Clusters of galaxies are the largest structures of our observable Universe. They consist of hundreds of galaxies bound together by their own gravitational pull. Between galaxies there is much matter, much more matter that in the galaxies themselves, this matter is gas more or less hot, and micro particles of dust or soot. The hot gas whose temperature can reach 100 million degrees, forming a plasma, i.e. a soup of matter where atoms are not together but broken. In this soup low density 1000 particles per cubic meter, there are charged particles, in other words separated ions and electrons. This plasma is a strong X-ray emitter. This is what is seen on the right image, showing the Coma cluster of galaxies.
This seemingly ordinary image is very interesting if you look closely carefully because it shows thousands of galaxies, not in an empty universe of matter, but in the middle of huge bubble of hot gas.
This gas is visible through the Chandra space telescope that allows us to see in the field of x-rays. The Coma cluster is a cluster of galaxies, spherical, dense in the center, which contains more than 1000 galaxies identified and which lies 300 million light-years with the Virgo Cluster in the constellation Virgo. These huge arms of hot gas that can be seen in the Coma cluster of galaxies cover at least half a million light years. This field of view gives us a glimpse of how the Coma cluster has grown and continues to grow through mergers of smaller galaxy clusters groups. It is currently one of the largest structures in the Universe held together by gravity. The optical data of the composite image shows hundreds of galaxies belonging to the Coma cluster. These galaxies represent little matter compared with the overall cosmic structure , they contain only about one-sixth of the mass of hot gas. More, on this processed using data from Chandra image, we see only the brightest X-ray emission, in reality the hot gas completely fills the field of view .
Researchers believe that these gigantic arms probably formed with the lost gas by clusters of galaxies in their movement. The gas was ripped by "wind" created by the movement of the cluster galaxies. In fact you can see the enlarged image, galaxies trailing behind, a cloud of hot gas (pink). NB: galaxy comes from the Greek "galactos" which means "milk", hence the name of our galaxy: the Milky Way.
Coma is an unusual cluster of galaxies, because it does not contain one, but two giant elliptical galaxies near the center. These two giant elliptical galaxies are probably the result of fusion in the past small groups of galaxies. Most theoretical models predict that mergers between groups such as Coma produce strong turbulence, as on the surface of the sea, brewed by the passage of many ships. But the observation of the Coma cluster shows that its long arms of hot gas to the smooth shape are located in a environment rather quiet, even after many mergers.
Although the amount of turbulence in clusters of galaxies is difficult to estimate, astrophysicists believe that it is the large-scale magnetic fields that are probably responsible for the lack of turbulence found in Coma. These data on the Coma cluster were obtained after six days of observation time.
An article on Chandra observations was published in the journal Science on September 20, 2013. The lead author of the article is Jeremy Sanders, Institute for Extraterrestrial Physics Max Planck Institute in Garching, Germany.
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Image: Coma cluster of galaxies. This seemingly ordinary image is very interesting if you look closely carefully because it shows thousands of galaxies, not in an empty universe of matter, but in the middle of huge bubble of hot gas, visible through the space telescope Chandra x-ray. This gas fills the space between the galaxies is much more important than the mass galaxies themselves. Credit: X -ray: NASA / CXC / MPE / J . Sanders et al ; optic: SDSS.