Talk:Triple-alpha process

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⁸Be decay

The decay time of ⁸Be is about 10^-16 seconds and not 10^-6 seconds as far as I know. It says so here and here. 193.171.121.30 6 July 2005 15:33 (UTC)

It is, in fact, 2.6 x 10^-16 s. Ref.: Wong, Samuel S.M. Introductory Nuclear Physics, p. 16. Betaneptune (talk) 03:52, 25 December 2012 (UTC)

How about 8.7 x 10^-17 seconds in isotopes of beryllium article.WFPM (talk) 17:40, 7 February 2013 (UTC)

Whoever argues about such things as in the comments above do not know how difficult such measurements are to make, and that the digits like "8.7" and "2.6" are just estimates. The numbers listed above round off to 1.0 x 10^-16 for all practical purposes.98.67.97.54 (talk) 02:41, 6 September 2013 (UTC)

Helium flash

I'm surprised by the statement that the helium flash lasts minutes and burns a large percentage of the helium. My recollection is that it lasts seconds and does not burn a significant percentage of the helium. Can you give a citation? 128.165.87.144 23:30, 12 March 2007 (UTC)

A suggestion: the helium flash is comparable to a type 1a supernova. Mention the comparison, and link to the article: https://en.wiki.x.io/wiki/Type_Ia_supernova Johnm307 (talk) 18:11, 9 February 2020 (UTC)

4He + 4He ↔ 8Be + γ?

The text doesn't like a γ in 4He + 4He ↔ 8Be, but the diagram does. Should this be changed?

On that note, I made some consitancy changes to the page and noticed that it says "Be + He <-> C + γ + e", instead of "Be + He -> C + γ + e" (notice the difference in arrows). I'm assuming this is an error, but I am not a physicist, so I won't change it without confirmation. SkyLined (talk) 23:24, 2 March 2008 (UTC)

Another thing I noticed: "The net energy release of the process is 7.275 MeV." whereas the equations imply that "7.367 MeV" is produced... where does the difference come from? SkyLined (talk) 23:31, 2 March 2008 (UTC)

Presumably this is the net energy, i.e. add the energy produced by the two equations given. 141.211.184.143 (talk) 15:38, 9 March 2009 (UTC)

There's still an inconsistency between the text and diagram as to whether the first stage emits a gamma ray or not. Naively I imagine that it does not, but may be wrong. Either way, it should be consistent. Modest Genius ^talk 21:53, 4 July 2009 (UTC)

All you have to do is to apply the Law of Conservation of Mass-Energy, and you can figure it out about the gamma rays.98.67.97.54 (talk) 02:46, 6 September 2013 (UTC)

Diagram is wrong. Does not match text

Modest Genius is right. The diagram shows an incorrect reaction.

The initial reaction is endothermic. It is the inverse of Alpha decay. There are no other particles involved.

The text states that the second reaction produces an electron and a positron, but the diagram shows a gamma ray.--Bartosik (talk) 08:47, 7 October 2010 (UTC)

There may well be two channels for the release of energy after Be-8 combines with an alpha. 7 Mev is more than enough energy to create e+,e- pairs. SBHarris 17:33, 7 October 2010 (UTC)

The gamma ray on the first reaction is likely correct. Remember that in order to fuse, the two alphas have to overcome the coulomb barrier to get close enough. I'd expect the resulting Be nucleus to be in an excited state and have to emit a gamma to relax to the ground state.

That said, it's quite possible that my expectation is wrong about this. Does anyone have an astrophysics text handy? That should sort out the question very quickly. --Christopher Thomas (talk) 18:37, 7 October 2010 (UTC)

I read through one of the references: "Nuclear Reactions in Stars Without Hydrogen". It looks like your (Christopher Thomas) expectation is correct. Even though there is a overall energy loss in the first reaction, it requires 95 kev of input energy. Since the mass of Be-8 is 8.005305, and the mass of two He-4 is 8.005206, there is a net mass gain of 0.00099. Since 1 u = 1.49 x 10-10 J = 931 MeV, the extra mass equals 92.1789 kev of energy that stays with the atom as increased mass and leaves 2.8 kev to be released as a gamma ray. Contrary to my first assumption, it looks like the diagram is right, and the text is wrong.--Bartosik (talk) 11:40, 9 October 2010 (UTC)

That small an amount of energy might just end up as kinetic energy of the reaction products, actually. I have a friend who may have a textbook that specifically discusses it (I'll ask). -Christopher Thomas (talk) 09:40, 10 October 2010 (UTC)

Bartosik, Gamma Rays have energy greater than 100 keV. A 2.8 keV photon would be a soft X-ray. If the excited Be-8 state releases a 2.8 keV photon its NOT a gamma ray, and the diagram should show an emitted X-Ray instead. Or, as Christopher says, 2.8 keV is a modest kinetic recoil for a Be-8 nucleus, and no photon need be released at all? Zirconscot (talk) 14:59, 30 June 2012 (UTC)

