Talk:Stellar evolution

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In the section for low mass stars, it says "A star of less than about 2.6 space and solar mass.."..guess there is a problem here...could someone correct this? —Preceding unsigned comment added by 210.212.168.161 (talk) 14:36, 29 November 2010 (UTC)

 Done — Better now, four years later? The sentence is no longer there. TNKS, Charles Edwin Shipp (talk) 16:45, 13 April 2014 (UTC)

Undefined Symbol

The symbol \begin{smallmatrix}M_\odot\end{smallmatrix} for solar mass is used without definition. TommoB (talk) 01:38, 1 April 2011 (UTC)

You're right. Corrected that. -- Stiip (talk) 12:50, 24 June 2011 (UTC)

Layout

The image "Life cycle of the sun" quite at the beginning of the page (http://en.wikipedia.org/wiki/File:Solar_Life_Cycle.svg) scrambles layout at any resolution below 1280 x 1024 in FF 5. Don't know whether that's a FF issue (IE in this case handles it better) only, but is there any chance to correct that? (I'm not a CSS native so I won't change the code right away.) -- Stiip (talk) 12:40, 24 June 2011 (UTC)

It'd be nice if that image could be modified so that it has a vertical orientation rather than horizontal; doing so would probably make it a better fit for many Wikipedia page layouts. Maybe I'll give it a shot... Regards, RJH (talk) 14:37, 12 September 2011 (UTC)

Massive Stars

Stars cannot be more than about 120 solar masses because the outer layers would be expelled by the extreme radiation. Although lower mass stars normally do not burn off their outer layers so rapidly, they can likewise avoid becoming red giants or red supergiants if they are in binary systems close enough so that the companion star strips off the envelope as it expands, or if they rotate rapidly enough so that convection extends all the way from the core to the surface, resulting in the absence of a separate core and envelope due to thorough mixing

Not true....

http://io9.com/5596886/the-largest-star-ever-found-is-300-times-bigger-and-10-million-times-brighter-than-the-sun

Thank you and keep up the good work peeps — Preceding unsigned comment added by 41.145.81.60 (talk) 09:12, 23 November 2011 (UTC)

Massive star pre-supernova state core composition discrepancy

Silicon burning process says that the end product of the nuclear burning process is Nickel-56 with minutes of Zinc-60 produced. It also says that silicon-burning process lasts about a day or so. Half-life of Nickel-56 is about 10 days and then decays into cobalt-56 with a half-life about 77 days which decays into iron-56. The discrepancy is that various images on Wikipedia show that pre-supernova state star's core consists of iron, rather than nickel and cobalt, despite only small amounts of iron being created within a day before supernova occurs. Unless a star releases energy via decay of nickel-56 and cobalt-56, should the main element in star's core be nickel with some cobalt instead of iron? --Artman40 (talk) 11:44, 25 June 2012 (UTC)

The Silicon burning process article says the supernova explosion occurs once the iron starts to be fused with helium to produce nickel. Hence it should be an iron-nickel core. My understanding is that additional radioactive elements are produced during the explosion itself. Regards, RJH (talk) 15:11, 26 June 2012 (UTC)

Evolutionary tracks

Do we have an entire article about stellar evolution without a picture of evolutionary tracks on the HR diagram? The closest is that absolutely horrible and inaccurate indication of the sun's evolution. This picture is better although not without it's faults: http://en.wikipedia.org/wiki/File:Stellar_evolutionary_tracks-en.svg Lithopsian (talk) 22:24, 14 November 2012 (UTC)

Ugg. That solar evolution track is pretty hideous. Yours is good but doesn't replace it. If we can't find a free source track, I'm tempted to generate one using Mesa, but fear that would constitute WP:OR. --Yaush (talk) 00:08, 15 November 2012 (UTC)

I have created a blank evolutionary tracks image and put it into this article with annotations. It looks a little bare at the moment and needs a better caption, but I think it is the start of something useful for this article. Anyone can edit the annotations so we can easily make it a lot better, or use it in different ways in different locations. The solar track image is still there for comparison, but it is so horrible that I'm going to delete it soon whatever else happens. Lithopsian (talk) 18:56, 21 November 2012 (UTC)

