A new study raises questions about the ring of dark matter reported to exist inside a galaxy cluster.
The cluster, called Cl0024+17, is actually thought to be two merging clusters, and some suggest that the ring was caused by their collision. To test the idea, John ZuHone, now at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and his colleagues simulated cluster collisions under varying conditions. They could not produce a ring unless the dark-matter particles had circular orbits.
Because such orbits are unlikely to occur in galaxy clusters, the results suggest that the ring report is questionable, says ZuHone.
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Cosmology: No ring or reason. Nature 459, 13 (2009). https://doi.org/10.1038/459013b
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DOI: https://doi.org/10.1038/459013b