More precise than ever before

Next-generation gravitational-waveforms from inspiraling black holes are calculated using mathematical methods from particle physics, such as Feynman diagrams, originally developed for the evaluation of quantum scattering amplitudes. This breakthrough was achieved by calculating the most complex Feynman diagrams ever. Credit: R. Patil (Max Planck Institute for Gravitational Physics), background image: James Webb Space Telescope, ESA/Webb, NASA & CSA, H. Dannerbauer

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To the point:

• New detectors: Over the next decade, new gravitational-wave observatories on Earth and in space will begin operations. They will be much more sensitive than current detectors and will observe signals in much greater detail.


• New models: The waveform models used for data analysis — mathematical methods for calculating the expected signals — must be about 100 times more accurate than the current models in order to exploit the full potential of the new observatories.


• Important milestone: Researchers at the Max Planck Institute for Gravitational Physics in Potsdam, together with international colleagues, have now taken the most difficult step towards new, more precise analytical waveform models. They have improved methods from particle physics, enabling predictions to be made with unprecedented precision across the four fundamental forces.

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Breakthrough on the path to highly accurate prediction of gravitational-wave signals

The key to understanding black holes

Pairs of merging black holes reveal their presence only through their gravitational waves and remain invisible to other astronomical methods. The first gravitational wave, detected 11 years ago by the LIGO detectors, originated from such a merger. Even today, the vast majority of the nearly 400 published signals originate from merging black holes. Gravitational-wave astronomy has evolved into a successful method of observing and studying the dark side of the universe.

To detect and understand these signals, scientists need not only highly sensitive laser interferometers but also precisely tailored waveform models. These mathematical predictions provide the templates that researchers use to identify the signals in the observational data.

They also use these models to identify the sources of the detected gravitational waves and determine their properties. How massive were the two black holes? Where and when did they merge? Did they merely orbit each other, or did they also spin around their own axes? How fast were they rotating, and around which axes? If researchers can answer these questions using precise waveform models, they can decipher how the black holes formed. They can also put Einstein's general theory of relativity to increasingly rigorous tests.

The next generation of gravitational-wave detectors and waveform models

A new era is dawning for gravitational-wave astronomy in the coming decade. The LISA detector in space is designed for low-frequency gravitational waves that cannot be detected from the ground. At the same time, the planned 'third-generation' ground-based detectors — the Einstein Telescope and Cosmic Explorer — will observe gravitational waves similar to those detected by current instruments. However, these detectors will be up to ten times more sensitive in their final design and will capture a large number of very long and very loud signals.

The waveform models must also become significantly more accurate so that researchers can correctly interpret the data. “Our waveform models must be around 100 times more accurate than the current models,” says Jan Steinhoff, group leader in the Astrophysical and Cosmological Relativity department at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in the Potsdam Science Park. “Only with such precise theoretical models can we fully exploit the potential of the new observatories and gain new insights into the universe.”

Complex mathematics for a precision record

As a first step towards developing such highly precise waveform models, the researchers have focused on the initial phase of the merger. During this phase, two black holes orbit each other at a greater distance, emit gravitational waves and slowly continue to draw closer. The effects of general relativity are still very small during this phase. Therefore, their motion can be described by post-Newtonian theory: This essentially adds corrections from Einstein's general theory of relativity to Newton's theory of gravity. Complex mathematical methods originally developed in particle physics are employed to continually refine these corrections, accounting for parameters such as the black holes’ intrinsic spin.

Calculating black holes? Try particle physics!

In their study, published recently in the journal Physical Review Letters, the scientists treat black holes as particles to describe the initial phase of the merger and the resulting gravitational waves, using post-Newtonian theory.

This enabled the scientists to make predictions on the motion of black holes around each other with unprecedented accuracy across the four fundamental forces: gravity, electromagnetism, the weak interaction and the strong interaction.

Raj Patil, a doctoral student at the AEI, explains: “We had to perform highly complex calculations to take this most difficult step towards the new waveform models. Never before have researchers been able to calculate fundamental interactions with such precision.” Patil adds: 'While there is still a lot of work ahead of us before we have the final waveform templates, we are now very confident that we will achieve our goal following this breakthrough.”

Source: Max Planck Institute for Gravitational Physics/News

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Media contact:

Dr. Elke Müller
Press Officer AEI Potsdam, Scientific Coordinator
Tel: +49 331 567-7303
Email: elke.mueller@aei.mpg.de

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Science Contacts:

Raj Patil
PhD Student
Tel: +49 331 567-7186
Email: raj.patil@aei.mpg.de

Dr. Jan Steinhoff
Group Leader
Tel: +49 331 567-7125
Email: jan.steinhoff@aei.mpg.de

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Publication:

Brunello, G.; Mandal, M. K.; Mastrolia, P.; Patil, R.; Pegorin, M.; Ronca, J.; Smith, S.; Steinhoff, J.; Torres Bobadilla, W. J.
Six-loop gravitational interactions at the sixth post-Newtonian order. Physical Review Letters 137, 111401 (2026)
 MPG.PuRe | | DOI | pre-print

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Further information

Homepage of the “Astrophysical and Cosmological Relativity” Department

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Do black holes pretend to have large masses?

A closer look at the gravitational-wave event GW231123

© Simulation: I. Markin (University of Potsdam), H. Pfeiffer (Max Planck Institute for Gravitational Physics), T. Dietrich (University of Potsdam and Max Planck Institute for Gravitational Physics); Collage: B. Knispel, M. Zumalacárregui (Max Planck Institute for Gravitational Physics)

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To the point

• The signal: On 23 November 2023, both LIGO observatories in the US detected gravitational waves from the most massive black hole merger to date.


• The mystery: According to previous studies, the two black holes had masses approximately 100 and 140 times that of our Sun, respectively. However, according to standard models of stellar evolution, black holes of these masses are difficult to form. How they could have evolved remains a mystery.


• A possible solution: Scientists at the Max Planck Institute for Gravitational Physics in Potsdam have now proposed an explanation for these unusual masses. The signal may have been magnified by a galaxy and diffracted by an object within it, making the black holes appear more massive than they really are.

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A potential explanation for a mysterious gravitational wave signal.

The gravitational-wave signal GW231123, detected by the two LIGO detectors in the US on 23 November 2023 from the merger of two black holes, continues to puzzle scientists. Given their large masses, the existence of these black holes cannot be explained with the standard understanding of stellar evolution. However, they are not only very massive, but also spin very quickly. This makes interpreting the signal particularly challenging and suggests an unusual formation history for the binary system.

