Neutron capture is a nuclear process where an atomic nucleus absorbs a neutron. This can occur in various elements, particularly in heavy nuclei like those of uranium or plutonium. When a nucleus captures a neutron, it may become unstable and can either emit radiation or undergo fission, splitting into smaller nuclei and releasing energy. This process is significant in nuclear reactions, including those in nuclear reactors and stellar nucleosynthesis. In stars, neutron capture contributes to the formation of heavier elements through processes like the s-process and r-process, which occur during different stages of stellar evolution.