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Abell S1063, a galaxy cluster, was observed by the Hubble Space Telescope as part of the Frontier Fields programme. The huge mass of the cluster – containing both baryonic matter and dark matter – acts as cosmic magnification glass and deforms objects behind it. In the past astronomers used this gravitational lensing effect to calculate the distribution of dark matter in galaxy clusters. A more accurate and faster way, however, is to study the intracluster light (visible in blue), which follows the distribution of dark matter.
In recent decades astronomers have tried to understand the true nature of the mysterious substance that makes up most of the matter in the Universe – dark matter – and to map its distribution in the Universe. Intracluster light is a byproduct of interactions between galaxies. In the course of these interactions, individual stars are stripped from their galaxies and float freely within the cluster. Once free from their galaxies, they end up where the majority of the mass of the cluster, mostly dark matter, resides.
Currently, all that is known about dark matter is that it appears to interact with regular matter gravitationally, but not in any other way. To find that it self-interacts would place significant constraints on its identity.
Image Credit: NASA, ESA, and M. Montes (University of New South Wales, Sydney, Australia)
Image enhancement: Jean-Baptiste Faure
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