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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Are we ready for the next gravitational-wave observing runs?

Fig. 1: The illustration shows the distribution of galaxies in the sky that could host gravitational-wave sources and the measured sky location for three future gravitational-wave observatories – shown using contours – if inaccurate models are used. All three observatories miss the true host galaxy—shown in yellow—which is important for an accurate estimation of the universe's expansion rate and age. © A. Dhani (Max Planck Institute for Gravitational Physics)

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A study by AEI researchers reveals how even the most advanced waveform models can introduce systematic errors when used to measure key properties of black holes.

To the point:

• Researchers use state-of-the-art waveform models to infer the masses, spins, and location of black holes from simulated gravitational-wave events in order to prepare for future observations.


• The models often misestimate these values, particularly when one or both black holes are processing similar to a spinning top, or when their masses differ significantly.


• These inaccuracies can mislead our understanding of how black hole systems form and evolve, and they may affect measurements used to estimate the expansion rate of the Universe.

Gravitational waves from binary black hole coalescences can help answer important astrophysical, cosmological, and fundamental physics questions. How are black holes born, and how do they evolve? How fast is our Universe expanding? Is Einstein’s theory of general relativity still valid in the strong gravity regime?

When analyzing data from these coalescences, researchers employ the most advanced waveform models to simulate the complex dynamics of these systems and match them to observational data. But how do scientists know their waveform models are accurate and which parameters influence the models’ accuracy? As detectors become more sensitive, researchers have to rely more than ever on the high accuracy of their waveform templates to correctly interpret the data. As they prepare for future observing runs of facilities such as LIGO, Virgo, KAGRA and the upcoming Cosmic Explorer and Einstein Telescope, the reliability of these models becomes increasingly important.

In a new study, researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) in the Potsdam Science Park found that state-of-the art approximate gravitational waveform models used to infer the properties of coalescing black holes and neutron stars can introduce systematic errors that significantly skew estimates of key astrophysical parameters. These parameters include the masses, spins, and distances of merging objects, as well as the inferred value of the Hubble constant, which is a fundamental measure of how fast the Universe is expanding. The study shows that, although the cutting-edge waveform models are trying to capture the complexity of real astrophysical systems, they still don’t provide an accurate enough description for the very precise observations we expect to make in the future.

“Even the most advanced models are not sufficiently accurate for upcoming observing runs,” says Arnab Dhani, a postdoctoral scientist in the Astrophysical and Cosmological Relativity department at the AEI and the lead author of the study. “Biased estimates of black hole properties occur, in particular, when the component masses in a binary are highly unequal and one or both black holes are rapidly spinning. Such biases can mislead our understanding of how black hole systems form and evolve,” he adds. "Reliably predicting these biases across state-of-the-art waveform models required crucial improvements to existing data analysis techniques,"says Sebastian Völkel, also a postdoctoral scientist from the same department and co-author of the study.

Impact on cosmology

The biases also can have profound implications for the so-called “Hubble tension” – the growing discrepancy between different, independent measurements of the Hubble constant. Some methods based on the cosmic microwave background suggest a slower expansion rate than methods using supernovae. Observations of gravitational-wave standard sirens provide a third independent measurement, enticing the possibility of resolving the conflict. However, it requires accurate measurements of the distance and the location of the event in the sky to identify the galaxy hosting the event. The researchers demonstrate, using an example, how current waveform models can lead to inaccurate localization of the event impacting our measurement (see figure 1).

These results imply that errors in gravitational-wave modeling could significantly contribute to the Hubble tension, which could undermine the credibility of the standard siren method. “The standard siren method in gravitational-wave astronomy holds immense promise for cosmology, but its success depends on the accuracy of our waveform models,” explains Alessandra Buonanno, co-author of the publication and director of the Astrophysical and Cosmological Relativity department. “If we don’t account for spin, tidal deformations, or asymmetric mass ratios, we’re not just making small errors – we’re potentially misreading the expansion history of the Universe.”

Neutron stars or black holes?

Biased gravitational-wave observation may also impact nuclear physics. Neutron star mergers are the only astrophysical phenomena in which scientists have observed the formation of heavy elements such as gold and uranium. An accurate measurement of the maximum neutron star mass would expand our understanding of nuclear matter at densities that cannot be attained in human experiments on Earth. The researchers found that inaccurate measurements of masses can lead to black holes being identified as neutron stars, thereby misleading our understanding of nuclear matter.

Testing Einstein’s theory

Binary black hole mergers provide one of the most extreme conditions in which to test Einstein’s theory of general relativity. The theory precisely predicts the amount of energy released in such collisions, as well as the mass of the remaining black hole. However, the researchers found that model inaccuracies can lead to incorrect predictions of these quantities, resulting in apparent inconsistencies with the observed data. Quantifying the relevance of systematic effects is crucial for assessing whether possible future tests claiming deviations from general relativity are really due to new physics beyond Einstein’s theory, which would be revolutionary.

