Neutron Star Merger Illustration (IMAGE) Simons Foundation Caption When neutron stars collide, they emit light and gravitational waves, as seen in this artist's illustration. By comparing the timing of the two emissions from many different neutron star mergers, researchers can measure how fast the universe is expanding. Credit R. Hurt/Caltech-JPL Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.