What makes supernova explode?

[steevey]

You are moving the goal posts here. You previously disputed that antimatter could have anything to do with a star going supernova. Now you are disputing the concept of a true pair instability supernova, which is lesser claim. That said, here is what you asked for:

 

 

 

When did I ever say antimatter could cause a supernova?

[D H]

When did I ever say antimatter could cause a supernova

Oh please. In post #21 you said that antimatter production is completely irrelevant. In post #24, after being asked to google the term "pair instability supernova" you apparently softened your stance. That is "moving the goalposts".

 

 

 

So let's look at post #21.

It's scientifically impossible that any anti-matter could ever survive in a star at all. ANY anti matter that appears is a result of some weird quantum mechanics thing, and appears of the seeming nothingness of space with another normal particle, and then the pair annihilates itself. These matter-anti-matter pairs are very small and usually can't be observed. I can prove with simple physics and some complex math that the only reason a supernova happens, is because fusion ceases.

There is so much that is wrong with this post that it needs to be dissected point by point.

 

 

 

 

It's scientifically impossible that any anti-matter could ever survive in a star at all.

 

So what? It doesn't to survive for long to result in extreme havoc.

 

 

 

ANY anti matter that appears is a result of some weird quantum mechanics thing, and appears of the seeming nothingness of space with another normal particle, and then the pair annihilates itself.

Wrong. You apparently are talking about virtual pairs. The pair production in supermassive stars instead involves a real gamma ray colliding with a real atomic nucleus, resulting in a real electron and a real positron. That positron will soon annihilate with some other electron, but that annihilation does not occur immediately. The result is that pair production slows down the transport of energy from the star's core to its surface. The star begins to lose hydrostatic equilibrium. In supermassive stars the onset of pair production triggers a runaway reaction. This happens well before the star runs out of fuel.

 

 

 

These matter-anti-matter pairs are very small and usually can't be observed.

Observed by whom?

 

 

 

I can prove with simple physics and some complex math that the only reason a supernova happens, is because fusion ceases.

Wrong. While this is descriptive of the prototypical core collapse supernova, it is not the only reason a supernova happens. A pair instability supernova happen well before fusion ceases. It is the onset of carbon-carbon fusion that triggers the pair instability supernova. Another example where your statement is blatantly false is a type IA supernova, which happens when fusion restarts (explosively) due to accumulation of mass stolen from a binary pair.

[steevey]

Oh please. In post #21 you said that antimatter production is completely irrelevant. In post #24, after being asked to google the term "pair instability supernova" you apparently softened your stance. That is "moving the goalposts".

 

 

 

So let's look at post #21.

 

There is so much that is wrong with this post that it needs to be dissected point by point.

 

 

 

 

 

 

So what? It doesn't to survive for long to result in extreme havoc.

 

 

 

 

Wrong. You apparently are talking about virtual pairs. The pair production in supermassive stars instead involves a real gamma ray colliding with a real atomic nucleus, resulting in a real electron and a real positron. That positron will soon annihilate with some other electron, but that annihilation does not occur immediately. The result is that pair production slows down the transport of energy from the star's core to its surface. The star begins to lose hydrostatic equilibrium. In supermassive stars the onset of pair production triggers a runaway reaction. This happens well before the star runs out of fuel.

 

 

 

 

Observed by whom?

 

 

 

 

Wrong. While this is descriptive of the prototypical core collapse supernova, it is not the only reason a supernova happens. A pair instability supernova happen well before fusion ceases. It is the onset of carbon-carbon fusion that triggers the pair instability supernova. Another example where your statement is blatantly false is a type IA supernova, which happens when fusion restarts (explosively) due to accumulation of mass stolen from a binary pair.

 

That's not changing goal posts at all, that's saying even with clear current logic, it STILL wouldn't work. This positron thing doesn't work how you think it works. Here's what happens: Some force causes an up quark in a proton to change into a down quark. The result is the atomic number of whatever element has gone down by one. Because of the conversion, a positron, neutrino and gamma ray are emitted 6C=>5B + e+ + ve + .96 Mev. The positron will want to and probably will combine with a nearby electron, converting the electron and positron after they collide, into nothing more than electro magnetic energy.

Edited December 7, 2010 by steevey

[D H]

That's not changing goal posts at all, that's saying even with clear current logic, it STILL wouldn't work.

The only logic that isn't working here is yours.

 

 

This positron thing doesn't work how you think it works. Here's what happens: Some force causes an up quark in a proton to change into a down quark. The result is the atomic number of whatever element has gone down by one. Because of the conversion, a positron, neutrino and gamma ray are emitted 6C=>5B + e+ + ve + .96 Mev. The positron will want to and probably will combine with a nearby electron, converting the electron and positron after they collide, into nothing more than electro magnetic energy.

