 The signal of GW170104 measured by Hanford and Livingston. | |
| Date | 4 January 2017  |
|---|---|
| Redshift | 0.18 ±0.08 |
| Total energy output | ≈ 2 M☉ × c2 |
| Other designations | GW170104 |
 Related media on Commons | |
GW170104 was a gravitational wave signal detected by the LIGO observatory on 4 January 2017. On 1 June 2017, the LIGO and Virgo collaborations announced that they had reliably verified the signal, making it the third such signal announced, after GW150914 and GW151226, and fourth overall. [1] [2]
The signal was detected by LIGO at 10:11:58.6 UTC, with the Hanford detector picking it up 3 milliseconds before the Livingston detector. Automated analyses did not initially identify this event as information about the state of the Hanford detector was not being correctly recorded. [1] The event was found by a researcher at the Max Planck Institute for Gravitational Physics by visual inspection of triggers from the Livingston detector. [1] [3] [4] The gravitational wave frequency at peak GW strain was 160 to 199 Hz.
Analysis indicated the signal resulted from the inspiral and merger of a pair of black holes (BBH) with 31.2+8.4
−6.0 and 19.4+5.3
−5.9 times the mass of the Sun, at a distance of 880+450
−390 megaparsecs (2.9+1.5
−1.3 billion light years) from Earth. The resulting black hole had a mass of 48.7+5.7
−4.6 solar masses, two solar masses having been radiated away as gravitational energy. The peak luminosity of GW170104 was 3.1+0.7
−1.3×1049 W . [1]
The spin axes of the black holes were likely misaligned with the axis of the binary orbit. The probability that both spin axes were positively aligned with the orbit is less than 5%. This configuration suggests that the binary black hole system was formed dynamically in a dense star cluster such as a globular cluster, i.e., as a result of gravitational interaction between stars and binary stars, in which case randomly aligned spin axes are expected. The competing scenario, that the system was formed out of a binary star system consisting of two normal (main sequence) stars, is not ruled out but is disfavored as black holes formed in such a binary are more likely to have positively aligned spins. [1]
The analysis of GW170104 yielded a new upper bound on the mass of gravitons, if gravitons are massive at all. The graviton's Compton wavelength is at least 1.6×1016 m , or about 1.6 light-years, corresponding to a graviton mass of no more than 7.7×10−23 eV/c 2. [1] This Compton wavelength is about 9×109 times greater than the gravitational wavelength of the GW170104 event.
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 which are capable of detecting a change of less than one ten-thousandth the charge diameter of a proton.
The Max Planck Institute for Gravitational Physics is a Max Planck Institute whose research is aimed at investigating Einstein's theory of relativity and beyond: Mathematics, quantum gravity, astrophysical relativity, and gravitational-wave astronomy. The institute was founded in 1995 and is located in the Potsdam Science Park in Golm, Potsdam and in Hannover where it closely collaborates with the Leibniz University Hannover. Both the Potsdam and the Hannover parts of the institute are organized in three research departments and host a number of independent research groups.
GEO600 is a gravitational wave detector located near Sarstedt, a town 20 km 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). GEO600 is capable of detecting gravitational waves in the frequency range 50 Hz to 1.5 kHz, and is part of a worldwide network of gravitational wave detectors. This instrument, and its sister interferometric detectors, when operational, are some of the most sensitive gravitational wave detectors ever designed. They are designed to detect relative changes in distance of the order of 10−21, about the size of a single atom compared to the distance from the Sun to the Earth. Construction on the project began in 1995.
The gravitational wave background is a random background of gravitational waves permeating the Universe, which is detectable by gravitational-wave experiments, like pulsar timing arrays. The signal may be intrinsically random, like from stochastic processes in the early Universe, or may be produced by an incoherent superposition of a large number of weak independent unresolved gravitational-wave sources, like supermassive black-hole binaries. Detecting the gravitational wave background can provide information that is inaccessible by any other means about astrophysical source population, like hypothetical ancient supermassive black-hole binaries, and early Universe processes, like hypothetical primordial inflation and cosmic strings.
The Virgo interferometer is a large Michelson interferometer designed to detect gravitational waves predicted by general relativity. It is located in Santo Stefano a Macerata, near the city of Pisa, Italy. The instrument's two arms are three kilometres long, housing 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.
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 an emerging field of science, concerning the observations of gravitational waves to collect relatively unique data and make inferences about objects such as neutron stars and black holes, events such as supernovae, and processes including those of the early universe shortly after the Big Bang.
In cosmology, primordial black holes (PBHs) are hypothetical black holes that formed soon after the Big Bang. In the inflationary era and early radiation-dominated universe, extremely dense pockets of subatomic matter may have been tightly packed to the point of gravitational collapse, creating primordial black holes without the supernova compression needed to make black holes today. Because the creation of primordial black holes would pre-date the first stars, they are not limited to the narrow mass range of stellar black holes.
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.
GW 170817 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 a binary pair of neutron stars' inspiral process, ending with their merger. It is the first GW observation that has been 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 GW 170817 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.
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