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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.
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
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