Neutrino “Flavor Change” During neutron Star Mergers Could Substantially Impact Heavy Element Creation & Detectable Emissions
New simulations reveal that the behavior of neutrinos – frequently enough called “ghost particles” – during the violent collision of neutron stars can dramatically influence the production of heavy elements and the emissions detectable from Earth. Researchers have found that accounting for neutrino “flavor change” (a change between different types of neutrinos) can increase the production of heavy elements by up to a factor of ten.
the study, published August 26, 2025, in Physical Review Letters, focuses on how neutrinos interact within the extreme surroundings of a neutron star merger. Specifically, electron neutrinos can convert neutrons within the merging stars into protons and electrons. Though, muon neutrinos cannot perform this conversion. This difference in behavior means that the “mixing” or change in neutrino type during a merger directly impacts the neutron availability, a crucial factor in the creation of heavy metals and rare earth elements.
“Accounting for mixing neutrino can increase the production of elements as much as factor 10,” the researchers state.
This neutrino mixing also affects the material ejected from the merger, altering the composition and amount of emissions detectable on Earth. These emissions typically include gravitational waves – ripples in spacetime – and electromagnetic radiation like X-rays and gamma rays.
“In our simulation, the mixing of neutrino affects the electromagnetic emissions of neutron stars and maybe gravitational waves too,” explained researcher David Radice.
With advanced detectors like LIGO, Virgo, and Kagra currently operational, and future observatories like the proposed Cosmic Explorer, astronomers are poised to detect gravitational waves with increasing frequency. A better understanding of how these emissions are generated during neutron star mergers will be vital for interpreting future observations.
the simulation process was described by the team as analogous to an inverted pendulum, initially exhibiting rapid changes before settling into a stable state. However, the researchers acknowledge that many aspects of thier work rely on current theoretical understanding, which is still evolving.
“There is still a lot that we don’t know about theoretical physics of this neutrino transformation,” said researcher Yi Qiu. “Our understanding now shows that they are very possible, and our simulation shows that, if they happen, they can have the main effect, so it is indeed critically important to enter them in models and analysis in the future.”
The team, comprised of Yi Qiu, David Radice, Maitraya Bhattacharyya (Penn State and Cosmos Gravitational institute), and Sherwood Richers (University of tennessee, Knoxville), has created infrastructure for these complex simulations, anticipating that other research groups will utilize the technology to further explore the effects of neutrino mixing.
“The neutron star merger functions like a cosmic laboratory, providing important insights about extreme physics that we cannot copy safely on earth,” radice concluded.
The research was supported by funding from the US Energy Department, Sloan Foundation, and the US National science Foundation.
Reference: “Neutrino Taste transformation in Neutron Stars Mergers” by Yi Qiu, David Radice, sherwood Richers and Maitraya Bhattacharyya, August 26, 2025, Physical Review Letters. Doi: 10.1103/h2q7-kn3v.
