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Groups & Clusters of Galaxies

Another intriguing question is the ultimate fate of the colossal gas reservoirs in galaxy clusters. The crush of all the gas and dark matter in the cluster pushes the particles in the center of the cluster closer together. This causes them to collide more frequently and to slowly lose their energy to radiation, like a tire with a slow leak. In a billion years or so, this radiation leak will take its toll and, if there is no energy source to offset the losses, the gas will cool and slowly settle – in what is called a cooling flow – onto a massive galaxy in the center of the cluster.
Perseus Galaxy Cluster
Core of the Perseus Galaxy Cluster in X-rays.
Early X-ray observations indicated that the cooling was occurring at such a rate that hundreds of new stars or cool gas clouds should be forming every year in the centers of many clusters. As astronomers began searching for this cool matter, they found some, but not nearly enough.

New observations of galaxy clusters by Chandra and the XMM Newton X-ray Observatory, together with radio observations, may point to a resolution of this problem. They show that in a number of cases, the inflow of cooling gas appears to be deflected by magnetic fields, and perhaps heated by explosions from the vicinity of a supermassive black hole at the core of the central galaxy. Whether or not such violent activity will explain the shortage of cool gas should become clear in the next few years.

Clues to the origin, evolution and destiny of the universe

More: The Coma Cluster and the Virgo Cluster

Galaxy Clusters
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