[TML] Jewelry was Re: Personal Armor Noise

[shadow at shadowgard.com]

On 7 May 2008 at 16:18, Joseph Paul wrote:

>  >Kelly St.Clair wrote:
>  >
>  >> Pretty much every atom heavier than helium - including the carbon that
>  >> makes up both diamonds and us - was, at some point, in the
>  >heart of a star.
>  >
>  >Actually, I think the stuff actually in the heart of the star generally
>  >stays there; what escapes is mostly outer layers.
> 
> Do we have stars that go boom and pretty much completely unravel ie leave no
> core? Where is the Fe layer in a star?

Yes,

And even the ones that leave a remnant blast a lot of the layers 
including those quite close to the core out into space.
 
> If stellar fusion only goes up to Fe how do we get the elements heavier than
> that?

Fusion can form heavier elements. But it does so at a net *loss* of 
energy.

So when the core of the star has fused everything init down to Fe-56, 
the core starts collapsing. It stops when the degeneracy pressure is 
enough to stop the infalling matter. 

The shock wave from the sudden halt (the infalling material will have 
built up quite a respectable velocity before this happens) is enough 
to supply energy to fuse atoms clear up into the transuranics.

And as the shockwave propogates it causes "prompt" fusion of a lot of 
the elements lighter than Fe-56. Wghich supplies the energy to blow 
off the outer layers and even a lot of the outer core (thus releasing 
the elements out past iron.

That's for "red giant" supernovas. 

For "white dwarf/neutron star in a close binary" superbova, you get 
material (mostly hydrogen) lost from the companions building up on 
the surface of the white dwarf. If it builds slowly, it'll eventually 
have enough pressure on the lower part of the layer to initiate a 
fusion reaction.

That's a nova. Novas can (and often do) repeat. Many have an actual 
cycle.

If it builds up rapidly, it can cause a supernova when it finally 
triggers. And that destroys the white dwarf or neutron star in the 
process. 
--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com