Gravitational Waves : First Detection with Triple Detectors Ligo and Virgo

Scientists from Ligo and Virgo Collaborations have announced on the 27th of September 2017 the first triple-detector observation of gravitational waves from a binary-black hole merger. This was made possible by the upgrade to the Virgo instrument called “Advanced Virgo”, which joined in science observations with the two detectors of LIGO and their upgraded instruments “Advanced LIGO” on the 1st of August, and opens the way for greater precision in locating sources of gravitational waves in the sky. The international collaboration, including the Optomechanics and Quantum Measurement Group of Laboratoire Kastler Brossel, report this first as an accepted publication in the journal Physical Review Letters.

This new event confirms that black-hole pairs are relatively abundant, and mergers will contribute to the future study of black hole phenomena. The two initial black holes, of 25 and 31 solar masses respectively, merged together into a black hole of 53 solar masses, with the equivalent of 3 solar masses of energy released in the form of gravitational waves. This event took place around 1.8 million light-years from Earth ; in other words, the gravitational waves propagated through space for 1.8 million years before being detected on the 14th of August 2017 by first the Advanced LIGO Louisiana USA detector, then 8 milliseconds later by Advanced LIGO Washington State USA, and finally 6 milliseconds later by Advanced Virgo located near Pisa, Italy.

With the third detector Advanced Virgo, it allows significantly greater sky localisation of astrophysical sources of gravitational waves. These violent events can also in certain cases produce electromagnetic radiation, such as light. With only two gravitational-wave detectors, the search zone in the sky is equivalent to several thousand times the size of a full Moon. With Advanced Virgo, this search zone is around 10 times smaller, and the estimation of the source distance is also 2 times better. With a precise search zone, it offers the real chance to observe these events with optical and radio telescopes quickly.

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GW170814 : A three-detector observation of gravitational waves from a binary black hole coalescence.
The LIGO Scientific Collaboration and The Virgo Collaboration
, accepté à Physical Review Letters.
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Link to press release : CNRS

LKB Contact : Pierre-Francois Cohadon