You just described the beta decay of one particular isotope, [math]^{11}_6C[/math], into [math]^{11}_5B[/math]. I take it that you cut that right out of the wikipedia article on positron emission. Other than the fact that both pair production and beta decay are both described by quantum physics, the one has little or nothing to do with the other.

 

Some advice: Stop embarrassing yourself. I am starting to wonder whether you are a troll.

Edited December 8, 2010 by D H

[pioneer]

One consideration this often overlooked is heavy atoms, like iron, may not exist as just nuclei within a star, but will contain some inner electrons. What that does is define the density of the iron as the mass of an iron atom divided by the volume of the attached electron orbital space. If we had fully ionized oxygen, for example, it is denser than the iron atoms with say two inner electrons, simply because the volume of the oxygen is that of the nuclei. allowing the O to sink as fuel. (Fe: 1s2 2s2 2p6 3s2 3p6 4s2 3d6 or Fe+26 (plus say 1S2) versus O+8.

 

An easy way to see this is with an analogy. An aluminum ball will sink in water, yet an iron ship will float even though iron is denser than aluminum, simply because the mass of the iron is distributed over a larger volume that includes empty space (inner electrons). If we hammer the iron into a ball, the opposite is true.

 

What this suggests is the iron will float above the fusion core forming a shell over time. To much core heat will ionize the iron further causing it to get denser. When this iron shell gets too dense and begins to prevent the diffusion of the denser fully ionized atoms for fusion, the core starts to cool. This cooling will impact the highly ionized iron shell, by causing it to gain electrons, lowering density. This expands the shell allowing material to diffuse again. If the diffusion is done locally, we get a solar flare with the heat sealing the breach as the local iron gets denser. Eventually, the core cools permanently and the iron shell and star collapses. One result are the electrons that will be gained by the iron during the cooling, will ionize very quickly to reflect the short term extreme density of the quickly compressed iron.

Edited December 7, 2010 by pioneer

[swansont]

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Moderator Note

I think we can cease with the he said/he said. steevey, you might want to consider that our experts earned their stars and give their posts a good reading before you start telling them they're wrong. The odds are extremely good that they're right.

[steevey]

The only logic that isn't working here is yours.

 

 

 

You just described the beta decay of one particular isotope, [math]^{11}_6C[/math], into [math]^{11}_6B[/math]. I take it that you cut that right out of the wikipedia article on positron emission. Other than the fact that both pair production and beta decay are both described by quantum physics, the one has little or nothing to do with the other.

 

Some advice: Stop embarrassing yourself. I am starting to wonder whether you are a troll.

 

 

 

 

 

I checked my own "wiki-answers" which I replied to some time ago for someone else, if that's what you mean, otherwise I checked wikipedia.org myself and did not see that on wikipedia.org. I can show you a screen shot if you'd like.

If pair-instability explosions are exactly as you describe, then at most there would just be a mass ejection. If it's only a partial collapse and a drop in pressure, but it's before when the star is metal rich and it has an inert iron core, then almost as soon as gravity is starting to pull the star together and condense the core as I mentioned earlier to produce resistance, it fuses the non-metallic core to a point where the fusion process INcreases temporarily, creating a greater output of energy from fusion due to the increasing pressure and therefore the higher rate of fusion, the star would not supernova, but eventually return to their original state, or at least near to their original state gradually since the star would start to expand again and pressure would be taken off the core. You can see mass-ejections in numerous super-massive stars. If "supernova" or "hypernova" had yet more ways to occur and at an earlier stage in a star's life, we might not even be here. At the most, there's one gamma ray burst a day from any random direction in the universe, and not even all of those are from super or hypernova. We would see more explosions from the core of our galaxy, since that's where many super-massive stars are.

 

Also @swan: I know what you mean, but the internet is not the only source of expertise.

Edited December 8, 2010 by steevey

[D H]

First, a correction to post #29. The β⁺ decay that steevey described in post #28 is ¹¹C to ¹¹B.

 

 

I checked my own "wiki-answers" which I replied to some time ago for someone else, if that's what you mean, otherwise I checked wikipedia.org myself and did not see that on wikipedia.org. I can show you a screen shot if you'd like.

It doesn't matter whether you used wikipedia directly, some site that rehosts wikipedia content, or some other site entirely. The important thing is that you don't know the difference between β⁺ decay and pair production. Given that, who do you think comes off as more credible, you or technical paper after technical paper after technical paper on pair instability supernova published in peer-reviewed journals? I cited two such articles in post #25 above, one published in Nature ('nuff said) and the other in ApJ (no slouch of a journal either). Think about it for a second.

 

At this point I call troll.

