Astronomers have a weakness for big explosions and collisions, and it always seems like they’re trying to outdo themselves by finding a bigger, brighter one. There is a new entrant in this category – an event so large that it created a particle explosion over a billion years ago that is still visible today and is 60 times larger than the ‘together Milky Way.
This shock wave was created by the merger of two galaxy clusters to create a supercluster known as Abell 3667. It was one of the most energetic events in the universe since the big Bang, according to the calculations of Professor Francesco de Gasperin and his time from the University of Hamburg and INAF. When this happened over 200 million years ago, it shot out a wave of electrons, similar to how a particle accelerator would. All these years later, these particles are still traveling at Mach 2.5 (1500 km/s), and when they pass through magnetic fields, they emit radio waves.
These radio waves are what Dr de Gasperin and his colleagues observed using a new network of telescopes in South Africa known as MeerKAT. However, radio signals alone were not enough to characterize the shock wave itself – the XMM-Newton X-ray Observatory also spent time focusing on Abell 3667.
The result of all these observations is a better understanding of the physics of the merger of these clusters of galaxies, which were “much more complex than we initially thought”, said Dr de Gasperin. The shock waves themselves look like “filaments that trace the location of giant magnetic field lines”. What’s clear from the images is that even when scientists are simply looking for large collisions, the resulting radio images can be impressive in themselves.
Originally published on Universe today.
For more on this discovery, see A massive cosmic shock wave that spans 6.5 million light-years.