This is a list of observed/candidate

gravitational wave Gravitational waves are waves of the intensity of gravity generated by the accelerated masses of an orbital binary system that propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1 ...

events. Direct observation of gravitational waves, which commenced with the detection of an event by

LIGO 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 ...

in 2015, constitutes part of

gravitational wave astronomy Gravitational-wave astronomy is an emerging branch of observational astronomy which aims to use gravitational waves (minute distortions of spacetime predicted by Albert Einstein's theory of general relativity) to collect observational data about ...

. LIGO has played a role in all subsequent detections to date, with

Virgo Virgo may refer to: *Virgo (astrology), the sixth astrological sign of the zodiac *Virgo (constellation), a constellation *Virgo Cluster, a cluster of galaxies in the constellation Virgo *Virgo Stellar Stream, remains of a dwarf galaxy *Virgo Supe ...

joining in August 2017.

Nomenclature and timeline

Gravitational wave events are named starting with the prefix GW, while observations that trigger an event alert but have not (yet) been confirmed are named starting with the prefix S. Six digits then indicate the final two digits of the year the event was observed, two digits for the month and two digits for the day of observation. This is similar to the systematic naming for other kinds of astronomical event observations, such as those of

gamma-ray burst In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from ten milli ...

s. Probable detections that are not confidently identified as gravitational wave events are designated LVT ("LIGO-Virgo trigger"). Known gravitational wave events come from the merger of two

black holes A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can def ...

(BH), two

neutron stars A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...

(NS), or a black hole and a neutron star (BHNS). Some objects are in the

mass gap In quantum field theory, the mass gap is the difference in energy between the lowest energy state, the vacuum, and the next lowest energy state. The energy of the vacuum is zero by definition, and assuming that all energy states can be thought of ...

between the largest predicted neutron star masses (

Tolman–Oppenheimer–Volkoff limit The Tolman–Oppenheimer–Volkoff limit (or TOV limit) is an upper bound to the mass of cold, nonrotating neutron stars, analogous to the Chandrasekhar limit for white dwarf stars. If the mass of the said star reaches the limit it will collapse to ...

) and the smallest known black holes. Observations are made in "runs", three of them so far, with maintenance and upgrades of the detectors made between runs. The first run, O1, ran from 12 September 2015 to 19 January 2016, with O2 from 30 November 2016 to 25 August 2017. O3 began on 1 April 2019; it is divided into O3a, from 1 April to 30 September 2019, and O3b, from 1 November 2019 to 27 March 2020. Suspension of observation during October 2019 was for instrument upgrades and fixes, and cessation in March 2020 was due to the

COVID-19 pandemic The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identif ...

. The fourth run, O4, is planned (as of June 2022) to begin in March 2023.

List of gravitational wave events

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Spin Spin or spinning most often refers to: * Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning * Spin, the rotation of an object around a central axis * Spin (propaganda), an intentionally b ...

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GW150914 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 t ...

09:50:45 , , 2016-02-11 , , , , , , , , , , , style="background:#888888; text-align:center;", BH
, , , style="background:#888888; text-align:center;", BH
, , , bgcolor="888888", , , , , , , First GW detection;
first BH merger observed , , , - , BGCOLOR="#fff0f0",
09:54:43 , , 2016-06-15 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , Formerly candidate LVT151012;
accepted as astrophysical since February 2019 , , , - , BGCOLOR="#fff0f0",

GW151226 GW151226 was a gravitational wave signal detected by the LIGO observatory on 25 December 2015 local time (26 Dec 2015 UTC). On 15 June 2016, the LIGO and Virgo collaborations announced that they had verified the signal, making it the second such ...

03:38:53 , , 2016-06-15 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , , , , - , BGCOLOR="#fffff0",

GW170104 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 ...

10:11:58 , , 2017-06-01 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , , , , - , BGCOLOR="#fffff0",

GW170608 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 12^_\,M_\odot and 7^_\,M_\odot. The resulting black hole had a mass aro ...

