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Understanding elementary particles and black holes with modern mathematics – November 05, 2024

Feynman diagrams are used to represent scattering amplitudes. The figure shows colliding particles and four Feynman diagrams of increasing complexity, which are increasingly difficult to calculate. © Simulation of a particle collision (CERN), collage of Feynman diagrams (A. Kleinschmidt, B. Knispel, (Max Planck Institute for Gravitational Physics))

The European Research Council has granted 10 million euros to fund research into a comprehensive theoretical framework relevant for predicting experimental results.

What do the interactions of elementary particles in accelerators such as the Large Hadron Collider have in common with inspiraling black holes? The study of these two very different processes is based on the same theoretical concept: scattering amplitudes describe the interactions of physical objects and form the basis for predicting measurement results. Experiments at particle accelerators and detections by gravitational-wave detectors have reached a very high level of accuracy with even more sensitive measurements on the horizon. Scientists now want to develop a novel comprehensive theoretical framework to enable the efficient calculation of scattering amplitudes to predict and interpret this data. The European Research Council (ERC) is funding the project with a Synergy Grant of a total of almost ten million euros over the next six years. In addition to the Max Planck Institute for Gravitational Physics in the Potsdam Science Park, Trinity College Dublin, the University of Oxford and the University of Uppsala are also involved in the project.

The project “GWSky” funded by an ERC Synergy Grant will tackle a variety of binary black holes in different environments. This image shows a schematic representation of these systems and the gravitational-wave signals they emit. © Ana Carvalho / Max Planck Institute for Gravitational Physics (Albert Einstein Institute)

The Max Planck Institute for Gravitational Physics is one of the four partners in the international consortium GWSky, which the European Research Council has awarded 12 million euros to develop a deeper understanding of gravitational waves.

Existing and future gravitational-wave detectors will be capable of observing signals with such precision that they may reveal possible deviations from Einstein’s general theory of relativity and the standard model of particle physics. To fully exploit this unique instrumental capability, fundamental advances are required in the theoretical description of black holes and their dynamics, the gravitational waves they emit, their cosmic environment, and the physics beyond the standard model. To provide the necessary theoretical framework, the project GWSky has been awarded 12 million euros over the next six years by the European Research Council. The ERC Synergy grant involves four nodes: the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) at the Potsdam Science Park, the Niels Bohr Institute in Copenhagen, the SISSA (Scuola Internazionale Superiore di Studi Avanzati) in Trieste, and the University of California, in Los Angeles.

The goal of the workshop is to discuss new tools needed to take full advantage of LISA’s capabilities. © A. Carvalho

Experts meet at the Max Planck Institute for Gravitational Physics
In early 2024, the European Space Agency adopted the first gravitational-wave observatory in space called LISA, which is scheduled for launch in 2034. The strength, number, and nature of the signals observed by LISA will significantly differ from those detected by ground-based detectors, opening up a whole new part of the gravitational- wave spectrum. This poses many challenges for the scientists, who must now prepare the theoretical and data-analysis tools that will allow them to take full advantage of LISA’s capabilities. To discuss these tools, about 140 researchers will attend the workshop “Fundamental Physics Meets Waveforms with LISA” at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) in the Potsdam Science Park from September 2 to 6, 2024.

Prof. J. Anton Zensus, Direktor am Max-Planck-Institut für Radioastronomie (MPIfR) in Bonn und Leiter der Forschungsabteilung „Radioastronomie / VLBI“ am MPIfR. © Industriefotografie Steinbach https://www.industriefotografie-steinbach.de/

MPIfR-Direktor erhält höchste Auszeichnung der Astronomischen Gesellschaft

Die Astronomische Gesellschaft verleiht die Karl-Schwarzschild-Medaille an Prof. Dr. Anton Zensus, Direktor am Max-Planck-Institut für Radioastronomie in Bonn. Mit dieser höchsten Auszeichnung für Astronomen in Deutschland wird seine Führungsrolle bei der Weiterentwicklung radioastronomischer Beobachtungsmethoden mit sehr hoher Winkelauflösung und Empfindlichkeit gewürdigt.

Die Radiointerferometrie mit sehr langen Basislinien (Very Long Baseline Interferometry; VLBI) hat sich, insbesondere durch den Einfluss von Anton Zensus und seiner Forschungsgruppe, zu einer Schlüssel-Beobachtungsmethode entwickelt. Sie findet heute neben der Astrophysik ebenso breite Anwendung in den Feldern Astrometrie und Geodäsie. Dank dieser Fortschritte und der internationalen Zusammenarbeit werden bahnbrechende astronomische Beobachtungen möglich. Die einzigartigen Bilder des Event-Horizon-Teleskop-Projekts, die die supermassereichen Schwarzen Löcher in der elliptischen Galaxie M87 und im Zentrum unserer Milchstraße zeigen, haben weltweit für Aufsehen gesorgt und neue Wege zur Erforschung von aktiven Galaxienkernen geöffnet.

Die Verleihung der Medaille findet am Dienstag, dem 10. September, auf der Jahrestagung der Astronomischen Gesellschaft in Köln statt.

Ten exotic pulsars were discovered in globular cluster Terzan 5 – here in an artist’s impression – bringing its total to 49. © US NSF, AUI, NSF NRAO, S. Dagnello

Astronomers find and study multiple rare and unusual pulsars in dense stellar cluster using the South African Radio Astronomy Observatory’s MeerKAT and the U.S. National Science Foundation Green Bank Telescope.
An international team led by researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI), the Max Planck Institute for Radio Astronomy (MPIfR), and the U.S. National Science Foundation National Radio Astronomy Observatory (NRAO) has discovered ten rapidly rotating neutron stars in the globular cluster Terzan 5. Many of them are in unusual and rare binaries, including a potential candidate for a record-breaking double neutron star, a pulsar in an extremely elliptical orbit, and several “spider” systems in which the neutron stars are evaporating their companions. These finds in data from the MeerKAT radio telescope array increase the number of known millisecond pulsars in this very dense stellar cluster by more than a quarter to a total of 49. The research team hopes to discover more pulsars in possibly even more extreme binaries: They plan to sift through all Terzan 5 data recorded with MeerKAT by using the massive computing power of the citizen science project Einstein@Home run at AEI.

Picture of the laser system from Hannover set up in a clean room at the ETpathfinder in Maastricht. © N. Knust/Max Planck Institute for Gravitational Physics

High-precision laser source from Hannover for the ETpathfinder in Maastricht

Researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) and Leibniz University Hannover have set up, tested, and commissioned a laser source in a laboratory at the ETpathfinder site in Maastricht. ETpathfinder is a research and development facility for the Einstein Telescope, the future third-generation European gravitational-wave observatory. Later this year, in addition to further characterization, the first preliminary tests are planned to integrate the laser system into ETpathfinder. Full integration and regular experiments with the new laser source in ETpathfinder are scheduled to begin next year.

Gustav Mogull, postdoctoral researcher at the Max Planck Institute for Gravitational Physics © sevens+maltry

Gustav Mogull receives the Karl Scheel Prize of the Physikalische Gesellschaft zu Berlin, endowed with 5,000 euros
Gustav Mogull, a postdoctoral researcher at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Potsdam and at Humboldt University in Berlin, investigates mathematical methods and models of particle physics for a more precise prediction of gravitational waves. The award recognizes his outstanding contributions to general relativity and gravitational-wave physics. He will receive the award today at the Magnus House of the German Physical Society in Berlin.

Mohammed Khalil © G. Secara (Perimeter Institute)

Otto Hahn Medal for Mohammed Khalil

Mohammed Khalil, a former PhD student at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in the Potsdam Science Park, has been awarded the Otto Hahn Medal for his outstanding doctoral thesis. Khalil, who is now a postdoctoral researcher at the Perimeter Institute for Theoretical Physics in Canada, received the award for his significant contributions to making theoretical waveform templates precise enough for gravitational-wave astronomy. Khalil received the medal and a prize of 7500 euros today during the Annual Meeting of the Max Planck Society in Berlin.