Gamma rays are defined by their origin, not by their wavelengths. IIRC, there is one isotope (although not of helium) that is predicted to (it's not been observed to decay yet) emit gamma rays in the UV range! Double sharp (talk) 06:45, 8 September 2012 (UTC)

The triple alpha process in stellar nucleosynthesis does not involve gamma-ray emission in the reaction "He4 + He4 <-> Be8". Three astronomy textbooks:

1. Principles of stellar evolution and nucleosynthesis (p. 411-412, Clayton 1968):

"He4 + He4 <-> Be8

Be8 + He4 -> C12 + gamma" (based on the Fig 5-18, second gamma may be followed down to the ground state of C12).

2. Cauldrons in the Cosmos (p.390, Rolfs & Rodney 1988):

"The overall process can be looked as:

alpha + alpha <-> 8Be

alpha + 8Be <-> 12C** -> 12C + 2 gamma (or e+ e- pair)"

3. NUCLEOSYNTHESIS AND CHEMICAL EVOLUTION OF GALAXIES (pp 175-176, 2nd edition, BERNARD PAGEL 2009):

"2 alpha <-> 8Be -0.09 MeV

8Be + alpha <-> 12C** (7.65 MeV) -> 12C + 2 gamma (ground state)"

Diagrams all three textbooks of the He4+He4<->Be8 reaction suggest that no photon is involved.

Even in "Synthesis of the Elements in Stars" B^2FH 1957 paper, they only mention "alpha + alpha <-> 8Be". So unless something happened in the past 2 decades, I am pretty sure the diagram is wrong. 149.217.47.250 (talk) 12:19, 7 August 2024 (UTC)

References

SI Units Please

Can we have energy in Joules please ? Surely this is not too much to ask for now we are in the 21st century ? Also can someone please show us how these energies are calculated ? — Preceding unsigned comment added by 82.32.50.178 (talk) 05:15, 17 June 2012 (UTC)

Physicists use electron volts, not joules, when working with nuclear reactions. Actually, MeV (Mega electron volts) is commonly used. This is much more convenient than joules. Joules are good for ordinary earthbound phenomena involving energy, especially work and heat. (That's "work" in the physicist's sense: when one system does work on another, the work is the amount of energy transferred. For example, you can compress a gas with a compressor. The compressor does work on the gas.) Calories are convenient in other cases.

SI units are not always the best:

Astronomy: light-year, parsec, astronomical unit (equal to the radius of the earth's orbit). Each is useful for a different reason in astronomy. And astronomers don't convert years to seconds.

Pressure: That on the earth is 1 atmosphere. Useful when comparing to the Earth's atmosphere.

G forces: You wouldn't use newtons, would you?

The electrical charge of particles, in many cases, is more conveniently measured in multiples of that of a proton, as in the charge on an electron (which would be -1), or quarks, which, depending on which quark you're dealing with, is +/- 1/3 or +/- 2/3 of that amount of charge. Would you instead use coulombs or esu? The charge on a proton is 4.803 X 10^-10 esu, or 1.602 X 10-19 coulombs. I think not.

There's also a foot (of cable, or patch cord, if you will), which is how far light travels in one nanosecond. This is useful in high-energy physics experiments for estimating signal delays.

Time: years, months, weeks, and days are not metric units, yet scientists use days and years, at least. The dinosaurs were wiped out 65,000,000 years ago. No one converts that to seconds.

Bottom line: Use the units that are appropriate for the job. Betaneptune (talk) 03:46, 25 December 2012 (UTC)

Reaction Rate

The Fusion process comparative reaction rate is reported as being proportional to an exponent of the very high ambient temperature which doesn't sound reasonable, and probable should be instead related to the ratio of the 2 considered temperatures.WFPM (talk) 18:09, 7 February 2013 (UTC)

Reference Update

The third reference is 404.

G. Audia,§, O. Bersillonb, J. Blachotb and A.H. Wapstrac, http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf/ The NUBASE evaluation of nuclear and decay properties, (2001)

Temperature as keV

"until the central temperature rises to 10^8 K (8.6 keV). " This sounds like a mistake to me. eV is not a temperature unit. Asgrrr (talk) 19:10, 5 May 2016 (UTC)

Maybe the author meant average energy per helium nucleus in some model. But if nobody can find a source saying 8.6 keV, it should be removed. Rolf H Nelson (talk) 02:52, 6 May 2016 (UTC)

The electron volt can be treated as a unit of temperature. The conversion factor works out at 11,605 K/eV. So 8.6 keV comes out at 99.8 million Kelvin, which seems correct to me. Lithopsian (talk) 15:59, 12 May 2016 (UTC)

