# Talk:Type II supernova

Type II supernova has been listed as one of the Natural sciences good articles under the good article criteria. If you can improve it further, please do so. If it no longer meets these criteria, you can reassess it.
Type II supernova is part of the Classes of supernovae series, a good topic. This is identified as among the best series of articles produced by the Wikipedia community. If you can update or improve it, please do so.
WikiProject Astronomy / Astronomical objects  (Rated GA-class, High-importance)
Type II supernova is within the scope of WikiProject Astronomy, which collaborates on articles related to Astronomy on Wikipedia.
GA  This article has been rated as GA-Class on the project's quality scale.
High  This article has been rated as High-importance on the project's importance scale.
WikiProject Physics (Rated GA-class, Mid-importance)
This article is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
GA  This article has been rated as GA-Class on the project's quality scale.
Mid  This article has been rated as Mid-importance on the project's importance scale.

## Supernova article

The body of this article was formed from a section of the FA'd supernova page. The material was copied here primarily to reduce the length of the supernova article. This should allow for expansion of the content. — RJH (talk) 21:42, 1 May 2007 (UTC)

Nice work! ··coelacan 18:58, 6 May 2007 (UTC)

## New article?

This article was just started? Nice work! Trevor GH5 21:28, 6 May 2007 (UTC)

I was "blown away" by this too ... seems it was split off from an existing FA, but it's still a great article. Kudos to those who wrote it! Antandrus (talk) 21:30, 6 May 2007 (UTC)

## Good article nomination on hold

This article's Good Article promotion has been put on hold. During review, some issues were discovered that can be resolved without a major re-write. This is how the article, as of May 30, 2007, compares against the six good article criteria:

1. Well written?: This article fail to pass the well written criteria for good articles. But don't worry there is nothing groundbreaking in that article that can't be fixed, I allready fixed myself some of the litle.
First of all the Lead of the article, the guideline "In general, specialized terminology should be avoided in an introduction. Where uncommon terms are essential to describing the subject, they should be placed in context, briefly defined, and linked" is not met here "However the nuclear fusion of iron produces no net energy to sustain the star, so the core becomes an inert mass that is supported only by the degeneracy pressure of electrons." what does degeneracy pressure of electrons means ? You need to provide a short definition of degeneracy pressure. (the article linked is definitivly not a good article and provide a rather complicated definition).
I inserted a very, very simple explanation that is hopefully sufficient. (I didn't want to divert the lead into a full explanation, which would require one or more paragraphs.) — RJH (talk) 19:11, 31 May 2007 (UTC)
Now the main problem of the article, jargon, please read Wikipedia:Explain jargon "Type II-L supernovae show a linear decay of the light curve following the explosion, whereas Type II-P have a plateau in their light curve followed by a normal decay. Type Ib and Ic supernovae are a type of core-collapse supernova for a massive star that has shed its outer envelope of hydrogen and (for Type Ic) helium." do not meet it. "Linear decay" is jargon. "A plateau blablabla" could be perhaps rewritten as "conserve their luminosity then begin to lose light" or something like that much more understandable by a non expert in the subject. "Type Ib and Ic supernovae are a type of core-collapse supernova for a massive star that has shed its outer envelope of hydrogen and (for Type Ic) helium." I didn't understood that part... But perhaps it doesn't matter because it's not directly related to that article, doesn't it ? "Standard Model of particle physics" should be explained. "presence of hydrogen Balmer absorption lines in the spectra." what are those line ? "wave ionizes the hydrogen" what is ionization ? "(collapsars)" neologism ?
I've attempted to address your concerns. The word "collapsar" is being used in a significant number of scientific publications, so it's a a valid moniker. — RJH (talk) 15:34, 1 June 2007 (UTC)
2. Factually accurate?: Source checking in progress , Wikipedia:Avoid weasel words The interactions between neutrinos and the other particles in the supernova take place with the weak nuclear force which is believed to be well understood. However, the interactions between the protons and neutrons involve the strong nuclear force which is much less well understood." Who said that ? source it and perhaps delete believe and for strong nuclear say it is "not fully understood" or still unknown. Don't forget to provide some source for those fact.
I think this may belong under the "Quantum chromodynamics (QCD) in the non-perturbative regime" topic on the unsolved problems in physics page. The 2004 Nobel Prize page had a decent article on the Strong Force, so I linked that. (See the "A weaker coupling sets the particles free" section.) Hopefully that's satisfactory. — RJH (talk) 18:51, 30 May 2007 (UTC)
4. Neutral point of view?: What about the Flying Spagethi Monster and his noodly viewage ? (just kidding, )
5. Article stability?
6. Images?: Image:Evolved_star_fusion_shells.png The note in this picture seems to say that this picture is inacurate, someone should check it and eventually replace that picture if there is a problem. Also some graph for the different types of light curves may be usefull (a picture worth a thousands words).
Actually I think the illustration is correct. The (PDF) paper by Woosley et al on the evolution of massive stars shows Ne burning occurs before Oxygen fusion begins. I put a comment on the commons image talk page. There's already an image on light curves down in the "Light curves and unusual spectra" section. — RJH (talk) 15:08, 30 May 2007 (UTC)
- Esurnir 15:30, 30 May 2007 (UTC)

