Neutron stars are among the densest objects in our Universe, with “Sun-like” masses but “city-size” radii. When two of these extremely dense objects collide, they give rise to a cataclysmic event that is so powerful that it can be observed at very large distances. In August 2017, the collision of two neutron stars a trillion billion (1 followed by 21 zeros) kilometers away from Earth was detected as a gravitational wave signal and across the full electromagnetic spectrum as well. This simultaneous detection provided an unprecedented opportunity to address long-standing, fundamental, questions in (astro)physics, including the origin of some heavy elements like gold and platinum, properties of matter at densities exceeding those inside atomic nuclei and the expansion rate of our Universe.
