Many heavy elements, such as gold, are thought to form in cosmic environments rich in neutrons—think supernovae or mergers of neutron stars. In these extreme settings, atomic nuclei can rapidly capture neutrons and become heavier, creating new elements. At the far reaches of the nuclear chart, which arranges all known nuclei according to their number of protons and neutrons, lie unexplored nuclei that are crucial to understanding the details of this rapid neutron-capture process. This is especially the case for nuclei with fewer than 82 protons and more than 126 neutrons.
Source:
https://phys.org/news/2020-02-isolde-unexplored-region-nuclear-exotic.html