s-process

A process of nucleosynthesis in which heavy elements are created from light ones by the successive capture of neutrons. The "s" stands for slow. In the s-process there is time for a newly formed nucleus to decay by the emission of an electron (beta decay) before another neutron is captured, in contrast with rapid neutron capture - the r-process - in which this is not the case. The s-process is believed to occur within stars of less than 9 solar masses during the red giant phase of evolution. Some isotopes of heavier elements can be formed only by the s-process, and their abundance in the solar system is strong evidence that the s-process was responsible. These elements were created in a generation of stars that existed prior to the formation of the solar system. When those sufficiently massive to do so exploded as supernovae, they enriched the interstellar material with the products of nuclear processes from their interiors.