Nikhef press release: gravitational waves detected 100 years after Einstein's prediction

Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained. Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.

The gravitational waves were detected on 14 September 2015 at 10.51 hours a.m. Central European Time by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, USA. The LIGO Observatories are funded by the National Science Foundation (NSF), and were conceived, built, and are operated by Caltech and MIT. The discovery, accepted for publication in the journal Physical Review Letters, was made by the LIGO Scientific Collaboration (which includes the GEO Collaboration and the Australian Consortium for Interferometric Gravitational Astronomy) and the Virgo Collaboration using data from the two LIGO detectors.

Dutch scientists played an important role in the discovery of gravitational waves
Dutch scientists were closely involved in this groundbreaking discovery. As members of the 'LIGO Scientific Collaboration - Virgo Collaboration' (LVC) physicists from the National Institute for Subatomic Physics (Nikhef) and VU University Amsterdam, as well as astronomers from Radboud University made vital contributions to validating the measurement, to the data analysis for these gravitational waves, and they collaborated on the astrophysical interpretation. More details about the Dutch contribution can be found further on in this press release.

Enthusiastic reactions
The Minister of Education, Culture and Science, Jet Bussemaker, and her state secretary Sander Dekker are delighted about this historic scientific discovery: “This demonstrates the importance of fundamental research that forms the basis for our knowledge about life now and about our history and the origin of the universe. The fact that Einstein's prediction has been confirmed 100 years later is a major posthumous compliment to Einstein but most definitely to the scientists of today as well. In particular, we would like to congratulate the physicists from the Dutch institute Nikhef and VU University Amsterdam and the astronomers from Radboud University who have contributed to this outstanding global achievement.”

“Incredible - what a fantastic discovery. I would also like to congratulate the Nikhef scientists involved and their colleagues from LIGO and Virgo. The observation of two black holes merging is where extreme precision in knowledge and instrumentation come together with the most audacious imagination,” says Stan Bentvelsen, director of Nikhef.

Gravitational waves specialist Jo van den Brand, Professor of Subatomic Physics at VU University Amsterdam and initiator and leader of the gravitational physics programme of Nikhef adds: “What we have measured is fantastic. The signal captured is so clear that you can see it in the raw data with the naked eye. A surprise aspect of this discovery is that the black holes that have merged are far heavier than the black holes we know in binary stars in our Milky Way.”

Chris Van Den Broeck, scientist at Nikhef, is one of the two coordinators of all data analysis related to the measurement. For months he worked with his colleagues on the detailed analysis: "The signal agrees exactly with what you would expect according to Einstein's theory. Now we can test the theory in the most extreme situations.”

Astronomer Gijs Nelemans (Radboud University & KU Leuven and affiliated to Nikhef) is also extremely enthusiastic: "This is the start of a new era for astronomy. We now have a completely new way of looking at the universe and studying the most extreme objects. With the new instruments we can now for the first time accurately pinpoint the end of the complex evolution of massive binary stars."

'Building blocks of matter, foundations of space and time' is one of the 16 exemplary routes in the Dutch National Research Agenda. This fundamental curiosity-driven theme is based on questions that the Dutch public posed. “This research is directly related to that theme,” says Bentvelsen. “One of the prominent questions in this theme is: 'What is the real nature of gravity, space and time and what can you learn from black holes, for example?' The discovery of gravitational waves is a big step towards answering this question.”

About LIGO and Virgo
LIGO research is carried out by the LIGO Scientific Collaboration (LSC), a group of more than 1000 scientists from universities around the United States and in 14 other countries. More than 90 universities and research institutes in the LSC develop detector technology and analyze data; approximately 250 students are strong contributing members of the collaboration. The LSC detector network includes the LIGO interferometers and the GEO600 detector. The GEO team includes scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI), Leibniz Universität Hannover, along with partners at the University of Glasgow, Cardiff University, the University of Birmingham, other universities in the United Kingdom, and the University of the Balearic Islands in Spain.

Virgo research is carried out by the Virgo Collaboration, consisting of more than 250 physicists and engineers belonging to 19 different European research groups: 6 from Centre National de la Recherche Scientifique (CNRS) in France; 8 from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; 2 in the Netherlands with Nikhef; the Wigner RCP in Hungary; the POLGRAW group in Poland and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo detector near Pisa in Italy.