02:01:16 , , 2017-11-16 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , Smallest BH progenitor
masses to date , , , - , BGCOLOR="#fffff0", GW170729
18:56:29 , , 2018-11-30 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , Largest progenitor masses until GW190521 , , , - , BGCOLOR="#fffff0", GW170809
08:28:21 , , 2018-11-30 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , , , , - , BGCOLOR="#fffff0",

GW170814 GW170814 was a gravitational wave signal from two Binary black hole, merging black holes, detected by the LIGO and Virgo interferometer, Virgo observatories on 14 August 2017. On 27 September 2017, the LIGO and Virgo collaborations announced the o ...

10:30:43 , , 2017-09-27 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , First announced detection by
three

observatories An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysical, oceanography and volcanology are examples of disciplines for which observatories have been constructed. His ...

; first polarization measurement , , * , - , BGCOLOR="#fffff0",

GW170817 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 . The signal was produced by the last minutes of a binary pair of neutron stars' inspir ...

12:41:04 , , 2017-10-16 , , , , , , , , , , , bgcolor=AADDDD, , , , bgcolor=AADDDD, , , , style="background:#AADDDD; text-align:center;", NS
, style="text-align:center;", ≤ 2.8 , , , , First NS merger observed in
GW; first detection of EM counterpart ( GRB 170817A; AT 2017gfo); nearest event to date , , , - , BGCOLOR="#fffff0", GW170818
02:25:09 , , 2018-11-30 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , , , , - , BGCOLOR="#fffff0", GW170823
13:13:58 , , 2018-11-30 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , , , , - , BGCOLOR="#f0fff0", GW190408_181802
2019-04-08 , , 2020-10-27 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , , , , - , BGCOLOR="#f0fff0",

GW190412 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 r ...

2019-04-12
05:30:44 , , 2020-04-17 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , First possible observation of a merger of two black holes of very different masses , , , - , BGCOLOR="#f0fff0", GW190413_052954
2019-04-13 , , 2020-10-27 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , , , , - , BGCOLOR="#f0fff0", GW190413_134308
2019-04-13 , , 2020-10-27 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , , , , - , BGCOLOR="#f0fff0", GW190421_213856
2019-04-21 , , 2020-10-27 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , , , , - , BGCOLOR="#f0fff0", GW190424_180648
2019-04-21 , , 2020-10-27 , , , , , , , , , , , bgcolor="888888", , , , bgcolor="888888", , , , bgcolor="888888", , , , , , , , , , - , BGCOLOR="#f0fff0", GW190425
2019-04-25
08:18:05 , , 2020-01-06 , , , , , , , , , , , bgcolor=AADDDD, , , , bgcolor=AADDDD, , , , , , , , , , , Originally designated S190425z (z:26th trigger, UTC day), this trigger was detected by a single LIGO instrument (of three LVC stations), and is considered by some scientists to have been confirmed as a binary neutron star merger. It was published in 2020 that a

was detected ( GRB 190425) ~0.5 seconds after the LIGO trigger, lasting 6 seconds and bearing similarities to GRB170817 (such as weakness ost_power_in_sub-100_keV,_or_soft_X-rays)_bands.html" ;"title="X-rays.html" ;"title="ost power in sub-100 keV, or soft X-rays">ost power in sub-100 keV, or soft X-rays) bands">X-rays.html" ;"title="ost power in sub-100 keV, or soft X-rays">ost power in sub-100 keV, or soft X-rays) bands elevated energetic photon background levels [signal exceeding background by less than a factor of 2], and similar differences from other transients classified as short GRBs). Confidence was established for interpretation of a set of peaks through a control interval of only 2 days prior to the LIGO-Livingston trigger in

INTEGRAL In mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented i ...

Electronic anticoincidence Electronic anticoincidence is a method (and its associated hardware) widely used to suppress unwanted, "background" events in high energy physics, experimental particle physics, gamma-ray spectroscopy, gamma-ray astronomy, experimental nuclear phys ...

, could not be corroborated by other instruments and wasn't initially noted as a significant event. Non-detection in other instruments may be a consequence of an Earth-occulted source as the

Fermi Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian (later naturalized American) physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. He has been called the "architect of the nuclear age" and ...

telescope attempted follow-up. , , , - , BGCOLOR="#f0fff0",

GW190521 GW190521 (initially S190521g) was a gravitational wave signal resulting from the merger of two black holes. It was possibly associated with a coincident flash of light; if this association is correct, the merger would have occurred near a third ...

