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19th of August 2022
The "wrong-way" relic in Abell 3266
by Christopher Riseley and Tessa Vernstrom
Galaxy clusters contain hundreds, or even thousands, of individual galaxies. However, these galaxies represent only a few percent of a cluster's total mass. About 80% of it is dark matter, and the rest is a hot plasma: gas heated to above 10,000,000 degrees and interwoven with weak magnetic fields. An international team led by Chris Riseley have identified a series of rarely observed radio objects -- a radio relic, a radio halo and fossil radio emission -- within a particularly dynamic galaxy cluster called Abell 3266. The team used new data from the ASKAP radio telescope and the Australia Telescope Compact Array (ATCA) to study Abell 3266 in detail. "Radio relics" are arc-shaped features that sit towards a cluster's outskirts, powered by shockwaves travelling through the plasma, which cause a jump in density or pressure, and energise the particles. An example of a shockwave on Earth is the sonic boom that happens when an aircraft breaks the sound barrier. The concave shape of the relic pictured above is unusual, earning it the moniker of a “wrong-way” relic. Overall, the new data break our understanding of how relics are generated, and the team are still working to decipher the complex physics behind these radio objects. More information is given in this article in The Conversation.

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