gravitational waves detected 100 years after Einstein’s prediction
Feb. 11th, 2016, 17:00, Hamburg
LIGO Opens New Window on the Universe with Observation of Gravitational Waves from Colliding Black Holes
Scientists at Hamburg University are involved in sensational discovery
For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at the earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.
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 September 14, 2015 at 5:51 a.m. Eastern Daylight Time (9:51 a.m. UTC) 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.
Since spring 2015, the University of Hamburg has been a member of the GEO600 Team and the LIGO Scientific Collaboration (LSC) represented by the team of Prof. Roman Schnabel at the Institute of Laser Physics and the Centre of Optical Quantum Technologies. Before R. Schnabel moved to Hamburg, he was at the Leibniz University of Hannover where he had been researching quantum technologies for future gravitational-wave detectors since 2002. In Hannover he developed the first source of light that has a ‘squeezed’ quantum noise and that was suitable for continuous operation in a gravitational-wave detector. Since implementation in 2010, this source has been operating in GEO600. The two LIGO detectors that eventually detected the gravitational wave are not yet equipped with squeezed light; however, a source of squeezed light could also further improve the measurement sensitivity of these detectors. At the University of Hamburg Schnabel's team is now in the process of researching new ways to improve the measurement sensitivity of gravitational-wave detectors. Since 2013, R. Schnabel has been the chair of the LSC ‘Quantum Noise Working Group’.
Further information about LIGO and the international Collaboration
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.
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.
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.
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 of New York, and Louisiana State University.
The Scientific Breakthrough: The Observation of Gravitational Waves and the Observation of Merging Black Holes
In 1916, the year after the final formulation of general relativity, Albert Einstein predicted the existence of gravitational waves. Scientists have now observed these mysterious waves for the first time, using the two 4 kilometre long detectors of the „Laser Interferometer Gravitational-Wave Observatory“ (LIGO).
As electromagnetic radiation is produced by acceleration of charges, so are gravitational waves produced by accelerating mass distributions, such as supernova explosions or binary neutron stars that spiral into each other. Gravitational waves are oscillating deformations of space-time that propagate at the speed of light. The deformation occurs perpendicular to the direction of wave propagation (Fig. 1). Laser interferometers such as LIGO, GEO600 and Virgo can directly observe gravitational waves in terms of changes of distances. The analysis of the waves’ spectrum and their time evolution provides information about the nature of the astrophysical and cosmological event that produced the wave. In the past, astronomy was mainly based on electromagnetic radiation, such as visible light, radio waves or gamma rays. The possibility of observing gravitational waves opens a new window onto the universe. In principle gravitational waves allow for “looking” into neutron stars and for observing the early big bang, at times when light not even existed.
The analysis of the event GW150914 has shown that it was produced by two merging black holes at a distance from earth of about 1.3 billion light years. The masses of the two initial black holes and the mass of the final black hole could also be determined (36 and 29 and 62 solar masses). The missing mass of about 3 solar masses was radiated away in terms of gravitational waves.
The observation of GW150914 is not just the first observation of gravitational waves but also the first observation of merging black holes and the first proof of the existence of stellar mass black holes.
In case of questions please contact:
Prof. Dr. Roman Schnabel
Institut für Laserphysik und Zentrum für Optische Quantentechnologien
Tel. 040 8998-5102