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The first evidence of radio-emitting plasma bridge connecting two galaxy clusters detected by astronomers approximately one billion light-years away. A filament in the mysterious cosmic web connecting the Universe.

For the first time, a huge magnetic field was found stretching between two clusters of galaxies. Approximately one billion light-years away, the radio-emitting plasma bridge spans 10 million light-years, following a filament in the mysterious cosmic web connecting the Universe. It was the first evidence of radio-emitting plasma bridge connecting two galaxy clusters detected by astronomers.

The space between galaxy clusters is not entirely dark and empty. Long stretches between them of diffuse and tenuous gas and plasma; these are called filaments. The entire network of which is the cosmic web.

But, as faint as they are in a universe full of bright stuff, they are very hard to study.

Previous observations with ground-based radio telescopes showed radio emission halos showing the existence of a magnetic field in the core area of some clusters. Some containing thousands of galaxies but none had ever seen a magnetic field linking one cluster to another.

So, it’s something exceptional to discover a magnetic field in the filament between merging clusters Abell 0399 and Abell 0401.

“Our team found that both clusters have a radio halo. Recently, the Planck satellite showed that both systems are linked by a thin filament of matter,” said astronomer Federica Govoni of the Italian National Institute of Astrophysics (INAF).

“The existence of this filament stimulated our curiosity and led us to explore whether the magnetic field could extend beyond the cluster center. Permeating the material filament that connects them.”

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Using the LoFar low-frequency radio telescope, consisting of 25,000 antennas across 51 places, the team settled in on the filament. Detecting a ‘ ridge ‘ of low-frequency radio emissions stretching between them.

(M. Murgia/INAF)

This is synchrotron radiation generated by zipping electrons at relativistic velocities along the filament. Only feasible when the magnetic field acts as a synchrotron or accelerator of particles.

“Typically, in individual galaxies and even in galaxy clusters, we observe this emission mechanism in action. But never before has a radio emission been observed connecting two of these systems,” INAF astronomer Matteo Murgia said.

But there’s a slight hiccup. The electrons cover much more distance than anticipated -which implies another component has to be at play. And the clusters themselves could be that component.

Although separated by a range of millions of light-years, Abell 0399 and Abell 0401 create much gravitational disruption in the room around them as they draw closer together inexorably.

The team conducted computer simulations to see if any of this merger’s dynamics could influence the electrons ‘ speed. Lo and behold, they found an answer. Shock waves produced by the merger re-accelerated high-speed electrons in the simulations. Leading in emissions consistent with LoFar findings.

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But that’s just one mechanism of potential. Until more observations are made, we won’t understand for sure.

We also do not understand whether other filaments also contain magnetic fields. Whether it is a property distinctive to Abell 0399 and 0401, or it is discovered only in galaxy mergers.

We don’t understand where the pre-existing relativistic electrons came from. Their speed means an energetic source that might have expelled them at speed, like supernovae. Nor do we understand how common in the cosmic web are these pre-existing relativistic electrons.

If their origin is common, such as supernovae, there might be more around them than we could ever have guessed.

Scientists definitely have a lot to think about. Not to mention how great it is to see and pay off researchers after a hunch.

“The picture acquired with the LoFar radio telescope confirmed our intuition with excellent satisfaction,” Govoni said. Demonstrating what can be characterized as a kind of ‘Aurora’ on cosmic scales.

The study has been released in Science.