Edited December 8, 2010 by D H

[Martin]

Steevey, you aren't listening. Please read post #17 again. When a high enough temperature is reached the gamma radiation is no longer efficient at supporting outer layers. And the hotter it gets the less effective fusion becomes at supporting outer layers. That is why your reasoning just now is bad.

 

Be careful about dismissing people if you don't always know what you are talking about, Steevey. Nobody knows it all (not me anyway.)

 

Arch gave a fairly clear (if very brief) mention of the pair-instability hypernova mechanism. Indeed it is believed to proceed by a kind of chain reaction which in effect traps increasing numbers of gamma photons once they reach a certain threshhold energy---so they no longer help to support the outer layers by radiation pressure.

 

The gamma photon reacts with an atomic nucleus to produce an electron positron pair. The particles and antiparticles in the core then annihilate to produce more gamma photons with the required energy to repeat the interaction.

 

This can happen in a massive (>150 solar) star long before she has run out of fuel. The core full of good stuff ready for a runaway thermonuclear explosion if the temperature gets high enough.

 

All that needs to happen is the temperature reaches the threshhold where photons are diverted by the pair-production reaction from their job of supporting the outer layers. Then there is an abrupt drop in pressure. The outer layers come crashing. Temperature rises. More gamma photons are absorbed by the pair-production. More outer layer crashes down. And the remaining fuel in core experiences runaway detonation.

 

In a pair-instability hypernova you don't even necessarily get a neutron-star or black hole remnant, at least according to the theoretical model.

 

It's cool. I think that was what Arch was trying to say in a few words.

 

Your reasoning in this post is bad. A typical "non-metallic" core in this case might be primarily oxygen and around 100 solar masses. (star more massive, core say 100 solar). All that oxygen is potential fusion fuel.

 

But the fusion energy is now being bled off into the pair creation reaction and no longer serves to support outer layers. And the hotter the core gets the less effective a given amount of fusion energy becomes, because more gets trapped into pair creation. So the star cannot "return to normal" by increasing rate of fusion in core.

 

... If it's only a partial collapse and a drop in pressure, but it's before when the star is metal rich and it has an inert iron core, then almost as soon as gravity is starting to pull the star together and condense the core as I mentioned earlier to produce resistance, it fuses the non-metallic core to a point where the fusion process INcreases temporarily, creating a greater output of energy from fusion due to the increasing pressure and therefore the higher rate of fusion, the star would not supernova, but eventually return to their original state, or at least near to their original state gradually since the star would start to expand again and pressure would be taken off the core...

 

This stabilizing feedback is what fails to work when pair-instability conditions are reached.

 

Please let us know if you have contributed anything to Wikipedia or to Wiki-answers, and give us links to articles you have edited. There is a serious possibility that your work is unreliable and the relevant admins should be warned.

 

Thanks.

 

If you show consistent refusal to listen to physical reasoning we will have to think of some way to get your attention.

Edited December 8, 2010 by Martin

[steevey]

Steevey, you aren't listening. Please read post #17 again. When a high enough temperature is reached the gamma radiation is no longer efficient at supporting outer layers. And the hotter it gets the less effective fusion becomes at supporting outer layers. That is why your reasoning just now is bad.

 

 

 

Your reasoning in this post is bad. A typical "non-metallic" core in this case might be primarily oxygen and around 100 solar masses. (star more massive, core say 100 solar). All that oxygen is potential fusion fuel.

 

But the fusion energy is now being bled off into the pair creation reaction and no longer serves to support outer layers. And the hotter the core gets the less effective a given amount of fusion energy becomes, because more gets trapped into pair creation. So the star cannot "return to normal" by increasing rate of fusion in core.

 

 

 

This stabilizing feedback is what fails to work when pair-instability conditions are reached.

 

Please let us know if you have contributed anything to Wikipedia or to Wiki-answers, and give us links to articles you have edited. There is a serious possibility that your work is unreliable and the relevant admins should be warned.

 

Thanks.

 

If you show consistent refusal to listen to physical reasoning we will have to think of some way to get your attention.

 

 

http://wiki.answers....sitron_produced

that's the post I made

 

Otherwise, I see what your saying, but not all energy generated by the core is gamma rays. There is probably a decent percentage of a super-massive star's output energy from fusion that is energetic enough to be gamma rays, and yet there aren't any recorded super-massive stars (at least as far as I've seen) which have died in a supernova before their natural time from an iron core. Whenever there's just a star, and it's completely gone, as in there's no more star, NOT a mass ejection, there's always heavier elements and iron. You can look at any recorded supernova remnant and find iron. There might be some cases where a mass ejection is very large which dims a star and some scientists are looking for an answer as to why that happens, and they think that this might be a theory that explains why but probably isn't. And the reason I can say it "probably isn't" is because my friend who is a plasma physicist who knows all about stars had never heard of this theory before.

