The rapid neutron capture process, or the so-called r-process, occurs in neutron-rich environments such as neutron star mergers or certain types of supernovae. This process is thought to produce many of the chemical elements heavier than iron, but the details are poorly understood and cannot be studied in the lab. In new research, Los Alamos National Laboratory theoretical physicist Matthew Mumpower and his colleagues analyzed r-process element abundances previously observed in stars. They identified correlated excess abundances of certain elements in some stars, which is consistent with these elements being fission products of even heavier elements. These results indicate that some r-process events make elements heavier than uranium, which then decay into the elements observed in stars.
“People have thought fission was happening in the cosmos, but to date, no one has been able to prove it,” Dr. Mumpower said.
“Using the latest observations, we found a correlation between light precision metals like silver and rare earth nuclei like europium.”
“When one of these groups of elements goes up, the corresponding elements in the other group also increase — the correlation is positive.”
Astrophysicists have long believed heavy elements beyond iron were formed in stellar explosions called supernova or when two neutron stars merged.
As the name implies, the latter are composed largely of neutrons, which together with protons form the nuclei of all atoms.
Through the r-process, atomic nuclei grab neutrons to form heavier elements. Whether some grow too heavy to hold together and split, or fission, forming two atoms of lighter but still heavy elements (and releasing tremendous energy) has remained a mystery for a half century.
In 2020, Dr. Mumpower and co-authors first predicted the distributions of fission fragments for r-process nuclei.
A subsequent study predicted the co-production of light precision metals and rare earth nuclei.
This co-production of…
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