I appreciate the much-improved image. However, I might suggest that you get it ready for display with edits in your userspace before putting it in the article, as getting that right will require a good bit of tweaking. A couple comments: 1) The image is too wide at 500px; it takes most (but not all) of a column). 350px would be better. I would have made that change myself, but it requires modifying all the annotation indices too. 2) The title should not be "proposed stellar evolutionary tracks image"! —Alex (ASHill | talk | contribs) 21:48, 21 November 2012 (UTC)

I improved the caption. Too much? The width is tricky. I tried 350px (easy, just downsize all the annotations by 0.7) and I couldn't read it clearly. Remember that annotated images can't be expended like a thumbnail, what you see (or can't see) is what you get. Lithopsian (talk) 00:15, 22 November 2012 (UTC)

Is this how to use the talk page? Sorry if this is off topic, but I've never used one before. FluxLightSpectrum (talk) 05:05, 7 January 2017 (UTC)

star generations

It would be great if someone could do a section (better yet - a new article) about the different generations of stars (currently, Star Generation goes to the James Brown song!) and what their properties are. For example, to discuss how first generation stars and their respective solar systems have only the lightest elements such as H and He, their comparatively short lifespans and how they are likely to only have gas-giant "superearths" orbiting at extremely close distances as planets; how after a supernova you get heavier elements in the second generation, what type of planets are likely; how a new supernova leads to generation III with the heaviest elements, etc; and to discuss what the likely timespans are for each generation and between the generations... and to say when (second/third generation...?) life is likely to occur thanks to the presence of the elements C, N, O, P, etc...

So, please someone in the know create such a section, or better yet new article. Thanks! BigSteve (talk) 10:03, 16 February 2014 (UTC)

Already exists. See Population I, for example. That is the correct terminology. Maybe those sections could be expanded. Lithopsian (talk) 14:32, 16 February 2014 (UTC)

Thanks! I knew I'd read it way back when, but spent ages looking for it yesterday in vain. I disambig'd the song page. Cheers! BigSteve (talk) 09:33, 17 February 2014 (UTC)

Plasma Recombination

Why is there no mention of plasma recombination or heterolysis? Are we talking about stars here or pseudoscience?Wavyinfinity (talk) 19:37, 5 November 2014 (UTC)

This is just plainly a preposterous proposition. This has absolutely nothing to do with stars or stellar evolution at all. Arianewiki1 (talk) 06:43, 24 March 2015 (UTC)

Dreadful : Stellar Evolution, Figure: Evolution of a Sun-like star & Text

@John: As a former teacher and educator on Stellar Evolution, I am appalled at the standard of quality in this article. There are so many errors and contrivances of the truth, that it fails to meet even the basics. It really doesn't meet the standards of the average high school student, who if reading it in its present state, would see it does not match their curriculum. I've already greatly fixed some of the introductory paragraphs text here to be factual, but after this, the text is a bit of a mishmash of facts and false statements. For example;

Now under the sub-title "Red-giant branch phase" is a Figure "Evolution of a Sun-like star" is just wrong. The figure's curve shows the H-R evolution curve of a star above 2.25 solar masses (2.3 in some references), which undergoes helium core burning. The Sun is only 1.0 solar mass, and but rises dramatically in luminosity in a near straight line. Hence, ending on the AGB. This is clearly shown in the earlier figure in "The evolutionary tracks of stars."

Option: Either change the caption, then fix the Fiure's text, or just remove the figure entirely.

Worst here is the statement "When the temperature and pressure in the core become sufficient to ignite helium fusion (triple alpha ignition), a helium flash will occur if the core is largely supported by electron degeneracy pressure (stars under 1.4 M☉)" is quite wrong. Stellar evolution ignition of helium does not occur in stars below 2.25M☉ NOT 1.4 M☉, which applies to white dwarfs and very heavy +15☉supernova cores. More precisely, helium flashes also only occur in stars above about 3.0 solar masses, not 2.25 or 1.4!! When a star starts helium burning from the new energy source, making the star shine again, and this is why it moves from right to left, increasing in surface temperature and but not changing in luminosity, mostly as the star also shrinks in size. When the star (again) crosses the instability strip, these stars become pulsating Cepheids. (The Sun will not become a Cepheid.)

