Hunting dark matter 'stars' that mimic black holes

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. 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 sun, collided and merged. Or at least, that was the initial theory.