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Stellar Events May Reveal How Heavy Elements Were Formed

Sean Liddick

To determine how the universe’s heavy elements – gold, silver and many others – came about, a team of international researchers is studying both the largest and smallest things known to us – stars and atoms.

The team, led by scientists from Michigan State University, is providing critical data to computer models of what are known as stellar events – supernovas and neutron stars mergers, to be exact.

By matching the computer models with real observations of these cataclysmic events, it could help answer one of astronomy’s most puzzling questions.

A supernova is a star that, in its old age, collapses and then catastrophically explodes under its own weight; a neutron-star merger occurs when two of these small yet incredibly massive stars come together and spew out huge amounts of stellar debris.

By conducting experiments in MSU’s National Superconducting Cyclotron Laboratory, the researchers were able to come a bit closer to determining what actually goes on during these stellar events, an important step in determining how heavy elements were formed.

What the researchers were looking at, at the atomic-sized level, is something called neutron capture. This is when an atom latches onto a neutron, increasing its mass number and helping it attain “heavy” status.

The heavy elements produced in these processes have atomic numbers greater than 26. The atomic number is the number of protons in the nucleus of an atom.

“What we’re trying to do is infer, or re-create, the probability of neutron capture, because it’s almost impossible to measure directly,” said Sean Liddick, an MSU associate professor with appointments in chemistry and the NSCL. “We want to match the theoretical models to the stellar observations.”

Using a telescope, the observational astronomers were able to determine the amount of heavy elements in that spectrum. “Then,” said Liddick, “what you would like to be able to do is compare that to a theoretical prediction for what happens during these explosive events.

“What we’re doing is trying to remove some of the uncertainty and build a better theoretical model.”

The research is published in the journal Physical Review Letters. Liddick said this research is a harbinger of the work that will be done at the Facility for Rare Isotope Beams, currently under construction at MSU.

“We’re laying the groundwork that will be significantly extended by the broader reach provided by FRIB,” he said.

MSU is establishing FRIB as a new scientific user facility for the Office of Nuclear Physics in the U.S. Department of Energy Office of Science.

Under construction on campus and operated by MSU, FRIB will enable scientists to make discoveries about the properties of rare isotopes in order to better understand the physics of nuclei, nuclear astrophysics, fundamental interactions, and applications for society, including in medicine, homeland security and industry.

– Tom Oswald, Sean Liddick via MSU Today


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