These basics of stellar evolution still apply, and now have been only slightly refined.

Also reference 11 by Alan C. Edwards (1969) is now an unreliable source, which is updated significantly by many others since.

The standard and simple source for the basis of stellar evolution should be something like Iben, I. Jr (1985) "The life and times of an intermediate mass star - In isolation/in a close binary" [1] , which has all the basics and the figures to match, and can be used to be extended or refined using later sources. This useful reference has been deleted for some reason here. Looking at Figure 1 in this reference, by Iben (1985) shows clearly this fact very simply. Fig 2, shows what is happening in the core.

Later, under sub-title "Asymptotic-giant-branch phase" states "After a star has consumed the helium at the core, fusion continues in a shell around a hot core of carbon and oxygen." This is also wrong. CNO-cycle applies to star above 15 solar masses, and burning CNO does not happen in the Sun at 1.0 solar masses. Amazingly, in both sections, there is no absolutely differentiation between various masses and the evolutionary effects that we observe. I.e. Saying "star" or "a star" is just inadequate editing.

The article says, under 'Massive stars'; "If the core of the star is not too massive (less than approximately 1.4 M☉, taking into account mass loss that has occurred by this time), it may then form a white dwarf (possibly surrounded by a planetary nebula) as described above for less-massive stars, with the difference that the white dwarf is composed chiefly of oxygen, neon, and magnesium." is plainly gobbledygook and is wrong and has at least five errors within one single sentence!

This STELLAR EVOLUTION page should be blocked except to auto-confirmed users (hence pinging John), and we should seek someone with formal expertise on the subject. Stellar Evolution is the ultimate king-pin in understanding about the nature of stars, and is a crucial part of education and knowledge on a cornerstone of important astrophysical theory. I've already counted more than two dozen simple errors in this page, which continues to have reedits by individuals that do not have the necessary knowledge to edit properly here. Worst every single figure presented, either is wrong or has incorrect captions. (Except the one showing 'The evolutionary tracks of stars' , but there is notable explanation of the abbreviations within the graphic.)

I would also openly request, that if editors are to make changes in the article structure, they should first discuss it within the talk page.

I'm happy to change the text here by a drastic edit, but I'd appreciate some open discussion of the flaws before I attempting to do so. Furthermore, there need some development on how this centrepiece article relates to astrophysical theory. I.e. The relationship to metallicity is a good example, as highlighted by BigSteve in the section 'Star generations' above. Arianewiki1 (talk) 08:26, 24 March 2015 (UTC)

Although so much thought and effort might be better directed at improving the article, in this case I would request that you don't do so until you get your facts straight. For example, your description of which stars undergo a helium flash is exactly opposite to the actual cases. Stars *below* 2.3 M_☉ (more or less, but Iben says 2.3) undergo a helium flash followed by triple alpha helium fusion in the core (followed by helium shell burning in the TP-AGB phase), while stars with higher masses ignite helium smoothly before the core becomes degenerate. Read Iben (1985) if you don't believe me. Lithopsian (talk) 11:47, 24 March 2015 (UTC)

Wow. Of all this text, and you have pick this as a bone of contention! Of all the gross errors in this whole article, and this is the most important one? The main article says stellar evolution ignition of helium does occurs in stars at 1.4 M☉, so now is this true? My point is that the evolutionary behaviour of stars is based on the masses of ~2.3 M_☉ and 3.0 M_☉. There is also a big difference between helium core burning and helium shell burning. (See Iben pg.5, and figure 1 & 2). However, the article is inferring that 1.0 M_☉ mass stars do this, which isn't quite true. (This is why Figure "Evolution of a Sun-like star" is quite wrong.) After stellar evolution is complete, a single 1.0 M_☉ produces a Helium white dwarf of ~0.61.0 M_☉. This applies to 1.4 M_☉ too. Stars above 2.3 M_☉ solar masses produce CO white dwarfs. Solar like stars have little conversion of CNO in their cores (or shells) - hence they are Helium white dwarves.