Please address these matters soon and then leave a note here showing how they have been resolved. After 48 hours the article should be reviewed again. If these issues are not addressed within 7 days, the article may be failed without further notice. Thank you for your work so far. — Esurnir 00:41, 30 May 2007 (UTC)

I agree with Esurnir's comments regarding the use of jargon. Some jargon maybe important for the article, but the density of jargon makes it difficult for a non-expert to follow. This reduces the effectiveness of what is otherwise a well-researched, well-illustrated article. --Volcanopele 22:28, 31 May 2007 (UTC)
Thanks for the feedback. I've tried to clear things up a bit. Please let me know if there are any more particular elements that need addressing. — RJH (talk) 15:34, 1 June 2007 (UTC)

## Successful good article nomination

I am glad to say that this article which was nominated for good article status has succeeded. This is how the article, as of June 3, 2007, compares against the six good article criteria:

1. Well written?: All the potentially obscure jargon has been explained. In the future perhaps some edit could be usefull to "lighten" the lead" (it's just my point of view on the lead, but it pass WP:LEAD) the rest of the article is just great.
2. Factually accurate?: There is no problem everything is well sourced
3. Broad in coverage?: This article give all the important information on the matter, personnaly I found reading that article great for my knowledge (particulary the Core collapse section)
4. Neutral point of view?: No problem of point of view.
5. Article stability? It's stable, no edit war.
6. Images?: Picture are appropriate, all free license.

If you feel that this review is in error, feel free to take it to a GA review. Thank you to all of the editors who worked hard to bring it to this status. — Esurnir 19:44, 3 June 2007 (UTC)

Thank you. — RJH (talk) 14:47, 4 June 2007 (UTC)

## How exactly degeneracy pressure fails?

Article says: "When the core's size exceeds the Chandrasekhar limit, degeneracy pressure can no longer support it, and catastrophic collapse ensues."

From my understanding, electron degeneracy pressure rises with density. New electrons crammed into each cubic meter get higher and higher speeds just because lower energy levels are all taken by electrons which were already there. This fails when new electron's energy is so high that it can fuse with proton (ordinarily it is not possible, e + p weigh less than n). Such electron "disappears", it no longer contributes to degeneracy pressure. Density starts to rise fast, more electrons fuse.

That's how degeneracy pressure fails. If this description is correct, can it be added to the article?—Preceding unsigned comment added by 89.102.207.196 (talkcontribs)

Well, first it would need a reference. I think it also needs some modifications to comply with the Wikipedia:MoS, such as avoiding unnecessary vagueness. But yes I think something like this would make a nice addition.—RJH (talk) 16:15, 12 May 2008 (UTC)

## Humming core autodestruct

The middle C humming model for patching the missing link between core collapse and explosion HERE. Use or dismiss at your option, while I dig into other matters. Said: Rursus () 20:46, 3 November 2008 (UTC)