Aerialview from GEO600 in Ruthe. © MPI for Gravitational Physics

Visit the gravitational-wave detector near Sarstedt on 31 August 2024

On Saturday, August 31, 2024, the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and the Institute for Gravitational Physics of Leibniz Universität Hannover invite you to visit the German-British gravitational-wave detector GEO600 near Sarstedt. Between 12:00 and 16:00 CEST, visitors can speak with researchers at the detector site about the current state of gravitational-wave astronomy, the crucial contributions of GEO600 as a think tank of international research, and visit the detector.

What? Cutting-edge research up close: Open Day at the GEO600 gravitational-wave detector.
When? Saturday, August 31, 2024 from 12:00 to 16:00 CEST.
Where? Ruthe near Sarstedt, directions described on the right. Come by public transport, bicycle, or car.
Prior registration is not required. We’re looking forward to your visit!

Inspiral of a lower mass-gap black hole (dark gray surface) and a neutron star (orange sphere). The emitted gravitational waves are shown in colors from dark blue to cyan. © I. Markin (Potsdam University), T. Dietrich (Potsdam University and Max Planck Institute for Gravitational Physics), H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics)

Shortly after the start of the fourth observing run, the LIGO-Virgo-KAGRA collaborations detected a remarkable gravitational-wave signal.

The LIGO Livingston detector observed the signal, called GW230529, on May 29, 2023, from the merger of a neutron star with an unknown compact object, most likely an unusually light-weight black hole. With a mass of only a few times that of our Sun, the object falls into the “lower mass gap” between the heaviest neutron stars and the lightest black holes. Researchers at the Max Planck Institute for Gravitational Physics contributed to the discovery with accurate waveform models, new data-analysis methods, and sophisticated detector technology. Although this particular event was observed only because of its gravitational waves, it increases the expectation that more such events will also be observed with electromagnetic waves in the future.

LIGO news item on GW230529

Past and planned observing runs of the LIGO, Virgo, and KAGRA gravitational-wave detectors. The colored bars shows the times during which each detector participated in a given run. The distances above that, given in Megaparsecs (Mpc), are the average distances at which the given detector would be able to observe gravitational waves from a merging neutron star binary. Virgo is reconsidering its plans for O5 and both the date on which we will be able to enter O5 and the target sensitivity are currently unclear. We expect to be able to define our plans for O5 around mid-2024. graphic: LVK

O4b to start on 10 April 2024

Next week, the LIGO and Virgo detectors will resume their observing campaigns, which promise to collect more than 200 gravitational-wave events by the end of this current observing run (O4) in early 2025. Astronomers also hope that new multi-messenger events will be detected. Multi-messenger events are those observed both in gravitational and electromagnetic waves, and can be further followed up by other telescopes.

LIGO news item on O4 resume

GRACE Follow-On is a tandem of two satellites, circling the Earth separated by 220 kilometers in the same orbit 490 kilometers above ground. It measures inter-satellite distances with microwaves and a new laser interferometer (red). © NASA VTAD/NASA Visible Earth/UF S. Barke/AEI

The next generation of the satellite pair will use a high-precision laser instrument with key contributions from the AEI Hannover to monitor indicators of climate change.

“Gravity Recovery and Climate Experiment – Continuity” (GRACE-C) will continue more than 20 years of space-based measurements of the Earth’s gravity field. The observations, which enable studies of global groundwater levels and other indicators of climate change, are important for climate research. GRACE-C is a joint mission of the German Space Agency at the German Aerospace Center (DLR) and the US space agency NASA. The Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover is involved in implementing the German contribution, the construction of the central laser-based measurement system. The launch is scheduled for 2028.

Sho Fujibayashi, senior scientist at the Max Planck Institute for Gravitational Physics © sevens+maltry

Postdoc at the Max Planck Institute for Gravitational Physics honored for his research on neutron star mergers
Every year, the Physical Society of Japan (JPS) presents its Young Scientist Awards to young researchers to recognize outstanding achievements in their early research careers. The prize is awarded to excellent young researchers who promise to make a lasting contribution to the future of physical research in Japan. Sho Fujibayashi will deliver an award lecture at the next annual meeting of the JPS on March 20, 2024.

In this issue we hear about the completion of the first part of Observing Run 4 (O4a) and what we can look forward to in the rest of O4. We learn about what’s been happening and why commissioning breaks are important for gravitational-wave observatories and much more.

Around sixty milliseconds after the merger, the simulation shows the jet emitted from the poles of the magnetar (up and down in this still image). The left panel shows the neutron richness of the ejected material. Blue denotes neutron-rich matter, and red denotes matter that contains neutrons and protons in roughly equal proportions. The middle panel shows surfaces of constant rest mass density. The purple curves indicate magnetic field lines. The right panel shows surfaces of constant magnetic field strength. The scale bar shows a length of 500 kilometers. © Kota Hayashi (Max Planck Institute for Gravitational Physics)

New computer simulation reveals the dynamo that generates large-scale magnetic fields in merging neutron stars

Merging and colliding neutron stars produce powerful kilonova explosions and gamma-ray bursts. Scientists have long suspected that a large and ultra-strong magnetic field is the engine behind these high-energy phenomena. However, the process that generates this magnetic field has been a mystery until now. Researchers at the Max Planck Institute for Gravitational Physics and at the universities in Kyoto and Toho have revealed the underlying mechanism by performing a super-high resolution computer simulation taking into account all fundamental physics. The researchers showed that ultra-strongly magnetized neutron stars, also known as magnetars, cause very bright kilonova explosions. Telescopic observations could test this prediction in the future.

© NASA/JPL-Caltech/NASAEA/ESA/CXC/STScl/GSFCSVS/S.Barke (CC BY 4.0)

The LISA mission is an international collaboration between ESA, its member states, and NASA. It will consist of three identical spacecraft forming a near equilateral triangle that exchange laser beams over the 2.5 million km long arms. LISA will use precision laser interferometry to compare separations between test masses that are protected by the spacecraft from non-gravitational disturbances. LISA will coherently measure spacetime strain variations as a function of time, including frequency, phase, and polarisation, forming a continuous, all-sky observatory sensitive to all sources simultaneously.

LISA’s science objectives cover a wide range of outstanding questions in astrophysics, fundamental physics and cosmology including ESA’s Cosmic Vision questions such as “What are the fundamental laws of the Universe?” and “How did the Universe originate and of what is it made?”.

The red book is a comprehensive document which just got published with the LISA adoption. It describes the mission in its whole and is the result of the relentless effort of the LISA Science Study Team.

Artist’s impression of a LISA spacecraft. © AEI/MM/exozet

Following today´s Adoption, the LISA mission advances to the construction phase

LISA, the Laser Interferometer Space Antenna, has passed a major review with flying colours: the entire concept – from the definition of the overall mission and operations to the space hardware to be built – stood up to the intense scrutiny of ESA´s reviewers. Now the space agency´s Science Programme Committee (SPC) has confirmed that LISA is sufficiently mature and that mission development can proceed as planned. LISA should go into orbit in the mid 2030s.

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.

This diagram shows the frequencies (horizontal axis) and damping times (vertical axis) of the two tones observed in the decay of GW190521 as colored areas. The search found two tones consistent with the predictions of general relativity.

Observation of multiple ringdown modes in a black hole merger
An international team led by researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) in Hannover has found strong observational evidence for multiple gravitational-wave frequencies in a binary black hole ringdown. The team discovered that the intermediate-mass black hole formed in the GW190521 event vibrated briefly at at least two frequencies after the merger. This ringdown is a fundamental prediction from general relativity. Its observation allows tests of the theory and of the black hole no-hair theorem. The scientists found no violations of the theorem or deviations from general relativity. It was widely assumed that this observation of multiple tones would be impossible before the next generation of gravitational-wave detectors. Nevertheless, the unexpected massive merger remnant of GW190521 together with exquisite data analysis methods make the detection possible. The results were published in Physical Review Letters.

