Groups & Clusters of Galaxies
Chandra images provide dramatic evidence of these mega-mergers. Cosmic "weather systems" millions of light years across are observed, as relatively cool 50
million degree Celsius clouds of gas fall into much larger and hotter
It takes a long time to build a galaxy cluster. Exactly how long depends on
details such as the amount of dark matter in the universe, whether the dark
matter is hot or cold, how fast
the universe is expanding, etc. The pressure in the hot gas is an accurate probe
of the amount of dark matter in clusters of galaxies. By using this information,
and X-ray surveys to count the number of large clusters in the
universe, astronomers can test the various theories for the content and evolution
of the universe.
Chandra image of the galaxy cluster Abell 2142 in X-rays.
Chandra observations of the clouds of hot gas in clusters of galaxies will
provide other clues to the origin, evolution and destiny of the universe.
Combined X-ray and microwave
observations can measure the effect of the cluster gas as it scatters the cosmic
microwave background streaming through the cluster from the depths of the
universe. The amount of scattering makes it possible to estimate the distance to
the cluster. This information can be used to estimate the size and age of the