Talk:Metallicity

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Corrected a statement

"regular chemistry has almost no relevance in astrophysics. This is patently false - I believe it was meant to read "regular chemistry has not relevance in a discussion of stellar interiors. I changed it as such. —Preceding unsigned comment added by 160.39.157.91 (talk) 23:12, 1 May 2008 (UTC)

Unfortunately, it has come back in the lead (as of 8/14/2017). There is a HUGE literature on the chemical species present in stars!!!! I can't be any more clear. The only debate possible between reasonable and informed minds is whether "present in stars" means "present in the interior of stars" or "present as part of stars". Generally, the atmosphere of an astronomical object IS considered part of that object, imho. I am removing the offending sentences in the lead. I believe the term was coined at the time when there was no clear distinction between a star's atmospheric composition and the star's (interior) composition. There is no significant chemistry in the deep interior of stars. At temperatures in the Sun's chromosphere (4500 K to 6000K) and possibly its photosphere (6000 - 8500 K) molecules exist (hence chemistry exists, by definition). It may even be possible for molecules to exist just below the photosphere (in what is considered the interior of the Sun), however we can't directly observe this zone. It is factually wrong to suggest that the term was created at a time when it was believed that there was "no chemistry" going on in the Sun (whether in the interior or in the stellar atmosphere). To my best understanding, the term was created by the people studying the atomic absorption and emission spectra obtained by the (primitive, arguably) instruments of the time. That is, it was created by people with no opinion about whether there was or was not chemistry going on, it was adopted to describe their atomic results.40.142.187.175 (talk) 19:38, 14 August 2017 (UTC)

Biggest star that can form today

"The most massive star that can form today is about 110 solar masses with a possible extreme maximum upper limit of 150 solar masses" i.e. "The maximum mass for a star today is 110 solar masses, with a maximum mass of 150 solar masses". Which is it? 110 or 150? Or is it that 110 is the largest mass that a star can start with, and 150 is the largest mass that a star can have and still be stable after accretion etc? AstroDave (talk) 10:50, 14 April 2008 (UTC)

Merger from Stellar population

I see that Stellar population has been merged into this article. This seems a bit odd to me - while metalicity is a big part of the population classes, the population classes also have other aspects with stellar and galaxy formation, and as such I think that they deserve to be in their own article. Mike Peel 18:16, 22 November 2006 (UTC)

Perhaps that is the case, but there was nothing in that article that was not in the reconstituted Metallicity article. If there are other factors which inlfluence stellar classification, then perhaps they could be added to a newer version of the article, but the article, as written, was only a shorter version of this one. Serendipodous 18:51, 22 November 2006 (UTC)

Fair enough. I'd like to see them split back at some point, but for now I guess they're OK being combined. Mike Peel 19:27, 22 November 2006 (UTC)

A real shame they were merged as now the needed splitting will be much harder. - Rod57 (talk) 12:55, 8 April 2015 (UTC)

Population 0 stars

Population 0 stars redirects here but I can't find any information about them in any of the five articles I combined to create this one, nor can I find any information on them in Google or Google Scholar. I even went back and checked every past edit in Stellar population, to which the redirect linked originally, but found no mention of them. Does anyone know what they are? Serendipodous 16:59, 25 November 2006 (UTC)

Never heard of it – maybe confused by luminosity class 0?? As much as I can understand, they represent a far future luminosity class. Rursus 17:29, 8 January 2007 (UTC)

Now the really bad qualities of Wikipedia occurs – there really are hits on "population 0 stars". All of them obviously being information copied from wikipedia! No real information, but as soon as desinformation occurs on wikipeda, it propagates over Internet. This is neither a conventional responsibility issue, nor a honesty issue - this is a mathematical complexity issue: imagine a situation when desinformation overweights the true information (YES, there is a truth, and there is an objectivity – otherwise my involvement here is meaningless) then desinformation will propagate over internet despite being removed from wikipedia, if desinformation propagates more than true information, the meaning of Internet will be truly destroyed. (Conclusion: I will delete "population 0 stars". Rursus 19:12, 8 January 2007 (UTC)