## The onion

The onion star picture seems to be incorrect. Oxigen inside Neon? I don't think so. Dauto (talk) 19:56, 21 February 2009 (UTC)

Actually I believe that is correct. See: http://commons.wikimedia.org/wiki/File_talk:Evolved_star_fusion_shells.png Yes it is contrary to intuition.—RJH (talk) 19:51, 22 February 2009 (UTC)
It is correct. Neon burning occurs at lower temperatures than Oxygen burning. ... said: Rursus (bork²) 20:47, 10 May 2009 (UTC)

## GA Sweeps Review: Pass

As part of the WikiProject Good Articles, we're doing sweeps to go over all of the current GAs and see if they still meet the GA criteria. I'm specifically going over all of the "Stars, constellations, and clusters" articles. I believe the article currently meets the criteria and should remain listed as a Good article. I have made several minor corrections throughout the article. Altogether the article is well-written and is still in great shape after its passing in 2007. Continue to improve the article making sure all new information is properly sourced and neutral. I would recommend going through all of the citations and updating the access dates and fixing any dead links. If you have any questions, let me know on my talk page and I'll get back to you as soon as I can. I have updated the article history to reflect this review. Happy editing! --Nehrams2020 (talk) 02:21, 3 March 2009 (UTC)

Thanks for checking on this article.—RJH (talk) 19:46, 3 March 2009 (UTC)

## SNII = core-collapse?

For this grand confusion, I dislike the good-article assessment ― it's not good enough. ... said: Rursus (bork²) 21:04, 10 May 2009 (UTC)
To further strengthen my argument, a neutron star, which is a physical model, has a separate article from pulsar, which is an object type defined by certain fast and regular radio pulses, and later on other similar observational signatures. This is a good thing since it seems that there are actually neutron stars out there, that don't exhibit pulsar signatures. It should be this way with the articles on supernovae too. ... said: Rursus (bork²) 21:12, 10 May 2009 (UTC)
I'll considering demoting this article actively. ... said: Rursus (bork²) 21:17, 10 May 2009 (UTC)
While I agree with your concern, note also the final sentence in the lead. The issue would be simple enough to fix with a bit of judicious editing. Improving the article would be the constructive approach. Demoting it will not resolve your problem, but perhaps it would scratch an itch you have? Good luck with that approach.—RJH (talk) 20:39, 11 May 2009 (UTC)
Demoting will just issue an alarm that there's something wrong with this article, and as you say it itches me and has done so each time I've read it. The article must be improved by making the SNII stuff "independent" of the core collapse stuff. I think it requires more thinking and planning than actual rewriting, since the section Light curves and unusual spectra could constitute a future article on Type II supernova, while the rest, cleaned-up to remove the confusions, can constitute the basis for Core collapse supernova. But f.ex. the intro
a type II supernova belongs to a sub-category of cataclysmic variable star known as a core-collapse supernova, which results from the internal collapse and violent explosion of a massive star
confuses matter by starting at the fact conclusional end and not the defining criteria. While the claims are perfectly correct (probably, unless new unexpected discoveries are made), it bundles SNII and CCSN in a way that makes it hard to elaborate why the theory of CCSN was developed independently but soon merged with the taxon SNII. This is not just a matter of philosophy, this is a matter of presenting a topic in a correctly authored way for a public. ... said: Rursus (bork²) 08:02, 14 May 2009 (UTC)
Okay. Well I've probably put in the most work on this article, at least in terms of getting it cited. The prospect of losing GA status doesn't alarm me in the slightest. Suit yourself. =)
Rather than splitting this into two even smaller articles, another approach would be to merge in the Type Ib and Ic supernovae article, creating a combined "core collapse supernova" article.—RJH (talk) 22:13, 14 May 2009 (UTC)
Three years on and this would seem to be as pressing as ever. I have no idea how to change titles or merge articles, but am willing to do other edits as needed to make a "Core Collapse" article work. Lithopsian (talk) 10:44, 1 June 2012 (UTC)

## Luminosity?

Why doesn't this article say anything about how bright a type II supernova can be? We see a nice luminosity curve, but nothing about how bright the darn things tend to be. I came here hoping for some information on that. John Baez (talk)

