Expert: Jayendra Upadhye - 12/8/2004

Question
Would there be any fission reactions in a star aside from the prominent fusion reactions?

Also, would fission reactions be distinguishable or measurable if they occured in a star?

Thanks for your time.

Answer
Hi Ken,
All stars are more than 99% hydrogen when they start.

By fusion in the core, the other elements are built up but that chain never crosses the step of building iron.

Iron building is an endothermic reaction and absorbs vast quantities of energy, sapping the fusion process itself.

That is the time, this "thermal shutoff" cools the core sufficiently for gravity to implode it.

This implosion is very quick (in order of seconds rom what i read). It quickly forms the core nuetron star in case of supernovas.

The overlying layers of the star follow suit and impinge and rebound from the diamond hard (or harder) neutron star surface.

The rebounding material meets the still inward falling outer layers and "punch" through, triggering a supernova.

Elements beyond iron, and possibly radioactive transient isotopes (with quick half lives) are also generated and so are the uranium, thorium etc in trace quantities.

THAT is the ONLY PART where fission reactions happen. when the newly formed isotopes with neutron proton ratio in unstable region (1.5 1.7) fission into various products as dictated by their half lives.

No! Because they NEVER occur when the star is normal. *As the fissionable material is not there in the first place or is in very very small quantities. [That is inherited from previous super-novas].

During the supernova explosion proper {trans-iron nucleo synthesis], the fission component is swamped by the fusion component.


ref:-http://www.vectorsite.net/tastga4.html
Jayen