Dark Matter

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, e.g., iron, 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.

The Spiral Galaxy M66; taken from the European Southern Observatory


Globular Cluster NGC 6093; taken from the Hubblesite
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