I don't think so. 8.6 keV=99800000K=/=100000000K. 32ieww (talk) 21:28, 25 February 2017 (UTC)

@32ieww: I don't see what you mean. Your two numbers are 99 800 000 and 100 000 000 -- the same within round-off error. Eric Kvaalen (talk) 11:42, 7 March 2017 (UTC)

Improbability and fine-tuning

The section "Improbability and fine-tuning" seems out of place and a bit of a stretch for this article. Perhaps is should be moved to Fine-tuned universe with a mention of the idea on this article. Zedshort (talk) 16:43, 24 August 2016 (UTC)

You could maybe chop it down to one or two sentences, given that it is already linked to the main article. Unfortunately the "main article" then links back here :) Lithopsian (talk) 21:20, 24 August 2016 (UTC)

@Zedshort and Lithopsian: I don't think it's out of place at all. This coincidence has often been cited in arguments about fine tuning. By the way, Rolf_h_nelson recently added a sentence sayin', "some scientists believe different regions of a vast "multiverse" have different fundamental constants", with a reference to a recent article in New Scientist: "Stars burning strangely make life in the multiverse more likely".. When that article came out, I sent a letter to New Scientist sayin':

The discovery that carbon could be produced much more easily in many other parallel universes is actually an argument against the “multiverse”. It is usually assumed that we should be in a typical universe among those that can support intelligent life. So finding that this is actually not the case under the hypothesis of a multiverse undermines the credibility of the multiverse.

(They didn't publish it.) What do you think of that? Eric Kvaalen (talk) 16:46, 5 February 2017 (UTC)

I don't think this section is out of place at all. It is one of the intriguing aspects of the "Hoyle resonance" and deserves a mention, although the article should not dwell on it. It should be noted here that Hoyle was an avowed atheist, so I doubt he was arguing for the existence of God in the same manner that the theistic intelligent design proponents do, like Dembsky or Behe. I am not sure that Hoyle's "intelligent design" should be associated with the article of that name in Wikipedia since that article clearly (and not entirely accurately) insists on associating the term with the theists at the Discovery Institute. Nonetheless, the cited reference really only shows that Leonard Susskind has rejected Hoyle's "ID" argument. I am sure that there are others in the "scientific community" that also do, but the reference does not say that. So I fixed it. To overstate this rejection is to violate wp:NPOV and wp:CITE. 108.20.213.77 (talk) 17:22, 26 October 2017 (UTC)

Good stuff. Hard to go wrong stating what references say, although some people sure do manage it. There's now a whole article at Fine-tuned universe, so I'm perilously close to nuking this section down to a one-liner, or a description of the physics and a brief mention of the philosophy. We don't really need this sort of discussion bogging down an article about a well-described physical process. You could really have at the new article - it mentions this issue but links back here for "further information". The short paragraph there hardly does justice to the subject. Lithopsian (talk) 18:10, 26 October 2017 (UTC)

Well, there has long been an article Fine-tuned Universe as well as Anthropic principle. Just as long as this article, I believe. I do not support any notion of "nuking this section down to a one-liner". The whole article is about physics and only this section is about this notable philosophical issue (and at least half of the section is just the physics). It's best left as it is without any anti-ID POV crapping it up. They have done enough damage at the Intelligent design and some satellite articles. 108.20.213.77 (talk) 03:53, 27 October 2017 (UTC)

Careful now. The term "anti-ID POV" implies that ID is somehow on a par with "reliable science" rather than a fringe theory hijacked as a religious trojan horse. Even Hoyle's prediction has been spun into some sort of "proof" of intelligent design, aided by a number of somewhat tongue-in-cheek statements later in his life. Don't go down that road, even the current "some say this, some say that" form of words is dangerously close to WP:NPOV just by setting fringe and mainstream theories on the same level. Lithopsian (talk) 11:06, 27 October 2017 (UTC)

Lith, I am very careful, forensically, about this. But what the editors of the Intelligent design article (and some related to it) do is not careful NPOV and hasn't been for more than a decade. The first thing they do is equate ID with DI. ID≠DI. It is a shame that they give the Discovery Institute so much credibility to be the sole definers of what the term "intelligent design" means. The term has existed long before there was ever a Discovery Institute or crappy disingenuous books like Of Pandas and People or the Kitzmiller v Dover case. The editors who think they own that article have done some very nasty things to other editors that have tried to tone down the POV so that the article would look at least a little balanced.

ID is not science. It is philosophy. It is a philosophy with a long history. It is a philosophy informed by science, such as anthropic coincidences such as the topic of the present article, but it is not science. Like any decent philosophy, it has to accept refinement or modification when new knowledge refutes items in the philosophy. It is not just the philosophy of science that has to do that.