More accurate waveform models for future observing runs

Future observing runs at current facilities, such as LIGO, Virgo, and KAGRA are expected to detect thousands of binary black hole mergers. Next-generation observatories, such as the Cosmic Explorer and Einstein Telescope, will detect almost all stellar-origin binary black hole merger in the Universe, totaling millions. Accurately estimating black hole properties is essential to achieve the promising scientific goals of gravitational-wave astronomy. By identifying the most problematic regions in black hole parameter space, the researchers provide a roadmap for improving waveform accuracy in the future. The ERC Synergy Grant “Making Sense of the Unexpected in the Gravitational-Wave Sky” aims to address this accuracy challenge, making it possible to infer properties of gravitational-wave sources limited only by measurement uncertainty.

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
Tel: +49 331 567-7220
Fax: +49 331 567-7298
alessandra.buonanno@aei.mpg.de

Dr. Arnab Dhani
Junior Scientist/Postdoc
Tel: +49 331 567-7236
arnab.dhani@aei.mpg.de

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

Dr. Jonathan Gair
Group Leader
Tel: +49 331 567-7306
Fax: +49 331 567-7298
jonathan.gair@aei.mpg.de

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

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

Dr. Alexandre Toubiana
Assistant Professor
alexandre.toubiana@unimib.it
University of Milano-Biccoca

Dr. Sebastian Völkel
Senior Scientist/Leibniz Fellow
Tel: +49 331 567-7199
sebastian.voelkel@aei.mpg.de

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Publication:

Arnab Dhani, Sebastian H. Völkel, Alessandra Buonanno, Hector Estelles, Jonathan Gair, Harald P. Pfeiffer, Lorenzo Pompili, and Alexandre Toubiana

Systematic Biases in Estimating the Properties of Black Holes Due to Inaccurate Gravitational-Wave Models
Phys. Rev. X 15, 031036 (2025)

Source | DOI

Further information:

Homepage of the “Astrophysical and Cosmological Relativity” department GWSky

GWSky is an ERC Synergy Grant project led by Enrico Barausse (SISSA), Zvi Bern (University of California, Los Angeles (UCLA), Alessandra Buonanno (AEI), and Maarten van de Meent (NBI).

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Triple Stellar Systems as Gravitational Wave Sources

Scientific visualization of numerical relativity simulations showing gravitational waves emitted by inspiraling compact objects. Credit: T. Dietrich, S. Ossokine, H. Pfeiffer, and A. Buonanno (Max Planck Institute for Gravitational Physics).

A schematic diagram of possible key processes that drive the evolutionary phases of a triple evolution leading to the formation of double white dwarfs in the LISA frequency bandwidth. Depending on the separation of the inner binary and the inclination angle of the two orbital planes, the third star can interact in various ways with the inner binary. Just over half the systems retain the third star, though it is typically too distant to affect the gravitational wave signal significantly. © MPA

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Ground-based gravitational wave detectors like LIGO and Virgo have brought significant attention to binary systems composed of black holes and neutron stars as gravitational wave sources. However, two white dwarfs in a binary system are expected to be far more numerous. In particular, the pre-merger phase of double white dwarfs could lead to high-energy astrophysical events that would emit gravitational waves detectable by the European Space Agency’s upcoming Laser Interferometer Space Antenna (LISA) mission. Understanding how these double white dwarfs form is essential to interpreting the future LISA data. For the first time, researchers at the Max Planck Institute for Astrophysics (MPA) have now quantitatively assessed the impact of triple evolution on LISA sources. This study underscores the importance of triple interactions in the formation of double white dwarfs, revealing previously unexplored pathways that contribute to the gravitational-wave sources LISA will observe.

Stars often form in hierarchical triples, where a close binary system is orbited by a distant third star. These triple systems undergo complex gravitational interactions, which can dramatically alter the evolution of the stars. Such interactions can induce mass exchange between stars, mergers, or the disruption of one of the stars, all of which influence the final configuration of the system. Thus, triple dynamics can play a pivotal role in driving white dwarf binaries into the gravitational wave frequency range detectable by LISA.

In this research, doctoral student Abinaya Swaruba Rajamuthukumar, along with a group of MPA researchers, studied how triple star systems contribute to the population of double white dwarfs detectable by LISA. They combined simulations of triple star evolution using the Multiple Stellar Evolution (MSE) code with a Milky Way-like galaxy from the cosmological simulation TNG50. The study found that approximately 7.2 million double white dwarfs emitting gravitational waves in the LISA frequency band originate from triple systems, nearly double the number formed in isolated binaries, which account for about 3.8 million. Moreover, about 57% of the LISA double white dwarfs from triples retain a bound third star, though it is typically too distant to leave an observable imprint on the gravitational wave signal.

The team identified five key evolutionary pathways through which triple systems can produce LISA-detectable sources. These include induced mass transfer, outer binary mergers, ejected tertiaries, triple common envelope phases, and effectively isolated inner binaries (see graphic). The overall population properties of double white dwarfs from triple systems and those with a binary-origin are largely indistinguishable. Interestingly, the triple channel introduces a rare but intriguing subset of highly eccentric systems that emit burst-like gravitational wave signals, offering a distinct observational signature for LISA.

This study provides the first detailed exploration of triple-star evolution in the context of gravitational wave astrophysics. As LISA prepares for launch in 2035, these findings will be essential for accurately interpreting the Galactic population of gravitational wave sources and refining data analysis techniques. The results underscore the need to account for triple evolution when modeling LISA sources, paving the way for a more comprehensive understanding of the Milky Way’s gravitational wave sources.