The entire sky as seen by NASA’s Fermi Gamma-ray Space Telescope. The plane of the Milky Way runs along the horizontal line in the middle. The grey scale shows the intensity of the observed gamma radiation. Small blue circles mark the pulsars in the now published catalog. Yellow and red circles show the 53 gamma-ray pulsars discovered by scientists at the Max Planck Institute for Gravitational Physics in Hannover. The yellow circles mark the gamma-ray pulsars discovered by the Einstein@Home distributed computing project, and red circles the gamma-ray pulsars found with the Atlas computer cluster. © The Fermi-LAT collaboration/MPI fpr Gravitational Physics

One in six of the discoveries were made by researchers at the Max Planck Institute for Gravitational Physics.
An international team of astronomers has produced a new catalog of 294 gamma-ray emitting pulsars discovered in data from NASA’s Fermi Gamma-ray Space Telescope, plus 34 suspects awaiting confirmation. This is 27 times the number known before the mission’s launch in 2008. Researchers at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Hannover, Germany, contributed 53 pulsars to the catalog. They made their discoveries by implementing novel, highly efficient data analysis methods on the Einstein@Home volunteer distributed computing project and the Atlas computing cluster.

Prof. Dr. Alessandra Buonanno © Markus Scholz for the Leopoldina

Memorial Lecture on November 23, 2023
Alessandra Buonanno, Director at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Potsdam, will receive the 2023 Oskar Klein Medal by the Stockholm University and the Nobel Committee of the Royal Swedish Academy of Sciences. Each year, a distinguished physicist is invited to deliver the Memorial Lecture and to receive the Oskar Klein medal. Buonanno will give the Memorial Lecture on “Gravitational-Wave Astronomy: Theoretical Advances and Challenges” on November 23 at the AlbaNova Center in Stockholm.

A pulsar is a compact neutron star that accelerates charged particles to relativistic speeds in its extremely strong magnetic field. This process produces gamma radiation (violet) far above the surface of the compact remains of the star, for example, while radio waves (green) are emitted over the magnetic poles in the form of a cone. The rotation moves the emission regions across the terrestrial line of sight, making the pulsar light up periodically in the sky. © NASA/Fermi/Cruz de Wilde

Citizen scientists can now also use their eyes and brains to help find new pulsars.
Since its launch in 2005, the Einstein@Home volunteer distributed computing project hosted at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Hannover, Germany, and at the University of Wisconsin-Milwaukee has been searching for and finding new neutron stars, compact remnants of exploded massive stars. Einstein@Home aggregates the otherwise idle computing power on the PCs of more than 15,000 active participants, making it one of the world’s largest projects of this kind. Since 2009, Einstein@Home has analyzed data from the Arecibo radio telescope and found 31 new radio pulsars, a special type of neutron star. Now Einstein@Home is teaming up with Zooniverse. On this successful citizen science web portal, volunteers will be able to classify graphical representations of Einstein@Home’s computational results, with the goal of discovering more pulsars in the Arecibo data.

Prof. Dr. Harald Pfeiffer Foto: E. Müller (Max Planck Institute for Gravitational Physics)

Harald Pfeiffer, research group leader in the “Astrophysical and Cosmological Relativity” department at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Potsdam, has been elected Fellow of the American Physical Society (APS). This honor is bestowed only on half a percent of the about 55,000 APS members. It recognizes the awardee’s outstanding contributions to physics.

1st prize in the Berthold Leibinger Innovationspreis 2023 for Henning Vahlbruch, Benno Willke, and Hartmut Grote (from left to right). Picture: Berthold Leibinger Stiftung

First prize for high-precision laser sources in gravitational-wave astronomy, fundamental research, and more
At a ceremony on the evening of September 22, 2023, the Berthold Leibinger Stiftung honored the winners and finalists of this year’s Innovation Award. Researchers from Leibniz University Hannover, the Max Planck Institute for Gravitational Physics (Albert Einstein Institute), and Cardiff University receive the 1st prize for their work on “ultra-high precision beam sources not only for basic research”. The award includes 50,000 Euros of prize money. This breakthrough exemplifies the work in scientific research that is driven by technological progress and is an example of how today’s discoveries are tomorrow’s tools, said Eckhard Elsen, member of the award jury, who gave the laudation for the prize.

Dr. Elisa Maggio © D. Niakhaichyk (Max Planck Institute for Gravitational Physics)

After being already awarded a prize from the Amaldi Research Center at La Sapienza University in Rome, Elisa Maggio, postdoctoral researcher at the Max Planck Institute for Gravitational Physics in Potsdam receives two more awards for her outstanding thesis on tests of general relativity.

In this issue, we explore how the GW community prepares for an observing run, and hear from behind the scenes of the recent PTAs announcement, the race to set up GOTO, and the memorable experience of rapidly responding to candidate S230518h – plus much more!

Prof. Dr. Alessandra Buonanno © A. Klaer

The inauguration ceremony will be held on November 10, 2023, in Rome
The Accademia Nazionale dei Lincei is one of the oldest and most prestigious European scientific institutions. It was founded in Rome in 1603 as the first private institution for the promotion of natural sciences in Europe. Today, the Accademia Nazionale dei Lincei is the Italian National Academy of Sciences.

Visit the gravitational-wave detector near Sarstedt on 30 September 2023
On Saturday, September 30, 2023, the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and the Institute for Gravitational Physics of Leibniz Universität Hannover invite you to visit the German-British gravitational-wave detector GEO600 near Sarstedt. Between 12:00 and 16:00 CEST, all visitors can speak with researchers at the detector site about the current state of gravitational-wave astronomy, the crucial contributions of GEO600 as a think tank of international research, and visit the detector.

High-performance compute cluster Urania, located at the Max Planck Computing and Data Facility (MPCDF) in Garching. © L. Hüdepohl (MPCDF)

New energy-efficient high-performance compute cluster for the Max Planck Institute for Gravitational Physics in Potsdam
The new supercomputer “Urania” has been put into operation by the Max Planck Institute for Gravitational Physics in Potsdam. With 6,048 compute-cores and 22 Terabyte of memory it is just as powerful as its predecessor, but requires only half the electricity to operate. Scientists at the Astrophysical and Cosmological Relativity department are now able to compute gravitational waveforms of coalescing black holes in ever more complex encounters.

Dr. Hao Jui Kuan © D. Niakhaichyk (Max Planck Institute for Gravitational Physics)

Excellent doctoral thesis on tidal effects in coalescing binary stars
Hao-Jui Kuan, postdoctoral researcher at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Potsdam, has been awarded the Dr. Friedrich Förster Prize for his outstanding dissertation. The prize honors young scientists in the fields of physics and physical chemistry who have completed their work in Tübingen within the last three years. The award is endowed with 1,000 euros.

Numerical-relativistic simulation of a binary neutron star merger ©K. Hayashi, K. Kiuchi (Max Planck Institute for Gravitational Physics & Kyoto University)

Complex numerical simulation sheds light on an extreme cosmic process
Scientists from the Max Planck Institute for Gravitational Physics in Potsdam and from the Universities of Kyoto and Toho have succeeded for the first time in studying the entire process of two neutron stars orbiting and merging with each other in a long numerical-relativistic simulation. Until now, only simulations describing about 0.1 seconds of the entire process were feasible for such binary systems. The new modeling, which took the Japanese high-performance computer Fugaku 200 days to compute, maps a time span ten times longer and provides new insights into the formation of heavy elements. The study has now appeared in the journal Physical Review Letters.

Pictures of the instruments of the current global gravitational-wave detector network. From top to bottom and from left to right: LIGO Hanford, LIGO Livingston, Virgo, KAGRA, GEO600. Pictures: LIGO Hanford, LIGO Livingston, Virgo, KAGRA, GEO600

Today the LIGO-Virgo-KAGRA (LVK) Collaboration begins a new observing run with upgraded instruments, new and even more accurate signal models, and more advanced data analysis methods. The LVK collaboration consists of scientists across the globe who use a network of observatories—LIGO in the United States, Virgo in Europe, and KAGRA in Japan—to search for gravitational waves, or ripples in space-time, generated by colliding black holes and other extreme cosmic events. During the last years, researchers from the Max Planck Institute for Gravitational Physics in Potsdam and Hannover and the Leibniz University Hannover have prepared for this observing run by developing novel waveform models and data-analysis methods for extracting more information from the data, and by providing observational coverage.