As another explanation, perhaps someone confused the term with a class 0 protostar? Sadly, I see that there's no reference of classes on the protostar page, so I guess that's something else to go on the to do list... Spiral Wave 17:26, 27 January 2007 (UTC)

Uh, turns out the class descriptions are tucked away in the Herbig-Haro objects article. Seems to me a short description should go in the protostars article too - a more 'obvious' place to look - but duplicating material seems a waste (and it's too good to remove from the featured article). Unless anyone has any thoughts, I'll just leave it then... Spiral Wave 00:02, 28 January 2007 (UTC)

Forgive me if I'm being dense, but, by extrapolation, wouldn't population zero stars be super-metallic stars that will form when the population I stars start dying and blasting their materials into space? I was actually looking for information on such occurrences in this article and was curious about it's lack. Is this because nobody's done an extrapolation of what the next generation of stars will look like (unlikely) or because there is a reason to think such a generation will not happen (which should probably be mentioned). --Suttkus (talk) 03:00, 26 March 2009 (UTC)

More needed

Ordinary school books (university level) tells us more – mostly about subpopulations betw popI and popII. More is also needed for my carbon stars extras to make sense. L8R Rursus 17:27, 8 January 2007 (UTC)

Done (L8R) Rursus 00:27, 9 January 2007 (UTC)

article missed out a candidate Pop III HII galaxy.

Might I comment that the article has left out the possible detection of a Pop III starburst at z~3.

http://news.bbc.co.uk/2/hi/science/nature/3227221.stm (the BBC's summary of the work).

As Fosbury et al. (2003 ApJ 596 797) explain, the spectrum of this HII galaxy are difficult to explain in terms of photoionization by a 'normal' starburst - very hot stars (~80,000 K) seem to be required. 132.248.1.196 00:02, 18 January 2007 (UTC)

Then include it. This is Wikipedia. Serendipodous 11:13, 18 January 2007 (UTC)

The article is intriguing indeed, but it does not mentions population III, it mentions that a Lynx arc is a structure with early super-luminous stars nearest to what we believe the "earliest stars" to be – we believe that means pop III, but that's not what's observed in the Lynx arc. The article is vaguely relevant – but maybe not enough so ??? Rursus 22:08, 28 January 2007 (UTC)

I'm inclined to agree with Rursus - the article is 3 years old, if there was any further suspicion here I expect we'd have heard of it by now. If anyone knows of any such newer research on this nursery, that might well be worthy, but I think this by itself is too vague. We'll probably have to wait until the James Webb is launched before we get any real observations. Spiral Wave 00:06, 29 January 2007 (UTC)

Contradiction

The intro says Pop I was created first, then Pop II, then Pop III, to which the sun belongs. Later the text says the sun is Pop I, and the oldest are Pop. III. I don't know which is right, just that they contradict. UnitedStatesian 03:09, 31 March 2007 (UTC)

Thank you, I have fixed this. (Pop III stars came first.) Spiral Wave 07:37, 31 March 2007 (UTC)

Deblippification

I removed lot's of ":s and some ":s. F.ex. "Big Bang" is replaced with Big Bang because it's an established term. "Heavy" is not "heavy" but in real life heavy. When highlighting a newly introduced term I use to use gizmo (bold), at other emphasis I prefer italic is a necessity. Blips should be preferred when citing in running text, or just using a simile, like: he "exploded" from rage (not me, not now, be calm!) Rursus 17:07, 1 April 2007 (UTC)

Units of metallicity

I keep running across the unit of "dex" for metallicity, which seems to be for [Fe/H]. However, I haven't seen an explanation/derivative of this, and am having a fair few problems finding one. Does anyone know more about this, and if so could they post it either here or on the article, please? Thanks Mike Peel 07:42, 19 April 2007 (UTC)

It's one of those irritating things that it's always assumed you already know about. As such, I don't know of any papers explaining it; but this Caltech page explains the units, and this page from North Carolina explains the etymology: it's a (now-deprecated) contraction of decimal exponent. Spiral Wave 17:23, 20 April 2007 (UTC)

