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Around a billion years ago, a collision of epic proportions took place between two galaxy clusters. And that colossal encounter produced the most monstrous shock waves ever seen by man. Today, the intense light in the form of radio waves from these waves, which continue to spread through space, has reached astronomers’ telescopes, who have been able to determine their extension: 6.5 million light years, that is, 65 times the length of our galaxy from end to end. The collision, according to the researchers, is one of the events that has released the most energy in the Universe since the Big Bang itself.
The Universe we live in is populated by
trillions of galaxies that are not evenly distributed throughout space, but are grouped together, forming gigantic structures. Individual galaxies coalesce into groups, groups of galaxies into clusters, clusters into superclusters…Galaxy groups travel as huge filaments of light, attracted by the gravity of superclusters, the ‘nodes’ of the immense ‘ cosmic web’ that shapes our Universe. And sometimes, two galaxy clusters begin to gravitationally attract each other, leading to an inevitable collision. These are the most powerful events that have occurred since the Universe was formed, and they can generate spectacular ‘fireworks’ that are captured by radio telescopes.
But not only that. When two galaxy clusters collide, they produce two shock waves, somewhat similar to the sonic booms of supersonic airplanes, but of gigantic proportions. And that is precisely what an international team of astronomers has been able to see with the MeerKAT radio telescope in South Africa, made up of 64 individual antennas each 13.5 meters in diameter and one of the largest in the world. The collision between the two galaxy clusters responsible for these shock waves is forming the super cluster called Abell 3667. The work has just been published in
‘Astronomy & Astrophysics’.
In their paper, led by Francesco de Gasperin of the University of Hamburg, the researchers carried out the most detailed study yet of these cosmic shock waves. “These structures -explains de Gasperin- are full of surprises and are much more complex than we thought at first. Shock waves act as giant particle accelerators that accelerate electrons to speeds close to the speed of light. When these electrons As rapids cross a magnetic field, they emit the radio waves we see. The shocks are intertwined by an intricate pattern of glowing filaments that trace the location of giant magnetic field lines and regions where electrons are accelerated.”
Abell 3667, well, is still forming. At the moment it consists of 550 galaxies, and shock waves propagate through it at regarding 1,500 km/s, which means that the shock front would cross the entire Earth in the time needed to read this sentence.
The size of the main shock wave is impressive, spanning the entire width of the galaxy cluster with a total size of 6.5 million light-years. For comparison, the Milky Way, the galaxy we live in, is regarding 65 times smaller.
