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Hi Shane, I was wrong on lots of points in this post. Iron 56 is indeed the end point for the fusion process. The "bottom of the energy valley". Oyggen is not that hard to "light". Silicon is a bit hard to "burn" and the reaction of silicon plus silicon seems not to occur. Rather an exchange of alpha particles forms iron one step at a time as some silicons loose particles and some gain them. > > I need to knit pick here 8o) > > On Tue, 27 Sep 1994, Jason Rogers wrote: > > *snip* > > > In a large star (I think about twice ours or more, but I don't have the > > figures) as the hydrogen runs out the innner part of the star contracts and > > heats up. (in our star the end will be different, but this bit is much the > > same) The outer part of the star will expand, as it is held up by the great er > > flux of radiation pressure generated by the hotter interior. It will now > > Actually expansion is caused by conservation of angular momentum. > As the inner part of the start contracts, the outter must expand in > order to conserve angular momentum. Expansion is halted by the increase > in radiation pressure that comes about for the collapsing core. I disagree with this one. In this case expansion caused by rotation of any sort would cause a flattened disk of gas/plasma to form. This is not the case, the star seems to expand radially. This would be easily explained by an increase in the light pressure forcing the outer parts of the star further away. I don't see how an increase in radiation pressure could halt the expasion. Any transfer of momentum should be outward from the hot core toward the colder space. > > > start "burning" the helium and as that runs out, other elements. > > These reactions produce less energy than the hydrogen burning and the star > > contracts further in the center. Eventually an "ash of a hard to fuse eleme nt > > builds up in the centre of the star. (I think it's oxygen, but don't quote me) > > Depends on the size of the star, larger ones could have iron cores toward > the end of their lives. > > *snip* > > > Eventually the stars fires go out and it collapses gravitaionally. The cent er > > all fuses at once and all the elements we know that are above oxygen on the > > periodic table get created all at once. This blows the star to bits and the > > It's actually above what ever the star core consists of, large stars will > have iron. > > > new elements are spewed out all over at great speed. This is were most of t he > > stuff that makes up your body (and the earth) were created. Making these > > elements requires that energy is put in (oposite to making the lighter > > elements where you get energy out) so most of these elements "want" to break > > up and make iron56 which is the lowest energy element. They do this by > > emitting an Alpha particle (He atom without electrons). This is called > > "radioactivity" and is the source of Helium we use here on earth. > > *snip* > > Helium would be a lot more expensive if it was distilled from the air. > There is very little helium present in the air. > > Cheers! > > Shane > -- > \ > To go o/\__ Shane Jensen > where only < \__,\ (602) 621-2054 > lizards have "> . | Steward Observatory > gone before. ` .-\ jensen@as*.ar*.ed* > . | > > -- > Send mail for the `techdiver' mailing list to `techdiver@opal.com'. > Send subscription/archive requests to `techdiver-request@opal.com'.
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