Added a line about "dex" units based on Spiral Wave's comment above Gaba p (talk) 19:39, 28 July 2010 (UTC)

Worse, stars that have Metallicity in their infoboxes do not appear to use any standard. I see various units in play with no real consensus. ex Sun, 36 Ophiuchi, Tau Ceti. Is there a preferred system or unit to use? Either log10 or "% Sun" or something different? --Robert Keiden (talk) 07:06, 11 July 2012 (UTC)

Thank you, Robert Keiden, I agree the units should be standardized or at least better identified in Wikipedia info sidebars. For example the metallicities of Alpha Centauri A and B are given as 0.20 and 0.23 with no units. From the cited paper these figures seem to be [Fe/H], which I understand is a logarithm of a proxy for metallicity (iron portion), and relative to the solar proportion, and so radically different from the "Z" units, which is the portion of non-H, non-He elements. For the Sun this is shown, Z = 0.0122. There's already a standard for showing many other units in absolute and solar-relative forms. Perhaps metallicity could be shown in both unit systems, absolute-metallicity (Z) and log-solar-metallicity (lSm?). — Preceding unsigned comment added by Bob Stein - VisiBone (talk • contribs) 14:35, 18 January 2016 (UTC)

How do they get these figures?

"The number of iron and hydrogen atoms per unit of volume respectively" are stated as requirements for the metallicity equation yet the entry makes no mention of how these measures are actually detected (for our own star and others). MatthewKarlsen 17:53, 25 May 2007 (UTC)

I believe that with a Spectrometer —Preceding unsigned comment added by 86.122.202.153 (talk) 20:44, 1 January 2008 (UTC)

How could Population III stars create the first 26 elements if they contained no metals?

About half of the first 26 elements are metals, so how could they create these metals via nuclear fusion without containing them? —Preceding unsigned comment added by 72.65.160.182 (talk) 08:44, 7 March 2008 (UTC)

After the elements were fused within the star, the star then contained metals. But the terms metal-rich or metal-poor (or metal-less) generally refer to stars early in their lives when they are fusing Hydrogen to Helium and the heavy metals that were left over from previous stars can be identified. 24.117.155.195 (talk) 03:51, 12 March 2008 (UTC)

Pop III - Link Dump

Don't know what to do about this relevant link. I'm not sure whether it's a secondary or tertiary source, but it's good, because it deals with the physics explaining why Pop III is a good hypothesis. Said: Rursus ☻ 07:53, 4 August 2008 (UTC)

Thinking a little, maybe Pop III should have a separate article dealing with this Universe astrophysics stuff. L8R. Said: Rursus ☻ 07:59, 4 August 2008 (UTC)

Population III stars and Pair-Instability Supernovae

Shouldn't the Population III stars section bring up (link) to Pair-instability supernova? Seems relevant. 24.18.236.67 (talk) 20:47, 27 May 2010 (UTC)

Metallicity of Galaxies and the Interstellar / Intergalactic Medium?

The article currently focusses upon the metallicity of individual stars. The comparative metallicity of different kinds of galaxies and the distribution of metals in the interstellar and intergalactic medium are well-researched matters that should also be included. — Preceding unsigned comment added by 82.71.43.37 (talk) 16:18, 22 January 2012 (UTC)

Pop III star?

The article cites that no Pop III star is known. In 2011, Herschel telescope found SDSS J102915+172927, which has no more than 0.00007% metals and is probably more than 13 billion years old. For me this indeed looks like a Pop III star, or at least it is a nice candidate. 187.42.228.56 (talk) 12:12, 14 July 2012 (UTC)

J102915+172927 is (apparently) very old, and very primitive, but the problem is- it's way too small. In all the sources I've found, Pop III are expected to have been massive and short-lived. I'd agree this star is something like a candidate, but it needs a better citation, otherwise OR to me. :) --Robert Keiden (talk) 08:28, 15 July 2012 (UTC)

What metallicities for pop 1 and pop 2

It says pop 3 have [Fe/H] < -6 but what is the boundary between pop 1 and pop 2 ? - Rod57 (talk) 02:44, 6 November 2012 (UTC)