2019-05-21
03:02:29 , , 2020-09-02 , , , , , , , , , , , bgcolor=888888, , , , bgcolor=888888, , , , bgcolor=888888, , , , , , , Originally designated S190521g. Largest progenitor masses to date. , , , - , BGCOLOR="#f0fff0",

GW190814 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 astronomi ...

2019-08-14 21:11:18 , , 2020-06-23 , , , , , , , , , , , bgcolor="888888", , , , , , , , bgcolor="888888", , , , , , , No optical counterpart was discovered despite an extensive search of the probability region. The mass of the lighter component is estimated to be 2.6 times the mass of the Sun, placing it in the mass gap between neutron stars and black holes. , ,
, - , BGCOLOR="#f0f0ff", GW200105
2020-01-05 16:24:26 , , 2021-06-29 , , , , , , , , , , , bgcolor="888888", , , , bgcolor=AADDDD, , , , bgcolor="888888", , , , , , , First event confirmed to be a black hole and neutron star merger. Originally designated S200105ae. , , , - , BGCOLOR="#f0f0ff", GW200115
2020-01-15 04:23:09 , , 2021-06-29 , , , , , , , , , , , bgcolor="888888", , , , bgcolor=AADDDD, , , , bgcolor="888888", , , , , , , Second event confirmed to be a black hole and neutron star merger. Originally designated S200115j. , , , - Gravitational Wave Transient Catalog 1

Candidate events and marginal detections

Marginal detections from O1 and O2

In addition to well-constrained detections listed above, a number of low-significance detections of possible signals were made by LIGO and Virgo. Their characteristics are listed below:

Observation candidates from O3/2019

From observation run O3/2019 on, observations are published as

Open Public Alert Open or OPEN may refer to: Music * Open (band), Australian pop/rock band * The Open (band), English indie rock band * Open (Blues Image album), ''Open'' (Blues Image album), 1969 * Open (Gotthard album), ''Open'' (Gotthard album), 1999 * Open (C ...

s to facilitate multi-messenger observations of events. Candidate event records can be directly accessed at the Gravitational-Wave Candidate Event Database (GraceDB). On 1 April 2019, the start of the third observation run was announced with a circular published in the public alerts tracker. The first O3/2019 binary black hole detection alert was broadcast on 8 April 2019. A significant percentage of O3 candidate events detected by LIGO are accompanied by corresponding triggers at Virgo. False alarm rates are mixed, with more than half of events assigned false alarm rates greater than 1 per 20 years, contingent on presence of glitches around signal, foreground electromagnetic instability, seismic activity, and operational status of any one of the three LIGO-Virgo instruments. For instance, events S190421ar and S190425z weren't detected by Virgo and LIGO's Hanford site, respectively. The LIGO/Virgo collaboration took a short break from observing during the month of October 2019 to improve performance and prepare for future plans, with no signals detected in that month as a result. The Kamioka Gravitational Wave Detector (

KAGRA The Kamioka Gravitational Wave Detector (KAGRA), is a large interferometer designed to detect gravitational waves predicted by the general theory of relativity. KAGRA is a Michelson interferometer that is isolated from external disturbances: its m ...

) in Japan became operational on 25 February 2020, likely improving the detection and localization of future gravitational wave signals. However, KAGRA does not report their signals in real-time on GraceDB as LIGO and Virgo do, so the results of their observation run will likely not be published until the end of O3. The LIGO-Virgo collaboration ended the O3 run early on March 27, 2020 due to health concerns from the

. On 15 June 2022, LIGO announced to start the O4 observing run in March 2023.

Notes

References

External links

* * {{Portal bar, Physics, Astronomy, Stars, Spaceflight, Outer space, Solar System *List

Gravitational waves Gravitational waves are waves of the intensity of gravity generated by the accelerated masses of an orbital binary system that Wave propagation, propagate as waves outward from their source at the speed of light. They were first proposed by Oliv ...

Observational astronomy Binary systems