In March, astronomers spotted the brightest gamma-ray burst they’d ever seen. It had detonated from halfway across the universe but was so bright it was visible to the naked eye. What made it so dazzling? It turns out it was a sort of cosmic death ray – when a massive star in the distant universe died, it shot out a high-speed jet of particles straight at Earth. It’s a good thing the star lay safely 7.5 billion light years away – GRBs within 6500 light years of Earth could produce enough radiation to strip away the ozone layer and cause a mass, or even total, extinction – a terrifying prospect indeed.