We should add a reference for that claim ([Fe/H]<-6), I'll add a 'citation needed' tag. If anybody has a proper reference please add it. Cheers. Gaba p (talk) 10:21, 6 November 2012 (UTC)

Pop 1 and Pop 2 are distinguished by a combination of metal content and stellar kinematics. The metallicity ranges overlap; there are clear Pop 1 stars with metallicities as low as [Fe/H] ~= -1.1 or so, while there are stars with Pop 2 kinematics as metal-rich as -1 to -0.5. In principle age also should be in there as well, but determining ages for stars is much harder than either space velocity or metal abundance. Mind you, with the clear knowledge that the Galaxy has consumed dwarf galaxies and their stellar content over its history, there are stars whose origins lie outside the framework that gives rise to the Pop 1/Pop 2 distinction. Finding a concise reference that says all that won't be easy, but I'll keep it in mind and hopefully find one. BSVulturis (talk) 20:19, 16 April 2013 (UTC)

Relation between Z and [M/H]

I corrected the formuli for [M/H] -- they previously stated that it was simply log(Z/Z_sun), which ignores the fact that it is the ratio of metals to Hydrogen, and the amount of Hydrogen varies between stars.

I also noted that stating that [Fe/H] and [M/H] are proportional is a common assumption, rather than a fact. Trefusius (talk) 12:18, 30 June 2013 (UTC)

Hi Trefusius, I tried coming up with a suitable source for that equation but the only thing I could find was this article where the formula is stated as (see eq. 9):

• log(Z) = log(X/Xo) + log(Zo) + [Fe/H]

which would mean that the correct relation between Z and [Fe/H] is:

• log(Z*Xo/Zo*X) = [Fe/H]

Where did you get the relation that you edited into the article? It'd be great if we could find a source like an astronomy book expressing this relation. Regards. Gaba ^(talk) 20:48, 30 June 2013 (UTC)

Bolding

On first look, I agree with the removal of bolding done today. However, the article has quite some incoming redirects, which one could justify to bold. I'm not sure what exactly would be the best style here, but it feels like bolding the most comon redirects would be good. But only the first occurence after the redirect target, not later mentions (some of which are bolded now). — HHHIPPO 17:28, 26 August 2013 (UTC)

Alright, bold font readded for the class names in their section. I've also gone through some of the redirects and directly targeted them to sections. — Reatlas (talk) 12:05, 27 August 2013 (UTC)

Looks good. Thanks! — HHHIPPO 14:57, 27 August 2013 (UTC)

HD 164922

The article states that population I stars are young, metal-rich and more likely than stars of other populations to have planets. So what population would HD 164922 belong to? It is metal-rich and has a planet, so it should be in population I, but it is 13.4 billion years old, making it among the oldest stars in our galaxy. John Sauter (talk) 14:34, 14 December 2013 (UTC)

another article to integrate

Detailed Abundances of Planet-Hosting Wide Binaries. I. Did Planet Formation Imprint Chemical Signatures in the Atmospheres of HD 20782/81? looks like it might also affect the article(s) for exoplanets. --Smkolins (talk) 12:40, 20 May 2014 (UTC)

Desperately Need For Article Repairs and an Attached Figure

The figure showing the distribution of Populations I and II star is plainly wrong.

Pop II in the Milky Way are distributed in both the galactic hub and are also equally distributed in the thin disk. Pop I's are mostly on the outline of the spiral arms. The figure clearly implies that there is an evolutionary process is moving from the core outwards, which is simply not true. As such, the figure should be removed entirely, or replaced with a more realistic graphic.

There are also a ton of errors, wrong statements, and contradictory inconsistencies in this article, to the extent it needs a severe edit and clean up. There also needs some general references to the text, rather than just high-powered and difficult to understand formal astrophysical papers.

- There is no mention of Walter Baade in 1940s who come up with the ideas of different populations.

- It mentions Pop III stars, which are basically theoretical, but sacrifices the important development of differentiating between Population I and II.