This reply will probably get lost in all the ranting, but let me clarify. My one example was just pointing out one of your most glaring errors, blatantly contradicting your own preferred source. Almost everything you have stated about the evolution of stars is incorrect and can easily be checked in numerous textbooks including the ones you seem to regard as gospel. I have not contradicted each point individually because it would be a waste of time and space. Lithopsian (talk) 13:55, 25 March 2015 (UTC)

Yes. Stars JUST *below* 2.3 M_☉ undergo a helium flashes, stars above 3.0 M_☉ undergo helium core burning. For 1.0 M_☉ it is pretty trivial.

Yet the whole "Stellar Evolution" article doesn't even mention it!!

As for "...in this case I would request that you don't do so until you get your facts straight." Um. This is a talk page, not an article edit. Clearly there are many gross errors here that need correcting. (Issues with editing the main page, then feel feel quite free to correct it or discuss it here.)

Q: Under the sub-title "Red-giant branch phase" is a Figure "Evolution of a Sun-like star", is this figure caption correct? Arianewiki1 (talk) 13:22, 24 March 2015 (UTC)

I agree with Lithopsian. Arianewiki1, I'm afraid that essentially every one of your comments is inconsistent with the sources (and I would assert wrong, but my opinion counts for no more or less than yours). And the biggest point: you fundamentally misunderstand how Wikipedia works. Administrators don't protect pages because the content is wrong. That makes it nearly impossible to improve the page, since it locks out "knowledgable" editors as effectively as it locks out unknowledgable editors (and those who make up words). And, of course, it's not the claimed expertise of the editor that matters (though I could claim similar or stronger credentials to what you have claimed, FWIW); it's what the reliable sources say.

Specifically: The existing evolution of a sun-like star is reasonably accurate. You're plain wrong on the helium flash, as already noted. Agreed that Edwards (1969) could be replaced with a more recent ref and the numbers in the sentence it's used for might change, but the qualitative idea hasn't. AGB/CNO cycle: the CNO cycle is part of H -> He burning, not C burning. (It's the faster, higher temperature H -> He burning process by comparison to the proton-proton chain.) So your AGB comment is irrelevant to the CNO cycle. The sentence that you say "is just plain gobbledygook" is mostly or entirely correct, though it (like much of the article) should have a reference; pretty much any intro astronomy textbook will do). I completely agree that stellar evolution is fundamental to pretty much everything about astronomy, but I disagree that this article has major factual errors (having given it a quick re-read). I agree that more discussion of metallicity effects would not be a bad thing, but the article is right to focus on mass as the primary effect. —Alex (Ashill | talk | contribs) 12:14, 24 March 2015 (UTC)

"I agree with Lithopsian. Arianewiki1, I'm afraid that essentially every one of your comments is inconsistent with the sources (and I would assert wrong, but my opinion counts for no more or less than yours)." Wow, that's a glowing endorsement. (Straight off the top, I'm put in my box. Care to actually qualify this here? Are you really judging me or the article here?)

I think this page needs some protection so that the article can be brought back into line as a level-4 vital article in Science article. At the moment it is far from it. Looking at the last 500-edits makes it clear how this article has degraded. Experienced editors, those assumed with many edits, which only what an auto-confirmed editor is defined as. It would just save the issues of the causes of the degradation. 'Expertise' has little do do with this, though a expert on the subject would be very useful. (I actually never said it should be me, though.) You disagree. That's OK. (talk) 16:06, 24 March 2015 (UTC)

I misread your comment; I thought you were requesting full protection. But read WP:PP; there's no evidence of vandalism, so I'm not sure there's a good policy reason to use even semi-protection; anonymous editors are often helpful too. —Alex (Ashill | talk | contribs) 17:55, 24 March 2015 (UTC)

