Scientists have conducted a simulation that explains the collision between two clusters of galaxies. Clusters of galaxies are the biggest objects that exist in the universe. They are collections of hundreds of thousands of galaxies pulled together by gravity. Rare, extreme examples of clusters caught in the act of colliding seem to be challenging the accepted view that dark matter is made up of heavy particles. n general, galaxy clusters grow in size by merging with each other to become increasingly larger. Gravitational forces cause them to slowly come together over time despite the expansion of the universe. The system known as "El Gordo," the biggest known cluster of galaxies, is in turn the result of the collision between two large clusters. It was found that the collision process compresses the gas within each cluster to very high temperatures so that it is shining in the Xray region of the spectrum. In the Xray spectrum this gas cloud is comet shaped with two long tails stretching between the dense cores of the two clusters of galaxies. This distinctive configuration has allowed the researchers to establish the relative speed of the collision, which is extreme (~2200km/second), as it puts it at the limit of what is allowed by current theory for dark matter.
For more details:omicsgroup.org/journals/geophysics-remote-sensing.php