Source: Max Planck Institute for Astrophysics/News

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Authors:

Abinaya Swaruba Rajamuthukumar
PhD student
tel:2248
abinaya@mpa-garching.mpg.de

Valeriya Korol
Postdoc
tel:2252
korol@mpa-garching.mpg.de

Jakob Stegmann
tel:2237
stegmaja@mpa-garching.mpg.de

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Original publication

Rajamuthukumar, Abinaya Swaruba; Korol, Valeriya; Stegmann, Jakob; Preece, Holly; Pakmor, Rüdiger; Justham, Stephen; Toonen, Silvia; de Mink, Selma E.
The role of triple evolution in the formation of LISA double white dwarfs
submitted Source

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Massive black hole in the early universe spotted taking a ‘nap’ after overeating

Computer-simulated image of a supermassive black hole at the core of a galaxy.
Credit: NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel (STScI)

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Gravitational waves data held clues for high-mass black holes’ violent beginnings

The size and spin of black holes can reveal important information about how and where they formed, according to new research. The study tests the idea that many of the black holes observed by astronomers have merged multiple times within densely populated environments containing millions of stars.

The team, involving researchers from the University of Cambridge, examined the public catalogue of 69 gravitational wave events involving binary black holes detected by The Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo Observatory for clues about these successive mergers, which they believe create black holes with distinctive spin patterns.

They discovered that a black hole’s spin changes when it reaches a certain mass, suggesting it may have been produced through a series of multiple previous mergers.

Their study, published in the journal Physical Review Letters, shows how spin measurements can reveal the formation history of a black hole and offers a step forward in understanding the diverse origins of these astrophysical phenomena.

“As we observe more black hole mergers with gravitational wave detectors like LIGO and Virgo, it becomes ever clearer that black holes exhibit diverse masses and spins, suggesting they may have formed in different ways,” said lead author Dr Fabio Antonini from Cardiff University. “However, identifying which of these formation scenarios is most common has been challenging.”

The team pinpointed a clear mass threshold in the gravitational waves data where black hole spins consistently change.

They say this pattern aligns with existing models which assume black holes are produced through repeat collisions in clusters, rather than other environments where spin distributions are different.

This result supports a robust and relatively model-independent signature for identifying these kinds of black holes, something that has been challenging to confirm until now, according to the team.

“Our study gives us a powerful, data-driven way to identify the origins of a black hole’s formation history, showing that the way it spins is a strong indicator of it belonging to a group of high-mass black holes, which form in densely populated star clusters where small black holes repeatedly collide and merge with one another,” said co-author Dr Isobel Romero-Shaw, from Cambridge’s Department of Applied Mathematics and Theoretical Physics.

Their study will now help astrophysicists further refine computer models which simulate the formation of black holes, helping to shape how future gravitational wave detections are interpreted.

“Collaborating with other researchers and using advanced statistical methods will help to confirm and expand our findings, especially as we move toward next-generation detectors,” said co-author Dr Thomas Callister from the University of Chicago. “The Einstein Telescope, for example, could detect even more massive black holes and provide unprecedented insights into their origins.”

Reference:

Fabio Antonini, Isobel M. Romero-Shaw, and Thomas Callister. 'Star Cluster Population of High Mass Black Hole Mergers in Gravitational Wave Data.' Physical Review Letters (2025). DOI: 10.1103/PhysRevLett.134.011401

Source: University of Cambridge/News

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Note: The text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright ©University of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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NSF–DOE Rubin Observatory’s Unparalleled Vision Will Revolutionize Multi-Messenger Astronomy

PR Image noirlab2421a
Artist’s Illustration of Multi-Messenger Event

PR Image noirlab2421b
Night Light

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Vera C. Rubin Observatory will unite coordinated observations of cosmic phenomena using the four messengers of the Universe

Photons, neutrinos, cosmic rays and gravitational waves all carry information about the Universe. Multi-messenger astronomy brings together these four signals to investigate astronomical events from multiple cosmic perspectives. With its sensitive camera and suite of filters, NSF–DOE Vera C. Rubin Observatory will increase the population of known multi-messenger sources by obtaining crucial color information and localizing events for follow-up observations by other telescopes.

Astronomy has always relied on light to convey information about the Universe. But capturing photons is no longer the only technique scientists have for studying astronomical phenomena. Subatomic particles, such as neutrinos and those that are delivered in the form of cosmic rays, as well as gravitational waves — ripples in the fabric of space-time — are also messengers. Multi-messenger astronomy aims to combine the information from more than one of these signals to give researchers a deeper understanding of some of the most extreme events in the Universe. NSF–DOE Vera C. Rubin Observatory will soon contribute to this emerging field by using its powerful camera and wide field of view to find faint multi-messenger sources and point other telescopes in the right direction for follow-up observations.

Rubin Observatory is jointly funded by the U.S. National Science Foundation (NSF) and the U.S. Department of Energy, Office of Science (DOE/SC). It is a Program of NSF NOIRLab, which, along with SLAC National Accelerator Laboratory, will jointly operate Rubin.

Multi-messenger astronomy is an enhanced way of studying cosmic events that are predicted to emit more than one type of signal, such as stellar explosions, actively feeding black holes, and collisions between compact objects, to name just a few. Each messenger communicates unique information about the physical processes and energies involved. When a single source is observed using multiple signals the data can be combined to reach a deeper level of insight. “The result is more than the sum of its parts,” says Raffaella Margutti, associate professor at the University of California at Berkeley.