In a new study, a research team at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) in the Potsdam Science Park investigated whether the measured masses and spins appeared larger than they actually were due to the effect of a gravitational lens.

Light on Curved Paths and Distorted Gravitational Waves

Light traveling through the universe is deflected by massive objects, resulting sometimes in multiple images of the same astrophysical source. This gravitational lensing effect needs to be accounted for to correctly interpret observations. Lensing is routinely observed on electromagnetic sources such as stars and galaxies, and expected to occur in a fraction of gravitational-wave sources.

“Like light, gravitational waves can also be deflected, magnified and split into multiple signals by massive objects,” says Miguel Zumalacárregui, group leader in the Astrophysical and Cosmological Relativity Department at the AEI. “For gravitational waves, diffraction and interference effects give us an additional way to identify and study lensed signals.”

Detecting these subtle lensing diffraction effects requires sensitive detectors and novel data-analysis methods. To make this analysis possible, the team developed a mathematical description of gravitational-wave lensing and software fast enough to analyze the data.

“If we assume that GW231123 was deflected and distorted by a compact object of about 190 to 850 solar masses—or by an extended structure such as a globular cluster—we can understand the observed high masses,” says Srashti Goyal, co-lead author and postdoc at the AEI Potsdam when working on the topic. “Moreover, the lensing interpretation does not require unusually high spins.” Taking these effects into account, the total mass of the source would be around 140 solar masses rather than about 230 solar masses. The system would then be much less extreme and easier to accommodate within known black-hole formation scenarios.

Across the Universe

The study’s title, “Across the Universe”, is a nod to the Beatles — but here the journey really does change how the source appears. As gravitational waves travel through the expanding Universe, their wavelengths are stretched and their frequencies lowered (an effect known as cosmological redshift) — the equivalent of lowering a sound’s pitch. Just as a cello played back at a lower pitch might be mistaken for a double bass, a distant black-hole binary can appear more massive than it really is. Gravitational magnification adds to the illusion by making the distant source appear closer.

“Our analysis also suggests that the compact lens was embedded in a larger gravitational field, such as that of the galaxy hosting it,” adds Héctor Villarrubia-Rojo, co-leading author of the study and a postdoctoral scholar at the Universidad Complutense in Madrid, Spain. “By including this external potential, we can describe the small-scale diffraction and the large-scale magnification within a single framework.”

New insights from lensed gravitational waves

So far, researchers have not unambiguously detected any signals affected by gravitational lensing in the data from gravitational-wave detectors. According to the new study, GW231123 is a promising candidate for such an event.

“The nature of the lens remains a major mystery in our analysis, as individual compact lenses with 100–1,000 solar masses should be exceedingly rare,” adds Zumalacárregui. “Future work will need to establish whether such lenses can form, or whether an ensemble of lighter objects, including stars, can explain this event.”

Current data do not yet allow an unambiguous claim of gravitational lensing. Following further upgrades to the detectors, however, the scientists expect to be able to detect and interpret lensed gravitational waves using new data analysis methods.

The detection — or lack thereof — of gravitational waves deflected by the gravity of other objects will provide new insights into gravitational-wave astronomy: Gravitational magnification may reveal black-hole mergers beyond the distance current detectors can normally reach, while diffraction can probe compact objects and dark-matter structures along the line of sight. Consequently, these deflected gravitational waves could become a new method for exploring the universe.

Source: Max Planck Institute for Gravitational Physics

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Media contact:

Dr. Elke Müller
Press Officer AEI Potsdam, Scientific Coordinator
Tel: +49 331 567-7303
Email: elke.mueller@aei.mpg.de

Science contacts:

Dr. Srashti Goyal
Postdoc
Email: srashti.goyal@iucaa.in
Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, India

Dr. Héctor Villarrubia-Rojo
Postdoctoral scholar
Email: hectorvi@ucm.es
Universidad Complutense, Madrid, Spain

Dr. Miguel Zumalacarregui
Group Leader
Tel:+49 331 567-7322
Fax: +49 331 567-7298
Email: miguel.zumalacarregui@aei.mpg.de

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Publication

Goyal, S.; Villarrubia-Rojo, H.; Zumalacarregui, M.
Across the Universe: GW231123 as a magnified and diffracted black hole merger. The Astrophysical Journal Letters 1008, L12 (2026)

MPG.PuRe - DOI - pre-print

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Related information

1. Homepage of the “Astrophysical and Cosmological Relativity” department

2. YouTube video: The Next Frontier: Lensing of Gravitational Waves

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The AEI plays a leading role in the development of LISA’s key instruments

Artist's impression of the LISA mission satellites in the solar system observing gravitational waves from a distant galaxy.
Credit: University of Florida / Simon Barke (CC BY 4.0)

This picture shows a Back-End Electronics (BEE) module of LISA’s Phasemeter during tests with simulated signals in the Interferometric Signal Processing Lab at the AEI Hannover. In LISA, the BEE tracks signals from each satellite’s optical bench, containing information about the passing gravitational waves. © Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI)

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To the point:

• Preparations for LISA: LISA is a space-based observatory for gravitational waves and a mission of the European Space Agency (ESA) with contributions from NASA. It is scheduled to launch into space in the 2030s and will gather entirely new information about the Universe. The satellites and their high-precision measurement instruments are currently being developed.


• Scientific expertise: The AEI is receiving a grant from the DLR. Under this grant, the institute is entrusted with leading the development of key LISA instruments as well as the investigation and verification of additional components through 2030. The grant totals 35 million euros.


• Next steps for the phasemeter: On behalf of and under the leadership of the AEI, OHB Systems AG will develop and manufacture the engineering models, qualification models, and flight hardware for one component of the phasemeter. The phasemeter is LISA’s central measuring instrument.

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The AEI receives a grant totaling 35 million euros from the DLR to develop key components of the instruments for the satellite mission

"This grant underscores the leading role of our institute and that of the Max Planck Society in the development of LISA, the European Space Agency’s gravitational-wave observatory

Guido Müller, director at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI)

Scientific expertise at the AEI

“The grant strengthens the scientific expertise – grown over decades – at the Max Planck Institute for Gravitational Physics in the development, investigation, and verification of methods and instruments for gravitational-wave observation in space,” says Jens Reiche Program Manager for space projects at the AEI.

With this latest grant of 35 million euros, the German Space Agency at the German Aerospace Center (DLR) is funding the next phase of development of instruments for LISA’s optical measurement system at the AEI. Additional funding for subsequent project phases has already been planned.

