In the final moments of merging, two neutron stars don't merely emit gravitational waves, but a catastrophic explosion that echoes across the electromagnetic spectrum. Image credit: University of Warwick / Mark Garlick.
“This is going to have a bigger impact on science and human understanding, in many ways, than the first discovery of gravitational waves. We’re going to be puzzling over the observations we’ve made with gravitational waves and with light for years to come.” -Duncan Brown
Detecting black holes and the gravitational wave signals from them was an incredible feat, but doing the same thing for neutron star mergers is a true game-changer. Instead of fractions of a second, neutron star mergers show up for up to half a minute. Unlike black holes, there’s an electromagnetic counterpart. Because of that, we can verify that the speed of gravity really is identical to the speed of light: to better than 1 part in 1,000,000,000,000,000.
All massless particles travel at the speed of light, including the photon, gluon and gravitational waves, which carry the electromagnetic, strong nuclear and gravitational interactions, respectively. Image credit: NASA / Sonoma State University / Aurora Simonnet.
And perhaps most spectacularly, we can bring the electromagnetic and gravitational-wave skies together for the first time. Even though LIGO has seen more merging black holes, the fact is that there are more merging neutron stars. The key, now, is finding them. We live at a moment where gravitational wave astronomy is just in its infancy, giving us a whole new way to look at the Universe.