Expert: Jayendra Upadhye - 12/13/2005

Question
Hi,
I read in a book that productoin of elements in the core of stars is terminated to iron.
how heavier elements produce?
Thanks

Answer
Hi Alireza,
The answer is a bit complicated.
Most stars in spiral galaxies (rather the arms of spiral galaxies) are 2nd or even 3rd generation stars.
These form out of gas and dust clouds near supernova explosiions, by the shock wave of the supernova ejecta hitting the cloud. (eadle nebula M16 on the messier catalog is a good example).

Such stars inherit a lot of heavier trace elements that are trans-iron elements on the periodic table.
These elements reside in the stellar core all thru the stars life! and are re-ejected when it itself goes supernova. Or remain locked up in the stellar cores as the stars become white dwarfs and die a slow death over 10s of billions of years.

In the supernovas themselves, The supernova is started or triggered by
1 - the shutting off of the thermal source as no fusion is possible beyond iron.
2 - The core collapses as a result of this thermodynamic imbalance as pressure is lost due to loss of heat source.
3 - The overlying layers follow suit.
4 - The iron nucleus collapses in seconds to form a "diamond hard" neutron star. (100s of times harder actually).
5 - The infalling material hits this core and rebounds.
6 - This results in a standing or outward moving shock wave.
7 - The shock wave literally punches thru the massive inflowing matter, and the wavefront generates all trans-iron elements in a bang that equals the whole galaxy in in its brilliance!
8 - Uranium thru plutonium and all the unstable (neutron proton ratio >=1.5 are also formed here, and in blow the hell out of the chaotic infalling matter in terrible nuclear fission explosions as they randomly come together and exceed critical mass! But! all these fission explosions are masked by the overall energy from the fusion reactions as the trans iron fusion progresses along the wavefront.

The leftover crumbs (ejecta) travels outwards and seeds the births of other stars near by.
These in turn secret away the trans iron elements in their cores or the planets formed around them keep these as their "ores"!

Even later puny humans make "bombs" out of them and imitate the original supernova when the set off their h bomb or u235 or plutonium bombs!

Hope that suffices.
Jayen