In addition to conducting a massive study of the southern sky called the Legacy Survey of Space and Time (LSST), Rubin will also perform ‘Target of Opportunity’ observations in quick response to alerts of potential multi-messenger sources. As the fastest-slewing large telescope in the world, Rubin can point to targets in as little as three minutes. Such observations will provide crucial information about an event’s optical — meaning wavelengths detectable by the human eye — properties, which in turn helps localize the event for follow-up by other telescopes.

However, in order to coordinate multiple telescopes capable of detecting the different types of messengers, scientists have to know where to look. Signals such as gravitational waves and neutrinos can point scientists in the general direction of a source, but in order to pinpoint its exact location you need light. This is where Rubin, equipped with the largest and most sensitive camera ever built for astronomy and astrophysics, will shine.

Margutti, whose studies focus specifically on finding the electromagnetic counterparts to gravitational wave events, explains, “Gravitational wave observatories can only tell you ‘look at this large area and search for something very faint.’ But you don't know exactly where to look.” Furthermore, the distance at which current observatories are capable of detecting gravitational waves can be far beyond the limit of what they can detect with photons, making it hard to observe an event with both messengers.

With its deep and wide capabilities, Rubin will help mitigate both of these challenges. “Rubin wins twice,” says Margutti. “Its strong light-collecting power and ability to scan large sections of sky mean it’s very sensitive to faint optical signals, like those we would be seeking from a gravitational wave source.”

So far only one multi-messenger gravitational wave event has been observed: a merger between two neutron stars that sent both space-time ripples and photons careening across the cosmos. Other events predicted to emit more than one messenger are black hole-neutron star and black hole-black hole mergers. “I would be super excited if we found photons coming from these types of mergers,” says Margutti. “Rubin is uniquely positioned to confirm or expand on the types of mergers that produce light.”

Rubin’s ability to detect faint sources will also be a game changer for studying neutrinos. Robert Stein, California Institute of Technology postdoctoral scholar, explains: “In neutrino science there are many different types of possible sources, but existing optical telescopes are only able to see the brightest, most unusual ones.” Based on the number of neutrinos arriving at detectors here on Earth, scientists believe there to be a vast population of neutrino sources at varying distances throughout the Universe. However, given the limits of existing telescopes, Stein estimates that only 5–10% of them are also detectable with photons. By bringing myriad faint sources to light for the very first time, Rubin could increase that to 50%.

“Neutrino science is in its infancy, so our list of possible sources is still emerging,” says Stein. “In ten or fifteen years we will likely discover that events we’ve already known about are also neutrino source populations.”

Margutti and Stein are both confident that the overarching power of Rubin in the era of multi-messenger astronomy will be in uncovering the unexpected. As it covers vast swaths of the southern hemisphere sky, there’s no telling what Rubin’s unparalleled vision is going to reveal. “The best use of Rubin is as a discovery machine,” says Margutti. Stein echoes a similar sentiment, saying, “I hope to learn what new types of sources we should investigate next. If Rubin could give us that clarity, and I believe it will, that would be amazing.”

Source: NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)/News

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More information

The NSF–DOE Rubin Observatory is a joint initiative of the U.S. National Science Foundation (NSF) and the Department of Energy (DOE). Its primary mission is to carry out the Legacy Survey of Space and Time, providing an unprecedented data set for scientific research supported by both agencies. Rubin is operated jointly by NSF NOIRLab and SLAC National Accelerator Laboratory (SLAC). NOIRLab is managed for NSF by the Association of Universities for Research in Astronomy (AURA) and SLAC is operated for DOE by Stanford University. France provides key support to the construction and operations of Rubin Observatory through contributions from CNRS/IN2P3. Additional contributions from a number of international organizations and teams are acknowledged.

The U.S. National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 to promote the progress of science. NSF supports basic research and people to create knowledge that transforms the future.

NSF NOIRLab (U.S. National Science Foundation National Optical-Infrared Astronomy Research Laboratory), the U.S. center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.

SLAC National Accelerator Laboratory is a vibrant multiprogram laboratory that explores how the Universe works at the biggest, smallest, and fastest scales and invents powerful tools used by scientists around the globe. With research spanning particle physics, astrophysics and cosmology, materials, chemistry, bio- and energy sciences and scientific computing, SLAC helps solve real-world problems and advance the interests of the nation.

SLAC is operated by Stanford University for the U.S. Department of Energy’s Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.

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Links

• Vera C. Rubin Observatory website
• Vera C. Rubin Observatory images
• More Rubin images
• Rubin videos
• Rubin multimedia resources

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Contacts

Raffaella Margutti
Associate Professor
University of California Berkeley
Email: rmargutti@berkeley.edu

Robert Stein
Postdoctoral Scholar
California Institute of Technology
Email: rdstein@caltech.edu

Bob Blum
Director for Operations
Vera C. Rubin Observatory / NSF NOIRLab
Tel: +1 520-318-8233
Email: bob.blum@noirlab.edu

Željko Ivezić
Director of Rubin Construction
Professor of Astronomy, University of Washington / AURA
Tel: +1-206-403-6132
Email: ivezic@uw.edu

Josie Fenske
Jr. Public Information Officer
NSF NOIRLab
Email: josie.fenske@noirlab.edu

Manuel Gnida
Head of External Communications
SLAC National Accelerator Laboratory
Tel: +1 650-926-2632 (office)
Cell: +1 415-308-7832 (cell)
Email: mgnida@slac.stanford.edu

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Using small black holes to detect big black holes

Simulation of two colliding supermassive black holes emitting gravitational waves that could be detected with this novel method. Credit: NASA's Goddard Space Flight Center/Scott Noble; simulation data, d'Ascoli et al. 2018.