Yes you're right, we should include some information about that, even though the absolute magnitude varies quite a bit for a Type II.—RJH (talk)
All the more reason to provide the info. The quantity of data now available on supernova luminosity, ranging from "faint" to "hypernova", deserves to be expressed here. Lithopsian (talk) 10:45, 1 June 2012 (UTC)

## Comment?

Until I read this article I thought I had understood the Chandrasekhar limit as being about 1.4 times the mass of the Sun. This article, however, says that the Chandrasekhar limit relates to the mass of the iron core within a star, and the star itself must be about 9 solar masses to obtain an iron core of 1.44 solar masses. Glad I read it!! And I guess it must be so.

You might also want to read the Type 1a supernova article.—RJH (talk) 15:11, 31 July 2009 (UTC)

## First Sentence

The cdsweb web site, which is based on the General Catalogue of Variable stars, categorizes Supernovae under cataclysmic variables.—RJH (talk) 17:14, 19 October 2009 (UTC)

## Supernova 1987 A Image

Just curious if anyone thinks this too, but it looks like a face in the center of the supernovae remnant! Does anyone else see this? Syntheticalconnections (talk) 02:19, 10 March 2010 (UTC)

Nope.—RJH (talk) 19:20, 10 March 2010 (UTC)

## Core evolution

"Eventually, as the hydrogen at the core is exhausted, fusion starts to slow down and gravity causes the core to contract."

Actually burning hydrogen into helium causes the core to heat up because it is more dense. This is why old Sol is getting brighter all the time. Hcobb (talk) 23:41, 13 November 2010 (UTC)

The significant word there is "exhausted".—RJH (talk) 20:30, 15 November 2010 (UTC)

I'm concerned that the introduction especially and a few places elsewhere are not clear and unambiguous to a general reader. A few points are obscure, some are apparently misleading. Poor readability is one of the most common criticisms of Wikipedia's current articles. I've tried to improve it and been reverted on some points, hence bringing it here for discussion. Specific draft edits:

Previous As edited Rationale
1 When the mass of the iron core exceeds 1.44 solar masses (the Chandrasekhar limit), a sudden implosion ensues. In stars of this mass, electron degeneracy is unable to counter gravity. When silicon burning has ceased and the mass of the core reaches the Chandrasekhar limit (1.44 solar masses), a sudden, rapid and catastrophic implosion follows.

or:

... a cataclysmic implosion of the core takes place within seconds.

1. Explains why the core size matters at this point and not earlier - otherwise as worded it sounds like the reason for collapse is that the core has gained mass rather than fusion ceasing to provide countering force.
2. The mention of 1.44 M as the point of collapse is very ambiguous here. The sentence mentioning this mass is given in the context of type 2 supernovae, and is followed by a statement that a supernova will result (and nothing else) so it leaves the article very ambiguous about the relevant significance of the 1.44 and 9 M limits stated. Depending upon which interpretation is intended, hopefully one of the 2 rewords makes it clearer.
3. Also noting rapidity as a feature of the implosion.
2 ...that result in the formation of neutrons and neutrinos from the reversed beta-decay process ...that result in the formation of neutrons and neutrinos (due to reversed beta-decay) and brief but exceedingly high energy production of neutrinos and gamma rays
3 The energy of this expanding shock wave is sufficient to detach the surrounding stellar material, forming a supernova explosion. [add] ... while the shock wave and extreme conditions briefly allows the production of elements heavier than iron.
1. Significant information for an article summary
2. Article body doesn't mention by name or link to r-process
4 It belongs to a sub-category of cataclysmic variable star known as a core-collapse supernova ? Highly confusing. Presumably the meaning is "Type II supernovae [the subjects of this article] are one of several kinds of core-collapse supernova. They are classified as cataclysmic variable stars". Needs rewriting to explain what exactly this is trying to say.
5 This continues until nickel-56 is produced (which decays radioactively into cobalt-56 and then iron-56 over the course of a few months). This continues until iron-52 and nickel-56 are produced via the silicon-burning process ....... Nickel-56 decays radioactively into cobalt-56 and then iron-56 however this process has a half-life of months, and the silicon burning cycle lasts only days, so it has little impact. Clarifies the two places iron arises, as a fusion product and as a decay product. As currently written suggests that the iron in the core is created by decay of Ni-56 over a period of "months".
6 iron core nickel/iron core Accuracy - a few places imply the core becomes pure iron
7 A star must have at least 9 times the mass of the Sun for this type of explosion [add] ... and (it is believed) not more than 40 - 50 times ... As stated the introduction implies all stars > 9 M can produce a supernova, which is incorrect; it isn't believed to happen beyond a certain size.

