title: LIGO and the opening of a unique observational window on the universe.
abstract: A unique window on the universe opened on September 14, 2015, with direct detection of gravitational waves by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors. This event culminated a half-century effort around the globe to develop terrestrial detectors of adequate sensitivity to achieve this goal. It also happened appropriately only a few months before the centennial of Einstein's final paper introducing the general theory of relativity. This detection provided the surprising discovery of a coalescing pair of "heavy" black holes (more massive than [Formula: see text] M[Formula: see text]) leading to the formation of a spinning [Formula: see text]62 solar mass black hole. One more binary black-hole detection and a significant candidate event demonstrated that a population of such merging binaries is formed in nature with a broad mass spectrum. This unique observational sample has already provided concrete measurements on the coalescence rates and has allowed us to test the theory of general relativity in the strong-field regime. As this nascent field of gravitational-wave astrophysics is emerging we are looking forward to the detection of binary mergers involving neutron stars and their electromagnetic counterparts, as well as continuous-wave sources, supernovae, a stochastic confusion background of compact-object mergers, known sources detected in unexpected ways, and completely unknown sources.
authors.affiliation: Center for Interdisciplinary Exploration & Research in Astrophysics and Department of Physics & Astronomy, Northwestern University, Evanston, IL 60208-3112.
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Kalogera
authors.affiliation: Laser Interferometer Gravitational-Wave Observatory Laboratory, California Institute of Technology, Pasadena, CA 91125-0001 lazz@ligo.caltech.edu.
authors.forename: Albert
authors.initials: A
authors.lastname: Lazzarini
keywords: LIGO; black holes; gravitational waves