"The existing evolution of a sun-like star is reasonably accurate. You're plain wrong on the helium flash, as already noted." Now who says otherwise. The point is, how significant is the helium flash in the core? Is it observable or theoretical? The quantity of CNO produced here is absolutely insignificant, which is why the stellar atmosphere that is discarded in most hydrogen and helium with a tiny fraction of other metals. The remnant core, is most helium, being the product of hydrogen burning (fusion) when it was on the main sequence. It's white dwarf is a helium white dwarf weighing 0.6 solar masses. Stars above ~3.0 produce mostly CO white dwarf stars weighing about 0.8 solar masses. Stars above about 3.0 solar masses burn lots of helium, stars below 2.3 burn very little. The article is wrong, because it doesn't say that, and the Figure "Evolution of a Sun-like star", shows a evolution path for a star bigger than 3.0 solar masses.

"AGB/CNO cycle: the CNO cycle is part of H -> He burning, not C burning. " Yes, but again it is trivial. Quantitatively, for the Sun, the amount is trivial. Hence, why a He core produces a helium white dwarf. Also what is happening in the RG phase (red giant phase) is different from what is happening in the AGB phase. The quantities converted are based on the temperature and density, and it is actually when helium shell burning (shell flash) is envelope that is caused by pressure variation. after this the star 'descends' from the red giant branch. For a helium flash to occur, the mass of the core must be about 0.5 solar masses. Due to this, so red giants never obtain any helium ignition at all, mostly because of stellar winds that blow away the mass. In the AGB phase, is the time when these additional fusion events take place, and not the earlier red giant phase

If there is helium core burning is star greater than 3.0 masses, helium flashes can occur AFTER it, as the shells can reach the critical density. but these are thermally unstable. These lead to thermal pulses. Arianewiki1 (talk) 16:06, 24 March 2015 (UTC)

There is helium core burning in 3 solar mass or larger stars; it just doesn't start with a helium flash (because the core gets hot enough to start core helium burning before the core collapses enough to be degenerate). —Alex (Ashill | talk | contribs) 17:55, 24 March 2015 (UTC)

"The sentence that you say "is just plain gobbledygook" is mostly or entirely correct, though it (like much of the article) should have a reference;" Um. This is the Talk page, not the article page, BTW. Where talking generally here, not specifics, and this is why I'm starting with an open discussion before the needed editing. Arianewiki1 (talk) 16:06, 24 March 2015 (UTC)

There may be a misunderstanding here; I meant that the sentence currently in the article is (I think) correct but unreferenced; I didn't mean to say that what you say on the talk page needs a reference. —Alex (Ashill | talk | contribs) 17:55, 24 March 2015 (UTC)

"...I disagree that this article has major factual errors (having given it a quick re-read)."

Why? Based on what? Adjudged on what? Saying "I'm afraid that essentially every one of your comments is inconsistent with the sources (and I would assert wrong, but my opinion counts for no more or less than yours)." What 'sources' do you refer? Arianewiki1 (talk) 16:06, 24 March 2015 (UTC)

The sources used in the article (though that statement is not attributed) as well as any standard textbook. I know Zeilik & Gregory best; I also use Prialnik. I will try to add refs for that statement and much of the rest of the article when I can (which probably won't be today as I don't have access to my library). —Alex (Ashill | talk | contribs) 17:55, 24 March 2015 (UTC)

If all my comments are inconsistent with the sources, without real proof, then I can only assume you comments are just a put down? If you saying; "The sentence that you say "is just plain gobbledygook" is mostly or entirely correct, though it (like much of the article) should have a reference;", then logically, saying "all my comments are inconsistent with the sources" are therefore already false.

