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(or how to weigh small particles with supermassive black holes)Supermassive black holes can be used to measure the mass of extremely light particles to unprecedented levels and rule out the existence of new exotic particles, perhaps constraining the nature of dark matter. These are the results of a recent study to be published in the prestigious Physical Review Letters. More here, for the original article click here. See also the New Scientist, Expresso, Phys.Org. and the American Physical Society coverage.