Supercomputer Reveals How Exploding Stars “Stir” the Galaxy from the Bottom Up
Caption (works for any): the explosions of dead stars extracted from a simulation of a galactic disk. The most intense colors indicate where the turbulence in the explosions is being generated from, which traces an unstable thin shell around the dead stars.
New research performed on the Trillium/SciNet Supercomputer at the University of Toronto reveals a fundamentally different mechanism by which exploding stars shape the turbulent structure of our galaxy. The study, authored by Dr. James Beattie, postdoctoral fellow at the Canadian Institute for Theoretical Astrophysics (CITA), was accepted for publication in The Astrophysical Journal Letters. It challenges long-standing assumptions about how turbulence is generated and sustained in the interstellar medium.
Turbulence—the chaotic, swirling motion of gas—is a fundamental process in astrophysics, influencing everything from star formation to the transport of energy and magnetic fields across galaxies. For decades, scientists have largely assumed that turbulence in the Milky Way follows a classical cascade: energy injected at large scales breaks down into progressively smaller eddies (vortices or “swirls”), consistent with the well-known Kolmogorov picture.
However, this new work demonstrates that supernova remnants—the expanding shells of gas left behind by stellar explosions—can instead inject turbulence at small scales that, then, propagates upward to larger scales through an inverse cascade. This finding suggests that the dominant source of galactic turbulence may not operate in the way previously thought. Instead of a top-down energy transference (dying out of energy), it’s a bottom-up build-up. His research shows that supernova explosions create microscopic, chaotic swirls first. Those tiny swirls then merge and push their energy upward, eventually creating the massive, large-scale turbulence that shapes our entire galaxy.
“Our results show that the structure of turbulence in the galaxy carries a direct imprint of the physical instabilities that occur in supernova remnants,” said Dr. Beattie. “Rather than simply decaying or cascading downward, turbulence generated at the interfaces within these remnants can grow and reorganize, ultimately influencing dynamics on galactic scales.”
The research identifies the contact discontinuity—the unstable boundary between hot, shocked ejecta and cooler surrounding gas—as a key site of turbulence generation. Instabilities and strong baroclinic effects at this interface drive the formation of vortical motions that seed turbulence at relatively small spatial scales. From there, nonlinear interactions transfer energy to larger scales, producing a turbulent spectrum that deviates significantly from classical expectations.
Crucially, these results were made possible by cutting-edge numerical simulations performed on the Trillium Supercomputer, one of Canada’s most advanced high-performance computing systems operated by SciNet at the University of Toronto. The scale and fidelity required to resolve both the small-scale instabilities and their large-scale consequences demand computational resources at the forefront of modern supercomputing.
This revised picture has broad implications. It provides a new framework for interpreting observations of interstellar turbulence, including velocity fluctuations and magnetic field structure, and may help explain why measured spectra in the Milky Way often differ from theoretical predictions. It also suggests that models of galaxy evolution and star formation may need to be re-evaluated to account for this alternative turbulent driving mechanism.
Beyond its implications for the Milky Way, the work points to a more general principle: that microscopic plasma processes and instabilities can leave lasting imprints on macroscopic astrophysical systems.
“This is a shift in perspective,” Dr. Beattie added. “If turbulence in galaxies is seeded at small scales by physical instabilities, then understanding those instabilities becomes essential for understanding the large-scale universe.”
The paper is available on arXiv: https://arxiv.org/abs/2509.07354
Beattie, J. 2026, American Astronomical Society, , , Supernovae Drive Large-scale, Incompressible Turbulence through Small-scale Instabilities. DOI 10.3847/2041-8213/ae6eed
SCIENCE CONTACT: Dr. James Beattie
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