- Section on "Stellar populations", should be mostly removed or greatly summarised, especially paragraphs 2,3 and 4. This should be then moved to the sub-paragraph actually on Pop III stars.

-In this same section, Paragraph 5 has many unsupported statement, without any supporting citations. It wrongly states.

"Across the Milky Way, metallicity is higher in the galactic center and decreases as one moves outwards. The gradient in metallicity is attributed to the density of stars in the galactic center: there are more stars in the centre of the galaxy and so, over time, more metals have been returned to the interstellar medium and incorporated into new stars. By a similar mechanism, larger galaxies tend to have a higher metallicity than their smaller counterparts."

This almost sounds like personal theory than almost anything else I've read. It is evolutionarily unsupported, and an presumably adopted from rejected ideas dating to the 1920s! (The figure discussed above reinforces this!) Furthermore, the reason Pop I stars exist is mostly due to the spiral arms and the density shockwave passing through the thin disk, while the even distribution of Pop II in in the hub and thin disk, apart from the orbital globular star clusters. Arianewiki1 (talk) 22:36, 12 January 2015 (UTC)

Important Fixes

"As the visible stars hold most of the matter in the universe in the form of hydrogen and helium,…"

This statement is quite wrong. Many sources.

According to Observable universe. Extrapolation from number of stars

"Ordinary matter (protons, neutrons and electrons) exists in ISM and IGM as well as in stars. In the reference, "The Cosmic Energy Inventory“, the percentage of each part is defined: stars = 5.9%, Interstellar Medium (ISM) = 1.7%, and Intergalactic Medium (IGM) = 92.4%.] Thus, to extrapolate the mass of the universe from the star mass, divide the 10^52 kg mass calculated for stars by 5.9%. The result is 1.7×10^53 kg for all the ordinary matter." .

I have therefore remove this statement for the article. Arianewiki1 (talk) 00:59, 13 January 2015 (UTC)

The article says; "metallic bonds are impossible within stars," then rather contradicts itself, saying; "and the very strongest chemical bonds are only possible in the outer layers of cool K and M stars. Earth-like chemistry therefore has little or no relevance in stellar interiors. "

Most of the atoms in stars are in a plasma state. The core is essentially nuclei in the Fermi Sea, with chemical bonds can form in the low density stellar atmospheres,. I.e. Zirconium Oxide.

This whole statement in unnecessary and is very confusing.

Bonds in compounds in K and M stars are weak, due to the temperatures by changing the chemical disassociation balance.

Only "This term should not be confused with the usual definition of "metal";" is relevant to the reader, which I have changed by adding the word "physical" I.e. "This term should not be confused with the usual physical definition of "metal"" I have removed the rest. (It doesn't need a citation, as the link to metal is self-explanitory. Arianewiki1 (talk) 01:26, 13 January 2015 (UTC)

Repairing this text is extremely difficult, because the facts are mixed with either speculation or unverified text. Those having tags of citation required are sentences I haven't been able to verify. (Much of what I have recently read and know, I would eliminate 90% of the citation required sentences.) I hate to say it, but it seems most of the text lacking citations was likely written as personal theory. Most circumstances, it would be best to just delete it, and start again.

Also, much of the problems with this article is that metallicity is only partly related to the Population types (though it is important.) Metallicity is actually far more important in the process of stellar evolution, which changes over time. Also the initial quantity of metals significantly affect the evolution of stars, their temperatures, and their ages. I.e. Cepheid variables can be divided by metallicity. (The article doesn't mention this at all.) Another is where stars are finally placed on the main sequence. (not mentioned here either.)

I think it would be much better if we keep the summary of the population classes, and the more technical details of the three population classes be made into separate articles - especially the Population II stars, which is of current interest.

Any disagreement in doing this? Arianewiki1 (talk) 09:48, 15 January 2015 (UTC)

ReSplit into Metallicity and Stellar populations

The previous merge has created a confusing article that seems more about stellar populations. We should probably rename this to stellar populations and extract a shorter article on metallicity ? - Rod57 (talk) 12:52, 8 April 2015 (UTC)

Actually the reverse. Stellar Populations are talked about in the later paragraphs, and these should be placed into individual pages. Metallicity was later defined after Stellar Populations, and this is why this article has evolved this way. I have earlier attempted to make this article more readable, but agree it should be split. (Note: I am unsure how to make new article pages, so some help would be required.)

