Dawn of an Era: Astronomers Hear and See Cosmic Collision

Two neutron stars merge into a kilonova. (Credit: Illustration by Robin Dienel, courtesy of the Carnegie Institution for Science) For hundreds of millions of years, two city-sized stars in a galaxy not-so-far away circled each other in a fatal dance. Their dimensions were diminutive, but each outweighed our sun. They were neutron stars — the collapsed cores left behind after giant stars explode into supernovas. Closer and closer they spun, shedding gravitational energy, until the stars traveled at nearly the speed of light, completing an orbit 100 times every second. By then, dinosaurs reigned on Earth, and the first flowers were just blooming. That's when, 130 million years ago, the dance ended. The collision was fast and violent, likely spawning a black hole. A shudder — a gravitational wave — was sent out across the fabric of space-time. And as the stars' outer layers launched into space, the force formed ...