The ESA has announced that it has used the XMM-Newton X-ray observatory to view hot gas sloshing around inside a galaxy cluster for the first time. This behavior may have been driven by turbulent merger events. The ESA says that galaxy clusters are the largest systems in the Universe bound together by gravity.
The clusters contain hundreds of thousands of galaxies and large quantities of hot gas known as plasma. The temperature of that gas reaches around 50 million degrees and shines brightly in X-rays. Little is known about how plasma moves, but scientists say that exploring its motions may be key to understanding how galaxy clusters form, evolve, and behave.
The scientist selected two nearby, massive, bright, and well-observed galaxy clusters called Perseus and Coma. The team mapped how the plasma moves, including whether it moved towards or away from the observers, the speed, and so on for the first time. The team measured large regions of the sky, roughly the size of two full Moons for Perseus and four for Coma.
The team found direct signs of plasma flowing, splashing, and sloshing around within the Perseus cluster. This sort of motion had been predicted, but this is the first time it has been observed. As for what is causing the plasma to move in such a manner, the scientists believe its due to smaller sub-clusters of galaxies colliding and merging with the main cluster itself.
Those collisions are energetic enough to disrupt the gravitational field of Perseus and start the sloshing motion that can last for many millions of years. Coma has no sloshing plasma and appears to be made of two major sub-clusters that are slowly merging.