Dying Stars May 'Dissolve' To Create Heavy Elements

As massive stars collapse into black holes, powerful jets tearing out from their hearts may "dissolve" the stars' outer layers, providing the ingredients to make heavy elements.

This is the conclusion of a new study by physicists from the Los Alamos National Laboratory in New Mexico, which could shine a light on the mysterious origins of the elements at the bottom of the periodic table.

"The creation of heavy elements such as uranium and plutonium necessitates extreme conditions," said paper author Matthew Mumpower in a statement.

"There are only a few viable yet rare scenarios in the cosmos where these elements can form, and all such locations need a copious amount of neutrons."

Free neutrons have a half-life of only 15 minutes—meaning that there are limited scenarios in which they are present in enough numbers to form heavy elements by the so-called rapid neutron capture "r process."

"We propose a new phenomenon where those neutrons don't pre-exist but are produced dynamically in the star," Mumpower added.

Massive stars start to die when their nuclear fuel runs out. Unable to keep pushing out against their own gravity, they begin to collapse in upon themselves, forming a black hole.

And if this hole is spinning sufficiently fast, powerful jets are launched along its rotational axes—jets that can end up containing a broad spectrum of photons, many at high energies.

Each jet, Mumpower explains, punches through the outer layers of the dying star in its path, "like a freight train plowing through snow."

In the researcher's scenario, high-energy photons interact with atomic nuclei, transforming protons into neutrons. At the same time, atomic nuclei are dissolved into their component parts, releasing more free neutrons to power the r process.

While protons are trapped in the jet by its strong magnetic fields, chargeless neutrons can get forced out of the jet into the surrounding hot cocoon of material.

Compared with the stellar material they are plowed into, the neutrons are extremely dense—providing just the conditions needed for the formation of heavy elements. These are then expelled out into space as the star is ripped apart.

The neutron-forming process proposed by the researchers could also help to explain another unusual astrophysical phenomena—why kilonovae often accompany the long-duration gamma ray bursts resulting from the collapse of massive stars into black holes.

A kilonova is a powerful burst of visible and infrared light. They are more commonly associated with the collision of two neutron stars, or the merger of a neutron star and a black hole.

With their initial study complete, the researchers are now hoping to run simulations of their high-energy jet framework and explore the complex microphysics involved.

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about nucleosynthesis? Let us know via science@newsweek.com.

References

Mumpower, M. R., Lee, T.-S. H., Lloyd-Ronning, N., Barker, B. L., Gross, A., Cupp, S., & Miller, J. M. (2025). Let There Be Neutrons! Hadronic Photoproduction from a Large Flux of High-energy Photons. The Astrophysical Journal, 982(2). https://doi.org/10.3847/1538-4357/adb1e3