Can you show me actual documented data-files where there's proof and the only explanation for the supernova is a pair instability reaction? In every picture of a supernova remnant that's been adjusted for us to see them in color as in our visible light spectrum, there's the color blue. What blue means in those pictures in "iron". If you can even find me an actual supernova remnant without any blue coloration, then I might consider this to be a considerable theory. But otherwise, there would have to be more supernova occurring in the universe if super-massive stars could collapse before they would in the process of fusing heavier and heavier elements, which with super-massive stars is already pretty fast.

Edited December 8, 2010 by steevey

[D H]

http://wiki.answers....sitron_produced

Your article should mention that there are many such isotopes that decay via β⁺ emission and that Carbon-11 is but one example. β⁺ decay is one way, but not the only way, to produce positrons. Pair production can be a much more prolific source of positrons that β⁺ decay. I suggest that you read http://www.aps.org/meetings/unit/dpp/vpr2008/upload/LLNL_Chen.pdf.

 

 

 

There is probably a decent percentage of a super-massive star's output energy from fusion that is energetic enough to be gamma rays, and yet there aren't any recorded super-massive stars (at least as far as I've seen) which have died in a supernova before their natural time from an iron core.

I gave two excellent references in post #25. I suggest you read them.

 

I also referred to Type Ia supernova in post #27. I suggest you read up on Type 1a supernova as well. While the evidence for pair instability supernovae is currently rather scanty, there is plenty of evidence for Type 1a supernovae, so much so that scientists use them as "standard candles".

 

 

[long winded use of the Chewbacca defense elided.]What blue means in those pictures in "iron".

Stop putting words in our mouths, steevey. Use of fallacies is strongly discouraged at this site. Nobody here has said that pair instability supernova or Type 1a supernova do not produce iron. In fact, they produce quite a bit of iron. The iron is produced by the supernova event in the case of a pair instability supernova or a Type 1a supernova. That the prior production of iron is the cause of the supernova event is true for core collapse supernovae but it is not true in general.

 

You appear to be making hasty generalizations here. I suspect that you read an article on β⁺ emission and assumed that this is the mechanism (the one and only mechanism) by which positrons can be created. I suspect you read an article on core collapse supernova and assumed that this is the one and only mechanism that fuel a supernova.

[Martin]

 

 

I gave two excellent references in post #25. I suggest you read them.

 

===quote DH==

 

... In fact, they produce quite a bit of iron. The iron is produced by the supernova event in the case of a pair instability supernova or a Type 1a supernova. ...

 

==endquote==

 

I have been reading the first of those two references in post #25---the one about SN 2007bi.

 

An important PISN (pair instab. SN) signature was the large amount of Nickel-56. Predicted by the PISN model. 56 is divisible by 4. 14 helium nuclei come together. Energetically favored.

 

Ni-56 is made at the time of the explosion and decays over a few days to iron.

 

I gather the PISN model has been around, been studied, for 30 years or more. It's clearly mainstream. Simply that PISN events are rare and the first clear instance was 2007bi. They knew what they were looking for (big release of Ni-56 etc etc.)

 

 

Also it's good you pointed out the similarity with the (much smaller) Type 1a! That is another one where it is not iron-core-collapse. There is a core of potentially good fusion fuel, it just needs something to set it off and you get a runaway thermonuclear explosion. The Chandrasekhar trigger. That should also have a Nickel-56 signature, I suppose, but it would be different from PISN in other ways.

[steevey]

While the evidence for pair instability supernovae is currently rather scanty, there is plenty of evidence for Type 1a supernovae, so much so that scientists use them as "standard candles".

 

Never had anything against type 1a supernova, other than the fact that what's supernova-ing isn't a star going its normal course therefore making it irrelevant stars, not white dwarfs, but how stars supernova. But otherwise, then we agree that there is less than adequet evidence to support pair-instability supernovae.

 

Ni-56 is made at the time of the explosion and decays over a few days to iron.

 

 

 

 

Whats wrong with isotopes being formed from an iron core supernova or other non instability supernova for that matter? Virtually all elements above iron to uranium are formed from supernova, and you don't even need supernova to produce large quantities of an isotope, just large amounts of certain types of radiation.

Edited December 9, 2010 by steevey

[Martin]

As DH said, stop putting words in our mouths. Nothing wrong with isotopes being formed in iron core supernova. Didn't say there was. You seem more interested in arguing than in learning. DH already called troll. I have to reluctantly go along.

[swansont]

!

Moderator Note

It's time to stop this. Argument from incredulity and a wikianswers post don't really match up against peer reviewed articles and years of study.