Heck. I actually taught stellar evolution! Your own credentials to make these broad sweeping statements I really look forward to hearing about. Arianewiki1 (talk) 16:06, 24 March 2015 (UTC)

I should not have brought my credentials into the discussion; I apologize for that and have struck my comments. It is the sources that matter. —Alex (Ashill | talk | contribs) 17:55, 24 March 2015 (UTC)

Further examples the first sentences, in sub-title "Red-giant-branch phase";

1) "The red-giant-branch phase of a star's life follows the main sequence" Wrong. The progression between these is the Hertzsprung gap. The text is also ambiguous, because it implies stars moves down (or up) the Main Sequence. This is a very common is misconception, that I've seen too many times. The star evolves away or across from the main sequence, from left to right, before meeting the bottom of the RG Branch. Arianewiki1 (talk) 16:06, 24 March 2015 (UTC)

Fair; there is a very brief time between the main sequence and the RGB. (It appears that I wrote that phrase, but you're right about the distinction. WP:SOFIXIT.) —Alex (Ashill | talk | contribs) 17:55, 24 March 2015 (UTC)

Although it is in fact true that the RGB phase follows the main sequence in that it is after the main sequence, even if there is the very-short-lived time in the Hertzsprung gap. —Alex (Ashill | talk | contribs) 20:19, 24 March 2015 (UTC)

2) "Initially, the cores of red-giant-branch stars collapse, as the internal pressure of the core is insufficient to balance gravity." Wrong. It is actually also the radiative pressure that stops the core collapsing, breaking the stars equilibrium when the energy source is diminished, then the star reacts to gravity. Also radiative pressure isn't a constant.

3) "This gravitational collapse releases energy, heating concentric shells immediately outside the inert helium core so that hydrogen fusion continues in these shells." Wrong. The gravitation collapse heats the core by pressure, increasing the reaction rate. The shells are formed by diffusion, where the lighter elements rise and the heavier ones fall. The reaction rate in the core heats the outer shells, and can cause fusion reactions. However, the core is also producing energy too, but at a diminished rate. This energy causes the winds, that blow the material back into interstellar space. It is at the end of in the AGB stage, when the core stops generating energy by fusion, where the radiative energy output is caused only by gravitation contraction.

4) "The core of a red-giant-branch star of up to a few solar masses stops collapsing when it is dense enough to be supported by electron degeneracy pressure. Once this occurs, the core reaches hydrostatic equilibrium: the electron degeneracy pressure is sufficient to balance gravitational pressure." Eh? ALL Cores and ALL stars do this during the whole lifetime of the star!! (Should this also be related in terms of mass, temperature or density, energy transport, opacity, etc.) Why just red giants? The cause of the collapse is more simply the reduced energy production by fusion.

5) "The core's gravity compresses the hydrogen in the layer immediately above it, causing it to fuse faster than hydrogen would fuse in a main-sequence star of the same mass. This in turn causes the star to become more luminous (from 1,000–10,000 times brighter) and expand; the degree of expansion outstrips the increase in luminosity, causing the effective temperature to decrease." Yes, but explain it is simpler terms Again, the hydrogen layer is caused by diffusion and the heavier elements sink, lighter ones rise.

6) All these above statement are dependant on the mass of the star in question. What is stated are "a few solar masses" or "a main-sequence star of the same mass." It conveys, like the associated Figure, the wrong impression. Worse, as it implies later, not all red-giant-branch star undergo these process. I.e. The helium flash or helium core burning.

A good main book on Stellar Evolution and the red giant phase is "An Introduction to the Theory of Stellar Structure and Evolution" By Dina Prialnik 2nd Edition Pub. Cambridge University Press (2009) pg. 146-152 [It is a recommended and popular undergraduate textbook] Another is by Maurizio Salaris & Santi Cassisi, "Evolution of Stars and Stellar Populations, Pub. John Wiley & Sons (2005). Arianewiki1 (talk) 16:06, 24 March 2015 (UTC)

I agree re the Prialnik book; don't know the Salaris & Cassisi one. —Alex (Ashill | talk | contribs) 17:55, 24 March 2015 (UTC)

To all: Wikipedia:Talk page guidelines#concise.   ~ Tom.Reding (talk ⋅contribs ⋅dgaf)  16:37, 24 March 2015 (UTC)

Noted, and I'm trying. —Alex (Ashill | talk | contribs) 17:55, 24 March 2015 (UTC)

The main evolutionary track schematic of the Sun (File:Evolution of a Sun-like star.svg) is correct (eg page 121 of this book), as it has a He-burning (horizontal branch) and AGB phase. However, this image File:Zams and tracks.png does not have a horizontal branch or AGB phase for the Sun. @Lithopsian:, it looks like you created that image; possible to fix? —Alex (Ashill | talk | contribs) 21:44, 24 March 2015 (UTC)

