Astronomers observe rippling shock waves in the cosmic web for the first time

Shock waves ripple across filaments spanning millions of light-years, emitting polarized radio light.

Key Takeaways

For the first time, astronomers have observed shock waves rippling along the cosmic web, confirming decades of predictions.
These shock waves illuminate faint magnetic fields along the massive filaments connecting galaxy clusters.

Researchers used stacked radio images of 600,000 galaxy cluster pairs to reveal the phenomenon.
The discovery offers a glimpse into large-scale magnetic fields and their role in the cosmic web.
Understanding these shock waves could shed light on the origins of cosmic magnetism and its importance.

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For the first time, astronomers have detected shock waves traveling along the cosmic web—the vast structure of galaxies, gas, and dark matter that forms the universe’s backbone. The discovery confirms simulations predicting such waves and provides an unprecedented glimpse into the magnetic fields that thread through the web. The findings, published in Science Advances, result from combining hundreds of thousands of radio telescope images.

The cosmic web consists of dense galaxy clusters connected by filaments of gas and dark matter, interspersed with vast voids. As these structures interact—clusters merge, filaments collide, and gas flows from voids—shock waves are generated. While such waves had been observed around galaxy clusters, they had never been spotted within the filaments, which are far harder to detect due to their faint nature.

An image of filaments and clusters in blue waves and pink light dots with a box to the right showing a yellow circle in the middle with a purple ring around it. — ong filaments and around galaxy clusters should emit weak radio signals (pink). The inset shows what combining many radio images of galaxy cluster pairs in the simulated web might look like, with colors representing gas temperature and density (high values are yellow, low values are purple and black). F. Vazza, D. Wittor and J. West

Revealing Magnetic Fields in Filaments

The research team, led by Tessa Vernstrom of the International Centre for Radio Astronomy Research, analyzed more than 600,000 galaxy cluster pairs linked by filaments. By stacking their radio telescope data, the team amplified faint signals, revealing a faint, polarized radio glow emanating from the filaments. This polarization—a rare cosmic feature—strongly indicates the presence of shock waves.

These shocks accelerate charged particles, causing them to emit radio light as they travel through magnetic fields. The observations not only confirm that such shock waves exist but also provide indirect evidence of large-scale magnetic fields around the filaments. “These shocks are able to show that there are large-scale magnetic fields forming a sheath around these filaments,” says astrophysicist Marcus Brüggen of the University of Hamburg.

The study opens new avenues for understanding cosmic magnetism, a fundamental force whose role in shaping the universe remains mysterious. Astronomers still debate how these magnetic fields originated and their influence on the cosmic web.