Four new articles should be created and linked. Namely, "Stellar Populations", "Population I", "Population II" and "Population III" (The last one being probably the most important, and the most popular in literature at the moment.)

Cheers. Arianewiki1 (talk) 22:31, 8 April 2015 (UTC)

Why would you need to split this not very long article into four? It makes no sense. Serendi^podous 22:34, 8 April 2015 (UTC)

@Serendipodous: @Rod57: So what do you actually proposing to call these three stellar Populations as a group? Arianewiki1 (talk) 15:09, 10 April 2015 (UTC)

Since I merged it in the first place, I'm not fond of the idea of splitting it; however, if it must be split, I would do what @Rod57: said: create an article on Metallicity and leave the rest under Stellar population. 16:09, 10 April 2015 (UTC)Serendi^podous

I think best to split to just 2. It might be simpler to just extract the stellar population content into a new stellar population article (currently a redirect) and split the talk page content to match (and more guidance at Wikipedia:Splitting ). My rational for the split would be that the two topics are quite distinct. It seems to me that metallicity is a technical measure that is just one of the factors used to characterise stellar populations. And there is ample material for 2 separate articles. I've added {{Split-apart|Metallicity|Stellar population}} to the main page. - Rod57 (talk) 09:16, 11 April 2015 (UTC)

I agree that a split into two articles is a good idea. I'd do it now if I had time but if it hasn't been done before I return to normal editing I'll get around to it. Sam Walton (talk) 18:51, 5 May 2015 (UTC)

I've split the article--Robert Treat (talk) 02:34, 6 July 2015 (UTC)

Great, but the maths is now quite unreadable. Arianewiki1 (talk) 08:47, 6 July 2015 (UTC)

Missing information / redirects

I came here to find out the definitions of Population I and Population II, and failed. The article says that the terms are related to metallicity, but does not say specifically what they mean. That's unfortunate, since the terms redirect here. At the very least, the article could describe the differences in metallicity that characterize the two classes, in a more definite way than merely saying that Population II stars are less metallic. Looie496 (talk) 14:50, 1 August 2015 (UTC)

Eh? If you were looking for "I came here to find out the definitions of Population I and Population II", then why look under metallicity instead of Population I or Population II? Metal content of stars is parameter that is spectroscopically measured, and is really unrelated to the Population of stars as their definition was originally based on their location in the galaxy. It was later found the older stars were metal-wise poor than those formed more recently in the spiral arms. (This is why the article was recently split.) So please explain how "...merely saying that Population II stars are less metallic." contradict what I've just said or what you are expecting? Arianewiki1 (talk) 19:01, 2 August 2015 (UTC)

Probably via one of the several redirects here, such as Population I and II (I got here via Hyperstar). These and maybe other incoming links need to be fixed following the split. --92.27.34.75 (talk) 14:32, 6 October 2015 (UTC)

Sorry, I somehow missed the response on August 2. I don't remember exactly which redirect brought me here, but even using the current redirects for Population I and Population II the same point applies: the Stellar population article describes some of the properties of those populations but don't actually define them in an explicit and specific way. It says they are defined in terms of spectral properties -- but how, precisely? Looie496 (talk) 14:46, 6 October 2015 (UTC)

