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A colossal magnetic field extending between two clusters of galaxies was observed for the first time. About a billion light-years away, the "bridge" of the radio-emitting plasma expands over 10 million light-years, following a filament in the mysterious cosmic network that connects the planet. ;Universe.
The space between clusters of galaxies is not completely dark and empty. Long strands of gas and diffuse and tenuous plasma spread between them; they are filaments, whose entire network constitutes the cosmic web.
But they are very hard to study, as weak as they are in a universe full of brilliant things.
Previous observations with ground radio telescopes had shown "halos" of radio broadcasts indicating the presence of a magnetic field in the central region of some groups, some of which contain thousands of galaxies, but no one's n & # 39; He had never seen a magnetic field connecting him. cluster to another.
Thus, the discovery of a magnetic field in the filament between Abell fusion groups 0399 and Abell 0401 is extraordinary.
"Our group had discovered that both groups had a radio halo.More recently, the Planck satellite showed that the two systems were connected by a thin filament of matter," said astronomer Federica Govoni of the radio. National Institute of Astrophysics in Italy (INAF). .
"The presence of this filament stimulated our curiosity and prompted us to investigate whether the magnetic field could extend beyond the center of the clusters, penetrating the filament of the material that connects them."
Using the LoFar Low Frequency Radiotelescope, consisting of 25,000 antennas spread across 51 sites, the team detected a low frequency radio broadcast "peak" extending between them.
(Mr. Murgia / INAF)
It is synchrotron radiation produced by electrons sliding along the filament at relativistic speeds, only possible if the magnetic field acts as a synchrotron accelerator or particle.
"We usually observe this emission mechanism in action in individual galaxies and even in clusters of galaxies, but no radio emissions have yet been observed linking two of these systems," said the reporter. astronomer Matteo Murgia of INAF.
But there is a slight hiccup: the electrons cover far more distance than expected – which means that another element has to play. And this element could be the clusters themselves.
Even if they are separated by a distance of several million light-years, Abell 0399 and Abell 0401 generate a lot of gravitational disturbances in the space around them as they inexorably get closer.
The team performed computer simulations to determine if any of the dynamics of this fusion could affect the acceleration of the electrons. And that's it, they found an answer. In the simulations, the shock waves generated by the fusion re-accelerated the electrons at high speed, producing an emission consistent with the observations of LoFar.
But this is only a potential mechanism. We will not know for sure until further observations are made.
We also do not know if other filaments also contain magnetic fields, it is a property of Abell 0399 and 0401 or it is only found in the fused galaxies.
We do not know where the preexisting relativistic electrons come from – their speed implies an energy source that could have ejected them quickly, such as the supernovae. Neither do we know what the prevalence of these relativistic electrons is in the cosmic web.
If their origin is common, such as supernovae, there could be more than we could have guessed.
Scientists certainly have a lot to think about. Not to mention how great it is to see scientists follow intuition and benefit from it.
"With great satisfaction," said Govoni, "the image obtained with the LoFar radio telescope confirmed our intuition, showing what we can define as a kind of". aurora "on the cosmic scale."
The search was published in Science.
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