propose a similar restructuring of this English article. Hans van Deukeren 16:38, 1 February 2006 (UTC)

Thanks for all your work on this article Hans.--Kalsermar 18:10, 5 March 2006 (UTC)

Why is a link to the Heinlein/Robinson book "non appropriate"?[edit]

It is conceivable someone looking for the book will go to "Variable star" rather than "Variable Star". --Lukobe 20:35, 24 July 2006 (UTC)

It is imho actually very unlikely that someone would look for that book in that way. Rather, they'd probably go to the author's page and go from there. Other than that, making a true Variable star (disambiguation) might be better, others can correct me on this if I'm wrong.--Kalsermar 21:10, 24 July 2006 (UTC)
I already created Variable Star as such a disambiguation page. I suppose that may be enough. --Lukobe 21:34, 24 July 2006 (UTC)
Sounds good to me :-) --Kalsermar 23:53, 24 July 2006 (UTC)
Lukobe got rid of the dab page, and redirected it directly to Heinlein's novel. Now there's a vote on to MOVE the Heinlein page to Variable Star, by Lukobe as a matter of fact, after already discussing it here! I've restored the dab, at the moment. Vote at Talk:Robert A. Heinlein's Variable Star to discuss the requested rename. 132.205.93.88 23:52, 31 July 2006 (UTC)
Note the proposal is to move the Heinlein page to Variable Star NOT Variable star. And this is because the book's name is not actualy Robert A. Heinlein's Variable Star, which is where the book currently resides. --Lukobe 00:57, 1 August 2006 (UTC)

H-R diagram illustration[edit]

As a suggestion, it may be beneficial to include an illustration of an H-R diagram showing the regions where various types of variability occur. I've seen this illustrated in astronomy textbooks, as well as some web sites. Here are some examples (which I'm sure could be improved upon):

http://www.astro.uiuc.edu/~kaler/sow/hrv.jpg
http://ircamera.as.arizona.edu/astr_250/images/hr_vars.gif
http://outreach.atnf.csiro.au/education/senior/astrophysics/images/binvar/hrpulsvar.jpg
http://universe-review.ca/I08-14-variables.jpg
http://www.astronomy.org.nz/aas/Journal/Nov2004/images/Instability%20Strip%202.gif
http://www.dil.univ-mrs.fr/~gispert/enseignement/astronomie/3eme_partie/variables_img/diagHR.gif

Thank you. — RJH (talk) 19:10, 16 May 2007 (UTC)

Thanks a lot. Good starting point. Said: Rursus () 16:43, 24 September 2008 (UTC)
Testing testing, by Jove!!
Does look so-so only: the HR diagram is cluttered with texts, often with the TLA disease. I'll ponder how to improve. Said: Rursus () 14:16, 15 October 2008 (UTC)
You might want to give it a new try based on http://www.helas-eu.org/outreach/index.php?option=com_content&task=view&id=17&Itemid=46 (however, pulsating stars only, not all variables generally) Bruddl (talk) 16:29, 20 May 2010 (UTC)
I like the diagram, almost essential in this article. It could probably stand a few additions for recent discoveries. I don't see TLA as a problem provided the acronyms are also clearly visible in the text. You could also explicitly key them at the bottom of the diagram itself. With full names that don't completely crowd eachother out, it would almost certainly need to be bigger and the version in the article would become an unreadable thumbnail. Lithopsian (talk) 14:54, 26 February 2013 (UTC)

Discovery Incorrect 1ST para[edit]

The first paragraph in section Discovery have decidedly got it in quite another way that I got it, namely:

The occurrence of Tycho's Star and Tycho Brahe's subsequent studies, showed that the fixed heaven is not as "fixed" as was previously believed. Fabricius described omicron Ceti as a nova. It was Holwarda that discovered that omicron Ceti was pulsating, and he determined the period to 11 months.

I suggest a rewrite to clarify. Said: Rursus () 09:35, 20 October 2008 (UTC)

Extrinsic/Intrinsic[edit]

Extrinsic/Intrinsic ― I suspect this division might be obsolete. Said: Rursus () 19:14, 31 October 2008 (UTC)

AAVSO divides like this:
  1. extrinsic
  2. eruptive
  3. intrinsic
Patrick Moore divides like this:
  1. extinsic:
  • eclipsing vars
  1. intrinsic:
  • rotating vars
  • ...
GCVS has nothing like "trinsic" whatsoever. It might be a confused term that have fallen out of usage becåse of confusion and/or new knowledge. In my opinion the rotavars are variable due to one "extrinsic" (geometric) and one "intrinsic" (real physical variability) mechanism. The ellipsoids are also "semi-intrinsic", since the stars deform each other physically. Said: Rursus () 19:50, 31 October 2008 (UTC)
Stars such as the RS Canum venaticorum variables also blur the distinction between intrinsic and extrinsic variables, as potentially do several other types. I would like to get rid of these sections, although they may seem like nice groupings for a lay reader. Even for the lay reader, the existing depth of nesting of the subsections is probably intimidating. Lithopsian (talk) 00:01, 26 February 2013 (UTC)

List of var discoveries[edit]

Acc2 Patrick Moore (The Guinness Book of Astronomy), the discovery list is:

1 Mira Holwarda 1638
2 Algol Montanari 1669
3 χ Cyg Kirch 1686
4 R Hya Maraldi 1704
5 α Her W. Herschel 1759
6 μ Cep W. Herschel 1782
7 R Leo Koch 1782
8 δ Cep Goodricke 1784
9 β Lyr Goodricke 1784
10 η Aql Pigott 1784

That makes 10 before 1786, unless Moore (and so me) missed some. Said: Rursus () 19:44, 1 January 2009 (UTC)

List of variable stars supports 10 before 1786, unless supernovae are counted. Said: Rursus () 20:27, 1 January 2009 (UTC)

Cataclysmic/Explosive[edit]

The RASC lists four sub-categories of variable stars, compared to five here. They put the cataclysmic and explosive variables under "Eruptive variables". The AAVSO has a similar organization. I'd like to suggest merging the Cataclysmic/Eruptive section under the "Eruptive variables" section.—RJH (talk) 19:58, 9 November 2009 (UTC)

I think it would be better to keep the current five classes (eruptive, pulsating, cataclysmic, rotating, and eclipsing) as they are the first five classes used by the GCVS [2] and by Sterken and Jaschek (ISBN 0521390168). (These sources also have a sixth class of variable X-ray sources which no-one has bothered to list here.) Spacepotato (talk) 00:53, 10 November 2009 (UTC)
Okay. In that case the Cataclysmic variable star article probably shouldn't be listed as the main article for it's section as it doesn't cover Type II supernovae.—RJH (talk) 00:06, 14 November 2009 (UTC)
In case anyone gets itchy about this topic in the future, the AAVSO now groups variables under the same five categories. Don't know if that is Wikipedia changing the world or just a coincidence. Makes sense anyway. Lithopsian (talk) 23:50, 25 February 2013 (UTC)

Section grouping[edit]

I've added several new variable types to this article, all pulsating variables. So now we have a fairly long list with little structure to it. I could group maybe three or four of them as main sequence variables, or perhaps a slightly different three as B type variables or some such. Any other ideas? Lithopsian (talk) 23:53, 25 February 2013 (UTC)