Star-Crushing Jets May Forge the Universe’s Heaviest Elements, Say Scientists

Understanding the origin of heavy elements—those majestic atoms that crown the periodic table like platinum, uranium, and plutonium—remains one of the most profound puzzles in modern physics. Where, exactly, do these elements come from? What cosmic furnaces are capable of producing such extreme material?

This question digs deep into the origins of the universe itself. And while science has come a long way in mapping the synthesis of elements like hydrogen, helium, and even iron in stars, the birthplaces of the heaviest elements have long eluded complete understanding. Now, a bold new theory proposed by a Los Alamos National Laboratory-led team opens an unprecedented window into this stellar mystery. The team is aiming its sights at one of the universe’s most violent and enigmatic events: gamma-ray bursts produced by collapsing stars, and the turbulent jets and cocoons that trail in their wake.

Their daring idea: heavy elements like uranium and plutonium could be forged not in slow cosmic processes, but in a high-speed astrophysical crucible, where light itself transforms matter and floods the surrounding space with neutrons. The theory reimagines the jet of a dying star not just as an outburst of light and fury, but as an elemental forge—a place where the building blocks of our planet may have first taken form.

Gamma-Ray Bursts: The Most Violent Light in the Universe

Gamma-ray bursts (GRBs) are among the most powerful explosions known, releasing in mere seconds as much energy as the Sun will produce in its entire 10-billion-year lifetime. They are not just impressive—they are cataclysmic. Most GRBs occur during the final moments of a massive star’s life, in a titanic collapse that leads to the birth of a black hole. From the dying core, a jet of material is expelled at nearly the speed of light, punching through the star and into space like a cosmic battering ram.

This jet, cloaked in a cocoon of stellar debris, releases a violent cascade of photons across the electromagnetic spectrum. But what if these bursts of high-energy light do more than just signal destruction? What if they act, paradoxically, as creators?

According to the framework proposed by physicist Matthew Mumpower and his colleagues, deep within the heart of the GRB jet, something extraordinary may happen. The photons created in this furnace are so energetic that they may transform protons into neutrons and disassemble entire atomic nuclei into their constituent particles. These neutrons then flood into the surrounding cocoon, creating just the kind of conditions needed for the mysterious and elusive process that builds heavy elements: the r-process.

The R-Process: Nature’s Alchemical Secret

The rapid neutron-capture process, or r-process, is the engine behind the formation of heavy elements. It’s the universe’s way of assembling the most neutron-rich, massive atoms—those that do not emerge from ordinary stellar fusion. But this method has a demanding appetite: it requires immense quantities of free neutrons in extremely short time spans, mere seconds or even milliseconds, to build up atomic nuclei before they can decay.

Therein lies the rub. Free neutrons are notoriously short-lived. With a half-life of just over 14 minutes, they can’t wander long before disintegrating into protons, electrons, and neutrinos. That means the conditions for the r-process must involve not only a large supply of neutrons but also rapid-fire reactions that occur before the neutrons disappear.

Where could such fleeting but neutron-rich conditions occur?

Until recently, scientists believed there were only a few viable answers: the violent collisions of neutron stars, the cores of certain supernovae, and perhaps rare black hole-neutron star mergers. But these events, while spectacular, are relatively rare. The observed abundance of heavy elements in our galaxy suggests something more frequent—or at least more efficient—must be at play.

Mumpower and his team propose a radical possibility: maybe the GRB jet itself, plowing through a collapsing star, becomes a neutron factory.

From Light to Neutrons: The Star’s Final Alchemy

In this scenario, the final act of a massive star plays out like an astrophysical opera. As its nuclear fuel dwindles, gravity wins the battle, and the core collapses into a black hole. If the black hole is spinning fast enough, it generates twisted magnetic fields that can launch an ultra-relativistic jet—material traveling outward at nearly the speed of light.

As this jet smashes through the outer layers of the star, it creates a seething, turbulent cocoon of gas and energy. Picture a freight train barreling through snow, throwing up waves of hot, shredded matter as it goes. That’s the jet, and the cocoon is the swirling chaos it leaves in its wake.

What’s unique in this proposal is what happens at the interface between the jet and the cocoon. The jet is brimming with high-energy photons—essentially light on steroids. These photons are so energetic that they can interact with protons, converting them into neutrons. Even more dramatically, the photons can dissolve entire atomic nuclei, scattering neutrons like cosmic seeds.

Charged protons are trapped by magnetic fields in the jet, but neutrons—uncharged and unconfined—escape into the cocoon, where their density may reach levels high enough to trigger the r-process. The entire sequence unfolds in mere nanoseconds.

