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The Cosmic Forge: How Ancient Stars Crafted Elements Beyond Earth’s Reach

Researchers have found that ancient stars could generate elements heavier than those naturally found on Earth, with atomic masses over 260. This discovery enhances our understanding of element formation in stars, particularly through the rapid neutron capture process (r-process) occurring in neutron stars. Credit:

New research reveals that ancient stars can create elements heavier than those on Earth, with atomic masses exceeding 260, advancing our understanding of cosmic element formation.

How heavy can an element be? An international team of researchers has found that ancient stars were capable of producing elements with atomic masses greater than 260, heavier than any element on the periodic table found naturally on Earth. The finding deepens our understanding of element formation in stars.

The Cosmic Element Factories

We are, literally, made of star stuff. Stars are element factories, where elements constantly fuse or break apart to create other lighter or heavier elements. When we refer to light or heavy elements, we’re talking about their atomic mass. Broadly speaking, atomic mass is based on the number of protons and neutrons in the nucleus of one atomAn atom is the smallest component of an element. It is made up of protons and neutrons within the nucleus, and electrons circling the nucleus.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>atom of that element.

The heaviest elements are only known to be created in neutron stars via the rapid neutron capture process, or r-process. Picture a single atomic nucleus floating in a soup of neutrons. Suddenly, a bunch of those neutrons get stuck to the nucleus in a very short time period – usually in less than one second – then undergo some internal neutron-to-proton changes, and voila! A heavy element, such as gold, platinum, or uranium, forms.

Instability of Heavy Elements

The heaviest elements are unstable or radioactive, meaning they decay over time. One way that they do this is by splitting, a process called fission.

“The r-process is necessary if you want to make elements that are heavier than, say, lead and bismuth,” says Ian Roederer, associate professor of physics at North Carolina State UniversityFounded in 1887 and part of the University of North Carolina system, North Carolina State University (also referred to as NCSU, NC State, or just State) is a public land-grant research university in Raleigh, North Carolina. NC State offers a wide range of academic programs and disciplines, including the humanities, social sciences, natural sciences, engineering, business, and education. It is known for its strong programs in engineering, science, and technology and is a leader in research and innovation. It forms one of the corners of the Research Triangle together with Duke University in Durham and The University of North Carolina at Chapel Hill. ” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>North Carolina State University and lead author of the research. Roederer was previously at the University of Michigan.

“You have to add many neutrons very quickly, but the catch is that you need a lot of energy and a lot of neutrons to do so,” Roederer says. “And the best place to find both are at the birth or death of a neutron starA neutron star is the collapsed core of a large (between 10 and 29 solar masses) star. Neutron stars are the smallest and densest stars known to exist. Though neutron stars typically have a radius on the order of just 10 – 20 kilometers (6 – 12 miles), they can have masses of about 1.3 – 2.5 that of the Sun.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>neutron star, or when neutron stars collide and produce the raw ingredients for the process.

“We have a general idea of how the r-process works, but the conditions of the process are quite extreme,” Roederer says. “We don’t have a good sense of how many different kinds of sites in the universe can generate the r-process, we don’t know how the r-process ends, and we can’t answer questions like, how many neutrons can you add? Or, how heavy can an element be? So we decided to look at elements that could be made by fission in some well-studied old stars to see if we could start to answer some of these questions.”

Previously Unrecognized Patterns Identified

The team took a fresh look at the amounts of heavy elements in 42 well-studied stars in the Milky WayThe Milky Way is the galaxy that contains our Solar System and is part of the Local Group of galaxies. It is a barred spiral galaxy that contains an estimated 100-400 billion stars and has a diameter between 150,000 and 200,000 light-years. The name "Milky Way" comes from the appearance of the galaxy from Earth as a faint band of light that stretches across the night sky, resembling spilled milk.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Milky Way. The stars were known to have heavy elements formed by the r-process in earlier generations of stars. By taking a broader view of the amounts of each heavy element found in these stars collectively, rather than individually as is more common, they identified previously unrecognized patterns.

Those patterns signaled that some elements listed near the middle of the periodic table – such as silver and rhodium – were likely the remnants of heavy element fission. The team was able to determine that the r-process can produce atoms with an atomic mass of at least 260 before they fission.

“That 260 is interesting because we haven’t previously detected anything that heavy in space or naturally on Earth, even in nuclear weapon tests,” Roederer says. “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.”

For more on this research, see “Incredibly Profound” Evidence of Nuclear Fission Across the Cosmos.

Reference: “Element abundance patterns in stars indicate fission of nuclei heavier than uranium” by Ian U. Roederer, Nicole Vassh, Erika M. Holmbeck, Matthew R. Mumpower, Rebecca Surman, John J. Cowan, Timothy C. Beers, Rana Ezzeddine, Anna Frebel, Terese T. Hansen, Vinicius M. Placco and Charli M. Sakari, 7 December 2023, Science.
DOI: 10.1126/science.adf1341

The work appears in Science and was supported in part by the National Science Foundation and the National Aeronautics and Space Administration.

Source: SciTechDaily