What was so elusive for so long is now almost commonplace.
A whole century passed between the time gravitational waves were predicted to when they were finally confirmed. But now, just two and a half years after that first announcement, suddenly we’re finding them four at a time. Scientists just laid out this discovery in a presentation at the Joint Space-Science Institute-Gravitational Wave Physics and Astronomy Workshop. and in two papers released on Arxiv.
Gravitational waves are distortions caused by energetic events in space. While they can be produced on a small scale, our current detection facilities, like the huge LIGO detector, are capable of detecting large events. The waves appear as ripples in the fabric of spacetime, not unlike what you’d see after dropping a large object in water. The most detectable ones come from the mergers of black holes with each other, or with neutron stars.
One of the just-seen mergers (officially called GW170817) is believed to be a merger between two neutron stars. Researchers pinpointed the location of that merger and watched some of it take place in the visible spectrum, providing independent corroboration of the merger. To date, no such mergers have conclusively been detected, though it’s possible the famous “kilonova” detection discovered last year involved two neutron stars. (Many researchers believe, however, that one of the objects in that merger was a black hole.)
These new papers have not yet been published in a journal, and they’re still being investigated by the scientific community. However, if they become widely accepted, they would mean scientists have made nearly a dozen observations of gravitational waves so far. As LIGO grows more sensitive, even more are on the way.