Today, Tuesday August 1st 2017, the Advanced Virgo (AdV) detector based in Europe, has officially joined “Observation Run 2” (O2) and is now taking data alongside the American twin Advanced LIGO (aLIGO) detectors. This major step forward for the VIRGO Collaboration marks the end of a multi-year upgrade program, whose primary goal was to significantly improve the detector performance in terms of sensitivity. «The last months have been spent on commissioning Advanced Virgo, and this went very well. We are eager to start our first science run, joining LIGO at this exciting time for our field», says Jo van den Brand of Nikhef and VU University Amsterdam, the spokesperson of the VIRGO collaboration.
Although the AdV sensitivity is for the time being, at a lower level of those of the aLIGO interferometers, it is adequate for confirming a potential detection with LIGO and would allow locating sources of gravitational waves in the sky with greater accuracy. The current AdV sensitivity exceeds the previous Virgo record sensitivity, achieved in 2011 before dismantling the detector to start its upgrade. AdV is now a brand new instrument comprising several new components, which have been integrated and made work together in less than one year, during the so-called commissioning phase. <Quotation from Federico Ferrini, the director of the European Gravitational Observatory>.
The O2 data-taking phase started on November 30, 2016 and will end on August 25, 2017. It has already led to the discovery of a third stellar-mass black hole binary coalescence, GW170104, recorded on January 4, 2017 and announced by LIGO and VIRGO last June 1st 2017. The joint data analyses are still ongoing while more data are being recorded, for the first time with three advanced instruments. <Quotation from David Shoemaker, the spokesperson of the LIGO Scientific Collaboration about the worldwide network>.
The present data taking period, which is more than an achievement, represents the beginning of a new era for the VIRGO Collaboration. After the completion of O2, the AdV operation will proceed to further improve the sensitivity of the detector and to gain more knowledge about the main sources of noise that are currently limiting it. Then, a new upgrade phase will start, where several key improvements will be made, among which the installation of monolithic suspensions. The mirrors will be indeed suspended by thin and strong fused-silica fibers, which will replace the current metal wires. Later, in Spring 2018, a new commissioning phase will start, with the goal of having a more sensitive detector by the time the LIGO-Virgo “Observation Run 3” (O3) starts in Fall 2018. <Quotation from Alessio Rocchi the commissioning coordinator of the VIRGO collaboration, about the challenges ahead>.
The VIRGO Collaboration, consists of more than 280 physicists and engineers belonging to 20 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; Spain with the University of Valencia; and the European Gravitational Observatory (EGO), the laboratory hosting the Virgo detector near Pisa in Italy.