The ALPS II laser (in the box in the back with the sticker), which was developed at the Max Planck Institute for Gravitational Physics, after integration into the experiment at DESY. Picture: K. Karan

World’s most sensitive instrument of its kind is to produce axions
The world’s most sensitive model-independent experiment to search for particularly light particles, of which dark matter might be composed, starts today at DESY in the form of the ‘light shining through a wall’ experiment ALPS II. Scientists believe that this mysterious form of matter is five times more abundant in the universe than normal, visible matter. Until now, however, no one has been able to observe particles of this substance; the ALPS experiment could now furnish such evidence. Key contributions to the novel experiment come from researchers at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) and the Institute for Gravitational Physics at Leibniz Universität Hannover.

Infografik: LVK-Kollaboration/Max-Planck-Institute für Gravitationsphysik/Sascha Rieger

The LIGO-Virgo-KAGRA collaboration is making progress towards the start of the next observing run.
After three years of work to improve the performance of the detectors, Observing Run 4 (O4) is expected to start on May 24th, 2023. The detectors continue to make progress towards their O4 sensitivity goals and the LIGO detectors just moved from commissioning to the Engineering Run (ER15) which needs to be completed before Observing Run 4 can begin. Virgo is also joining the Engineering Run, but for a limited fraction of time, giving priority to commissioning activities aiming at improving the sensitivity. KAGRA has not started the Engineering Run, but will continue commissioning to improve the sensitivity until the start of O4.

A machine learning method with robustness guarantees: By comparing to simulated waveforms, the DINGO neural network verifies its own results. DINGO first calculates the properties of the black holes from the measured gravitational-wave signal. Based on these calculated parameters, a gravitational wave is modeled, and then compared to the originally observed signal. © M. Dax (Max Planck Institute for Intelligent Systems)

Self-checking algorithm interprets gravitational-wave data
An interdisciplinary team from the Max Planck Institute for Intelligent Systems and the Max Planck Institute for Gravitational Physics has developed an algorithm that immediately checks its own calculations of merging black holes’ properties and corrects its result if necessary – inexpensively and rapidly. The machine learning method provides very accurate information about the observed gravitational waves and will be ready for use when the global network of gravitational-wave detectors starts its next observing run in May.

Michele Punturo (INFN) and Harald Lück (Leibniz University Hannover) to serve as coordinator and vice-coordinator, respectively
Michele Punturo, a researcher at INFN Perugia division, and Harald Lück, a researcher at the Institute for Gravitational Physics of Leibniz University Hannover and the Max Planck Society, will serve as coordinator and vice-coordinator, respectively, of the Einstein Telescope (ET) Scientific Collaboration. The announcement was made today by the ET Scientific Collaboration, which brings together universities and research institutes, including the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Leibniz University Hannover, involved in the design and construction of a third-generation European gravitational-wave observatory. The ET project is included in the ESFRI European Strategy Forum on Research Infrastructure 2021 Roadmap; the European strategic forum selects major research infrastructures to be funded at a European level.

Prof. Dr. Tim Dietrich © T. Roese (Potsdam University)

Astrophysicist Prof. Dr. Tim Dietrich receives IUPAP Early Career Scientist Prize in General Relativity and Gravitation and a scholarship from the Daimler and Benz Foundation

Tim Dietrich, assistant professor at the University of Potsdam and Max Planck Fellow at the Max Planck Institute for Gravitational Physics, has been honored by the International Union of Pure and Applied Physics (IUPAP) as the best young scientist in the field of general relativity and gravitation. Dietrich receives this prize for his fundamental contributions to the development of binary neutron star models and the understanding of extremely dense nuclear matter. The award comes with a prize money of 1,000 euros and a medal.

Read about the approaching fourth LVK Observing Run (O4), commissioning the detectors for O4, climate change & the LVK and much more.

A gamma-ray pulsar is a compact neutron star that accelerates charged particles to relativistic speeds in its extremely strong magnetic field. This process produces gamma radiation (violet) far above the surface of the compact remains of the star, for example, while radio waves (green) are emitted over the magnetic poles in the form of a cone. The rotation moves the emission regions across the terrestrial line of sight, making the pulsar light up periodically in the sky. © NASA/Fermi/Cruz de Wilde

Seven rare eclipsing binaries identified and five neutron stars weighed
Mankind has watched the cosmic ballet of eclipses for millennia. Solar and lunar eclipses, those of Jupiter’s moons, and stellar occultations by planets and asteroids have also provided new physical measurements and insights about our Universe. Using NASA’s Fermi Gamma-ray Space Telescope, astronomers have now identified seven rare stellar binary systems in which a neutron star is eclipsed by its stellar companion. This allowed the international research team led by scientists from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Hannover to weigh those neutron stars. Their results were published in Nature Astronomy today. Precisely measuring neutron star masses improves our understanding of matter in extreme conditions and has implications for fundamental physics. In the future, these seven binary systems could also provide new opportunities to observe Einstein’s theory of general relativity in action.

This image shows the entire sky as seen by Fermi’s Large Area Telescope. The most prominent feature is the bright, diffuse glow running along the middle of the map, which marks the central plane of our Milky Way galaxy. Many of the star-like features above and below the Milky Way plane are distant galaxies powered by supermassive black holes. Many of the bright sources along the plane are pulsars. For more than 2000 sources, no association is known. © NASA/DOE/Fermi LAT Collaboration

New discoveries from the Transients and Pulsars with MeerKAT Project
Nine millisecond pulsars, most of them in rare and sometimes unusual binary systems, have been discovered in a targeted survey with the South African MeerKAT telescope array. An international team of astronomers with significant contributions from researchers at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) published their results in Monthly Notices of the Royal Astronomical Society today. They selected 79 unidentified pulsar-like sources from observations of NASA’s Fermi Gamma-ray Space Telescope and observed them at radio frequencies with MeerKAT. Using this tried-and-tested method with a next-generation telescope array has significant advantages over previous surveys. The team discovered nine rapidly rotating neutron stars, most of them with unusual properties. They also performed multi-wavelength follow-ups, finding gamma-ray pulsations from two of these objects, optical counterparts, as well as X-rays from another one of the systems. AEI scientists also searched for continuous gravitational waves from one of the neutron stars. These results emphasize the value of targeted searches for radio pulsars in unidentified gamma-ray sources and hold promise for the future: the researchers are certain that several more millisecond pulsars can be discovered by future observations.

Simulation eines Neutronensterns, der mit einem Schwarzen Loch verschmilzt. Während der Verschmelzung wird der Neutronenstern von Gezeitenkräften zerrissen. © T. Dietrich (Universität Potsdam und Max-Planck-Institut für Gravitationsphysik), N. Fischer, S. Ossokine, H. Pfeiffer (Max-Planck-Institut für Gravitationsphysik), S.V.Chaurasia (Universität Stockholm), T. Vu

What is needed to distinguish between binary black hole and neutron star black hole mergers?
As the number of gravitational wave observations increase, many questions arise; one of growing importance is this: when a gravitational-wave from a low mass merger is detected without a concurrent electromagnetic signal how can one distinguish a light weight binary black hole merger from a neutron star black hole merger? Researchers at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute Hannover, AEI), at Leibniz University Hannover, and at Radboud University have used a simulated search for such gravitational-wave signals to answer this question. Their results were now published in The Astrophysical Journal. Third-generation detectors such as Cosmic Explorer and the Einstein Telescope will be able to make a clear-cut distinction under favorable circumstances. This shows that new instruments will be needed for precise gravitational-wave astrophysics.

