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"Dark matter’s tendrils revealed
Direct measurement of a dark-matter ‘filament’ confirms its existence in a galaxy supercluster.
Zeeya Merali
04 July 2012
Dark-matter filaments, such as the one bridging the galaxy clusters Abell 222 and Abell 223, are predicted to contain more than half of all matter in the Universe.
Jörg Dietrich, University of Michigan/University Observatory Munich
A ‘finger’ of the Universe’s dark-matter skeleton, which ultimately dictates where galaxies form, has been observed for the first time. Researchers have directly detected a slim bridge of dark matter joining two clusters of galaxies, using a technique that could eventually help astrophysicists to understand the structure of the Universe and identify what makes up the mysterious invisible substance known as dark matter.
According to the standard model of cosmology, visible stars and galaxies trace a pattern across the sky known as the cosmic web, which was originally etched out by dark matter — the substance thought to account for almost 80% of the Universe’s matter. Soon after the Big Bang, regions that were slightly denser than others pulled in dark matter, which clumped together and eventually collapsed into flat ‘pancakes’. “Where these pancakes intersect, you get long strands of dark matter, or filaments,†explains Jörg Dietrich, a cosmologist at the University Observatory Munich in Germany. Clusters of galaxies then formed at the nodes of the cosmic web, where these filaments crossed."