Does an exploding star fuel a future star?

13 April 2008

Question

I understand the sun gets its power from hydrogen fusion and gradually fusing together bigger and bigger atoms. Towards the end of its life and particularly if it goes supernova it blasts all of the heavier elements out into the surrounding space. I’ve often heard it said it’s what feeds the next generation of stars. Is it the spent star fuel that goes on to create the new star?

Answer

We put this question to Chris Davis:

It certainly happens if you burn hydrogen to form helium the star is the consequence of an equilibrium of forces. You've got the gravitational collapse of that body of gas, pulling inwards on it and heat generated by the nuclear reaction in it pulling the star out. You've got to have an intense amount of pressure in the middle to force hydrogen nuclei close enough together to form helium. There are various other burning cycles. You can burn helium to produce carbon but eventually when all the fuel is used up in the core there is no forcing out of the star. Gravity wins out and it collapses the star in on itself. When this happens, very briefly you get a large increase in density in the star's core. That can generate these much heavier elements and then the star will explode. Chris - So you can look at it as the stars are the uteruses of the universe, they give us everything that we're made of?Chris D - That's true. The star isn't going to be completely burned to the other element. There is going to be a large amount of hydrogen. Also, the universe is still very much dominated by hydrogen gas which is the primal fuel for stars. That dust, that matter, the heavier elements will be spread out into space. Some of it will contaminate the next generation of stars. As another cloud starts to collapse together under its own [gravity] you'll get some of that heavier element polluting, if you like, the new star that's formed. It won't be pure hydrogen to start with and you'll still have the majority of the gas will be hydrogen but with the heavier elements surviving.

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