MPA researcher proposes a new idea to detect pairs of the biggest black holes, which occupies the centres of galaxies, by analysing gravitational waves from nearby small black holes, which are the remnants of stars. This approach, now published in Nature Astronomy, which will require a deci-Hz gravitational-wave detector, would enable studying supermassive black hole binaries, which might remain inaccessible otherwise.

The origin of supermassive black holes found at the centres of galaxies, is still one of the biggest mysteries in astronomy. They may have always been massive and formed when the Universe was still very young. Alternatively, they may have grown over time by accreting matter and other black holes. When a supermassive black hole is about to eat another massive black hole, this will emit gravitational waves, which are ripples in spacetime that propagate through the Universe.

Gravitational waves have recently been detected, but only from small black holes which are the remnant of stars. Detecting the signals of individual pairs of big black holes is still impossible, because present-day detectors are not sensitive to the very low gravitational-wave frequencies they emit. Planned future detectors, such as the space-based ESA-led mission LISA, will remedy this, but detecting the most massive black hole pairs will still remain extremely challenging.

“Our idea basically works like listening to a radio channel. We propose to use the signal from pairs of small black holes similar to how radio waves carry the signal. The supermassive black holes are the music that is encoded in the frequency modulation (FM) of the detected signal.” said Jakob Stegmann, lead author of the study and postdoctoral research fellow at MPA. “The novel aspect of this idea is to utilise high frequencies that are easy to detect to probe lower frequencies that we are not sensitive to yet.”

Recent results from pulsar timing arrays already support the existence of merging supermassive black hole binaries. This evidence is, however, indirect and comes from the collective signal of many distant binaries that effectively create background noise.

The proposed method to detect individual supermassive black hole binaries leverages the subtle changes they cause in the gravitational waves emitted by a pair of nearby small stellar-mass black holes. The small black hole binary effectively works as a beacon revealing the existence of the bigger black holes. By detecting the tiny modulations in signals from small black hole binaries, scientists could thus identify previously hidden supermassive black hole binaries with masses ranging from 10 million to 100 million times that of our Sun, even at vast distances.

Lucio Mayer, who is a co-author of the study and black hole theorist at the University of Zurich, added, “As the path for the Laser Interferometer Space Antenna (LISA) is now set, after adoption by ESA last January, the community needs to evaluate the best strategy for the following generation of gravitational detectors, above all in which frequency range to focus – studies like this bring a strong motivation to prioritise a deci-Hz detector design.”

“This paper presents a very cool and clever idea, which is still Science Fiction until we have a deci-Hz detector”, says Selma E. de Mink, director at MPA who is not involved in this work, “but we really need creative and out-of-the-box ideas like this if we want a chance to solve the biggest mysteries in the Universe.”

Source: Max Planck Institute for Astrophysics/News

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Contact:

Jakob Stegmann
2237
stegmaja@mpa-garching.mpg.de

Selma E. de Mink
Director
2041
sedemink@mpa-garching.mpg.de

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Original Publication

Stegmann J.; Zwick L.; Vermeulen S. M.; Antonini F.; Mayer L.
Imprints of massive black-hole binaries on neighbouring decihertz gravitational-wave sources
Nature Astronomy (2024)

Source | DOI

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Studying neutron stars on many channels in parallel

Numerical simulation of the resulting ejecta material of two merging neutron stars. Red colors refer to ejected material with a high fraction of neutrons which will appear typically redder than blue material that contains a higher fraction of protons. © I. Markin (University of Potsdam)

International research team succeeds for the first time in analyzing very different signals simultaneously

An international team of researchers, including the Max Planck Institute for Gravitational Physics and the University of Potsdam, has developed a method to analyze most of the observable signals associated with neutron star mergers simultaneously. For the first time, it was possible to model and interpret the emitted gravitational waves, the kilonova, and the afterglow of the gamma-ray burst of the merger of two neutron stars observed on August 17, 2017. The study and the code infrastructure developed for it provide precise information about the properties of nuclear matter and form the basis for the analysis of future events. The research results have now been published in the journal Nature Communications.

“Our new method will help to analyze the properties of matter at extreme densities. It will also allow us to better understand the expansion of the universe and to what extent heavy elements are formed during neutron star mergers,” explains Tim Dietrich, Professor at the University of Potsdam and leader of a Max Planck Fellow group at the Max Planck Institute for Gravitational Physics. Dietrich is corresponding author of the paper.

