Hypothetical dark matter stars known as ‘boson stars’ could leave telltale ripples across the cosmos, offering researchers a new way to probe the invisible forces shaping the universe. By Jonathan O’Callaghan In 2019, a strange event was observed in the depths of space. Called GW190521, the event sent out gravitational waves – invisible ripples in the universe – that were picked up on Earth. These waves appeared to mark the moment when two massive black holes, dozens of times the mass of our...