This page contains a list of observed and candidate gravitational wave events.
Origin and nomenclature Direct observation of gravitational waves, which commenced with the detection of an event by LIGO in 2015, plays a key role in gravitational wave astronomy. LIGO has been involved in all subsequent detections to date, with Virgo joining in August 2017.
Joint observation runs of LIGO and Virgo, designated "O1, O2, etc." span many months, with months of maintenance and upgrades in-between designed to increase the instruments sensitivity and range. Within these run periods, the instruments are capable of detecting gravitational waves.
The first run, O1, ran from September 12, 2015, to January 19, 2016, and succeeded in its first gravitational wave detection. O2 ran for a greater duration, from November 30, 2016, to August 25, 2017. O3 began on April 1, 2019. The observing run was split in two, designated "O3a" and "O3b" with the first part suspended on September 30, 2019, for maintenance and upgrades. O3b began on November 1, 2019. Due to the COVID-19 pandemic O3 was forced to end prematurely. The early end meant that KAGRA did not have chance to participate in joint observations with LIGO and Virgo, so a short joint run was done in partnership with GEO. This run was designated "O3GK", and did not result in any additional detections.
O4 began on May 24, 2023; initially planned for March, the project needed more time to stabilize the instruments. The fourth observing run was divided into three parts, designated "O4a", "O4b", and "O4c". The run, initially planned to end after one year, was extended, following plans to make further upgrades for the O5 run. O4a started May 24, 2023 and ended January 16, 2024. O4b started April 10, 2024 and ended January 28, 2025 at 17:00 UTC. Unusually, O4c, followed directly from O4b, starting on January 28, 2025 at 17:00 UTC and concluded on November 18, 2025 at 16:00 UTC. There was a two month commissioning break from January to March 2024, and another from 1 April to a planned 11 June 2025, after which observations resumed. As of May 2025, O5 is planned to begin in late 2027. An intermediate six-month observing run has also been announced, expected to begin later summer/early fall of 2026. Updated observing plans are published on the official website.LIGO, Virgo and KAGRA Observing Run Plans
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 date of the event, with the two first digits representing the year, the two middle digits the month and two final digits the day of observation. This is similar to the systematic naming for other kinds of astronomical event observations, such as those of gamma-ray bursts.
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 (BH), two neutron stars (NS), or a black hole and a neutron star (BHNS). Some objects are in the mass gap (MG) between the largest predicted neutron star masses (Tolman–Oppenheimer–Volkoff limit) and the smallest known black holes.
List of gravitational wave events
+Confirmed events by distance+Initial objects by mass
GW eventand time (UTC) Datepublished LocationareaThe relatively large and distant area of the sky within which it is claimed to be possible to localize the source.(deg2) Signal toNoise Ratio(SNR) Luminositydistance(Mpc)1 Mpc is approximately 3.26 Mly. Energy radiated/c2 (M☉)c2M☉ is about , or . Chirp mass (M☉)The chirp mass is the binary parameter most relevant to the evolution of the inspiral gravitational waveform, and thus is the mass that can be measured most accurately. It is related to, but less than, the geometric mean of the binary masses, according to , thus ranging from ~87% of when the masses are the same to ~78% when they differ by an order of magnitude. Effective spin Primary Secondary Remnant Notes Ref. Type Mass (M☉) Type Mass (M☉) Type Mass (M☉) Spin GW15091409:50:45 2016-02-11 BH BH First GW detection;first BH merger observed 09:54:43 2016-06-15 Formerly candidate LVT151012;accepted as astrophysical since February 2019 GW15122603:38:53 2016-06-15 GW17010410:11:58 2017-06-01 GW17060802:01:16 2017-11-16 Smallest BH progenitormasses to date GW17072918:56:29 2018-11-30 Largest progenitor masses until GW190521 GW17080908:28:21 2018-11-30 GW17081410:30:43 2017-09-27 First announced detection bythree observatories; first polarization measurement GW17081712:41:04 2017-10-16 HMNS-BH≤ 2.8 First NS merger observed inGW; first detection of EM counterpart (GRB 170817A; AT 2017gfo); nearest event to date GW17081802:25:09 2018-11-30 GW17082313:13:58 2018-11-30 GW190403_051519 2019-04-03 05:15:19 2022-05-11 GW190408_181802 2019-04-08 18:18:02 2020-10-27 Originally designated S190408an. GW190412 2019-04-1205:30:44 2020-04-17 First possible observation of a merger of two black holes of very different masses. Originally designated S190412m. GW190413_052954 2019-04-13 2020-10-27 GW190413_134308 2019-04-13 2020-10-27 GW190421_213856 2019-04-21 2020-10-27 Originally designated S190421ar. GW190424_180648 2019-04-24 18:06:48 2020-10-27 GW190425 2019-04-2508:18:05 2020-01-06 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.