V. Varma © D. Niakhaichyk (Max Planck Institute for Gravitational Physics)

Scientist at the Max Planck Institute for Gravitational Physics is honored for his innovative research on merging black holes

Dr. Vijay Varma develops models to catch black holes that are ejected after a merger with a velocity of thousands of kilometers per second. He succeeded for the first time in identifying such a “runaway” black hole in gravitational-wave detector data – thus laying the foundation for a new observational method. With this award, the state of Brandenburg honors outstanding research work by postdocs at universities and non-university research institutions. The prize is endowed with 20,000 euros.

Simulation of two merging neutron stars, each with a mass of 1.35 solar masses. From red to blue, increasing densities are shown. © T. Dietrich (Potsdam University and Max Planck Institute for Gravitational Physics)

Tim Dietrich, Professor at the University of Potsdam and Max Planck Fellow at the Max Planck Institute of Gravitational Physics, receives a European Research Council (ERC) Starting Grant worth 1.5 million euros for his research project “SMArt” (“From Subatomic to Cosmic Scales: Simulating, Modelling, and Analyzing Binary Neutron Star Mergers”).

The prize is awarded about every three years for extraordinary contributions to general relativity and gravity

The prize, awarded by the Swiss Tomalla Foundation for Gravity Research, is endowed with 100,000 Swiss francs. Since 1981, the prize has been awarded every 3-4 years to outstanding researchers in gravity. The award ceremony will take place on October 14, 2022, in Geneva, Switzerland.

Read about commissioning work across the LVK collaborations as Observing Run 4 (O4) approaches, Quantum Squeezing in O4, the 10th anniversary of the LIGO Magazine and more!

The conference focuses on themes surrounding symmetries in supergravity and quantum gravity. These are central in the research of Hermann Nicolai whose contributions have sparked many important developments. © Photo: sevens+maltry Fotografen

International Conference at the Max Planck Institute for Gravitational Physics in Potsdam
The search for a theory that reconciles quantum field theory and general relativity is still one of the central research topics in theoretical physics. Prof. Dr. Dr. h.c. Hermann Nicolai, Director Emeritus at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI), is one of the world’s leading scientists in this field. He has initiated many important developments and has contributed significantly to the fact that the AEI today is one of the leading international research centers.

The gravitational-wave and experimental astrophysicist will establish a third department at the Max Planck Institute for Gravitational Physics in Hannover
Professor Guido Müller joins the Albert Einstein Institute in Hannover as director. He will establish the institute’s third department “Precision Interferometry and Fundamental Interactions” with a focus on precision interferometry for LISA and future space missions, as well as fundamental interactions beyond the standard model.

Numerical simulation of a black hole-neutron star merger. The density profile is shown in blue and green, the magnetic-field lines penetrating the black hole are shown in pink. Unbound matter is shown in white its velocity by green arrows. © K. Hayashi (Kyoto University)

For the first time, scientists model both the merger of a black hole with a neutron star and the subsequent process in one single simulation.
Using supercomputer calculations, scientists at the Max Planck Institute for Gravitational Physics in Potsdam and from Japan show a consistent picture for the first time: They modeled the complete process of the collision of a black hole with a neutron star. In their studies, they calculated the process from the final orbits through the merger to the post-merger phase, in which according to their calculations high-energy gamma-ray bursts may occur. The results of their studies have now been published in the journal Physical Review D.

Artist’s impression of the KAGRA gravitational-wave detector inside the Ikenoyama mountain in Kamioka, Japan. © KAGRA

Results from joint Japanese-German gravitational-wave observing run
Right after the third observing run of the international gravitational-wave detector network ended in March 2020, the Japanese KAGRA and the German-British GEO600 detector made an extra lap. They continued simultaneously taking data for two weeks in a joint observing run. KAGRA is the latest addition to the growing worldwide scientific collaboration, constructed underground with novel technologies. Results from the joint run were published in “Progress of Theoretical and Experimental Physics” (PTEP).

Artist’s impression combining a numerical-relativity simulation of a binary neutron star merger with a detection picture of the particles created in an gold-ion collision. © T. Dietrich (Potsdam University & Max Planck Institute for Gravitational Physics), A. Le Fevre (GSI Helmholtzzentrum für Schwerionenforschung GmbH), K. Huyser (NIKHEF); background: ESA/Hubble, Sloan Digital Sky Survey

Constraining neutron-star matter with microscopic and macroscopic collisions
For the first time, an international research team, including researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) and Potsdam University has combined data from nuclear physics experiments, gravitational-wave measurements and other astronomical observations with theoretical insights to more precisely constrain how nuclear matter behaves inside neutron stars. The results were published in the scientific journal Nature today.

Breakthrough discovery: EHT´s unprecedented observations improve our understanding of what happens at the very centre of our galaxy

Astronomers have unveiled the first image of the supermassive black hole at the centre of our own Milky Way galaxy. This result provides overwhelming evidence that the object is indeed a black hole and yields valuable clues about the nature of such giants, which are thought to reside at the centers of most galaxies. The image was produced by a global research team called the Event Horizon Telescope (EHT) Collaboration, using observations from a worldwide network of radio telescopes. The Max Planck Institute for Radio Astronomy (MPIfR) in Bonn plays a major role in all the aspects of this discovery, from founding and establishing the EHT collaboration to the final production and interpretation of the data.

The future gravitational-wave observatory in space completes a rigorous review
LISA, the Laser Interferometer Space Antenna, has reached an important milestone: it has passed the comprehensive “Mission Formulation Review” (MFR) and now enters the next phase of development. The review team, consisting of experts from ESA, NASA, the scientific community and industry, identified no showstoppers and confirmed that LISA has successfully reached a maturity sufficient to proceed to the next stage of development.

The GRACE Mission was launched in 2002 and gave us 13 years of data on Earth’s gravitational field and on the global water cycle. Its successor, GRACE Follow-On, was launched in 2018. This mission is making very reliable and precise measurements with a laser interferometer in space. This data is more important than ever to help monitor and understand climate change.

Find out more about building a gravitational-wave catalogue and new gravitational-wave signals, and read about the new double suspensions for A+ active mirrors in O4 in: Of magic mirrors, evil losses and small creatures.

SAGEX is an Innovative Training Network funded by the European Union to train the next generation of world-leading scientists in the field of scattering amplitudes. Explore the web app, which allows you to experience the wonderful world of quantum particles, from basic concepts to cutting-edge ideas, through short videos, games, and other interactive elements.

© M.A. Papa, MPI for Gravitational Physics, Hannover

Come along on a journey into our galaxy and learn how continuous gravitational waves are generated from neutron stars.

The new machine-learning algorithm accurately estimates all parameters characterizing a binary black hole source in only a few seconds. © M. Dax (Max Planck Institute for Intelligent Systems), S. R. Green, J. Gair (Max Planck Institute for Gravitational Physics), J. H. Macke (Max Planck Institute for Intelligent Systems), A. Buonanno Max Planck Institute for Gravitational Physics), B. Schölkopf (Max Planck Institute for Intelligent Systems)

Neural network analyzes gravitational waves in real time
Researchers trained a neural network to estimate – in just a few seconds – the precise characteristics of merging black holes based on their gravitational-wave emissions. The network determines the masses and spins of the black holes, where in the sky, at what angle, and how far away from Earth the merger took place.

The mergers of compact objects discovered so far by LIGO and Virgo (in O1, O2 and all of O3). The diagram shows black holes (blue), neutron stars (orange) and compact objects of unknown nature (grey), which were detected by their gravitational-wave emission. Each merger of a binary system corresponds to three compact objects shown: the two merging objects and the result of the merger. © LIGO-Virgo / Aaron Geller / Northwestern

Gravitational-wave catalog update lists 35 new signals
Today the LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration have published the latest version of their gravitational-wave catalog. The Gravitational-Wave Transient Catalog 3 (GWTC-3) now contains 90 signals, 35 of which were not published before and which were observed in O3b, the second half of the third joint observing run “O3”, which ended on 27 March 2020. All signals come from merging black holes and neutron stars. The new catalog contains some surprises, such as an unusual neutron-star–black-hole merger, a massive black hole merger, and binary black holes revealing information about their spins. In parallel, the researchers published companion studies of the underlying population of black holes and neutron stars and the history of the expansion of the Universe. The detectors are currently being upgraded for O4, their fourth joined observing run, which is expected to begin late in 2022.