FT2 (Talk | email) 23:54, 22 April 2011 (UTC)

Erm "sudden, rapid, and catastrophic" - the first two adjectives here are virtually synonymous in context, and their value is (I think) encompassed by "catastrophic" anyway, which carries a connotation of "BAM!" within it. I think "catastrophic" is ok if not used elsewhere but the other two adjectives are needless (I'll continue disecting in a minute...) Casliber (talk · contribs) 01:04, 23 April 2011 (UTC)
Also, "electron degeneracy" is a mouthful and possibly detracts more than it adds when placed in the lead. Casliber (talk · contribs) 01:05, 23 April 2011 (UTC)
• "Sudden" and "rapid" aren't synonyms. One refers to the process not evolving in a gradual manner, the other indicates that once commenced, collapse happens in a short period of time. "Catastrophic" by itself implies great scale but lacks any precision of the manner of collapse. Perhaps state facts rather than these kinds of words, see 2nd wording (above). Saying that collapse takes place in seconds is more descriptive than words like "rapid".
• "Electron degeneracy" is probably okay provided the intro isn't packed with dense technical terms. (Alternative: "the forces holding electrons apart"?)
FT2 (Talk | email) 01:54, 23 April 2011 (UTC)
• Okay, you are right in the broad sense in they are not synonyms - I still think their meaning in this case is similar enough to render the use of three adjectives as labouring the point. Casliber (talk · contribs) 03:38, 23 April 2011 (UTC)
• Point 4 - a ready reword should be easy. Casliber (talk · contribs) 03:40, 23 April 2011 (UTC)
• Point 6 is interesting as I've always seen in referred to as "iron core". I'll take a look at sources when I get a chance. Casliber (talk · contribs) 03:40, 23 April 2011 (UTC)
Also a result of the reaction sequence described at Silicon-burning process; it would be surprising if a sequence with final stage 52Fe + 4He -> 56Ni that lasted a matter of days and where the resulting Ni-56 had little chance to decay to iron (1% - 6% of a half-life), would result in an iron-only core. At best a significant proportion of Ni-56 would have decayed to Co-56 (6 day half-life), but even so Ni-56 would continue to be produced virtually up to collapse. FT2 (Talk | email) 03:57, 23 April 2011 (UTC)
I am happy with sources calling it thus. I won't second guess RJH on the issue but suspect he'll be okay with it. Casliber (talk · contribs) 04:02, 23 April 2011 (UTC)

My primary concern here is that the lead satisfy the WP:LEAD policy, which requires that it be a summary of the article, rather than detailing information not in the body. Beyond that, I have a few issues with your suggested changes:

• "In stars of this mass, electron degeneracy is unable to counter gravity."
I believe they are allowed to have an "inert" core of up to the Chandrasekhar limit that is supported by electron degeneracy pressure.[1] Hence I think this statement needs to be clarified a little since it seems ambiguous (at least to me). This discussion did point out something else important though: the article is not covering the case of the collapse of a degenerate O + NE + MG core.[2]
• "When silicon burning has ceased..."
Do you mean when silicon burning has ceased at the core? I think you still need silicon burning to generate the inert iron core.
• "(due to reversed beta-decay)"
To me the text generally reads better when there is a minimum use of parentheses. Unnecessary parentheses also make it more difficult for the visually impaired. Also, "neutrinos" is used redundantly. Regarding the use of "exceedingly high" here, please see Wikipedia:Manual of Style (dates and numbers)#Unnecessary vagueness.
• For number 4, I'd like "core-collapse supernova" and "cataclysmic variable star" to be mentioned somewhere in the lead. The first is a common alternate term and the later is the variable star supercategory.
• For number 5, is an improvement, but perhaps a little wordy for the lead.
• Number 6 makes sense.
• Number 7: ... and (it is believed) not more than 40 - 50 times ...
That makes sense, since it is mentioned at the end of the "Core collapse" section. But the "(it is believed)" could get tagged with a who template. Better to say something like "... and usually not more than 40–50 times".

