One of the longstanding open problems in physics is the quest to understand how the elements on the periodic table are created in nature. The heaviest of these elements, those above iron, are believed to be forged in cataclysmic astrophysical events such as supernova or the merging of compact objects, for instance, neutron stars. In the rapid neutron capture or r-process of nucleosynthesis, neutrons are absorbed by light nuclei at astonishing rates to create heavy nuclei. However, we do not yet know under exactly what conditions this process takes place in the universe.

One way to resolve the question of the site of the r-process is to compare the results of computer simulations of proposed astrophysical environments to the pattern of r-process abundances observed in the solar system. This approach requires the answer to many other questions and interweaves knowledge of both astrophysical events and nuclear structure. For example, one source of uncertainty in the abundance yields predicted by simulation is the adopted nuclear physics model. The nuclear models have large uncertainties since the nuclei that participate in the r-process are so neutron-rich they are tremendously difficult to produce in the laboratory. This lack of experimental information prevents scientists from using pattern comparisons to pinpoint the astrophysical event responsible for the r-process.

Researchers led by M. Mumpower at Los Alamos National Lab have developed a transformative approach to this problem. They have constructed a new technique to glean information about the r-process site from anticipated advances in nuclear physics. They use observations of r-process abundances in the solar system to place an additional constraint on the nuclear models. This approach allows the researchers to reverse engineer nuclear properties from well-defined astrophysical observations producing new nuclear model predictions. The researchers have found that each different type of r-process conditions produces a distinct signature in the updated nuclear model prediction, thus allowing an avenue for the site of the r-process to be tested in the laboratory.

The feasibility of this new frontier is closer than you might think, as new facilities are being constructed which utilize radioactive beams capable of producing some of the nuclei that participate in the r-process. Coupling these exciting new results with experimental campaigns will allow researchers to fine tune their measurements to look for the predicted theoretical signatures in the nuclear models. This combined theoretical and experimental effort will help to answer one of the most difficult open problems in all of physics: where in the universe are the heavy elements on the periodic table created?