A long time ago in a galaxy far away—NGC 4993, to be exact—two neutron stars collided and created a spectacular light show.

After billions of years spent slowly circling each other, in their last moments the two degenerate stars spiraled around each other thousands of times before finally smashing together at a significant fraction of light-speed, likely creating a black hole.

The merger was so violent it shook the universe, emitting some 200 million suns’ worth of energy as perturbations in the fabric of spacetime called gravitational waves. Those waves propagated out from the merger like ripples on a pond, eventually washing over Earth—and into our planet’s premiere gravitational-wave detectors, the U.S.-built LIGO and European-built Virgo observatories.

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