Thank you. Regards, RJH (talk) 15:31, 23 April 2011 (UTC)

I'd like to suggest an alternative wording for item 1:

"When the mass of the inert core exceeds the Chandrasekhar limit of about 1.44 solar masses, electron degeneracy alone is no longer sufficient to counter gravity. The result is a cataclysmic implosion that takes place within seconds."

I think this addresses both of our concerns. Thank you. Regards, RJH (talk) 16:59, 25 April 2011 (UTC)

cataclysmic is a good word, otherwise I was trying to think of another adjective that meant KA-BLAAM but couldn't quite think of one as apt. Casliber (talk · contribs) 18:37, 25 April 2011 (UTC)

Okay I think I've addressed most if not all of the concerns. Thank you for all the useful input. Hopefully these compromise changes are to everybody's satisfaction; if not please say so. There is still a need to add in a paragraph or two about the O + NE + MG core supernova for stars below 10 solar masses. Regards, RJH (talk) 16:17, 26 April 2011 (UTC)

## I thought the upper limit for a neutron star was 3 solar masses, not 4

article says very roughly 4 solar masses; here are a few references, all NASA, saying 1.3-2.5, or 1.4-3.2

Yes, unless I am misreading it, the cited Bombaci (1996) paper also says 1.5–3.0 solar masses. Possibly somebody just made a typo, or they were being extremely conservative, so I changed the article to match. Thanks for the catch. Regards, RJH (talk) 15:35, 22 March 2012 (UTC)

## Merge Type II and Type Ib/c?

As discussed at times on this page and elsewhere, type Ib/c and type II supernovae are only slight variants of the same thing: a core collapse supernova. Most of the things that could be said about one apply to the other. So here is a proposal to merge the two pages. Lithopsian (talk) 19:18, 4 June 2012 (UTC)

I removed the merge tags based on this from the article "A supernova is first categorized as either a Type I or Type II, then sub-categorized based on more specific traits. Supernovae belonging to the general category Type I lack hydrogen lines in their spectra; in contrast to Type II supernovae which do display lines of hydrogen. The Type I category is sub-divided into Type Ia, Type Ib and Type Ic supernovae." It didn't make sense to merge Type 1's into a Type 2 article. Maybe a merge into Type 1. AIRcorn (talk) 11:35, 18 October 2012 (UTC)
The type I/II classification is an early attempt to classify supernovae based on the gross appearance of their spectra. As discussed in the artcles, it does not reflect the true nature of the explosions or the progenitors. This has resulted in the split into type Ia and Ib/c which are entirely different objects, while type Ib/c and type II supernovae differ only in fairly superficial ways, essentially just the quantity of hydrogen remaining in their atmospheres. It absolutely would not be acceptable to merge the type Ia supernova article with any of the others. I have extensively revised the top level supernova article to reflect both the spectral classification system and the actual nature of the different types, but the sub-articles desperately need revision. My thought was to create sub-articles covering white dwarf supernovae (type Ia) and core collapse supernovae (everything else), but I would welcome other options. The status quo is not an option as the articles are badly out of date and misleading, and the content of the articles on type Ib/c and type II overlap heavily. Lithopsian (talk) 11:43, 18 October 2012 (UTC)
I think you're on the right track. Two articles - white dwarf supernovae and core collapse supernovae. Then have the type Ia redirect to the first article and type Ib/Ic and type II redirect to the second. If the first-paragraph summary includes mention of the specific numbered types it covers, that probably does the job. Tarl.Neustaedter (talk) 06:30, 19 October 2012 (UTC)
I think that merging it would be too broad. When I did some research for Science Olympiad some time, I found that the presence of different articles was helpful to keep the two concepts organised and away from each other, as merging them painted the subject too broadly and too generally. I think that supernovae should be separated by the general class (I, or II), as it keeps the topics different and away. Ifly6 (talk) 16:17, 8 May 2013 (UTC)