Virgo was born thanks to the visionary ideas of Alain Brillet and Adalberto Giazotto. The detector was designed based on innovative technologies expanding the sensitivity to the low frequency range. The construction started in 1994 and it has been funded by CNRS and INFN; since 2007 Virgo and LIGO have shared and jointly analysed the data taken by all the interferometers of the international network. After the start of the LIGO upgrade, Virgo took data until 2011.

The Advanced Virgo project, funded by CNRS, INFN and Nikhef, was then launched: the new detector will be in operation before the end of the year. In addition several institutes and universities of the five European nations of the Virgo Collaboration contribute both to the Advanced Virgo upgrade and to the discovery effort.

LIGO was originally proposed as a means of detecting these gravitational waves in the 1980s by Rainer Weiss, professor of physics, emeritus, from MIT; Kip Thorne, Caltech's Richard P. Feynman Professor of Theoretical Physics, emeritus; and Ronald Drever, professor of physics, emeritus, also from Caltech.

The discovery was made possible by the enhanced capabilities of Advanced LIGO, a major upgrade that increases the sensitivity of the instruments compared to the first generation LIGO detectors, enabling a large increase in the volume of the universe probed—and the discovery of gravitational waves during its first observation run. The US National Science Foundation leads in financial support for Advanced LIGO. Funding organizations in Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council, STFC) and Australia (Australian Research Council) also have made significant commitments to the project. Several of the key technologies that made

Advanced LIGO so much more sensitive have been developed and tested by the German UK GEO collaboration. Significant computer resources have been contributed by the AEI Hannover Atlas Cluster, the LIGO Laboratory, Syracuse University, and the University of Wisconsin-Milwaukee. Several universities designed, built, and tested key components for Advanced LIGO: The Australian National University, the University of Adelaide, the University of Florida, Stanford University, Columbia University in the city of New York, and Louisiana State University.

Dutch contributions
Nikhef makes important contributions to both instrumentation and data analysis within the LIGO-Virgo collaboration. In particular Nikhef is working on the software for the detection and modelling of gravitational waves originating from merging black holes and neutron stars, but also for the search for continuous gravitational waves from, for example, rapidly rotating neutron stars in binary systems.

For the Advanced Virgo detector, which will be commissioned this year as an extension of the LVC network, Nikhef is responsible for seismic isolation and for optical sensors that have to guarantee the stable functioning of the instrument. Nikhef is also playing an important role within the Einstein Telescope project, a future observatory for gravitational waves.

The astronomers from Radboud University are focusing on the astrophysical interpretation and the combination of gravitational wave information with data from traditional telescopes. For this they are developing, amongst other things, the BlackGEM telescope within the Netherlands Research School for Astronomy.

About Nikhef
The National institute for subatomic physics (Nikhef) performs research in the area of particle and astro-particle physics. Nikhef is a partnership between the Foundation for Fundamental Research on Matter (FOM) and five universities: Radboud University, University of Amsterdam, University of Groningen, Utrecht University and VU University Amsterdam. FOM is part of the Netherlands Organisation for Scientific Research (NWO). www.nikhef.nl

Radboud University is also an independent member of Virgo.

Images, videos, animations and further background information can be found at http://www.nikhef.nl/media 

For more information, please contact
Science Communications Department Nikhef, Dr. Vanessa Mexner, +31 20 592 50 75 or +31 20 592 20 75.
Prof. Jo van den Brand, Programme leader gravitational physics group Nikhef and professor of subatomic physics VU University Amsterdam, +31 20 592 20 15 or 31 6 20 53 94 84.
Prof. Stan Bentvelsen, Director Nikhef, +31 20 592 50 01 or +31 6 51 11 12 84.
Dr. Chris van Den Broeck, Senior researcher gravitational physics group Nikhef, +31 20 592 20 53.
Prof. Gijs Nelemans, Professor of astronomy, Radboud University & KU Leuven and affiliated to Nikhef,  + 31 24 365 29 83 or 31 6 45 12 01 89.