- Elements with nuclei heavier than that of iron. These elements cannot be produced in normal stars and are instead produced from iron cores built up at the centre of heavy stars before or during supernova explosions. The fusion process which builds up the lighter elements stops at iron because beyond it fusion uses up energy rather than releasing it. The small abundance of heavier elements by comparison with the lighter ones is due to the small amount of the universe’s total matter which has to date been reprocessed through supernovae.
Not what you were looking for?