Nuclear fission, never before observed in stars, suggests superheavy elements formed without the need for supernovae
Los Alamos National Laboratory researchers led by theoretical physicist Matthew Mumpower have identified a possible fission signature in data from elements in very old stars, suggesting that nature likely produces superheavy nuclei that exceed the heaviest known elements in the periodic table.
The study shows a connection between precision light metals such as silver and rare earth cores such as europium. This positive correlation suggests that a consistent process occurs in the formation of heavy elements. The team found that fission is the only plausible explanation that reproduces this trend. This marks the first evidence of splitting in the cosmos and confirms a theory put forward several years ago.
The research also suggests that there may be elements with an atomic mass (number of protons plus neutrons) of 260 that are heavier than those at the top of the periodic table. Mumpower developed the fission models to predict and control the observation results under the leadership of Ian Roederer of North Carolina State University.
Heavy elements are not only created from supernovae
Astrophysicists have long believed that heavy elements beyond iron are formed in stellar explosions such as supernovae or when two neutron stars merge. Through the process of rapid neutron capture, called the R-process, atomic nuclei capture neutrons to form heavier elements. It remains a mystery whether some of these elements become too heavy to hold together and split, or whether they split, creating two atoms of lighter but still heavy elements and releasing significant energy.
The analysis led by Roederer examined observational data from 42 stars and found exactly the predicted correlation, providing a clear sign of the split in the formation of these elements. This correlation is very robust for r-enhanced stars and shows that every time nature produces a silver atom, it also produces proportionately heavier rare earth nuclei.
The fission models developed at Los Alamos are essential for interpreting experiments and completing data when few measurements are available. These models, used in both nuclear weapons and reactor research, have demonstrated exceptional performance compared to measured data, lending credibility to their extrapolations.
The study was funded by Los Alamos National Laboratory’s Laboratory Directed Research and Development program and published in the journal Science.
REFERENCE
Element abundance patterns in stars indicate fission of nuclei heavier than uranium. Science.