I simply modified an earlier ZAMS diagram to remove some superfluous annotations so as to provide a basis for making more diagrams. The tracks are unchanged from the earlier diagrams. The tracks for loss mass stars appear to stop at some arbitrary point far short of the end of their lives. Lithopsian (talk) 13:58, 25 March 2015 (UTC)

OK. I've clarified in the caption. —Alex (Ashill | talk | contribs) 14:16, 25 March 2015 (UTC)

Alex. This book figure you highlight is plainly wrong. It likely is exaggerated just to show the stages, but it is certainly not exampling the sun's evolution. File:Evolution of a Sun-like star.svg therefore, whoever created this, is also wrong.

The red giant bump (RGB) is minuscule compared to this I.e. (See Figure 1.4 Beccari & Carraro, "Introduction to the Theory of Stellar Evolution" (2014) [2] Difference here is only about 20K NOT 2000K in the article's figure. Longest possible duration is one million years NOT 100 million!! Also compare this to Fig. 1.5, which is a 2.4 solar mass star, and Figure 1.7 shows the differences. This same paper says and explains this all this very well, ;

"It is important to specify that the He-flash is still not the phase of helium burning: only 5% of that element is consumed during the flash. The stable helium burning in the core according to the reaction starts along the so called Zero Age Horizontal Branch (ZAHB) defined, in the HR diagram, as the locus of points in which a star is positioned, in a very short time (10^6 yr), once the helium flash is finished. Notice that the ZAHB is located on the HR diagram at a lower luminosity with respect to the tip of the RGB, as a consequence of the expansion and relaxation of the nucleus of the stars after the He-flash."

It says on the page under Fig. 1.5; "Since the low-mass stars reach the tip of the RGB at constant mass of the nucleus, the location of these stars on the HB depends only on the mass of the envelope. In particular, the higher this value, and therefore the greater is the total mass of the star, the redder the point of the ZAHB in which it is positioned. In fact a thicker envelope is able to “shield” better the star, which then appears cooler and redder."

Plainly, Helium burning in the core does not happen (if it does, it is trivial) with the RGB conditions of the future Sun, else it would make a carbon-oxygen core white dwarf. (The sun produces a helium white dwarf - many sources.) Furthermore, the energy produced cannot be as hot as it was on the main sequence, because the efficiency of the Helium burning is a tenth as productive as hydrogen burning. According to our graph this last 100 million years! (If true, all the globular cluster HR diagrams would have this stars drawn out in the plots, which isn't seen. Also the book figure also plots magnitude versus log effective temperature, while out graph is luminosity versus linear temperature. I will have to do some more background, but most of the Java software shows similar variances. Evidence suggest both figures are incorrect. Arianewiki1 (talk) 02:43, 25 March 2015 (UTC)

The figure I highlight is almost exactly the same as Figure 8.19 from Prialnik's book (2000 edition), which is in turn adapted from Iben (1985). The RGB phase of a 1 solar mass star ends with a "core helium flash". Her Figure 8.19 includes the horizontal branch phase (with a thick line, meaning "long, nuclear burning evolutionary phases") as He -> C + O. Read her section 8.5, "Helium burning in the core", of which the first 2 paragraphs are about the core helium burning in 0.7-2 solar mass stars. Finally, on page 162, she notes that stars of initial masses 1 solar mass < M < 9 solar masses form CO white dwarfs, plainly contradicting your claim that stars <2.3 solar masses don't burn much helium. Note that Figures 1.3 and 1.4 of the reference you cite show only the main sequence, sub-giant branch, and RGB phases (as mentioned in section 1.3 and the caption to Figure 1.3); Figure 1.5 shows the subsequent, core helium burning horizontal branch. You're right that the helium flash is not when most of the core helium burning happens, but neither I nor the article say that. (The helium flash is the beginning of the core helium burning phase.)