The funding is being provided as part of the implementation phase: The AEI is initially responsible for developing and providing the engineering models of the phasemeter – which is classified as mission-critical – and its signal processing within the optical measurement system. This includes extensive testing, encompassing all relevant interfaces

Next steps for the phasemeter

The LISA phasemeter is the heart of this measurement system. It will measure the minute changes in the laser light imprinted by gravitational waves in the laser beams as they travel back and forth over millions of kilometers between the three LISA satellites. Therefore, the phasemeter is the instrument that will detect gravitational waves and thereby enable a new era of astronomy.

The AEI is responsible for the phasemeter’s hardware and software and their verification. To this end, the institute will develop and operate mathematical models, simulators, and experiments.

“On our behalf and under our leadership, our industry partner OHB Systems AG is developing and manufacturing the engineering models, qualification models, and flight hardware for one of the two components of the phase meter,” says Kanioar Karan, the project manager for phasemeter development at AEI.

The institute also organizes and supports the verification of the LISA measurement system and manages its interaction with other components of the satellite hardware. To this end, the AEI develops and operates technical models of the instruments and simulators, as well as various experimental setups. Using these setups, scientists at the AEI will test the functionality of several components of the satellite hardware and verify whether they meet the strict requirements for measurement accuracy. These experimental setups in the institute’s laboratories could also help during commissioning of LISA in space following its launch in the 2030s.

Preparing for LISA measurements

In addition, researchers at the AEI will work with ESA to further develop methods for LISA’s science operations. The goal is to analyze the LISA measurement data after launch and commissioning in the 2030s and to derive as many scientific insights from them as possible. To this end, the scientists will develop and operate models and simulators of LISA instruments and will develop and refine new methods for analyzing the LISA data.

“Beyond basic research and its application in astronomy with LISA, the AEI also supports technology transfer to industry,” says Guido Müller. “The insights and experience gained from our research on high-precision, laser-based measurements are intended to enable novel technical applications.”

Background information

LISA

LISA will be the first gravitational-wave observatory in space. It will consist of three satellites that will move in a triangular configuration – connected by 2.5 million kilometer-long arms of laser light – in an Earth-like orbit around the Sun.

LISA will be able to detect gravitational waves from sources throughout the Universe, going back almost to the Big Bang. These gravitational waves will cause tiny changes (smaller than the diameter of an atom) in the laser arms. LISA will measure these length changes by using laser light to monitor the movements of test masses that are in free fall inside the satellites.

LISA research at the AEI

The institute has LISA research groups at its locations in Hanover and Potsdam. It plays a leading role in the development of key hardware components, research into laser interferometry for LISA, and in source modeling, data analysis, and the application of scientific results.

Gravitational-wave astronomy with LISA

Gravitational waves are ripples in spacetime that arise when masses are accelerated. Current detectors on Earth measure gravitational waves originating from merging pairs of neutron stars and black holes with masses of up to several hundred solar masses.

LISA will detect gravitational waves in the as-yet unexplored window between 0.1 mHz and 1 Hz – at frequencies that detectors on Earth cannot observe. Waves in this frequency range are generated when black holes with masses ranging from about 10,000 to 100 million times that of the Sun collide and merge at the centers of distant young galaxies. LISA will detect these processes throughout the history of the Universe, thereby directly investigating the as-yet-unknown origin and growth of extremely massive black holes.

What makes LISA unique is its ability to detect gravitational waves originating from black holes with masses ranging from about 100 to 10,000 solar masses that orbit massive black holes in galactic centers. These signals allow us to study the geometry of spacetime and test the nature of gravity. LISA will not only detect a large number of binary and multiple systems of compact objects in our Milky Way – which will provide insights into the evolution of binary stars – but will also “see” the galaxy beyond the galactic center. This includes many objects that are invisible to all other astronomical instruments.

Since LISA uses gravity as a signal source, the mission will complete our understanding of the origin, evolution, and structure of our Universe. The study of gravitational waves also offers enormous potential for discovering previously inaccessible parts of the Universe; these include, among other things, the echo of the Big Bang (ripples in spacetime caused by disturbances in the plasma shortly after the Big Bang) and other, as yet unknown phenomena. Together with other astronomical methods and gravitational-wave observatories on Earth, LISA researchers will contribute to the next major discoveries to answer questions such as “What are the fundamental laws of the Universe?” and “How did the Universe come into being, and what is it made of?”

Source: Max Planck Institute for Gravitational Physics/News

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Media contact:

Dr. Benjamin Knispel
Press Officer AEI Hannover
Tel: +49 511 762-19104
Email: benjamin.knispel@aei.mpg.de

Prof. Dr. Guido Müller
Managing Director
Tel: +49 511 762-12424
Email:  guido.mueller@aei.mpg.de
v Dr. Jens Reiche
Project Leader
Tel: +49 511 762-12130
Tel: +49 511 762-5844
Email:  jens.reiche@aei.mpg.de

Dr. Kanioar Karan
Project Manager
Tel: +49 511 762-12181
Email:  kanioar.karan@aei.mpg.de

Dr. Ada Agnieszka Uminska
Project Leader
Tel: +49 511 762-14059
Email:  guido.mueller@aei.mpg.de

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Further information

Aeneas Rooch: LISA listens to space (MaxPlanckResearch 2/2024)>

The largest astronomical observatory is so large that it won’t fit on Earth. It’s called LISA, and it will be able to detect when a 2.5-million-kilometer segment of space shrinks by even one atomic diameter. Researchers at the Max Planck Institute for Gravitational Physics in Hanover and Potsdam helped develop the gravitational-wave detector. By observing cosmic waves, they hope to gain an insight into strange processes deep in outer space.

Observing gravitational waves in space with LISA

Benjamin Knispel, “Observing gravitational waves in space with LISA” in: Einstein Online Band 15 (2024), 1001

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The new LIGO-Virgo-KAGRA catalog sets records in precision gravitational-wave astronomy

The spectrograms of all gravitational-wave events in the new catalog GWTC-5.0 that were found in O4b and have a false-alarm rate of less than one per year. Credit: Derek Davis / University of Rhode Island / LIGO-Virgo-KAGRA

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To the point

• New gravitational-wave catalog: The LIGO-Virgo-KAGRA collaboration releases the largest gravitational-wave catalog, GWTC-5, with 161 new events, totaling 390 confirmed detections since 2015.


• A wealth of results: The catalog contains many astrophysical highlights: the gravitational-wave source with the most precise sky localization, the first measurement of three gravitational-wave tones from a black hole, evidence for the existence of second-generation black holes, and new measurements of how fast the Universe is expanding.


