Simulations show neutron star mergers can rapidly create magnetars

By the Everything Space news desk · 21 Oct 2026 · written from the sources below

Image: Phys.org

High-resolution modeling suggests turbulent mixing during low-mass neutron star collisions can boost magnetic fields over 300-fold within a millisecond.

A new simulation study suggests that magnetars, neutron stars with extraordinarily powerful magnetic fields, can form directly from the merger of two smaller neutron stars. The research, run on Japan's FUGAKU supercomputer, modeled what happens in the instants just before, during, and after such a collision.

Most neutron star mergers are thought to produce black holes, because the combined mass of the two stars usually exceeds the Tolman-Oppenheimer-Volkoff limit, a mass ceiling of roughly 2.6 solar masses beyond which a stable neutron star cannot exist. But when both merging stars are unusually low in mass, their combined total can stay under that threshold, allowing them to settle into a single surviving neutron star instead of collapsing.

To explore this scenario, the researchers simulated two identical, lower-mass neutron stars with magnetic field strengths near the upper end of what is typical, around 3 trillion gauss. Their models tracked the merger from just before contact through the immediate aftermath.

The simulations showed that within milliseconds of contact, the neutron fluid becomes turbulent through a process called Kelvin–Helmholtz instability, the same kind of fluid-mixing effect that turns a smooth stream of smoke chaotic as it rises. This turbulence thoroughly mixes the neutron material and drags the magnetic field along with it, amplifying it dramatically.

According to the simulation, the merged star's magnetic field can end up more than 300 times stronger than the fields of the original two stars, and further turbulence beyond what the simulation could capture might push it even higher. The amplification happens within about a millisecond, fast enough to potentially shape how the merger unfolds and how the resulting neutron star is structured.

The researchers say more work is needed to fully understand the consequences of this rapid field growth, but the findings indicate that magnetars, which are linked to energetic phenomena like fast radio bursts and gamma-ray repeaters, can indeed emerge from this kind of stellar merger.

Written in Everything Space’s own words by our news-desk model from the sources above, and checked against them in code: every number in this report appears in its sources, and no sentence is copied from them.