In theories of quantum gravity, the graviton is the hypothetical quantum of gravity, an elementary particle that mediates the force of gravitational interaction. There is no complete quantum field theory of gravitons due to an outstanding mathematical problem with renormalization in general relativity. In string theory, believed by some to be a consistent theory of quantum gravity, the graviton is a massless state of a fundamental string.
The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. Two large observatories were built in the United States with the aim of detecting gravitational waves by laser interferometry. These observatories use mirrors spaced four kilometers apart to measure changes in length—over an effective span of 1120 km—of less than one ten-thousandth the charge diameter of a proton.
GEO600 is a gravitational wave detector located near Sarstedt, a town 20 kilometres (12 mi) to the south of Hanover, Germany. It is designed and operated by scientists from the Max Planck Institute for Gravitational Physics, Max Planck Institute of Quantum Optics and the Leibniz Universität Hannover, along with University of Glasgow, University of Birmingham and Cardiff University in the United Kingdom, and is funded by the Max Planck Society and the Science and Technology Facilities Council (STFC).
The Virgo interferometer is a large Michelson interferometer designed to detect the gravitational waves predicted by general relativity. It is in Santo Stefano a Macerata, near the city of Pisa, Italy. The instrument's two arms are three kilometres long and contain its mirrors and instrumentation inside an ultra-high vacuum.
Gravitational waves are waves of the intensity of gravity that are generated by the accelerated masses of binary stars and other motions of gravitating masses, and propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1893 and then later by Henri Poincaré in 1905 as the gravitational equivalent of electromagnetic waves. Gravitational waves are sometimes called gravity waves, but gravity waves typically refer to displacement waves in fluids. In 1916 Albert Einstein demonstrated that gravitational waves result from his general theory of relativity as ripples in spacetime.
A gravitational-wave detector is any device designed to measure tiny distortions of spacetime called gravitational waves. Since the 1960s, various kinds of gravitational-wave detectors have been built and constantly improved. The present-day generation of laser interferometers has reached the necessary sensitivity to detect gravitational waves from astronomical sources, thus forming the primary tool of gravitational-wave astronomy.
Gravitational-wave astronomy is a subfield of astronomy concerned with the detection and study of gravitational waves emitted by astrophysical sources.
The LIGO Scientific Collaboration (LSC) is a scientific collaboration of international physics institutes and research groups dedicated to the search for gravitational waves.
INDIGO or IndIGO is a consortium of Indian gravitational wave physicists. It is an initiative to set up advanced experimental facilities for a multi-institutional observatory project in gravitational-wave astronomy to be located near Aundha Nagnath, Hingoli District, Maharashtra, India. Predicted date of commission is in 2030.
A binary black hole (BBH), or black hole binary, is a system consisting of two black holes in close orbit around each other. Like black holes themselves, binary black holes are often divided into stellar binary black holes, formed either as remnants of high-mass binary star systems or by dynamic processes and mutual capture; and binary supermassive black holes, believed to be a result of galactic mergers.
The first direct observation of gravitational waves was made on 14 September 2015 and was announced by the LIGO and Virgo collaborations on 11 February 2016. Previously, gravitational waves had been inferred only indirectly, via their effect on the timing of pulsars in binary star systems. The waveform, detected by both LIGO observatories, matched the predictions of general relativity for a gravitational wave emanating from the inward spiral and merger of a pair of black holes of around 36 and 29 solar masses and the subsequent "ringdown" of the single resulting black hole. The signal was named GW150914. It was also the first observation of a binary black hole merger, demonstrating both the existence of binary stellar-mass black hole systems and the fact that such mergers could occur within the current age of the universe.
GW151226 was a gravitational wave signal detected by the LIGO observatory on 25 December 2015 local time. On 15 June 2016, the LIGO and Virgo collaborations announced that they had verified the signal, making it the second such signal confirmed, after GW150914, which had been announced four months earlier the same year, and the third gravitational wave signal detected.
GW170817 was a gravitational wave (GW) signal observed by the LIGO and Virgo detectors on 17 August 2017, originating from the shell elliptical galaxy NGC 4993. The signal was produced by the last moments of the inspiral process of a binary pair of neutron stars, ending with their merger. It was the first GW observation to be confirmed by non-gravitational means. Unlike the five previous GW detections—which were of merging black holes and thus not expected to produce a detectable electromagnetic signal—the aftermath of this merger was seen across the electromagnetic spectrum by 70 observatories on 7 continents and in space, marking a significant breakthrough for multi-messenger astronomy. The discovery and subsequent observations of GW170817 were given the Breakthrough of the Year award for 2017 by the journal Science.
GW170814 was a gravitational wave signal from two merging black holes, detected by the LIGO and Virgo observatories on 14 August 2017. On 27 September 2017, the LIGO and Virgo collaborations announced the observation of the signal, the fourth confirmed event after GW150914, GW151226 and GW170104. It was the first binary black hole merger detected by LIGO and Virgo together.
GW170608 was a gravitational wave event that was recorded on 8 June 2017 at 02:01:16.49 UTC by Advanced LIGO. It originated from the merger of two black holes with masses of and . The resulting black hole had a mass around 18 solar masses. About one solar mass was converted to energy in the form of gravitational waves.
PyCBC is an open source software package primarily written in the Python programming language which is designed for use in gravitational-wave astronomy and gravitational-wave data analysis. PyCBC contains modules for signal processing, FFT, matched filtering, gravitational waveform generation, among other tasks common in gravitational-wave data analysis.
GW 190412 was a gravitational wave (GW) signal observed by the LIGO and Virgo detectors on 12 April 2019. In April 2020, it was announced as the first time a collision of a pair of very differently sized black holes has been detected. As a result of this asymmetry, the signal included two measurable harmonics with frequencies approximately a factor 1.5 apart.
GW 190814 was a gravitational wave (GW) signal observed by the LIGO and Virgo detectors on 14 August 2019 at 21:10:39 UTC, and having a signal-to-noise ratio of 25 in the three-detector network. The signal was associated with the astronomical super event S190814bv, located 790 million light years away, in location area 18.5 deg2 towards Cetus or Sculptor. No optical counterpart was discovered despite an extensive search of the probability region.
Ground-based interferometric gravitational-wave search refers to the use of extremely large interferometers built on the ground to passively detect gravitational wave events from throughout the cosmos. Most recorded gravitational wave observations have been made using this technique; the first detection, revealing the merger of two black holes, was made in 2015 by the LIGO sites.
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