Today, the US National Academy of Sciences has noted the important presence in the NASA Program of Record for the implementation and execution of the Laser Interferometer Space Antenna (LISA) Mission, led by the European Space Agency (ESA). Through observations of gravitational waves, LISA will offer an unprecedented and unique view of the Universe, quite different from any other space telescope. LISA will deliver pioneering scientific results enabling insights not available through electromagnetic observations, and combining LISA observations with those of other ground- and space-based facilities, will also allow scientists to make enormous advances in multi-messenger astronomy.

Find out more about first neutron star – black hole mergers as well as the search for young supernova remnants in O3 and more.

Artist’s impression of the underground Einstein Telescope. © NIKHEF

based on an INFN/Nikhef press release
The European Strategy Forum on Research Infrastructures (ESFRI) has announced that the 3rd generation gravitational wave observatory “Einstein Telescope (ET)” will be part of 2021 upgrade of the ESFRI roadmap. This confirms ET’s relevance for future research in Europe and gravitational wave research at global level.

Artist’s impression (in the style of a movie poster) of a black hole swallowing a neutron star. The poster illustrates GW200105 and the sequel GW200115 – the first robust detection of a neutron-star–black-hole merger. © A. S. Carvalho/A. Buonanno, D. Mihaylov, J. Steinhoff (Max Planck Institute for Gravitational Physics)

First robust detection of these rare events
LIGO, Virgo and KAGRA researchers present two new gravitational-wave events, which were detected within just ten days in January 2020 during the second half of the third observing run. The signal observed by the LIGO and Virgo detectors is the first robust detection of a black hole merging with a neutron star. The waves came from distances of more than 900 million light-years, where the neutron stars were swallowed whole by their black hole partners. While no light was seen from either event, the gravitational waves were heard loud and clear. They allow the researchers to draw first conclusions about the origin of these rare binary systems and how often they merge. The results were published in Astrophysical Journal Letters today. Scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Potsdam and Hannover and at Leibniz University Hannover have contributed to the discoveries and their interpretation.

A typical monthly gravity field map from GRACE Follow-On data. Shown in false colors is the change in Earth’s gravitation relative to January 2009, as a change in a nominal water height. Negative values correspond to a decrease, for example in ice mass loss in Greenland and Antarctica. © GFZ German Research Centre for Geosciences / AEI Hannover

Successful operation of the laser interferometer on board GRACE Follow-On began three years ago.
In mid-June 2018, it was “First Light!” for a novel laser instrument circling the Earth. The Laser Ranging Interferometer on both satellites of the German-US geodesy mission GRACE Follow-On was activated for the first time. At the first attempt, the instruments – 200 kilometers apart – were able to find each other 490 kilometers above the Earth’s surface. Since then, the system has been running reliably and has been delivering high-precision distance measurements in scientific data taking mode. Now, researchers at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) and Leibniz University Hannover look back the successful first three years and towards the future.

Artist’s impression of LISA Pathfinder operating in space © ESA/ATG medialab

It is May 4th 2021. The LPF mission has ended and the LISA mission is even now in the first phase of realization. LISA will be the largest space structure ever, but LISA is no Death Star. LISA’s mission: to probe the Dark Side of the Universe.
Happy Star Wars Day!

Polarisation in the very centre of galaxy M87. Polarization “field lines” are plotted atop an underlying total intensity image (the “shadow of a black hole” image from April 2019). The sweeping lines in the image indicate streamlines of the magnetic field. To emphasize the regions with stronger polarisation detections, length and opacity of the streamlines are scaled with the polarised intensity. © EHT-Kollaboration

Event Horizon Telescope Observations of Polarised Radio Emission of the Supermassive Object in the Centre of M87

The Event Horizon Telescope (EHT) team, including astronomers at the Max-Planck-Institut für Radioastronomie, has revealed today new observations that are key to explaining how the M 87 galaxy is able to launch an energetic jet from its core. The new view of the massive object at the centre of the M 87 galaxy shows how it looks in polarised light. For the first time, astronomers have been able to measure the polarisation, a signature of magnetic fields, this close to the edge of a black hole. They publish a key snapshot in order to understand how a jet larger than the galaxy is launched.

Find out more about art, music & gravitational waves as well as results from observing run 3a and more.

Fiber lasers are – due to their special beam properties – expected to be used in future gravitational-wave detectors, which will listen ten times more sensitively for gravitational waves. © LZH

Hannover research team develops most powerful laser system yet for gravitational-wave detectors

Future gravitational-wave detectors on Earth will use laser light with even higher power than in current instruments. Researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI), the Laser Zentrum Hannover e.V. (LZH), and Leibniz University Hannover have now developed a new laser system for this purpose. They combined the custom tailored light from two high-power lasers so precisely that it meets the requirements for use in gravitational-wave detectors. In a next step, the researchers will improve their system at AEI so that it can be used as a centerpiece for next-generation detectors. The results have now been published in the journal Optics Express.

LISA Pathfinder being encapsulated within the Vega rocket. © ESA–Manuel Pedoussaut

Relive the groundbreaking technology demonstrator’s mission milestones in a new Youtube mini-series released by the LISA Consortium.

GEO600 background noise measurements. The horizontal axis shows the frequency, the vertical axis the strength of the detector noise at these frequencies. The lower the curves are, the less noise is present and the better gravitational waves can be measured. The blue curve shows the noise without the squeezed light source, the red curve shows the noise with the squeezed light source. The improvements occur mainly at high frequencies. © Max Planck Institute for Gravitational Physics

German-British instrument mitigates quantum noise effects better than any gravitational-wave detector before

Gravitational waves cause tiny length changes in the kilometer-size detectors of the international network (GEO600, KAGRA, LIGO, Virgo). The instruments use laser light to detect these effects and are so sensitive that they are fundamentally limited by quantum mechanics. This limit manifests as an ever-present background noise which can never be fully removed and which overlaps with gravitational-wave signals. But one can change the noise properties – using a process called squeezing – such that it does not disturb the measurements as much. Now, GEO600 researchers have achieved the strongest squeezing ever seen in a gravitational-wave detector. They lowered the quantum mechanical noise by up to a factor of two. This is a big step to third-generation detectors such as the Einstein Telescope and Cosmic Explorer. The GEO600 team is confident to reach even better squeezing in the future.

The Institute for Gravitational Physics at Leibniz University Hannover will do research on and improve interferometric precision measurements and laser links between satellites

The collaborative research center (Sonderforschungsbereich / SFB) “Relativistic and Quantum-Based Geodesy (TerraQ)”, funded by the German Research Foundation (Deutsche Forschungsgemeinschaft / DFG), investigates novel methods of geodesy using fundamentally new sensors, measurement techniques, analysis methods and modeling approaches. Researchers of the Institute for Gravitational Physics at Leibniz Universität Hannover contribute their decades of experience and their worldwide leading role in the field of interferometric precision measurements and laser links between satellites. Basic research is thereby used in climate research and improves the precious data at its foundation.

The mergers of compact objects discovered so far by LIGO and Virgo (in O1, O2 and O3a). The diagram shows black holes (blue), neutron stars (orange) and compact objects of unknown nature (grey), which were detected by their gravitational-wave emission. Each merger of a binary system corresponds to three compact objects shown: the two merging objects and the result of the merger. A selection of black holes (violet) and neutron stars (yellow) discovered by electromagnetic observations is shown for comparison. © LIGO Virgo Collaboration / Frank Elavsky, Aaron Geller / Northwestern

New LIGO/Virgo catalog contains 50 gravitational-wave signals, several from unusual sources

The LIGO Scientific Collaboration and the Virgo Collaboration have published updates to their catalog of gravitational-wave signals, their astrophysical implications and more stringent tests of general relativity. The Gravitational-Wave Transient Catalog 2 (GWTC-2) now contains 50 signals compared to 11 signals in the previous version. The 39 new discoveries were found in O3a, the first six months of the third joint observing run “O3”, which began on 1 April 2019. The new signals come from different astrophysical systems of merging black holes and neutron stars in all possible combinations. Some exceptional events have already been published in the previous months. While the new catalog contains many binary black hole mergers found routinely, it also features some more surprises, such as the most light-weight merger of two black holes or a possible merger of a black hole and a neutron star. Results from the second half of O3 will be published later and should contain more surprises from the Dark Universe.