Extreme conditions in a cosmic laboratory

A neutron star is a superdense astrophysical object formed at the end of a massive star's life in a supernova explosion. Like other compact objects, some neutron stars orbit each other in binary systems. They lose energy through the constant emission of gravitational waves – tiny ripples in the fabric of space-time – and eventually collide. Such mergers allow researchers to study physical principles under the most extreme conditions in the universe. For example, the conditions of these high-energy collisions lead to the formation of heavy elements such as gold. Indeed, merging neutron stars are unique objects for studying the properties of matter at densities far beyond those found in atomic nuclei.

The new method was applied to the first and so far only multi-messenger observation of binary neutron star mergers. In this event, discovered on August 17, 2017, the stars' last few thousand orbits around each other had warped space-time enough to create gravitational waves, which were detected by the terrestrial gravitational-wave observatories Advanced LIGO and Advanced Virgo. As the two stars merged, newly formed heavy elements were ejected. Some of these elements decayed radioactively, causing the temperature to rise. Triggered by this thermal radiation, an electromagnetic signal in the optical, infrared, and ultraviolet was detected up to two weeks after the collision. A gamma-ray burst, also caused by the neutron star merger, ejected additional material. The reaction of the neutron star's matter with the surrounding medium produced X-rays and radio emissions that could be monitored on time scales ranging from days to years.

More accurate results for future detections

The new tool for simultaneously analyzing astrophysical data from different sources allows researchers to interpret all these signals at the same time and to incorporate additional information from radio and X-ray observations of neutron stars (e.g., from NASA's NICER telescope), from nuclear physics calculations, and even from heavy-ion collision experiments at accelerators on Earth. "We can now go beyond the usual step-by-step combination process that we have done before. By analyzing coherently and simultaneously, we get more precise results," says Peter T. H. Pang, scientist at Utrecht University, first author of the paper and lead developer of the code. To even further improve the developed software over the coming years, Dietrich was awarded with an ERC Starting Grant worth 1.5 million euros in 2022.

The gravitational-wave detectors are currently in their fourth observing run. The next detection of a neutron star merger could come any day, and the researchers are eagerly waiting to use the tool they developed again.

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
tel:+49 331 567-7298
elke.mueller@aei.mpg.de

Science contact:

Prof. Dr. Tim Dietrich
Max Planck Fellow
tel:+49 331 567-7253
tel:+49 331 567-7298
tim.dietrich@aei.mpg.de

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Publication

Peter T. H. Pang, Tim Dietrich, Michael W. Coughlin, Mattia Bulla, Ingo Tews, Mouza Almualla, Tyler Barna, Ramodgwendé Weizmann Kiendrebeogo, Nina Kunert, Gargi Mansingh, Brandon Reed, Niharika Sravan, Andrew Toivonen, Sarah Antier, Robert O. VandenBerg, Jack Heinzel, Vsevolod Nedora, Pouyan Salehi, Ritwik Sharma, Rahul Somasundaram, Chris Van Den Broeck

An updated nuclear-physics and multi-messenger astrophysics framework for binary neutron star mergers
Nature Communications, Vol. 14, p. 1-13 (2023)

Source

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Forget X-ray Vision: Using Gravitational Waves to Peer Inside the Sun

Pulsars, like the one illustrated on the right, may seem an unlikely component of a method to look inside the Sun.
[Left:NASA/Goddard/SDO; Right: Adapted fromNASA/JPL-Caltech]

Title: Probing the Solar Interior with Lensed Gravitational Waves from Known Pulsars
Authors: Ryuichi Takahashi
First Author’s Institution: Hirosaki University
Status: Published in ApJ

Forget X-ray vision — how about gravitational wave vision? In today’s article, a team of researchers examine the possibility of using gravitational waves from distant pulsars to learn about our own Sun. Much like the terrestrial seismologists and geologists who peer into Earth by listening carefully to the ways waves are distorted as they travel through its many layers, these imagined future gravitational heliophysicists would use the subtle distortions of gravitational waves that have passed through the Sun to learn about its inner contents.

Figure 1: Depiction of the arrangement of an Earth-based gravitational wave detector and an object that emits continuous gravitational waves that is of interest to the authors of today’s article. When gravitational waves from the source have to pass directly through the Sun to reach Earth, they can be deflected from their original path and distorted in ways similar to how light is distorted when passing through a traditional lens. Credit: Takahashi et al. 2023

Multi-messenger Seismology?

The idea of using the interaction between waves and normal matter to peer under the surface of otherwise opaque objects has a longstanding history in physics. Think for example of the idea of seismic tomography, one of the main tools used by seismologists and geologists to understand the makeup of Earth’s interior. As powerful shock waves move through Earth’s interior after seismic events like earthquakes, they come into contact with regions of material that may differ in their composition, density, temperature, and so on. Depending on the wave frequencies and the properties of the materials with which the waves come into contact, these waves will reflect, refract, diffract, or be otherwise altered from their initial waveform. Measuring the properties of these waves when they make contact with the surface again at different points around the world can thus tell us a great deal about what they may have encountered on their journey through the depths.

Similarly, when electromagnetic waves (light) encounter solid objects, they can undergo a number of interactions: certain wavelengths will be scattered or absorbed, and others may pass directly through an object. This is, roughly speaking, how X-ray imaging works: certain high-frequency electromagnetic rays can easily pass directly through your soft skin, but they will be reflected upon encountering denser material like bones, allowing us to reconstruct images of the interior of our own bodies without the need for invasive surgeries (thanks, science!).