• More results to come: Data from the last part of the fourth observing run are being analyzed at the moment. Information on the 68 signal candidates and new discoveries will be published in a catalog update in the coming months.

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Researchers at the Max Planck Institute for Gravitational Physics contribute to discoveries in the largest gravitational-wave catalog ever compiled.

Today, the LIGO-Virgo-KAGRA (LVK) collaboration published an updated catalog of the gravitational-wave events observed by its international network of gravitational-wave detectors in the United States, Italy, and Japan. The new version of the catalog, called Gravitational-Wave Transient Catalogue-5.0 (GWTC-5), has been posted as three core and three companion papers on the arXiv preprint server. These will be submitted to The Astrophysical Journal and The Astrophysical Journal Letters.

The detector network collected the data analyzed in this work between April 2024 and the end of January 2025, during O4b, the second part the fourth joined observing run (O4). A total of 161 new gravitational-wave events were discovered, of which scientists extracted parameters from 104. The latest revision of the catalog increases the grand total of confirmed events observed by the network since the first detection in September 2015 to 390.

As detector upgrades make the instruments increasingly more sensitive, the number of events detected in each successive observing run is growing significantly. This is underlined by the fact that 75% of all gravitational-wave signals observed so far have been discovered in the first and second part of O4.

An ever-growing treasure trove of data

“Our detectors have now become so sensitive that we discover new gravitational-wave signals about three to four times each week of our observing runs, unlocking an ever-growing treasure trove of data,” says Frank Ohme, group leader in the Precision Interferometry and Fundamental Interactions department at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover. “Each new signal helps to deepen our understanding of the dark, invisible side of the Universe.”

“Ten years after our first discoveries, we are now entering the era of precision gravitational-wave astronomy,” adds Karsten Danzmann, director emeritus at the AEI in Hannover. “What we can do with gravitational-wave astronomy today is truly amazing! We can study the population of coalescing black holes, conduct some of the most precise tests of general relativity, and obtain completely new measurements of the expansion of our Universe.”

“Our new catalog includes several exceptional and record-breaking signals,” says Alessandra Buonanno, director of the Astrophysical and Cosmological Relativity department at the AEI in the Potsdam Science Park. “We have found evidence for the existence of second-generation black holes, have pinpointed the sky position of a gravitational-wave source more precisely than ever before, and have for the first time measured or constrained three gravitational-wave tones from a black hole in the clearest gravitational-wave signal observed to date.” “The collaboration did an extraordinarily careful and comprehensive analysis of the detected gravitational waves,” confirms Harald Pfeiffer, group leader at AEI in Potsdam and the lead reviewer for the internal quality control of data-taking and analysis of the GWTC-5.0 results paper. “This makes today’s announcements not only scientifically extraordinarily important, but also very reliable.”

Pinpointing a black hole coalescence

One signal in the catalog, observed on 15 June 2024, sets a new record for the most precise sky localization of all gravitational-wave events. Its source was found to lie within an area of just 6 square degrees – a patch of the sky that could be covered by about 28 full moons. This exceptional performance was possible because LVK researchers could combine data from both LIGO instruments and the Virgo detector, which observed the gravitational waves.

Determining where a gravitational-wave source is located is crucial when searching for possible electromagnetic signals generated by events such as binary neutron star or black-hole–neutron-star coalescences. The smaller the sky region, the easier it is to point other astronomical observatories at them.

The record-setting event came from the coalescence of two black holes, weighing 34 and 26 times as much as our Sun, respectively. The gravitational waves were emitted from their merger about 3.4 billion years ago – at a time when the earliest known forms of life emerged on Earth – and traveled at the speed of light until reaching our planet in 2024.

Data analysis expertise and new waveform models

Whenever gravitational-wave signals reached Earth, an international expert team reviewed the performance of the algorithms that identified the potential signals and also discussed the next analysis steps. AEI members contributed week-long shifts of data analysis expertise during the observing run.

Gravitational-wave astronomy goes far beyond simply detecting a signal’s presence. Using highly sophisticated data analyses, it must be extracted it from the detectors’ background noise and its astrophysical properties must be inferred and understood. The clearer a signal stands out from the noise background, the “louder” it is and the better its astrophysics can be understood.

Extracting astrophysical properties from these loud signals requires a detailed understanding of the characteristic fingerprints these properties leave in the data. For this purpose, researchers at the AEI in Potsdam and Hannover have developed and made key contributions to the latest generation of improved waveform models. LVK researchers use these models to predict the gravitational waves emitted from binary black holes and to understand new signals once found.

“Our improved waveform models are more physically consistent and accurate and are key to reliably infer the properties of black hole mergers from the detector data,” explains Héctor Estellés Estrella, a former postdoc at AEI Potsdam, now a Postdoctoral Fellow at the Institute of Space Sciences in Barcelona.

“The additional physics incorporated by us into existing waveform models, now used in GWTC-5, brings us a step closer to precisely modeling these complex astrophysical systems,” adds Shrobana Ghosh a postdoc in the Precision Interferometry and Fundamental Interactions department at AEI Hannover.

Visualization of a binary black hole ringdown consistent with the gravitational-wave event GW250114.The gravitational waves are separated into two modes of the ringing remnant black hole, identified in the observation: the fundamental mode (green) and its first overtone (red). It also shows a predicted third tone (yellow) that the data places limits on. Visualization performed at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute), based on a numerical relativity simulation of the Simulating Extreme Spacetimes (SXS) Project. Credit: H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), K. Mitman (Cornell University)

The clearest gravitational-wave signal

GWTC-5 contains five exceptionally loud binary black hole mergers including the by far clearest gravitational-wave signal seen to date. GW250114, reported earlier, came from a coalescence of black holes with masses 34 and 32 times that of our Sun about 1.3 billion light-years away. It was observed on 14 January 2025 and its “clarity” made it possible to achieve outstanding scientific results, among them the most precise test of general relativity ever performed and confirmation of Stephen Hawking’s black hole area theorem.

During the ringdown phase, when the black hole settles into its final state right after the merger, the gravitational-wave signal contains a characteristic spectrum of modes, or tones. Characterizing multiple gravitational-wave tones – measuring the frequencies of the tones and how quickly they fade – enables unique and powerful tests of general relativity. GW250114 was clear enough for the researchers to measure two tones and constrain a third. All three agree with Einstein’s general relativity and the Kerr solution for rotating black holes.

