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Dark Matter Mystery
This ROSAT X-ray image has been superimposed on an optical picture of a cluster of galaxies and shows hot gas highlighted in false red color.
(Credit: ROSAT)
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What can the answer be? Is it possible that most galaxies are surrounded by some
"dark" form of matter that cannot be observed by radio, infrared, optical,
ultraviolet, X-ray, or gamma-ray telescopes? Could Einstein's theory of gravity,
which has proved to be correct in all cases so far, be somehow wrong?
X-ray telescopes have discovered vast clouds of multimillion
degree gas in clusters of galaxies. These hot gas clouds increase the mass of the
cluster, but not enough to solve the mystery. In fact they provide an independent
measurement of dark matter. The measurement shows that there must be at least
four times as much dark matter as all the stars and gas we observe, or the hot
gas would escape the cluster.
What can the dark matter be?
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