From the observation of the rotation of galaxies resembling our own
Milky Way, astronomers have found that there must be over ten
times more mass in them than is visible as light emitting stars. This
puzzling discrepancy indicates that there has to exist some matter which is
not emitting light and is therefore called Dark Matter. This invisible
matter makes up more than 90% of the mass of galaxies and also of
larger structures. It therefore makes up most of our universe, but it is still unclear what kind of matter it really is. This leads to one of the presently most challenging and intriguing questions of
physics: What does most of our universe consist of?
Dark
matter could be made of MACHOs, huge gas balls which are too small to
ignite and to shine as stars. Or it could be made of faint stars overlooked by our
telescopes. Or it could be made of black holes left over from the big bang. However
searches for all these dark matter candidates have failed,
re-emphasizing the significance of the search for elementary particle
dark matter undertaken by CRESST.
With CRESST, we search for
hypothetical massive elementary particles called WIMPs (Weakly
Interacting Massive Particles). It is believed that these WIMPs are
present everywhere in our galaxy and in a vast halo around it. In spite
of having a mass similar to that of a nucleus, like iron for example,
their extremely weak interaction with normal matter enables them to
travel easily through the earth or even through our galaxy without a single
interaction. This extremely weak interaction, combined with the important
role of these particles in our universe, makes the direct search for
WIMP dark matter one of the most challenging and difficult tasks of
modern astroparticle physics. |
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The Spiral Galaxy M66; taken from the European Southern Observatory
Globular Cluster NGC 6093; taken from the Hubblesite
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