Characterizing black holes with DINGO

In the past years, researchers at the AEI and at the Max Planck Institute for Intelligent Systems (MPI-IS) have been developing DINGO, a machine learning algorithm for gravitational-wave data analysis. In the production of GWTC-5 it has been used routinely for the first time.

“Our approach called DINGO employs deep neural networks. It is just as accurate and reliable as the conventional methods the LVK collaboration uses to determine the astrophysical characteristics of the gravitational-wave sources, but it only takes minutes instead of hours or days for the same task,” explains Annalena Kofler, a PhD student at the MPI-IS and the AEI in Potsdam.

“The LVK investigated 104 of the 161 of the new gravitational-wave signals, in detail. For 42 of those 104 signals in the new catalog, DINGO served as a cross-validation tool. The DINGO results agree exactly with those obtained with the conventional methods,” adds Nihar Gupte, a PhD student in the Astrophysical and Cosmological Relativity department at the AEI in the Potsdam Science Park.

Infographic about the two gravitational-wave events GW241011 and GW241110.
Credit: Shanika Galaudage / Northwestern University / Adler Planetarium

Second-generation black holes

In October and November 2024, just one month apart, the detector network observed gravitational waves from two very special black hole coalescences. GW241011 and GW241110 came from distances of approximately 700 million and 2.4 billion light-years, respectively. As reported earlier, certain characteristics of these mergers – in particular how fast and around which axis the black holes were spinning – indicate the objects involved could be “second-generation” black holes. These are black holes that themselves were formed in previous black hole coalescences, likely in very dense and crowded cosmic environments, such as stellar clusters. There black holes are more likely to collide and merge repeatedly.

The growing number of observed events has also enabled the LVK researchers to study and identify the properties of different populations of black holes. One of the articles accompanying the catalog deals with this specific aspect.

Studying the expansion of our Universe

LVK researchers have used the improving ability of the detector network to localize events and the increased number of events to measure the rate at which our Universe is expanding. They combined gravitational-wave based measurements of the distances to the sources with other measurements of how fast they are traveling away from Earth because of the Universe’s expansion.

The LVK improved the precision of its estimate of the Hubble constant, which measures the Universe’s expansion rate, by more than 25% compared to the value derived from the previous catalog. The estimated value is consistent with existing measurements from both our cosmic neighborhood and the early Universe. It is, however, not yet precise enough to resolve the “Hubble Tension” between those long-established measurements.

More signals in the next catalog update and the upcoming observing run

The analysis of O4c, the final part of O4 from the end of January 2025 until mid November 2025, is currently underway. The LVK collaboration will publish the results in the coming months. The 68 signal candidates already identified during O4c will further expand the catalog and offer new opportunities to study our Universe and the fundamental laws of physics.

At the moment, the detectors of the international network are undergoing upgrades to improve their sensitivity towards the next six-month observing run, called IR1, beginning in late October or mid November of 2026. More sensitive instruments will help discovering gravitational-wave signals at an even higher rate – potentially uncovering additional rare cosmic events.

Source: Max Planck Institute for Gravitational Physics/News

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Contacts:

Dr. Benjamin Knispel
Press Officer AEI Hannover
Tel: +49 511 762-19104
Email: benjamin.knispel@aei.mpg.de

Dr. Elke Müller
Press Officer AEI Potsdam, Scientific Coordinator
Tel: +49 331 567-7303
Email: elke.mueller@aei.mpg.de

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Scientific contacts:

Prof. Dr. Alessandra Buonanno
Director | LSC Principal Investigator
Tel: +49 331 567-7220
Fax: +49 331 567-7298
Email: alessandra.buonanno@aei.mpg.de
Homepage of Alessandra Buonanno

Prof. Dr. Dr. h.c. Karsten Danzmann
Director Emeritus | LSC Principal Investigator
Tel: +49 511 762-2356
Fax: +49 511 762-5861
Email: karsten.danzmann@aei.mpg.de
Homepage of Karsten Danzmann

Dr. Frank Ohme
Research Group Leader | LSC Principal Investigator
Tel: +49 511 762-17171
Fax: +49 511 762-2784
Email: frank.ohme@aei.mpg.de
Homepage of Frank Ohme

Dr. Héctor Estellés
Research Scientist
Email: hestelles@ice.csic.es
Institute of Space Sciences, Barcelona

Dr. Shrobana Ghosh
Postdoc
Tel: +49 511 762-14659
Email: shrobana.ghosh@aei.mpg.de

Nihar Gupte
PhD Student
Tel: +49 331 567-7169
Email: nihar.gupte@aei.mpg.de

Annalena Kofler
PhD Student / MPI for Intelligent Systems
Tel: +49 331 567-7369
Email: annalena.kofler@tuebingen.mpg.de

Prof. Harald Pfeiffer
Group Leader
Tel: +49 331 567-7328
Fax: +49 331 567-7298
Email: harald.pfeiffer@aei.mpg.de

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Additional experts:

Dr. Angela Borchers Pascual
Postdoc
Tel: +49 511 762-17172
Email: angela.borchers.pascual@aei.mpg.de
Dr. Raffi Enficiaud
Research Software Engineer
Tel: +49 331 567-7123
Email: raffi.enficiaud@aei.mpg.de

Cheng Foo
PhD Student
Tel: +49 331 567-7241
Email: cheng.foo@aei.mpg.de

Jannik Mielke
PhD Student
Tel: +49 511 762-14659
Email:jannik.mielke@aei.mpg.de

Dr. Gonzalo Morrás
Postdoc
Tel: +49 331 567-7321
Email: gonzalo.morras@aei.mpg.de

Dr. Lorenzo Pompili
Research Fellow
Email: Lorenzo.Pompili@nottingham.ac.uk
University of Nottingham, School of Mathematical Sciences

Elise Sänger
PhD Student
Email: elise.saenger@aei.mpg.de

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Core publications:

1.The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration

GWTC-5.0: An Introduction to Version 5.0 of the Gravitational-Wave Transient Catalog
arXiv:2605.27223 (2026)

Source | DOI

2. The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration

GWTC-5.0: Methods for Identifying and Characterizing Gravitational-wave Transients
arXiv:2605.27224 (2026)

Source | DOI

3. The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration

GWTC-5.0: Observations from the Second Part of the Fourth LIGO-Virgo-KAGRA Observing Run and Updates to the Gravitational-Wave Transient Catalog

arXiv:2605.27225 (2026)

Source | DOI

4. The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration

GWTC-5.0: Constraints on the Cosmic Expansion Rate and Modified Gravitational wave Propagation
arXiv:2605.27227 (2026)

Source | DOI

5. The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration

Open Data from LIGO, Virgo, and KAGRA through the Second Part of the Fourth Observing Run
arXiv:2605.27090 (2026)

Source | DOI

6. The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration
GWTC-5.0: Population Properties of Merging Compact Objects
arXiv:2605.27226 (2026)

Source | DOI

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Gravitational-wave detectors can now “autotune” their signals

Artist Impression of astrophysical calibration.
Carl Knox, OzGrav/Swinburne

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To the point

• New method: For the first time, the LIGO-Virgo-KAGRA collaboration has demonstrated a new method to improve the sensitivity of its international network of gravitational-wave detectors.