No, bad idea. Astronomers treat them as distinct entities; so should we. -- 101.119.14.206 (talk) 06:34, 11 November 2013 (UTC)

You're just making stuff up. Did you read the articles, or even the proposal? They are very much treated in the groupings I describe my modern researchers, with type Ib/c and type II generally considered together, and type Ia separately. Just because astronomers of the last century categorised them in a confusing way before they knew better, doesn't mean we can't describe them in a more helpful way for people. Lithopsian (talk) 12:34, 11 November 2013 (UTC)
• I don't think it's Wikipedia's job to redefine astronomical terminology. Searching through papers on Google scholar, references are to "type Ib supernovae" and "type Ic supernovae." They are spectrally distinct from "type II supernovae," and astronomers therefore distinguish them quite clearly. They share certain mechanisms, and it may be that some shared material could go in to a third article on those mechanisms. -- 101.119.15.183 (talk) 23:10, 12 November 2013 (UTC)

## Silicon burning process duration discrepancy

This article states that silicon burning process of a star with 25${\displaystyle {\begin{smallmatrix}M_{\odot }\end{smallmatrix}}}$ lasts about 5 days. Silicon burning process article states that silicon-burning process of (mass of the star not defined) lasts less than a day. Can someone find out which one of it is true and how much does the duration of silicon-burning process differ from stars of 10 ${\displaystyle {\begin{smallmatrix}M_{\odot }\end{smallmatrix}}}$ to 120 ${\displaystyle {\begin{smallmatrix}M_{\odot }\end{smallmatrix}}}$? --Artman40 (talk) 11:58, 25 June 2012 (UTC)

It depends. Asking how long without specifying in exactly what conditions is like asking how long a star lives for without specifying which star. Also "Silicon burning" is not an entirely well-defined event. It starts gradually as the core temperature increases, and may end before all Silicon is consumed, or it may build up to a substantial core largely depleted of elements lighter than the iron group, and may continue further in a shell. With some standard definitions about how the duration is defined, a typical 10 solar mass star (about 15 before mass loss) will burn silicon for 5-10 days, while a 15 solar mass star (initially around 60) will burn silicon for a day or less. If you want a real contrast, consider that in the conditions of a white dwarf supernova, complete silicon burning takes place in seconds. Lithopsian (talk) 13:48, 25 June 2012 (UTC)
Another thing is about the period after the silicon-burning process is finished. Does the star collapse start straight away after or does the majority of nickel-56 and cobalt-56 have to decay into iron-56 for a collapse to start? If the core is still composed mainly of nickel-56 and cobalt-56, should we replace some of the images of a star illustrating pre-supernova state by replacing iron in the core with nickel and cobalt as not a lot of iron-56 hasn't been created yet from the radioactive decay? --Artman40 (talk) 00:32, 26 June 2012 (UTC)
Absolutely not. The core does not consist mainly of Ni and Co. It consists mainly of Fe, that's why it is called an iron core :) Ni and Co are not energetically favoured (and are radioactive so they decay to iron anyway) and are only produced in large quantities when the supernova explosion occurs. The collapse itself does not occur until the core is too large to be supported by electron degeneracy, so silicon shell burning will continue adding iron to the core until it reaches about 1.4 solar masses. Lithopsian (talk) 10:39, 26 June 2012 (UTC)
Perhaps even more detail. The explosion produces mainly nickel-56 which then decays to cobalt-56 which then decays to iron-56, all the while powering the visible light curve. Details of the core formation are complex, and there is considerable mixing and convection. Because of this, the inner core may not form as near-pure iron and it may have a mass considerably larger than 1.4. But the basic idea is an iron core forms, it is degenerate because there is no further source of energy from fusion, it grows, it collapses, the energy forms masses of nickel and a big explosion.Lithopsian (talk) 11:16, 26 June 2012 (UTC)