Seven Years of LIGO-Virgo Science

I review the first seven years of gravitational wave detections. 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. The LIGO and Virgo gravitational–wave detectors carried out the third observing run in 2020. Several new signals where detected, including peculiar events not seen before such as coalescences with a large mass or large mass asymmetry, and coalescences of a neutron star-black hole pair. The analysis of these events is providing information about stellar compact object populations, the local expansion rate of the universe, the nature of black holes and the validity of general relativity. They can constrain the behavior of matter at densities higher than an atomic nucleus, and mergers that emit both gravitational and electromagnetic waves probe the formation of short gamma ray bursts and the nucleosynthesis of heavy elements. Other searches are constraining more and more the emission of isolated sources and the possible background of gravitational waves from unresolved sources of astrophysical or cosmological nature.