• Gravitational-wave auto-tuning: The new method called “astrophysical calibration” resembles auto-tune used in music production. It helps to find and correct “off-key” calibrations of the highly precise laser instruments, which can bias the astrophysical interpretation of the measured signals.


• Successful demonstration: A new publication in Physical Review Letters successfully demonstrates the method using two loud gravitational-wave signals from binary black hole coalescences.


• Testing Einstein’s theory: Researchers at the AEI have made crucial contributions to the effort by understanding the interplay between imperfect detector calibration and finding potential deviations from Einstein’s general theory of relativity.

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Crucial contributions by AEI researchers: How “off-key” detector calibration can bias signal-based tests of Einstein’s general theory of relativity.

Calibrating the instruments

The LIGO-Virgo-KAGRA (LVK) collaboration’s international network of gravitational-wave detectors consists of five kilometer-sized instruments. All of them reflect ultra-pure laser light back and forth between mirrors to measure the minute length changes – less than a billionth of a billionth of a meter – caused by passing gravitational waves.

To be sensitive to such tiny changes, the detectors must be carefully calibrated in real time. At the heart of this calibration is a precise model of how the detector reacts to gravitational waves. An imperfect detector calibration can compromise how the signal is received and as a consequence also bias the interpretation of the cosmic phenomenon that generated it.

Infographic explaining the astrophysical calibration as autotune for gravitational waves.
Graphics: Shanika Galaudage

Auto-tune for gravitational waves

Now, the LVK reports the first successful demonstration of a new method called “astrophysical calibration” to identify and correct an imperfect detector calibration retrospectively – after the measurement was done. This is similar to how a music production software such as Auto-Tune can correct a singer’s errant pitch after a song was recorded.

If a gravitational-wave signal is observed loud and clear, i.e., when it stands out from the detector’s background noise, the researchers can compare the signal to predictions from general relativity and to observations of the same signal in other well-tuned detectors. This way “off-key” measurements from a mis-tuned detector can be corrected retrospectively. The LVK scientists use the predictions from general relativity to know how the signal should sound like, similar to how musicians use musical scores to know a singer’s pitch.

Two loud gravitational-wave signals

In an article accepted in Physical Review Letters, LVK demonstrate how this technique has been applied to two particularly loud gravitational-wave signals, called GW240925 and GW250207, respectively.

At the times when both these signals were observed – on 25 September 2024 and 7 February 2025, respectively –, the calibration of the LIGO Hanford detector was not optimal. This made the interpretation of its data particularly difficult. By comparing LIGO Hanford data with theoretical predictions and observations of the same signals by the LIGO Livingston detector and the Virgo detector, the researchers were able precisely determine how the “off-key” LIGO Hanford instrument distorted the collected data.

The signal GW240925 served as an acid test for the new method. The astrophysical calibration passed it with flying colors. It confirmed the known calibration errors measured on-site at LIGO Hanford.

In the case of GW250207, however, it was essential to resort to astrophysical calibration to make full use of the data, because no reliable on-site calibration measurements were available for the LIGO Hanford detector. Using the astrophysically corrected calibration for the LIGO Hanford detector, LVK researchers could take calibration uncertainties properly into account, and avoid a biased interpretation of the astrophysical origin of the signal.

In their publication, the LVK astrophysicists report that GW240925 came from a coalescence of two black holes. They weighed 9 and 7 times, respectively, as much as our Sun and their gravitational waves traveled for about 1.0 billion years before reaching the LVK detectors. GW250207 was caused by the coalescence two more massive black holes weighing 35 and 31 times, respectively, as much as our Sun. The waves from this second merger traveled through the Universe for ca. 570 million years before reaching Earth.

Key contributions from AEI Potsdam

Researchers from the Astrophysical and Cosmological Relativity department at the AEI in the Potsdam Science Park showed that taking into account the calibration of the detectors is essential when using gravitational-wave signals for tests of general relativity.

“We found that neglecting imperfect detector calibration can potentially mimic or obscure deviations from Einstein’s theory which may be observed in different parts of black hole coalescence signals,” says Lorenzo Pompili, former member of the department and now a research fellow at the University of Nottingham.

“We used the signal GW250207 to obtain some of the most stringent tests of general relativity yet,” says Elise Sänger, a PhD student in the department. “We got lucky with GW250207, because it was observed so loud and clear and because the Universe gifted us a signal with properties very well suited for these tests.”

“This is the first LVK publication to use an improved waveform model, which we developed at the AEI. Our improvements are important to make increasingly accurate predictions for the gravitational-wave signals, which are key for carrying out these analyses,” says Héctor Estellés Estrella, a former postdoc of the department, now a Postdoctoral Fellow at the Institute of Space Sciences in Barcelona. “The next version of the Gravitational-wave Transient Catalog soon to be published will also make use of this waveform model.”

“We call the phase in which the black hole settles into its final state directly after the merger the ‘ringdown’. In it, the black hole emits a characteristic spectrum of gravitational-wave tones,” explains Elisa Maggio, a former postdoc at AEI Potsdam and now researcher at the Italian Institute for Nuclear Physics. “GW250207 was only the second signal ever in which we constrained one of the higher tones and could measure its properties.”

