The r-process Supernova nucleosynthesis

during supernova nucleosynthesis, r-process (r rapid) creates neutron-rich heavy isotopes, decay after event first stable isotope, thereby creating neutron-rich stable isotopes of heavy elements. neutron capture process occurs in high neutron density high temperature conditions. in r-process, heavy nuclei bombarded large neutron flux form highly unstable neutron rich nuclei rapidly undergo beta decay form more stable nuclei higher atomic number , same atomic mass. neutron flux extremely high, 10 neutrons per square centimeter per second. first calculation of dynamic r-process, showing evolution of calculated results time, suggested r-process abundances superposition of differing neutron fluences. small fluence produces first r-process abundance peak near atomic weight a=130 no actinides, whereas large fluence produces actinides uranium , thorium no longer contains a=130 abundance peak. these processes occur in fraction of second few seconds, depending on details. hundreds of subsequent papers published have utilized time-dependent approach. interestingly, modern nearby supernova, 1987a, has not revealed r-process enrichments. modern thinking r-process yield may ejected supernovae swallowed in others part of residual neutron star or black hole.