The entire sky as seen by the Fermi Gamma-ray Space Telescope and the new pulsar discovered by Einstein@Home. The field below the magnified inset shows the pulsar name and some of its measured characteristics, as well as its gamma-ray pulsations. The flags show the nationalities of the volunteers whose computers found the pulsar. © Knispel/Max Planck Institute for Gravitational Physics/NASA/DOE/Fermi LAT Collaboration

Volunteer distributed computing project Einstein@Home discovers neutron star in unusual binary system
After more than two decades, an international research team led by the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover has identified a Galactic “mystery source” of gamma rays: a heavy neutron star with a very low mass companion orbiting it. Using novel data analysis methods running on about 10,000 graphics cards in the distributed computing project Einstein@Home, the team identified the neutron star by its regularly pulsating gamma rays in a deep search of data from NASA’s Fermi satellite. Surprisingly, the neutron star is completely invisible in radio waves. The binary system was characterized with an observing campaign across the electromagnetic spectrum, and breaks several records.

Snapshots of the M 87* black hole obtained through imaging / geometric modeling, and the EHT array of telescopes in 2009-2017. The diameter of all rings is similar, but the location of the bright side varies. The variation of the thickness of the ring is most likely not real and results from the limited number of participating VLBI stations in earlier experiments. © M. Wielgus, D. Pesce & the EHT Collaboration

Turbulent evolution of the M 87* black hole image from 2009 to 2017

In 2019, the Event Horizon Telescope (EHT) Collaboration delivered the first image of a black hole, revealing M 87*—the supermassive object in the center of the Messier 87 galaxy. The EHT team, a collaboration with strong engagement of the MPI für Radioastronomie, has now used the lessons learned last year to analyze the archival data sets from 2009-2013, some of them not published before. The contribution of the APEX telescope is very important for the success of this analysis.

Together with their Virgo colleagues, the AEI researchers Harald Lück, Moritz Mehmet, and Henning Vahlbruch install the squeezed-light source, which was developed in Hannover, in a cleanroom at the Virgo gravitational-wave detector. © H. Lück/B. Knispel/Max Planck Institute for Gravitational Physics

A quantum mechanical effect demonstrated for the first time in the Advanced Virgo gravitational-wave detector
Quantum mechanics does not only describe how the world works on its smallest scales, but also affects the motion of macroscopic objects. An international research team, including four scientists from the MPI for Gravitational Physics (Albert-Einstein-Institut/AEI) and Leibniz University in Hannover, Germany, has shown how they can influence the motion of mirrors, each weighing more than 40 kg, in the Advanced Virgo gravitational-wave detector trough the deliberate use of quantum mechanics. At the core of their experiment published today in Physcial Review Letters is a squeezed-light source, developed and built at the AEI in Hanover, which generates specially tuned laser radiation and improves the detector’s measurement sensitivity during observing runs.

The proposal to include the Einstein Telescope, a pioneering third-generation gravitational-wave (GW) observatory, in the 2021 update of the European Strategic Forum for Research Infrastructures (ESFRI) roadmap has been submitted. The ESFRI roadmap describes the future major research infrastructures in Europe. The Einstein Telescope (ET) is the most ambitious project for a future terrestrial observatory for GWs.

Numerical simulation of two black holes that inspiral and merge, emitting gravitational waves. The black holes have large and nearly equal masses, with one only 3% more massive than the other. The simulated gravitational wave signal is consistent with the observation made by the LIGO and Virgo gravitational wave detectors on May 21st, 2019 (GW190521). © N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration

Far-away black hole collision is the most massive and most distant ever observed by the gravitational-wave detectors

The fourth gravitational-wave detection from LIGO’s and Virgo’s third observing run published today is very big news: the most massive merger of two black holes ever observed to date. The black-hole collision formed a 142 solar-mass black hole when the Universe was half its current age. This is the first direct observation of the birth of an intermediate-mass black hole. Even more surprising is the heavier black hole in the pair: with 85 times the mass of our Sun, it should not exist according to the current understanding of stellar explosions, but it could be born from an earlier binary merger. It is unknown whether this signal, GW190521, is the first observed representative of a new class of binary black holes or is simply at the upper end of a wide mass spectrum. Scientists at the Max Planck Institute for Gravitational Physics in Potsdam and Hannover and at the Leibniz University Hannover have made crucial contributions to the discovery and its interpretation.

Black hole scattering can be treated as a particle-like interaction, in which the black holes exchange gravitons. By calculating the quantum scattering amplitudes, researchers can obtain important information about merging black hole binaries that emit gravitational waves. © APS/Alan Stonebraker

The departments of Professor Alessandra Buonanno (Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI)) and Professor Zvi Bern (Mani L. Bhaumik Institute for Theoretical Physics (University of California in Los Angeles, UCLA)) will cooperate on developing waveform models for future gravitational-wave detectors. Senior researcher Dr. Justin Vines will perform the balancing act between particle physics at UCLA and gravitational wave modeling at the AEI. For the next two years, he will be based at AEI, then he will move over to UCLA. Long-term visits between both institutions are planned in order to maintain collaborations with researchers in Potsdam and Los Angeles. The goal is to foster the use of advanced computational techniques originating from quantum field theory to develop ever more accurate gravitational waveform models, enabling further discoveries with gravitational-wave detectors as they become more and more sensitive.

The Laser Interferometer Space Antenna (LISA) will be the first gravitational wave observatory in space, to be launched 2034. It is one of the European Space Agency’s (ESA’s) three large missions with contributions from NASA.

The LISA Symposium will take place online from September 1 to 3.

Besides live presentations on YouTube (or Zoom, then with discussion and commentary opportunities for registered participants) there will be recorded presentations, which are already available. More information:

LISA Consortium:
https://www.lisamission.org

Twitter: #LISAXIII

Registration is free. Please get in touch with if you have any questions or if you are looking for experts to talk to on various topics.

Contact:
Susanne Milde
Milde Marketing Science Communication
+49 172 393 1349
milde@mildemarketing.de

Visualization of the coalescence of two black holes that inspiral and merge, emitting gravitational waves. One black hole is 9.2 times more massive than the other and both objects are non-spinning. © N. Fischer, S. Ossokine, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes (SXS) Collaboration

LIGO and Virgo find another surprising binary system

The harvest of exceptional gravitational-wave events from LIGO’s and Virgo’s third observing run (O3) grows. A new signal published today comes from the merger of a 23-solar-mass black hole with an object 9 times lighter. The second object is mysterious: its measured mass puts it in the so-called “mass gap” between the heaviest known neutron stars and the lightest known black holes. While the researchers cannot be sure about its true nature, one thing is clear: the observation of this unusual pair challenges the current understanding of how such systems are born and evolve.

© Max Planck Institute for Gravitational Physics (Albert Einstein Institute) / Milde Marketing Science Communication / Exozet Effects

On the occasion of the 236th meeting of the American Astronomical Society the LISA Consortium launched a new movie about ESA´s LISA mission. LISA is a space mission led by ESA with contributions from NASA and many ESA member states. LISA will observe gravitational waves in space with three satellites connected by laser beams forming a constellation in a heliocentric orbit.

