Dark matter’s secrets could be unlocked by a peculiar gamma-ray signal in three galaxy clusters – or it may reveal a more exotic phenomenon, finds Karmela Padavic-Callaghan AN UNUSUAL gamma-ray signal could be the most direct evidence of dark matter yet. However, the signal could also be the result of a telescope anomaly or produced by something even stranger than dark matter. Dark matter forms the bones of much of our universe, driving how galaxies cluster, for example. It also far outweighs all the visible matter, yet for decades researchers have puzzled over what exactly it is. Part of the problem is that they can’t currently observe dark matter directly. Instead, they can only register its effect on its surroundings. …