The promises of gravitational-wave astronomy.

Abstract

In 2015, the first direct detection of gravitational waves was made by the Advanced LIGO detectors [1]. The signal observed originated from a binary black hole system, approximately 410 Mpc away from the Earth, in which two black holes of 36 and 29 solar masses spiralled into each other and merged to form a single black hole of 62 solar masses, radiating about three solar masses of energy as gravitational waves. This detection was recognized by the award of the 2017 Nobel Prize in Physics. Following the first detection, four more black hole mergers have been observed [2–4]. In addition, a binary neutron star inspiral has been observed [5]: this event has been associated with a gamma ray burst detected 1.7 s after the gravitational-wave event occurred [6–8]. Follow-up electromagnetic observations have identified a counterpart source close to the galaxy NGC 4993 which is consistent with the position and distance obtained from the gravitational-wave data [9–11]. An extraordinary amount of analysis has been carried out based on these detections, including a new measurement of the Hubble constant [12] based on the neutron star inspiral, while the black hole observations have confirmed the existence of stellar black holes in a mass range never before observed. These are just some examples of the power and promise of gravitational-wave astronomy. The ability to directly detect gravitational waves is the result of several decades of experimental work. Efforts began in the 1960s with the construction of detectors consisting of …