Gravitational waves detected from second pair of colliding black holes

June 15, 2016
Steve Orlando

Four months after stunning the world with the announcement that they had detected gravitational waves from a collision of two black holes and confirmed a major prediction of Albert Einstein’s 1915 general theory of relativity, scientists say they’ve done it again.

The second event, detected Dec. 25 by both of the twin Laser Interferometer Gravitational-Wave Observatory, or LIGO, detectors, located in Livingston, Louisiana, and Hanford, Washington, sheds new light on black holes and how common they are.
“This second detection confirms our expectations that binary black holes are abundant in the universe and LIGO will see many more in the future” said Sergey Klimenko, a University of Florida scientist who is analyzing the data from LIGO, the same detectors used in the first detection.  
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.
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 55 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.
The first detection of gravitational waves, which occurred Sept. 14 and was announced Feb. 11 F, was a milestone in physics and astronomy and marked the beginning of the new field of gravitational-wave astronomy.
“The contributions of the University of Florida LIGO group are everywhere in LIGO.” says Caltech's David H. Reitze, executive director of the LIGO Laboratory and Professor of Physics at the University of Florida. ”We led the design and construction of the Input Optics, and played important intellectual roles in many of the other subsystems.  The UFLIGO group also leads one of the main data analysis pipelines searching for the most general sources of gravitational waves, those coming from astrophysical sources that defy theoretical prediction.”
Before moving to Caltech in 2011, David Reitze managed the development of the Advanced LIGO Input Optics at UF, the optical system with the largest number of optical components. “When he left, we not only lost a good friend but also a great scientist with exceptional organizational skills in our department; but the IO was in such a good shape and the entire IO team at UF was so strong that finishing the five million dollar project turned out to be fairly straight forward”, said Prof. Guido Mueller who, together with Prof. David Tanner, has lead the UF Input Optics group since 2011.
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.
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: six from Centre National de la Recherche Scientifique (CNRS) in France; eight from the Istituto Nazionale di Fisica Nucleare (INFN) in Italy; two
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 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.

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