At these temperatures, silicon and other elements photodisintegrate by energetic thermal photons ejecting alpha particles.
Silicon burning differs from earlier fusion stages of nucleosynthesis in that it entails a balance between alpha-particle captures and their inverse photo ejection which establishes abundances all alpha-particle elements in the following sequence in which each alpha particle capture shown is opposed by its inverse reaction, namely, photo ejection of an alpha particle by abundant thermal photons: Zn photon In these circumstances of rapid opposing reactions the abundances are not determined by alpha-particle-capture cross sections; rather they are determined by the values that the abundances must assume in order to balance the speeds of the rapid opposing-reaction currents.
Each abundance takes on a stationary value that achieves that balance. Ar photon and its inverse, where the free densities of protons and neutrons are also set by the quasiequilibrium.
The silicon-burning quasiequilibrium is a unique construction, simultaneously the most abstract and the most beautiful of nucleosynthesis processes.
As a result of their ejection from supernovae, their abundances increase within the interstellar medium.
Elements heavier than nickel are created primarily by a rapid capture of neutrons in a process called the r-process.
The first is that a white dwarf star undergoes a nuclear-based explosion after it reaches its Chandrasekhar limit after absorbing mass from a neighboring star (usually a red giant).
The second, and more common, cause is when a massive star, usually a supergiant, reaches nickel-56 in its nuclear fusion (or burning) processes.
The latter synthesizes the lightest, most neutron-poor, isotopes of the heavy elements.
A supernova is a massive explosion of a star that occurs under two principal scenarios.