Source: Max Planck Institute for Gravitational Physics/News

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Media contacts:

Dr. Benjamin Knispel
Press Officer AEI Hannover
Tel: +49 511 762-19104
Email: benjamin.knispel@aei.mpg.de

Dr. Elke Müller
Press Officer AEI Potsdam, Scientific Coordinator
Tel: +49 331 567-7303
Email:elke.mueller@aei.mpg.de

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Scientific contacts:

Prof. Dr. Alessandra Buonanno
Director | LSC Principal Investigator
Tel: +49 331 567-7220
Fax: +49 331 567-7298
Email: alessandra.buonanno@aei.mpg.de
Homepage of Alessandra Buonanno

Prof. Dr. Dr. h.c. Karsten Danzmann
Director Emeritus | LSC Principal Investigator
Tel: +49 511 762-2356
Fax: +49 511 762-5861
Email: karsten.danzmann@aei.mpg.de
Homepage of Karsten Danzmann

Dr. Frank Ohme
Research Group Leader | LSC Principal Investigator
Tel: +49 511 762-17171
Fax: +49 511 762-2784
Email: frank.ohme@aei.mpg.de
Homepage of Frank Ohme

Dr. Héctor Estellés
Research Scientist
Email: hestelles@ice.csic.es
Institute of Space Sciences, Barcelona

Dr. Elisa Maggio
INFN Researcher
Email: elisa.maggio@aei.mpg.de
Istituto Nazionale di Fisica Nucleare, Rome

Dr. Lorenzo Pompili
Research Fellow
Email: Lorenzo.Pompili@nottingham.ac.uk
University of Nottingham, School of Mathematical Sciences

Elise Sänger
PhD Student
Email: elise.saenger@aei.mpg.de

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Publication

The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration
GW240925 and GW250207: Astrophysical Calibration of Gravitational-wave Detectors
Physical Review Letters (2026)

Source | DOI

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New method could reveal hidden supermassive black hole binaries

Artistic impression of gravitationally lensed starlight (orange) by a supermassive black hole binary. The Einstein ring is shown in blue.Credit: Physics simulation enhanced using AI

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To the point:

• New method: Researchers at Oxford University and the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in the Potsdam Science Park propose a new way to detect supermassive black hole binaries using gravitational lensing.


• Gravitational lensing: Black holes act as natural telescopes, bending light with their gravity. This magnification creates bright images of stars from the same galaxy that lie behind the supermassive black hole binary.


• Detectable signals: As the binary orbits, it produces repeating flashes of lensed starlight. Current and upcoming wide-field surveys may detect these bursts in the future. These bursts can provide information about the black holes’ properties and enabling entirely new studies.

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Bright flashes of lensed starlight guide the way

New method

Tightly bound supermassive black hole binaries form naturally when galaxies merge, but only widely separated systems have confidently been observed to date. In a paper published today in Physical Review Letters, the researchers suggest hunting down the hidden systems by searching for repeating flashes of light from individual stars lying behind the black holes as they are temporarily magnified by gravitational lensing as the binary orbits.

Supermassive black holes reside at the centers of most galaxies. When two galaxies collide and merge, their central black holes eventually form a bound pair, known as a supermassive black hole binary. These systems play a crucial role in galaxy evolution and are among the most powerful sources of gravitational waves in the Universe. While future space-based gravitational-wave observatories like LISA will be able to probe such binaries directly, researchers are now showing that they may already be detectable using existing and upcoming electromagnetic surveys.

Gravitational lensing

“Supermassive black holes act as natural telescopes,” says Miguel Zumalacárregui from the Max Planck Institute for Gravitational Physics. “Because of their enormous mass and compact size, they strongly bend passing light. Starlight from the same host galaxy can be focused into extraordinarily bright images, a phenomenon known as gravitational lensing.”

For a single supermassive black hole, extremely strong lensing occurs only when a star lies almost exactly along the line of sight. In contrast, a supermassive black hole binary acts as a pair of lenses. This produces a diamond-shaped structure, known as a caustic curve, along which stars can experience dramatic magnification.

“The chances of starlight being hugely amplified increase enormously for a binary compared to a single black hole,” explains Bence Kocsis from the University of Oxford’s Department of Physics and a co-author of the study.

A further key difference is that black hole binaries are not static. While the pair orbits under gravity the system slowly loses energy by emitting gravitational waves. As a result, the binary separation shrinks over time and the orbit gradually speeds up.

“As the binary moves, the caustic curve rotates and changes shape, sweeping across a large volume of stars behind it. If a bright star lies within this region, it can produce an extraordinarily bright flash each time the caustic passes over it,” says Hanxi Wang, a PhD student in Kocsis’ group who led the study “This leads to repeating bursts of starlight, which provide a clear and distinctive signature of a supermassive black hole binary.”

Valuable information from detectable signals

The researchers show that the timing and brightness of these bursts encode valuable information about the black hole binary. As the binary inspirals, gravitational-wave emission subtly alters the caustic structure, imprinting a characteristic modulation in both the frequency and peak brightness of the flashes. By measuring these patterns, astronomers could infer key properties of the underlying black hole binary, including its masses and orbital evolution.

With powerful wide-field surveys coming online such as the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope, researchers are optimistic that such repeating lensing bursts could be observed in the coming years.

“The prospect of identifying inspiraling supermassive black hole binaries years before future space-based gravitational wave detectors come online is extremely exciting,” concludes Kocsis. “It opens the door to true multi-messenger studies of black holes, allowing us to test gravity and black hole physics in entirely new ways.”

Source: Max Planck Institute for Gravitational Physics/News

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Media contact:

Dr. Elke Müller
Press Officer AEI Potsdam, Scientific Coordinator
Tel: +49 331 567-7303
Email: elke.mueller@aei.mpg.de

Science contact:

Dr. Miguel Zumalacarregui
Group; Leader
Tel: +49 331 567-7322
Fax: +49 331 567-7298
Email: miguel.zumalacarregui@aei.mpg.de

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Publication

Wang, H.; Zumalacarregui, M.; Kocsis, B.
Black holes as telescopes: Discovering supermassive binaries through quasi-periodic lensed starlight. Physical Review Letters 136, 061403 (2026)

MPG.PuRe - pre-print - publisher-version

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Testing Einstein’s theory of relativity with the clearest gravitational-wave signal yet

Visualization of a binary black hole ringdown consistent with the gravitational-wave event GW250114.The gravitational waves are separated into two modes of the ringing remnant black hole, identified in the observation: the fundamental mode (green) and its first overtone (red). It also shows a predicted third tone (yellow) that the data places limits on. Visualization performed at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute), based on a numerical relativity simulation of the Simulating Extreme Spacetimes (SXS) Project. Credit: H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), K. Mitman (Cornell University)

Ringing Black Hole Animation (GW250114)
Credit: H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), K. Mitman (Cornell University)

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To the point:

• Relativity put to the test: Relativity put to the test: A LIGO-Virgo-KAGRA team has conducted some of the most precise tests of Einstein’s theory of general relativity. The results were published in Physical Review Letters today.


