The first five years of gravitational-wave astrophysics

TL;DR

This paper reviews the first five years of gravitational-wave detections, highlighting discoveries of over fifty events that provide insights into astrophysics, tests of general relativity, and cosmology.

Contribution

It summarizes the observational achievements, scientific insights, and implications of gravitational-wave detections made by LIGO and other observatories over five years.

Findings

Over fifty gravitational wave events detected.

Insights into compact object formation and matter at extreme densities.

Probing cosmology and astrophysics through multi-messenger observations.

Abstract

Gravitational waves are ripples in spacetime generated by the acceleration of astrophysical objects. A direct consequence of general relativity, they were first directly observed in 2015 by the twin Laser Interferometer Gravitational-Wave Observatory (LIGO) observatories. I review the first five years of gravitational wave detections. More than fifty gravitational waves events have been found, emitted by pairs of merging compact objects such as neutron stars and black holes. These signals yield insights into the formation of compact objects and their progenitor stars, enable stringent tests of general relativity and constrain the behavior of matter at densities higher than an atomic nucleus. Mergers that emit both gravitational and electromagnetic waves probe the formation of short gamma ray bursts, the nucleosynthesis of heavy elements, and measure the local expansion rate of the Universe.