Gravitational waves detected from second pair of colliding black holes
The LIGO Scientific Collaboration and the Virgo collaboration identify a second gravitational wave event in the data from Advanced LIGO. On 26 December 2015 at 04:38:53 Dutch time, scientists observed gravitational waves - ripples in the fabric of spacetime - for the second time.
The gravitational waves were detected 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.
Gravitational waves carry information about their origins and about the nature of gravity that cannot otherwise be obtained, and physicists have concluded that these gravitational waves were produced during the final moments of the merger of two black holes —14 and 8 times the mass of the sun — to produce a single, more massive spinning black hole that is 21 times the mass of the sun.
"It's fantastic that we have already observed two powerful mergers within a few months. These black holes are much less massive than those observed in the first detection," says Jo van den Brand, leader of the gravitational physics group at Nikhef and Professor of Subatomic Physics at VU University Amsterdam. "It is a promising start to mapping the population of black holes in our universe."
During the merger, which occurred approximately 1.4 billion years ago, a quantity of energy roughly equivalent to the mass of the sun was converted into gravitational waves. The detected signal comes from the last 27 orbits of the black holes before their merger. Based on the arrival time of the signals — with the Livingston detector measuring the waves 1.1 milliseconds before the Hanford detector — the position of the source in the sky can be roughly determined.
"Before long, we will have three detectors that will be able to much more accurately determine the position of the sources of gravitational waves", says Stan Bentvelsen, director of Nikhef. "This is because the European interferometer Advanced Virgo is about to join the LIGO interferometers and this will enable it to deliver a significant contribution to the detection network of gravitational waves."
Samaya Nissanke, astronomer and Excellence Fellow of the Radboud University adds: "With this, we can more effectively point electromagnetic telescopes and thus study the physics of the mergers of black holes and neutron stars."
Dutch scientists played an important role in the discovery of gravitational waves
Just like with the first detection of gravitational waves, Dutch scientists were closely involved in this second detection. 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.
"Because we could observe many more orbital cycles of the two black holes before the merger, we were able to study different aspects of the theory of general relativity than before. The way in which gravitational waves are first generated by the black holes that swiftly move around each other, and are then scattered by the strong curvature of spacetime in their vicinity, was measured in detail. The results of the analyses done at Nikhef are also for this event in accordance with the predictions of Einstein's theory" says Chris Van Den Broeck, coordinator data-analysis of the collaboration and Nikhef researcher.
The first detection of gravitational waves, announced on 11 February 2016, was a milestone in physics and astronomy; it confirmed a major prediction of Albert Einstein's 1915 general theory of relativity, and marked the beginning of the new field of gravitational-wave astronomy.
"By uncovering this population of black holes, we made a start with gravitational wave astronomy. It is a very exciting week with first the excellent operations of LISA-Pathfinder and now another merger of black holes" says astronomer Gijs Nelemans of the Radboud University & KU Leuven, and affiliated to Nikhef.
Both discoveries were 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.
Advanced LIGO's next data-taking run will begin this fall. By then, further improvements in detector sensitivity are expected to allow LIGO to reach as much as 1.5 to 2 times more of the volume of the universe. The Virgo detector is expected to join in the latter half of the upcoming observing run.
About LIGO and Virgo
LIGO research is carried out by the LIGO Scientific Collaboration (LSC), a group of more than 1,000 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.
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 MTA 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.
The NSF 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, the ARCCA cluster at Cardiff University, the University of Wisconsin-Milwaukee, and the Open Science Grid. Several universities designed, built, and tested key components and techniques for Advanced LIGO: The Australian National University, the University of Adelaide, the University of Western Australia, the University of Florida, Stanford University, Columbia University in the City of New York, and Louisiana State University. 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 Germany, and the University of the Balearic Islands in Spain.
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).
Radboud University is also an independent member of Virgo.
More information
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
Vanessa Mexner, +31 20 592 50 75 or +31 (0)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
Prof. Stan Bentvelsen, Director Nikhef, +31 20 592 50 01
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