First-ever evidence of nuclear fission in cosmos reveals how elements never found on Earth form

Research suggests stars may produce elements heavier than those at high end of periodic table

Vishwam Sankaran
Friday 15 December 2023 05:10 GMT

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Astronomers have detected the first-ever signs of nuclear fission happening in stars, a discovery that sheds light on how elements heavier than those found naturally on Earth form in the cosmos.

Until now elements heavier than iron on the periodic table, including the gold and silver in our ornaments, are thought to be created from cataclysmic explosions like the merger of two neutron stars.

In the merger of such dying star remnants, a rapid capture process of neutrons, or r-process, is thought to produce many of the chemical elements in the universe heavier than iron.

But new research, published earlier this month in the journal Science, offers the first evidence of fission – the process behind most nuclear reactors on the Earth – operating in the cosmos and leading to the creation of such heavy elements.

Scientists, including those from the North Carolina State University in the US, identified excess abundances of certain elements in some stars.

This is consistent with these elements being products of nuclear fission of even heavier elements.

The latest discovery suggests stars may produce elements with an atomic mass over 260 – heavier than those at the high end of the periodic table.

“That 260 is interesting because we haven’t previously detected anything that heavy in space or naturally on Earth, even in nuclear weapon tests,” Ian Roederer, another author of the study, said.

“But seeing them in space gives us guidance for how to think about models and fission – and could give us insight into how the rich diversity of elements came to be,” Dr Roederer said.

In the study, researchers combed through the variety of elements residing in very old stars and found signs of nuclear fission – the process by which an atom’s nucleus splits into two smaller ones, producing lighter elements along with the release of enormous amounts of energy.

“People have thought fission was happening in the cosmos, but to date, no one has been able to prove it,” study co-author Matthew Mumpower from the Los Alamos National Laboratory in the US said.

Scientists estimated the amounts of heavy elements in 42 well-studied old stars in the Milky Way galaxy known to have heavy elements.

When researchers assessed the amounts of each heavy element found in these stars collectively, they identified previously unrecognised patterns.

These patterns suggested that some elements listed near the middle of the periodic table – such as silver and rhodium – are likely the remnants of heavy element nuclear fission.

“Every time nature produces an atom of silver, it’s also producing heavier rare earth nuclei in proportion. The composition of these element groups are in lockstep,” Dr Mumpower said.

“We have shown that only one mechanism can be responsible – fission – and people have been racking brains about this since the 1950s,” he added.

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