Pulsar Winds or Shock-Driven Protons? Galactic Center Filaments Look Alike
Simulations of radio filaments at the Milky Way's center barely distinguish pulsar winds from proton shocks, but suggest filaments lengthen as they age.
Near the center of the Milky Way, thin radio-bright threads stretch vertically through space, and astronomers still do not know what powers them. A new simulation study led by Mohan Richter-Addo of the University of Wisconsin-Madison and collaborators tests two candidate energy sources and finds they are hard to tell apart. The work is published in The Astrophysical Journal (ApJ), and AAS Nova highlighted it on October 20, 2026 as a featured image.
The structures are called galactic non-thermal filaments. They show up clearly in images of the galactic center from the MeerKAT radio array. Each is tens of parsecs long (a parsec is about 3.26 light-years) yet less than a tenth of a parsec wide. They are found throughout the central molecular zone, a complex region of dense gas around the galaxy’s core. “Non-thermal” means the radio glow does not come from hot gas. Instead, it appears to come from charged particles spiraling around magnetic field lines. What remains unknown is where those fast-moving particles come from.
The team used magnetohydrodynamics simulations, which model how electrically charged gas and magnetic fields move together, to examine two possible suppliers:
- The winds of a pulsar, which would carry electrons and their antimatter partners, positrons.
- A proton-rich mix of particles accelerated by interstellar shocks.
The simulated filaments lit up by these two sources showed few discernible differences. That means the appearance of a filament alone may not reveal which source is at work, at least in these models. The authors describe the result as opening new avenues for future exploration rather than settling the question.
One finding did stand out. In the simulations, filaments grow longer as they age, and the maximum length is set by the underlying magnetic field. The release says this hints that magnetohydrodynamic turbulence, the churning motion of magnetized gas, might help shape the filaments.
The result matters because these filaments trace magnetic fields and energetic particles in one of the most extreme environments in our galaxy. Understanding their origin would say more about how cosmic rays, fast charged particles moving through space, are produced and move around the galactic center. For broader context, see our galaxies guide and our galaxies news archive.
Primary source
This summary is based on AAS Nova and the peer-reviewed paper. Read the original for full details, data and caveats.
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