• Einstein holds fast: In all tests, the observations match the theory’s predictions. In some cases, the tests based on this signal alone are two to three times more stringent than those obtained by combining data from dozens of other signals.


• The clearest signal: The team used data from GW250114, the strongest gravitational-wave signal ever detected from the merger of two black holes.


• Like a bell: For the first time, detailed analyses of the complete signal and the ringdown phase, which occurs shortly after the merger, have identified or constrained three gravitational-wave tones.

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An international team, with key contributions from AEI researchers, identified three gravitational-wave tones in GW250114 for the first time and conducted the most stringent tests of general relativity.

Relativity put to the test

A year ago, almost to the day, the LIGO-Virgo-KAGRA collaboration observed by far the clearest gravitational-wave signal seen to date. GW250114 came from a coalescence of black holes with masses between 30 to 40 times that of our Sun about 1.3 billion light-years away.

“This signal has already proven to be a great boon for a test of the nature of black holes and of Hawking’s area law,” says Alessandra Buonanno, director of the Astrophysical and Cosmological Relativity department at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) in the Potsdam Science Park. “Now we have gone one step further and published some of the most stringent limits on deviations from Einstein’s theory of general relativity using GW250114.”

Additional analysis of the GW250114 data was published today in Physical Review Letters. The writing team included several AEI members: Alessandra Buonanno, who served as chair, and Lorenzo Pompili, Elisa Maggio, and Elise Sänger, who conducted several of the analyses reported in the publication.

Because GW250114 was observed so clearly, it can be compared in much greater detail to predictions from Einstein’s theory of relativity than other signals. This makes it possible to test whether general relativity holds true in the extreme conditions of a black hole coalescence, where strong gravitational fields meet rapidly changing dynamics. Any deviations from the predictions of general relativity could hint at new physics beyond Einstein’s theory.

Like a struck bell

The international research team obtained some of the key results using a method known as black hole spectroscopy. For this, the team focused on the ringdown of the GW250114 signal – the phase when the black hole settles into its final state right after the merger – and the characteristic spectrum of gravitational-wave modes, or tones, emitted during this phase. These tones resemble the sounds a bell makes when struck: Each tone is described by two numbers: its frequency and the rate at which it is fading. Measuring the spectrum of the tones and their fading times is called black hole spectroscopy.

For the first time, a triad of gravitational-wave tones

For the first time, researchers at the AEI in Potsdam found a third tone in the signal’s ringdown phase using a new data analysis tool they developed.

“Our analysis tool, originally proposed in 2018, takes into account the complete black-hole coalescence and makes no prior assumptions about the tones emitted during the ringdown phase,” explains Elisa Maggio, a former Marie Curie Fellow in the Astrophysical and Cosmological Relativity department and now an INFN Researcher in Rome, Italy. Maggio and Pompili collaborated on developing the most recent version of the tool and conducting the analysis. “By incorporating information from the entire signal, we constrained a higher-pitched tone at approximately twice the fundamental frequency for the first time, once again matching theoretical predictions.”

Together, the two tests – one looking at the ringdown alone and the other considering the full signal – complement each other. Once again, they empirically vindicate the rotating black hole solution discovered in 1963 by Roy Kerr.

One signal beats dozens of others

The research team also examined an earlier phase of the clearly observed black hole coalescence when the two black holes were orbiting each other more slowly.

“We used a flexible, theory-independent method developed earlier at the AEI to determine how much the gravitational-wave signal deviated from the predictions of general relativity early in the coalescence,” says Elise Sänger, a PhD student in the Astrophysical and Cosmological Relativity department who conducted the analysis. “Remarkably, using data from this one clearly observed signal alone allows us to set some of the most stringent constraints on possible deviations from general relativity.”

The constraints derived using the AEI-developed model are two to three times more stringent than those obtained by combining data from dozens of signals in the latest fourth Gravitational-Wave Transient Catalogue (GWTC-4.0).

Only the beginning

“These results demonstrate the great scientific value of accurate waveform models and ophisticated data analysis techniques,” says Alessandra Buonanno. “But this is only the beginning. Future observing runs will allow us to detect signals like GW250114 more frequently and more clearly. Each one will open new avenues for testing Einstein’s theory and searching for new physics.”

Source: Max Planck Institute for Gravitational Physics/News

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Media contact:

Dr. Elke Müller
Press Officer AEI Potsdam, Scientific Coordinator
Tel: +49 331 567-7303
elke.mueller@aei.mpg.de

Science contacts:

Prof. Dr. Alessandra Buonanno
Director | LSC
Principal Investigator
Tel: +49 331 567-7220
Fax: +49 331 567-7298
alessandra.buonanno@aei.mpg.de
Homepage of Alessandra Buonanno

Dr. Elisa Maggio
INFN Researcher
elisa.maggio@aei.mpg.de
Istituto Nazionale di Fisica Nucleare, Rome

Dr. Lorenzo Pompili
Research Fellow
Lorenzo.Pompili@nottingham.ac.uk
University of Nottingham, School of Mathematical Sciences

Elise Sänger
PhD Student
elise.saenger@aei.mpg.de

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Publication

The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration; Abac, A.; Abouelfettouh, I.; Acernese, F.; Ackley, K.; Adhicary, S.; Adhikari, D.; Adhikari, N. et al.

Black Hole Spectroscopy and Tests of General Relativity with GW250114. Physical Review Letters 136, 041403 (2026)

MPG.PuRe - DOI - pre-print - publisher-version

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Further information

LIGO Science Summary
of the publication “Black hole spectroscopy and tests of general relativity with GW250114”

MPG.PuRe - DOI - pre-print - publisher-version

more

Ten years of gravitational-wave astronomy and the clearest signal yet

September 10, 2025
The LIGO-Virgo-KAGRA collaboration and the Max Planck Institute for Gravitational Physics celebrate the anniversary and present new, exciting results.

more

LIGO-Virgo-KAGRA Collaboration successfully wraps up its fourth Observing Run

November 19, 2025
Further exciting results anticipated from O4’s remaining parts

more

Doubling the gravitational-wave transient catalogue

August 26, 2025

LIGO-Virgo-KAGRA researchers at the Max Planck Institute for Gravitational Physics and at Leibniz University Hannover make significant contributions to detect and analyze new gravitational-wave candidates

more

Brito, R.; Buonanno, A.; Raymond, V.
Black-hole Spectroscopy by Making Full Use of Gravitational-Wave Modeling. Physical Review D 98 (8), 084038 (2018)

MPG.PuRe - DOI - pre-print

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