Level 1 - Absolute Beginner

Scientists who study space have found 161 new signals from black holes and neutron stars crashing into each other. These signals are called gravitational waves.

A group of scientists called LIGO-Virgo-KAGRA work together with big machines in the USA, Europe, and Japan to find these waves.

The new list, called GWTC-5, now has 390 events in total. It was shared with the world on May 26, 2026.

One of the biggest discoveries is the heaviest pair of black holes ever found crashing together. Studying these crashes helps us learn about the universe.

gravitational waves

ripples in space caused by massive objects moving very fast

black hole

a region in space where gravity is so strong that nothing, not even light, can escape

neutron star

a very small, very dense star left behind after a big star explodes

catalog

an official list of things that have been collected and organised

detector

a machine that senses and measures something

collision

when two objects crash into each other with great force

universe

all of space and everything in it

signal

something detected by a machine that carries information

Level 2 - Elementary

The LIGO-Virgo-KAGRA collaboration published its fifth Gravitational-Wave Transient Catalog, known as GWTC-5, on May 26, 2026, adding 161 newly confirmed signals and bringing the total number of detected events to 390.

The signals were collected during the fourth observing run, which ran from April 2024 to January 2025. During this period, detectors in the United States, Italy, and Japan worked together to pick up tiny ripples in space-time.

Among the highlights is the heaviest binary black hole merger ever recorded. The two black holes each had a mass of roughly 130 times that of our Sun before they collided and merged into an even larger single black hole.

Scientists say the new catalog will help them better understand how black holes form, how fast the universe is expanding, and whether Einstein's theory of general relativity holds true in the most extreme environments in nature.

gravitational wave

a ripple in the fabric of space-time produced by an accelerating massive object

observing run

a set period during which detectors are actively collecting scientific data

binary black hole

a pair of black holes orbiting each other that eventually merge

merger

the joining together of two separate objects into one

space-time

the four-dimensional fabric combining space and time in Einstein's theory

solar mass

the mass of our Sun, used as a unit when measuring very massive objects in space

general relativity

Einstein's theory describing how gravity works as the curvature of space-time

expand

to become larger in size or volume

Level 3 - Intermediate

On May 26, 2026, the LIGO-Virgo-KAGRA collaboration released the fifth Gravitational-Wave Transient Catalog (GWTC-5), cataloguing 161 newly confirmed detections from the fourth observing run and raising the total number of confident gravitational-wave events to 390.

The headline result is a binary black hole merger with component masses of approximately 130 and 133 solar masses, the most massive system yet recorded, placing it squarely in the so-called pair-instability mass gap, a region above roughly 65 solar masses where standard stellar evolution models predict black holes should not be able to form via core collapse.

A second standout event, provisionally designated GW240615, was localised to just six square degrees on the sky, the tightest angular constraint for any gravitational-wave source to date. The precision opens realistic prospects for rapid electromagnetic follow-up and, if a host galaxy can be identified, an independent measurement of the Hubble constant.

The catalog also contains what the team describes as the first statistically robust test of the black hole no-hair theorem using a three-tone ringdown, the gravitational equivalent of a bell resonating at multiple frequencies after being struck, providing evidence consistent with the Kerr metric description of rotating black holes.

pair-instability mass gap

a predicted range of black hole masses that standard stellar evolution should not produce

component masses

the individual masses of the two objects in a merging binary system

angular constraint

a measurement of how precisely the direction of a source can be pinpointed on the sky

Hubble constant

the rate at which the universe is expanding, expressed in km/s per megaparsec

no-hair theorem

the principle that black holes are fully described by just three quantities: mass, spin, and charge

ringdown

the gravitational-wave emission as a newly formed black hole settles into a stable state

Kerr metric

the mathematical description of the space-time geometry around a rotating black hole

electromagnetic follow-up

observations of an event using telescopes sensitive to light, radio, or X-rays

Level 4 - Advanced

GWTC-5, released by the LIGO-Virgo-KAGRA collaboration on May 26, 2026, constitutes the most statistically comprehensive gravitational-wave event catalog assembled to date, adding 161 O4-run events to 229 previously catalogued detections and deploying an updated matched-filter pipeline with improved non-Gaussian noise subtraction that reduces the false-alarm rate at the canonical one-per-year threshold by approximately 30 percent relative to the O3-era analysis.

The astrophysically anomalous binary black hole GW260417, with component masses of roughly 130 and 133 solar masses, sits well within the pair-instability mass gap predicted by stellar evolution models above roughly 65 solar masses. Its existence challenges monolithic assumptions about black hole formation pathways and lends observational weight to hierarchical merger scenarios, in which second-generation black holes formed from earlier mergers in dense stellar environments such as nuclear star clusters or active galactic nuclei accretion discs accumulate mass beyond the pair-instability ceiling.

The high angular precision of GW240615, localised to a 90 percent credible region of just 6 square degrees, reflects the improved three-detector baseline geometry during the O4b sub-run when KAGRA operated at its highest sensitivity configuration. Host-galaxy identification efforts via the Rubin Observatory's LSST pipeline are ongoing; a confirmed optical counterpart would enable a sub-percent Hubble constant determination independent of the distance-ladder systematics that have fuelled the Hubble tension debate for over a decade.

The three-tone quasi-normal mode analysis, distinguishing the fundamental and first overtone ringdown modes alongside a subdominant higher-order mode, provides the first statistically meaningful evidence at greater than 3 sigma that post-merger ringdown is consistent with Kerr geometry, constituting the strongest observational test of the no-hair theorem to date. Should the planned O5 run in 2027 yield events at sufficient signal-to-noise, the LVK team projects that the Kerr hypothesis can be tested at the 5-sigma discovery threshold.

matched-filter pipeline

a signal-processing technique that searches noisy data for waveforms matching theoretical templates

false-alarm rate

the frequency at which a detector registers a signal that is not a real astrophysical event

hierarchical merger

the scenario in which black holes formed from previous mergers collide again to produce even more massive objects

active galactic nucleus

the extremely luminous, compact central region of a galaxy powered by a supermassive black hole

Hubble tension

the unresolved discrepancy between independent measurements of the universe's expansion rate

quasi-normal mode

a characteristic oscillation frequency of a black hole settling after a merger, analogous to a ringing bell