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DESY News: The Universe's largest particle accelerators are a whole lot bigger
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The Universe's largest particle accelerators are a whole lot bigger
Thanks to specialised gamma-ray telescopes, scientists have gained unprecedented insights into the Universe's largest particle accelerators. The international collaboration bringing together over 200 scientists from 13 countries has shown that the very high-energy gamma-ray emission from galaxies with a highly energetic nucleus is not concentrated in the region close to their central black hole but in fact extends over several thousand light-years along the jets of plasma emitted by these objects. This discovery shakes up current understanding of the maximum energy attainable by the particle acceleration processes. The work, published in the journal Nature, was carried out as part of the H.E.S.S collaboration, involving in particular the French research centre CNRS, the Max Planck Institute for Nuclear Physics and DESY in Germany, and the University of Innsbruck in Austria.

Using the High Energy Stereoscopic System (H.E.S.S.) observatory in Namibia, the international astrophysics collaboration observed a radio galaxy (a galaxy that is highly luminous when observed at radio wavelengths) for over 200 hours at unparalleled resolution in gamma rays. “As the nearest radio galaxy to Earth, Centaurus A, was favourable for such a study, because it enabled us to identify the region emitting the very high-energy radiation while studying the trajectory of the plasma jets,” explained H.E.S.S. Deputy Director Mathieu de Naurois from the Centre National de la Recherche Scientifique (CNRS) in France, also one of the corresponding authors of the publication.

The above composite complemented by gamma-ray observations by H.E.S.S. Credit: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray), H.E.S.S. collaboration (Gamma) CC BY 4.0
The discovery suggests that many radio galaxies with extended jets do indeed efficiently accelerate particles up to extreme energies. This finding therefore brings crucial new information to the debate on the origin of the X-ray emission. “This discovery revolutionises our understanding of large-scale jets and brings our understanding of cosmic particle acceleration a huge step forward,” said Taylor. “It is deeply satisfying to see long-term observational efforts paying off dividends like this. Indeed, we continue to enjoy being surprised by our close by cosmic friends when looked at in a different way.”
The results of this study required extensive observations and optimised analysis techniques. The next-generation observatory Cherenkov Telescope Array (CTA) will no doubt make it possible to observe this phenomenon in even greater detail. The H.E.S.S. International Observatory, consisting of five telescopes located in Namibia, involves laboratories from thirteen countries (France, Germany, Namibia, South Africa, Ireland, Armenia, Poland, Australia, Austria, Sweden, the United Kingdom, the Netherlands and Japan).
Reference:
Resolving acceleration to very high energies along the jet of Centaurus A; The H.E.S.S. Collaboration; Nature, 2020; DOI: 10.1038/s41586-020-2354-1
Further information:
H.E.S.S. homepage at DESY