Heavy elements

[Phybiz]

Can anyone explain to me how do elements heavier than iron form?

[Starry.Skies]

http://herschel.jpl.nasa.gov/chemicalOrigins.shtml

[[Tycho?]]

Supernovae, look it up on wikipedia.

[sunspot]

Is there any reason why the exothermic output from the lightest elements fusing could not create the endothermic potential to create higher atoms from iron, since these early reactions generate the highest energy output, well within the range needed for building higher atoms?

 

The way I see it, the iron core of the earth is assumed to form because of the weight of iron in the earth's gravitational field, causing it sink to the center of the earth. What is the problem with solar iron sinking due to solar gravity and thereby placing itself in a fusion environment that can build up higher atoms? Besides it won't be easy to excape the hydrogen and light atom density.

[SkepticLance]

Sunspot.

The short answer is that it does not happen because it does not happen. We have a reasonable idea of what is going on in the sun, and the fusion of iron is not it.

 

The reason, though, is related to energy. It just takes a hell of a lot to fuse iron atoms. Thus, it happens in supernovae.

[swansont]

Is there any reason why the exothermic output from the lightest elements fusing could not create the endothermic potential to create higher atoms from iron, since these early reactions generate the highest energy output, well within the range needed for building higher atoms?

 

 

That's what happens in the supernovae. But not during the course of main-sequence fusion, in any significant amounts.

[sunspot]

The thing I do not understand about supernova is why they explode. If all the exothermic fuel is spent and the building up of higher atoms like iron is higher enothermic, where does the energy for explosion come from? It would appear to me that gravity should overcome something so deplete in exothermic output potential.

 

Another observation about higher atoms is our ability to create higher than natural atoms on the surface of the earth. Some of the early ones were made with fission products and did not even require fusion caliber energy.

[swansont]

The thing I do not understand about supernova is why they explode. If all the exothermic fuel is spent and the building up of higher atoms like iron is higher enothermic, where does the energy for explosion come from? It would appear to me that gravity should overcome something so deplete in exothermic output potential.

 

Did you read the link that Starry.Skies gave?

 

 

Another observation about higher atoms is our ability to create higher than natural atoms on the surface of the earth. Some of the early ones were made with fission products and did not even require fusion caliber energy.

 

I'm not sure what "fusion caliber energy" is supposed to mean.

[Phybiz]

Thank for the link Starry.Skies! But after I visited it one more qestion emerged... I dont understand the part of the text:'a vast number of neutrinos blast out of the core' .What really happens there?

[sunspot]

I didn't read the link until now, but it seems reasonable. What I don't understand from the article is why do neutrinos form during the collapse. Is it due to atomic disentegtation? I also thought neutrinos can go through matter like crap through a goose.

 

That aside. One of things that world leaders are afraid of is Iran using a nuclear fission reactor to make plutonium from uranium. The Iranian are feared capable of adding two more protons to Uranium to make plutonium. That makes them more powerful than the sun, on par with super nova. Actually more powerful then supernova, since they don't even need the pressure of a shock wave.

 

When I was talking of only fission level energy I was saying just that. A fission device is used to light a fusion device in H-bombs. The difference in energy output is quite significant.

 

I am sorry if I question the state of the art thinking. But in the light of being able to making Kg quantities of plutonium, I do not see why it is necessary. All it does is assume conditions impossible to prove or disprove.

[swansont]

I didn't read the link until now, but it seems reasonable. What I don't understand from the article is why do neutrinos form during the collapse. Is it due to atomic disentegtation? I also thought neutrinos can go through matter like crap through a goose.

 

The neutrinos come from the fusion reactions. At various stages you are getting protons changing into neutrons, and a neutrino comes out of that reaction. At terrestrial densities they penetrate quite well, but not at the densities in the supernova environment.

 

 

 

That aside. One of things that world leaders are afraid of is Iran using a nuclear fission reactor to make plutonium from uranium. The Iranian are feared capable of adding two more protons to Uranium to make plutonium. That makes them more powerful than the sun' date=' on par with super nova. Actually more powerful then supernova, since they don't even need the pressure of a shock wave.

 

When I was talking of only fission level energy I was saying just that. A fission device is used to light a fusion device in H-bombs. The difference in energy output is quite significant.[/quote']

 

That last line is not necessarily a true statement. It's not that you get so much more energy out of a fusion reaction (you don't), it's the difficulty of getting that much uranium or plutonium to undergo fission rapidly. It tends to blow itself apart.

 

Fusion to form He-4 yields about 25 MeV. Fission of U-235 gives off about 200 MeV. On a reaction basis, fusion gives off less energy. On a "per unit mass" it gives off more. But the amount of mass in a bomb is not really, in and of itself, a limiting factor.