The result? A short-lived neutron bath where heavy elements can rapidly form, survive, and eventually be expelled into the galaxy as the star tears itself apart.

A Multi-Force Marvel

What makes this process especially remarkable is that it touches all four of nature’s fundamental forces. Gravity collapses the star and shapes the jet. Electromagnetism generates the magnetic fields that trap protons. The strong nuclear force binds the emerging heavy nuclei, while the weak force governs the conversion of protons to neutrons and the eventual decay of radioactive elements.

Few astrophysical phenomena weave together all these threads. This is science at its most complex and most poetic—where nuclear physics meets general relativity, where stellar death becomes elemental birth.

And it’s not just theoretical fireworks. The implications of this model reach from deep space to deep Earth.

Clues from the Bottom of the Sea

In recent decades, scientists have discovered deposits of iron-60 and plutonium-244 in deep-sea sediments. These isotopes are not of terrestrial origin—they must have rained down from space. But from where? Their presence suggests that nearby astrophysical events, sometime in the last few million years, showered Earth with heavy elements.

Neutron star mergers were once the prime suspects. But such collisions are extremely rare in the local region of the Milky Way. The GRB jet model opens a new possibility: perhaps a collapsar—a collapsing massive star producing a GRB—happened in the cosmic neighborhood, and its jet seeded our solar system with freshly minted heavy elements.

If so, then the story of Earth’s own uranium and plutonium might trace back not to ancient kilonovae, but to a single gamma-ray burst jet—a moment of cosmic violence that left an elemental fingerprint on our world.

Rethinking Kilonova and Stellar Death

This idea doesn’t just help explain deep-sea isotopes. It also challenges current interpretations of astronomical observations. Kilonovae—those brilliant flashes of optical and infrared light that follow some GRBs—are usually tied to merging neutron stars. But if collapsars can also produce the r-process and generate enough heavy elements, they may also trigger kilonova-like phenomena.

Mumpower’s theory provides a compelling alternative mechanism. In this view, the kilonova glow could arise not just from neutron star crashes but from the r-process taking place in the cocoon of a collapsing star’s jet. That means astronomers might need to revise their understanding of which cosmic events are true heavy-element factories.

Simulation on the Edge of Physics

To fully test this scenario, Mumpower and his colleagues plan to simulate the extreme conditions of the jet-cocoon interface. That’s no small feat. It requires modeling not just fluid dynamics and magnetic fields, but also nuclear reactions, neutrino transport, and relativistic particle behavior—all in an environment moving close to light speed.

This is a multiphysics problem in the truest sense. The computer models will need to handle dense nuclear matter, fast-changing energy fields, and the behaviors of particles that scientists have never observed on Earth. Many of the isotopes formed in this process are too unstable to create in laboratories. Their properties—such as decay rates, binding energies, and reaction pathways—remain unknown.

By simulating these processes, scientists hope to uncover not only how heavy elements are born, but also what they look like, how they behave, and how we might detect their signatures in space and on Earth.

Implications for National Security and Beyond

The implications of this research go beyond the purely cosmic. Understanding neutron production and nuclear behavior under extreme conditions has applications in national security, nuclear stockpile stewardship, and the detection of illicit nuclear activity. Insights from astrophysical nucleosynthesis could inform how we model nuclear explosions or interpret radioactive signatures.

Moreover, such studies deepen our understanding of the fundamental nature of matter. The heavy elements forged in these cosmic furnaces are not only the building blocks of planets but of human civilization—embedded in the microchips of smartphones, the shielding of spacecraft, the workings of nuclear medicine.

A Star Dies, and the Periodic Table Expands

In the end, what Mumpower’s team proposes is not just a new site for element formation. It’s a new narrative for how complexity arises in the universe. From a single, dying star—a monster devouring itself and ejecting a final breath of energy—could come the atoms that someday form a world.

Iron in our blood, iodine in our thyroid, uranium in our reactors—these may have once been neutrons hurled from a black hole’s jet. It’s a staggering thought, a reminder of how deeply connected we are to the chaos and beauty of the cosmos.

As simulations grow sharper and telescopes peer deeper into space, we may soon discover whether this cosmic alchemy is real. If it is, then the origin of heavy elements may lie not just in the quiet buildup of stars, but in the light-speed shockwaves of their deaths.

And in that death, as always, the universe creates anew.

Reference: Matthew R. Mumpower et al, Let There Be Neutrons! Hadronic Photoproduction from a Large Flux of High-energy Photons, The Astrophysical Journal (2025). DOI: 10.3847/1538-4357/adb1e3