Today’s article examines the feasibility of doing similar reconstructions but with waves of a different kind: gravitational waves. Gravitational waves, which have been discussed at length in previous Astrobites, are a hot topic right now within the astrophysics community given that the technology to directly detect their subtle presence has only come to maturity within the past decade or so. This is because gravitational waves, which are produced by the asymmetric motion of massive objects like black holes in binary orbits, produce extremely subtle effects here on Earth due in part to the weakness of the gravitational force and in part to the large distances the waves have typically traversed to reach us. Now that we are measuring these faint signals with regularity in ground-based gravitational wave detectors like LIGO, VIRGO, and KAGRA, interest has been growing in finding more and more exotic ways to use this brand new window into the universe to uncover its many secrets.

To understand the particularly out-there idea behind today’s article, we need to introduce at least one further concept: gravitational lensing. Gravitational lensing occurs when particles (or waves) travel close to a massive source and as a result have their trajectories altered. When a massive source (like a galaxy cluster) sits more or less directly between Earth and some distant object (like an individual galaxy), this deflection can act like a lens, focusing the light from the background galaxy towards Earth to make the galaxy appear bigger, brighter, or even more emoji-like. Additionally, as waves of any kind travel past such a lens, they will appear to take longer to reach the other side than they would have if there were no massive source. This effect is known as gravitational time delay, and it can sometimes manifest in ways not too dissimilar from the way in which light appears to “slow down” when passing through dense mediums like water. Gravitational lensing can cause all sorts of waves including gravitational waves to undergo many distorting effects similar to light traveling through media of varying densities or seismic waves traveling through Earth’s interior.

Taking all of these effects into account, we can begin to see why the idea of using gravitational waves to probe the interior of the Sun isn’t so far-fetched. While electromagnetic waves cannot typically pass into and out of the Sun due to their interactions with dense solar material, gravitational waves from a source behind the Sun would pass through easily, only experiencing distortion due to the aforementioned lensing effects caused by the varying density of the Sun along the line of sight between detectors on Earth and the source of the gravitational waves. While this idea has been explored before, today’s authors attempted a comprehensive analysis of what these distortions might look like for a set of real sources and examined how feasible it would actually be to detect them in present or future gravitational wave observatories. So can it be done? As it turns out, with some upgraded detectors, a dash of new millisecond (very fast-spinning) pulsar discoveries, and a bit of luck — it can!

Figure 2: Models for the amplification (left) and phase offset (right) of a potential continuous wave signal as their line of sight appears to pass behind the Sun from four pulsars that are known to be eclipsed in this way once each year. Credit: Takahashi et al. 2023

Looking for Magic Millimeter Mountains

Unlike with light waves or even some seismic waves, humans do not have the capacity to generate gravitational waves of sufficient power to be measured and manipulated for the purposes of doing experiments. Instead, if we want to use these new waves to our benefit, we have to get clever with what nature has provided for us. Firstly, what we will need is a source of continuous gravitational waves. Unlike most of what LIGO sees right now, which are the signature “chirps” of compact objects undergoing their last seconds of merging, the continuous waves (meaning gravitational wave signals that are continuously emitted from a source and detectable for some appreciable amount of time) that are expected to be seen by ground-based detectors are most likely to come from tiny (sub-millimeter scale) deformations (sometimes called “mountains”) on the surface of rapidly rotating pulsars. Once gravitational wave detectors increase in sensitivity enough to finally detect these waves, researchers will want to find sources that occasionally pass behind the Sun from our perspective here on Earth (Figure 1). Over the course of several hours as Earth moves along its orbit, detectors on Earth may be able to observe how this continuous signal changes as it appears to pass behind different parts of the Sun, like watching a straw appear to bend when lowered into a glass of water.

The authors of today’s article employ mathematical formulas (that are not too dissimilar from what one would see in an introductory optics course!) to calculate the amount of deflection, convergence, and time delay experienced by gravitational waves passing behind the face of the Sun at various angles relative to its center. Further wave-optics calculations are employed to find the corresponding amplification factors and phase offsets that waves of different frequencies would experience at these various angles. Their results are clearly shown in Figure 2: as each candidate pulsar (labeled by the different colored lines) appears to pass behind the face of the Sun, its corresponding gravitational wave signal will be amplified and offset in phase in complicated ways determined in part by the frequency of each gravitational wave and how closely the signal gets to passing directly behind the center of the Sun. By understanding how strong these effects are for continuous waves with different frequencies and amplitudes, the authors can begin to assess what it will take to detect them.

As it turns out, the ideal continuous-wave-emitting pulsars are those with high rotational frequencies (>10 Hz) that pass as close behind the Sun’s center as possible. When applying this cutoff to catalogs of known pulsars, only four currently fit the bill. While this doesn’t sound ideal, the authors go on to acknowledge that there are expected to be thousands more fast-spinning millisecond pulsars within our own galaxy that we have yet to discover, many of which could also turn out to pass behind the Sun on occasion.