I'm done going back and forth on claims on the talk page without any proposed edits. If you want to make improvements to the article, please do so. I've already added several references (tweaking the helium flash description in the process) and will continue to do so. It's much more productive to make cited changes to the article and then discuss if we disagree then to confront a wall of text on the talk page. —Alex (Ashill | talk | contribs) 13:58, 25 March 2015 (UTC)

@Arianewiki1: You might start by tagging specific claims in the article you object to with citation needed tags. That's much easier to address than a rant on a talk page. —Alex (Ashill | talk | contribs) 14:07, 25 March 2015 (UTC)

@Ashill:Thanks for the advice and suggestions. I so appreciate your responses to the Talk thread, and any future comments, I'll make them far more brief. If anything has come of this, it has made me more focussed on the issues here. It is crucial that this page is correct on many levels. Such discussion can only help. Thanx. Arianewiki1 (talk) 14:52, 25 March 2015 (UTC)

Speaking as a present educator, I strongly agree that this article is dreadful. The information the reader would be seeking often simply is not there or is very confusingly presented. The problem is the more serious as this article deals with an important and tricky subject. I am currently engaged in preparing educational material on stellar evolution and this article seems next to useless for that purpose. If I had the expertise to improve this article I would. I call on experts to urgently improve this article. Don't ask me what the specific problems are, they must be obvious to everyone who has even a basic insight into the subject. Asgrrr (talk) 00:20, 12 May 2016 (UTC)

Without specifics this comment is quite irrelevant, I am afraid. 194.230.147.232 (talk) 22:14, 9 March 2023 (UTC)

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• Added archive https://web.archive.org/20120204173630/http://www.dtm.ciw.edu/boss/definition.html to http://www.dtm.ciw.edu/boss/definition.html
• Added archive https://web.archive.org/20120608135141/http://www.mpa-garching.mpg.de/~hammer/lager/pair.pdf to http://www.mpa-garching.mpg.de/~hammer/lager/pair.pdf
• Added archive https://web.archive.org/20130402053638/http://space.newscientist.com/article/dn14968-first-pulsar-identified-by-its-gamma-rays-alone.html?feedId=online-news_rss20 to http://space.newscientist.com/article/dn14968-first-pulsar-identified-by-its-gamma-rays-alone.html?feedId=online-news_rss20

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Cheers. —^{cyberbot II}_{Talk to my owner:Online} 15:37, 27 August 2015 (UTC)

External links modified (January 2018)

Hello fellow Wikipedians,

I have just modified 2 external links on Stellar evolution. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

• Added archive https://web.archive.org/web/20030627124651/http://www.mpa-garching.mpg.de/HIGHLIGHT/2001/highlight0102_e.html to http://www.mpa-garching.mpg.de/HIGHLIGHT/2001/highlight0102_e.html
• Added archive https://web.archive.org/web/20030803015427/http://www.mpa-garching.mpg.de/HIGHLIGHT/2003/highlight0306_e.html to http://www.mpa-garching.mpg.de/HIGHLIGHT/2003/highlight0306_e.html

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This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 5 June 2024).

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Cheers.—InternetArchiveBot (Report bug) 23:51, 21 January 2018 (UTC)

History Section

An 'History' section has recently been added. It seems a bit off topic as it cover the Chronology of the universe more so than the history of stellar evolution. It originally included a sentence about the formation of heavier elements and the use op copper in Mesopotamia. Both statements were untrue and Mesopotamian metallurgy is very off topic. The one remaining sentence in the section includes no citation and contains little information. Does this section need to exist? If it must to exist it needs to be expanded and sourced. Kardoen (talk) 09:32, 1 October 2021 (UTC)

How about now? Lithopsian (talk) 20:06, 1 October 2021 (UTC)

Just like when I removed it before it got added back. This time it was even more gibberish.Kardoen (talk) 10:42, 2 October 2021 (UTC)

Just keep at it. Try to leave constructive edit messages, plus this talk page. Eventually they'll get the idea or get blocked. So far, it appears to be well-meaning, but not especially valuable. Lithopsian (talk) 15:18, 3 October 2021 (UTC)