Researchers from the LIGO and Virgo Collaborations have announced gravitational wave observations of four new binary black holes and released their first catalogue of gravitational wave events.
Since the detectors first started operation in September 2015 , the LIGO and Virgo Collaborations, which include researchers from the University of Birmingham, have completed two observation runs. During these they have detected gravitational waves from a total of ten stellar-mass binary black hole mergers - compact objects likely formed by the gravitational collapse of massive stars. They have also detected one binary neutron star coalescence - generated by two neutron stars spiraling into each other.
During the second observation run, four new gravitational wave events were discovered, all generated by the merging of binary black holes: GW170729, GW170809, GW170818 and GW170823. GW170729, detected on July 29th 2017, is the most massive and distant gravitational wave source ever observed. In the coalescence, that happened almost 9 billion years ago, an equivalent energy of almost five solar masses has been converted into gravitational radiation.
The scientific papers describing these new findings, which are being initially published on the arXiv repository of electronic preprints, present detailed information in the form of a catalog of all the gravitational wave detections.
The detections were made by the global network formed by the LIGO observatories located in Livingston, Louisiana, and Hanford, Washington, USA, and the Virgo interferometer near Pisa, Italy.
The University of Birmingham has been involved in the Advanced LIGO project since its inception. Members of the Institute for Gravitational Wave Astronomy have developed and built components for the LIGO instruments, such as the high-performance sensors and control electronics for the suspension systems. Birmingham physicists have contributed to the commissioning of the instruments leading to the performance that has enabled these remarkable observations.
Birmingham’s scientists have also developed the techniques essential to tease out the signatures of gravitational waves from the data and extensively contributed to the analysis of the data collected during the science runs that have led to the observation of these 11 binary systems. Birmingham’s researchers have pioneered the framework and analysis algorithms that are at the heart of the study of the physics of compact binary systems, their astrophysical evolution and tests of Einstein’s theory with gravitational-wave observatories.
Professor Alberto Vecchio , from the University of Birmingham’s Institute for Gravitational Wave Astronomy, said, “It’s a universe full of black holes: they pair up and collide, and they do it very frequently. Advanced LIGO has started to operate as an astronomical observatory providing us with a steady stream of new discoveries. The scene is now set to begin understanding the cosmos’ black hole factories. Three years ago only a fool would have thought we would be under a deluge of binary black holes, but now this is an intoxicating reality. And it is just the beginning”.
Professor Andreas Freise , from the University of Birmingham’s Institute for Gravitational Wave Astronomy, said, “When black holes collide they create vibrations in space and time. Now we know that this happens often: the LIGO detectors regularly detect faint echoes that tell of the last seconds in the life of a pair of black holes. These whispers from dark skies tell us about the size and the location of the dying black holes. We have become gravitational wave astronomers, creating new maps of the Universe.”
Riccardo Busciccchio, a Birmingham PhD student and member of the LIGO team, said, “We have a graveyard of 10 binary black holes that tells us a lot about their extreme violent last fractions of a second of life, and carry at the same time the signatures of their entire life both as individuals and as binary companions. As a PhD student, it has been a unique opportunity to have access to observations that are still so rare, and to study their characteristics as part of a clearly large population. You get so much enthusiasm from learning a lot to being able to participate actively in the production of scientific results of such great relevance.”
Dr Patricia Schmidt , a member of the Virgo Team who will be joining Birmingham’s Physics faculty in January 2019, said, “With almost a dozen confident gravitational-wave detections, we have truly established the field of gravitational-wave astronomy. The third observing run is on our doorstep. With an unprecedented number of gravitational-wave observations anticipated, the scientific prospects are enticing.”