With all this background knowledge in hand, the primary question left to tackle is this: can these slight deformations in continuous waves actually be detected with enough confidence to infer the density of different layers of the Sun? As to whether the lensing signal could be detectable at all, the authors of today’s article find that such a detection could be made with a high degree of confidence using known pulsars with about one year’s worth of observation time given a signal-to-noise ratio of around 100 or greater. The signal-to-noise ratio can depend on many factors including the loudness of a given source, the sensitivity of the detector, and the timespan of data collection, but to put this number in perspective, current signal-to-noise ratio upper limits for continuous wave detections from LIGO searches are estimated to be around 10.

Unfortunately, accurately measuring the solar density at several different solar depths is even trickier, as the accuracy of each measurement depends on a variety of factors including how many total layers of the Sun one attempts to measure and how one sets the distance between each layer (Figure 3). For one year of continuous wave observation of the three best pulsar candidates, the signal-to-noise ratio needed to accurately measure the solar density at two different layers is found to be ~10⁴, which is an order of magnitude higher than is even expected from the next-generation gravitational wave detectors Cosmic Explorer and the Einstein Telescope. To measure densities across 6 or 10 different layers of the Sun’s interior, the signal-to-noise ratio requirements grow to ~10⁶ and ~10⁷, respectively (Figure 4), well beyond the capabilities of planned detectors unless more rapidly spinning pulsars passing behind the Sun can be found and loudly heard in these future detectors.

Figure 3: Estimates of the solar density profile will have to be made at different chosen slices called “annuli” (depicted here as the numbered concentric circles). Choices for how to pick these annuli affect how accurately their densities can be recovered for a given continuous wave pass. Credit: Takahashi et al. 2023

Figure 4: This plot depicts the uncertainty in solar density measurements at various solar depths using the expected lensing signatures of three known pulsars as they pass behind the Sun. The solid black line depicts the expected solar density as a function of solar radius (measured here as the angular position on the face of the Sun relative to its center). In the case where one attempts to measure six distinct densities with a very high signal-to-noise ratio of 10⁶ over one year of observation (left plot), uncertainties can become fairly low close to or far away from the Sun’s center. To achieve similar uncertainties across 10 annuli, a comparative signal-to-noise ratio of 10⁷ is necessary.Credit: Takahashi et al. 2023

Prospects for Gravitational Wave Vision

In recent years, combining gravitational waves with gravitational lensing has been proposed as a way to learn all sorts of new things about our universe, from constraints on the Hubble constant to independent measurements of the masses of distant stars. While it may take many more years for this sort of analysis to mature to a point where it can give us useful information about the Sun’s density profile, the fact that it may be possible at all is remarkable. For many decades the detection of gravitational waves was thought to be impossible. Now, not only are we detecting them with regularity, but we are finding all sorts of new ways to learn about our universe with each passing day — and that’s something to be excited about, even if you won’t be seeing gravitational wave vision goggles in stores anytime soon!

Original astrobite edited by Jessie Thwaites.

 

Source: American Astronomical Society/AAS-Nova

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About the author, Lucas Brown:

I’m a current master’s student at Tufts University interested in cosmology, relativity, and gravitational physics. I am currently doing research on the stochastic gravitational wave background and pulsar timing arrays. Outside of physics I love playing piano, climbing, and spending time with my dog.

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Black Hole Collision May Have Exploded With Light

Image Credit: Caltech/R. Hurt (IPAC)

In a first, astronomers may have seen light from the merger of two black holes, providing opportunities to learn about these mysterious dark objects.

This artist's concept shows a supermassive black hole surrounded by a disk of gas. Embedded in this disk are two smaller black holes that may have merged together to form a new black hole.

When two black holes spiral around each other and ultimately collide, they send out gravitational waves - ripples in space and time that can be detected with extremely sensitive instruments on Earth. Since black holes and black hole mergers are completely dark, these events are invisible to telescopes and other light-detecting instruments used by astronomers. However, theorists have come up with ideas about how a black hole merger could produce a light signal by causing nearby material to radiate.

Now, scientists using Caltech's Zwicky Transient Facility (ZTF) located at Palomar Observatory near San Diego may have spotted what could be just such a scenario. If confirmed, it would be the first known light flare from a pair of colliding black holes.

The merger was identified on May 21, 2019, by two gravitational wave detectors – the National Science Foundation's Laser Interferometer Gravitational-wave Observatory, or LIGO, and the European Virgo detector – in an event called GW190521g. That detection allowed the ZTF scientists to look for light signals from the location where the gravitational wave signal originated. These gravitational wave detectors have also spotted mergers between dense cosmic objects called neutron stars, and astronomers have identified light emissions from those collisions.

Learn more: What Is a Black Hole?
Black Hole Image Makes History; NASA Telescopes Coordinated Observations

Editor: Yvette Smith

Source: NASA/Black Holes

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The spectrum of gravitational waves

Hi-res image

Gravitational waves are ripples in spacetime produced by the acceleration of very massive objects, such as black holes coming together and merging. 

Different objects in space produce gravitational waves of different timescales, ranging from milliseconds to billions of years. 

Some of these waves can only be observed from space.

This is the goal of ESA’s future mission LISA, which will be the first space-based gravitational wave observatory.

LISA will study gravitational waves that are produced by merging stellar mass black holes, supermassive black holes and white dwarfs. It will also pick up the waves produced by compact objects, like neutron stars or small black holes, that fall into a supermassive black hole.

• ESA
• Space Science
• LISA

Source: ESA

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