Binary black hole merger where the two black holes have distinctly different masses of about 8 and 30 times that of our Sun. © N. Fischer, H. Pfeiffer, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes project

LIGO and Virgo detectors catch first gravitational wave from binary black hole merger with unequal masses

The expectations of the gravitational-wave research community have been fulfilled: gravitational-wave discoveries are now part of their daily work as they have identified in the past observing run, O3, new gravitational-wave candidates about once a week. But now, the researchers have published a remarkable signal unlike any of those seen before: GW190412 is the first observation of a binary black hole merger where the two black holes have distinctly different masses of about 8 and 30 times that of our Sun. This not only has allowed more precise measurements of the system’s astrophysical properties, but it has also enabled the LIGO/Virgo scientists to verify a so far untested prediction of Einstein’s theory of general relativity.

Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Potsdam © Albert Einstein Institute

Visit founding director Prof Bernard F Schutz´ blog for the story:

Find out more about the O3 commissioning break, GW190425 and more here:

Numerical-relativity simulation of the first binary black-hole merger observed by the Advanced LIGO detector on September 14, 2015. Credit: S. Ossokine, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes project, W. Benger (Airborne Hydro Mapping GmbH)

International team led by Max Planck researchers finds promising new candidates for gravitational waves from binary black hole mergers in public LIGO/Virgo data

Researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover together with international colleagues have published their second Open Gravitational-wave Catalog (2-OGC). They used improved search methods to dig deeper into publicly available data from LIGO’s and Virgo’s first and second observation runs. Apart from confirming the ten known binary black hole mergers and one binary neutron star merger, they also identify four promising black hole merger candidates, which were missed by initial LIGO/Virgo analyses. These results demonstrate the value of searches in public LIGO/Virgo data by research groups independent of the LIGO/Virgo collaborations. The research team also makes available its complete catalogue in addition to detailed analysis of more than a dozen possible binary black hole mergers.

A neutron star is the densest object astronomers can observe directly, crushing half a million times Earth’s mass into a sphere about 22 kilometers across, according to the new results. This illustration compares the size of a neutron star to the area around Hannover, Germany, hometown of the Albert Einstein Institute Hannover. © NASA’s Goddard Space Flight Center

International team uses a novel approach combining gravitational-wave observations, multi-messenger astronomy, and nuclear physics to obtain the best measurement of neutron star size to date.

An international research team led by members of the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) has obtained new measurements of how big neutron stars are. To do so, they combined a general first-principles description of the unknown behavior of neutron star matter with multi-messenger observations of the binary neutron star merger GW170817. Their results, which appeared in Nature Astronomy today, are more stringent by a factor of two than previous limits and show that a typical neutron star has a radius close to 11 kilometers. They also find that neutron stars merging with black holes are in most cases likely to be swallowed whole, unless the black hole is small and/or rapidly rotating. This means that while such mergers might be observable as gravitational-wave sources, they would be invisible in the electromagnetic spectrum.

Jahed Abedi, a postdoctoral researcher at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute), shares the $10,000 First Prize of the annual 2019 Buchalter Cosmology Prize with Niayesh Afshordi (University of Waterloo and Perimeter Institute for Theoretical Physics). The winners of the prize have been announced on 6 January 2020 at the 235th meeting of the American Astronomical Society in Honolulu.

Numerical-relativity simulation of the binary neutron star coalescence and merger which resulted in the detected gravitational-wave event GW190425. The image shows the gravitational wave signal with colors ranging from red, yellow, green, blue with increasing strength, and the density of the neutron stars from light to dark blue ranging between 200 thousand to 600 million tons per cubic centimeter, respectively. © T. Dietrich (Nikhef), S. Ossokine, A. Buonanno (Max Planck Institute for Gravitational Physics), W. Tichy (Florida Atlantic University) and the CoRe-collaboration

The international gravitational-wave detector network has observed what is most likely its second signal from merging neutron stars. The signal dubbed GW190425 was identified as a highly significant event by the LIGO Livingston and the Virgo detector on April 25, 2019. The signal comes from a distance of about 520 million light-years, four times farther away than the first gravitational wave from a binary neutron star merger detected in August 2017. No observations by electromagnetic or neutrino observatories related to this signal have been reported. While a binary neutron star merger is the most likely explanation, the combined mass of the system is much higher than that of other known such systems. This could be due to special formation circumstances of the system. It is also possible that one or both objects are light-weight black holes not previously observed.

The NASA Group Achievement Awards for the German LRI team.

A group of 47 researchers in Germany received a NASA award for their teamwork on the novel and very successful Laser Ranging Interferometer on board the GRACE Follow-On satellite tandem. Among them are 13 researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) and the Institute for Gravitational Physics at Leibniz Universität Hannover. The NASA Group Achievement Award was presented to the team at the Jet Propulsion Laboratory at the end of October for “dedication and excellence in developing and successfully deploying” the laser instrument on board the GRACE Follow-On mission.

The background noise of the gravitational-wave observatory Virgo without squeezed-light source (black line) and with squeezed-light source (red line). It reduces the noise at frequencies above 100 Hertz by up to one third and thus makes it possible to detect weaker gravitational waves. The blue line shows increased noise that occurs when the squeeze light source is used in a sense “the wrong way round”. © Virgo Collaboration, Vahlbruch, Mehmet, Lück, Danzmann

A squeezed-light source developed by researchers at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) for the Virgo gravitational-wave detector near Pisa has impressively demonstrated its capabilities in recent months. This is shown by the latest data published from the third observation run (O3) of the international detector network. The squeezed-light source reduces the dominant quantum mechanical detector background noise by about one third. This allows Virgo, for example, to detect gravitational waves from merging neutron stars up to 26% more frequently. The use of squeezed light also plays an important role for planned third-generation detectors such as the Einstein Telescope. The squeezed-light source was delivered and commissioned at the beginning of 2018. Since the start of O3 on April 1, 2019, it has provided significantly improved Virgo sensitivity.

Cosmic evolution in a cyclic universe: the big bang is replaced by a bounce and our universe is born as a result of a smooth transition from an early epoch of contraction to the current expanding phase. © Anna Ijjas

Anna Ijjas, leader of the recently established Lise Meitner Research Group “Gravitational Theory and Cosmology” at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute / AEI) in Hannover, and Paul Steinhardt, Albert Einstein Professor in Science at Princeton University, receive 1.3 million US-dollars for four years from the Simons Foundation. The goal of the newly funded initiative “New Directions in Cosmology and Gravitational Theory” is to develop and test theories of the origin, evolution, and future of the universe that challenge the standard view that the universe began with a big bang about 14 billion years ago. Ijjas’ group at the AEI Hannover receives 500 000 US-dollars that she will use towards building her research team, including support for graduate students and postdocs, workshops, conferences, and visitors.

Fotoreportage über Prof. Dr. Karsten Danzmann, Direktor im Max-Planck-Institut für Gravitationsphysik ( Albert Einstein Institut ) inr Hannover am 8. Februar 2016

Prof. Karsten Danzmann, Director at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover and Director of the Institute for Gravitational Physics at Leibniz University Hannover, has been accepted into the Manager Magazine’s “Hall of Fame of German Research”. The award recognizes his lifelong, outstanding contributions to the advancement of research. The award was presented on 29 October in Berlin.

A black widow pulsar and its small stellar companion, viewed within their orbital plane. Powerful radiation and the pulsar’s “wind” – an outflow of high-energy particles — strongly heat the facing side of the star to temperatures twice as hot as the sun’s surface. The pulsar is gradually evaporating its partner, which fills the system with ionized gas and prevents astronomers from detecting the pulsar’s radio beam most of the time. NASA’s Goddard Space Flight Center/Cruz deWilde

An international research team led by the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover has discovered that the radio pulsar J0952-0607 also emits pulsed gamma radiation. J0952-0607 spins 707 times in one second and is 2nd in the list of rapidly rotating neutron stars. By analyzing about 8.5 years worth of data from NASA’s Fermi Gamma-ray Space Telescope, LOFAR radio observations from the past two years, observations from two large optical telescopes, and gravitational-wave data from the LIGO detectors, the team used a multi-messenger approach to study the binary system of the pulsar and its lightweight companion in detail. Their study published in Astrophysical Journal Letters today shows that extreme pulsar systems are hiding in the Fermi catalogues and motivates further searches. Despite being very extensive, the analysis also raises new unanswered questions about this system.