If it wants to continue to be consonant with science, particularly biology, ID has to accept physical abiogenesis and evolution as ostensibly undirected mechanisms for the emergence and development of life as we know it. But that does not mean that the philosophy has to cease recognition of patterns of ostensible design other places that it is observed.

Now, articles about science in Wikipedia are about science but not just about science in a vacuum. An NPOV article about climate change must include discussion of the political issues about it and that inclusion does not mean that the article takes a position of equivalence of competing scientific "theories" when there is simply no real controversy within the science. But it has to deal with it with something better than a "one-liner".

It's not just an issue of wp:NPOV (but it certainly includes NPOV as a consideration), it's an issue of completeness. Somewhere, in the article of the JFK assassination, there needs to be a reference regarding skepticism, particularly when the single bullet theory is brought up. Not to push the skeptic's POV, but to inform the reader that there is such a POV. (And say that the Warren commission has rejected it, but that does not mean that "The investigative community has rejected skepticism of the single bullet theory." because that is simply not true and there are cited references of investigators with credibility that are skeptical of it.)

Hoyle can speak for himself. So can Susskind. But neither are the entire "scientific community", which is why that statement was misleading before I fixed it. I can point to three physicists, right away, who will say that there is some ostensible design in evidence in the alignment of energy levels of the nucleii of the atoms involved in the triple-alpha process. (They are Freeman Dyson, John Polkinghorne, Owen Gingerich and, with some research I can find others, and I am not going to include douchebags like William Lane Craig.)

I am pretty confident that I am being completely consonant with both the letter and spirit of wp:NPOV. And I know that several of the editors of the ID page are not. But it's a political fight that I will not take on after observing what has happened with that page for over a decade. 108.20.213.77 (talk) 18:26, 27 October 2017 (UTC)

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Chemical consequences of carbon-oxygen

Since there is a mixture of carbon and oxygen, could these elements ignite in a conventional fire? — Preceding unsigned comment added by 142.161.218.253 (talk) 20:04, 15 December 2018 (UTC)

That would require elements and molecules. In the centre of a star, we're talking about bare nuclei, electrons off wandering on their own, so no conventional chemistry. Plus carbon dioxide, as an example, disassociates above 4,200 K so molecules don't exist even in the atmospheres of most stars. Lithopsian (talk) 21:05, 15 December 2018 (UTC)

I see. However, how about the case where a star, such as a white dwarf for example, cools down? (At least in theory) — Preceding unsigned comment added by 142.161.218.253 (talk) 01:00, 16 December 2018 (UTC)

A white dwarf (a lot) cooler than 4,200 K? Not really a white dwarf any more, eh? The core is out since it is degenerate, and the atmosphere of even a CO white dwarf is mostly hydrogen and helium, usually in two distinct layers. A very small number of white dwarfs have atmospheres with a lot of carbon, but usually only trace amounts. Gravity is very high, so white dwarf atmospheres rapidly stratify into separate elements. If you really want to look at molecular chemistry around stars, cool ones obviously, you'll find a slightly strange dichotomy between those that are dominated by oxygen and those that are dominated by carbon. Oxygen-rich stars are the norm, but in some cases sufficient carbon is convected to the surface that it becomes more abundant than the oxygen, and the chemistry changes completely. Read S-type star and carbon star for some more on this. Lithopsian (talk) 15:31, 16 December 2018 (UTC)

Back to the original question - regardless of everything above, "fire" isn't really on the cards. There are situations where carbon and oxygen (or oxygen and other elements) can be combined into molecules, but this only happens once and then they're done. Fire requires free oxygen to be produced, and the only situations where that can really happen is life. Lithopsian (talk) 15:33, 16 December 2018 (UTC)

Equilibrium

Lithopsian replaced what has been a mistake with another confusing stuff. A post-hydrogen star practically is in hydrostatic equilibrium. Gradual changes in its structure occur not because the core can’t withstand pressure of upper levels, but because in that age is loses more heat than produces, and consequently cools. Incnis Mrsi (talk) 09:26, 8 July 2019 (UTC)

Do you want to change this? It is accurate, but perhaps you think it misleads in some way? Or just confuses? It isn't really critical to this article. I don't like what was there before, "heat-transfer equilibrium", because that isn't "a thing". Looking at the current text, I also don't like that it could be read as saying that the production of carbon stops the core collapsing, rather than the production of energy. It also ignores the fact that, in the vast majority of stars, the onset of core helium fusion occurs in a degenerate core that was already in (a different kind of) equilibrium and not collapsing. Might be best to ignore the whole issue and just state that helium fusion begins when (and if) the core temperature gets hot enough. Lithopsian (talk) 12:52, 8 July 2019 (UTC)

Science

Task1 triple Alpha process: what is the result of the formation of atoms? 58.69.115.20 (talk) 14:43, 24 August 2022 (UTC)

Homework? Lithopsian (talk) 14:49, 24 August 2022 (UTC)