New simulations performed on a NASA supercomputer are providing scientists with the most comprehensive look yet into the maelstrom of interacting magnetic structures around city-sized neutron stars in the moments before they crash. The team identified potential signals emitted during the stars’ final moments that may be detectable by future observatories.
“Just before neutron stars crash, the highly magnetized, plasma-filled regions around them, called magnetospheres, start to interact strongly. We studied the last several orbits before the merger, when the entwined magnetic fields undergo rapid and dramatic changes, and modeled potentially observable high-energy signals,” said lead scientist Dimitrios Skiathas, a graduate student at the University of Patras, Greece, who is conducting research for the Southeastern Universities Research Association in Washington at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
New supercomputer simulations explore the tangled magnetic structures around merging neutron stars. Called magnetospheres, the highly magnetized, plasma-filled regions start to interact as the city-sized stars close on each other toward their final orbits. Magnetic field lines can connect both stars, break, and reconnect, while currents surge through surrounding plasma moving at nearly the speed of light. The simulations show that as these systems merge to produce one kind of gamma-ray burst — the universe’s most powerful class of explosions — they emit tell-tale X-rays and gamma rays that future observatories should be able to detect. NASA’s Goddard Space Flight Center
Download images and videos through NASA’s Scientific Visualization Studio
A paper describing the findings published Nov. 20, 2025, in the The Astrophysical Journal.
Neutron star mergers produce a particular type of GRB (gamma-ray burst), the most powerful class of explosions in the cosmos.
Most investigations have naturally concentrated on the spectacular mergers and their aftermaths, which produce near-light-speed jets that emit gamma rays, ripples in space-time called gravitational waves, and a so-called kilonova explosion that forges heavy elements like gold and platinum. A merger observed in 2017 dramatically confirmed the long-predicted connections between these phenomena — and remains the only event seen so far to exhibit all three.
Neutron stars pack more mass than our Sun into a ball about 15 miles (24 kilometers) across, roughly the length of Manhattan Island in New York City. They form when the core of a massive star runs out of fuel and collapses, crushing the core and triggering a supernova explosion that blasts away the rest of the star. The collapse also revs up the core’s rotation and amplifies its magnetic field.
In our simulations, the magnetosphere behaves like a magnetic circuit that continually rewires itself as the stars orbit.
Constantinos Kalapotharakos
Newborn neutron stars can spin dozens of times a second and wield some of the strongest magnetic fields known, up to 10 trillion times stronger than a refrigerator magnet. That’s strong enough to directly transform gamma-rays into electrons and positrons and rapidly accelerate them to energies far beyond anything achievable in particle accelerators on Earth.
“In our simulations, the magnetosphere behaves like a magnetic circuit that continually rewires itself as the stars orbit. Field lines connect, break, and reconnect while currents surge through plasma moving at nearly the speed of light, and the rapidly varying fields can accelerate particles,” said co-author Constantinos Kalapotharakos at NASA Goddard. “Following that nonlinear evolution at high resolution is exactly why we need a supercomputer!”
Using the Pleiades supercomputer at NASA’s Ames Research Center in California’s Silicon Valley, the team ran more than 100 simulations of a system of two orbiting neutron stars, each with 1.4 solar masses. The goal was to explore how different magnetic field configurations affected the way electromagnetic energy — light in all of its forms — left the binary system. Most of the simulations describe the last 7.7 milliseconds before the merger, enabling a detailed study of the final orbits.
“Our work shows that the light emitted by these systems varies greatly in brightness and is not distributed evenly, so a far-away observer’s perspective on the merger matters a great deal,” said co-author Zorawar Wadiasingh at the University of Maryland, College Park and NASA Goddard. “The signals also get much stronger as the stars get closer and closer in a way that depends on the relative magnetic orientations of the neutron stars.”
Magnetic field lines anchored to the surfaces of each star sweep behind them as the stars orbit. Field lines may directly connect one star to the other as the orbits shrink, while lines already linking the stars may break and reconfigure.
About The Author