Chemical Reactions- Lede

As has been stated already (see #1 Corrected a Statement on this talk page), it is false to claim that chemical reactions do not occur in a star. The sentence "The rationale for the astronomical usage is that in the high-temperature and pressure environment of a star, atoms do not undergo chemical reactions and effectively have no chemical properties, including that of being a metal as usually understood." is RISIBLE!!!!! "The rationale" is HISTORICAL, and has little to do with our current understanding of the physics and chemistry of stars' photospheres. As far as me offering justification for my (obvious to anyone who has the least bit of knowledge of the subject) claim that the article is false, I offer this quote from another Wikipedia article:"The hydrogen anion is an important constituent of the atmosphere of stars, such as the Sun. In chemistry, this ion is called hydride." Which refutes both the claim that chemistry doesn't "happen" in stars, and that atoms do not "undergo chemical reactions". It is true, and is perhaps what the author meant to say (but see below) that at sufficiently high temperatures of a stellar interior, no meaningful chemistry occurs because no chemical species is stable at those energies. The problem with simply modifying this stupidity is that with the exception of spectroscopy of supernovae, the stellar interiors (below the photosphere) are not directly observable. That is, it is certain that the astronomers who coined and/or first used the term were NOT discussing the stellar interior! And don't get me started on "metals as usually understood" ("usually"? by who? grade school drop-outs and the illiterate? Who determined that the "usual" understanding was? If I show people an iron nail completely turned to rust, will they "usually" say that there's no metal there?) Confusing physical state with chemical 'nature' is a grade school level blunder. I'd guess that an enormous number of "chemical" reactions are going on in the high pressure stellar interior, but the products aren't stable - life times are very short at the temperatures of those interiors. I agree that (as far as I know) the chemical reactions in a star's core does not influence the properties and processes going on there in any meaningful/useful way. I am not at all sure that there are (theoretically) no significant chemical reactions and/or molecules or molecular ions in the coldest stars below their photospheres. That means that even "interior" is problematic. No "chemical properties"? wow. So, a hydrogen cation doesn't have a emission spectra? Rubbish, remove the sentence - it's beyond salvation.Abitslow (talk) 11:11, 22 June 2016 (UTC)

Thank you for sharing this. I agree completely, it is false to claim that chemical reactions do not occur in a star.Trilliant (talk) 17:46, 7 September 2016 (UTC)

Calculation and HII Region Updates + Future

Did some restructuring and added info about common methods of calculation (photometric method) as well as info on metallicities in HII regions. For future editors - it would be good to expand the 'Metallicities of various astrophysical objects' section to explain more(at a high level):

- Stars
  - how stellar metallicities are observed and calculated, common values, etc. 
- HII Regions
  - 12 + log(O/H) method and origin
  - Obstacles in observations (e.g. degeneracies, observational limits / high redshift problems)
- Galaxies
  - metallicity gradients of galaxies (what are they, how are the observed and calculated, common values)
  - the mass metallicity relationship
  - metallicity evolving with redshift

Ariannasage (talk) 18:31, 13 June 2018 (UTC)

Proposed change in nomenclature

I don't like it that "metal" has two distinct definitions. One is used by chemists, most other scientists, and the general public. It means certain chemical elements, like iron or aluminum. The other is used by astronomers and astrophysicists, and it means any element heavier than helium, that is, lithium on up.

I propose that the elements of the latter definition be referred to as "mettals". It would be pronounced the same, but spelled slightly differently. This article would be renamed "Mettallicity", and so forth.

My purpose right now is to foment a debate on this matter. I would like to hear any reactions to this proposal.Josh-Levin@ieee.org (talk) 02:46, 30 September 2020 (UTC)

Conversion Formula, Please

Please provide the formula to convert [Fe/H] to Z, and back. 2601:441:5000:ADF0:890B:1DDD:CA4F:6D9B (talk) 15:18, 27 July 2023 (UTC)

Two different things, not strictly possible to calculate one from the other. Z is the number fraction of all elements other than hydrogen and helium. [Fe/H], strangely enough, is the log of the number fraction of iron relative to hydrogen, relative to the solar value. You could assume that the relative proportion of iron is the same as the relative proportion of all elements heavier than helium, but it isn't strictly and in practice can vary an awful lot. There used to be a section giving exactly this relation, but it was uncited and somewhat empirical (but not wrong). Just to save you a click, it basically amounted to A[Fe/H] = logZ + B, where B is 1.699 (depending on Z⊙, say 0.02) and A depends on the relation between Z and Fe, but generally works out between 0.9 and 1.0. Lithopsian (talk) 16:31, 27 July 2023 (UTC)