Scientists detect the most massive black hole collision yet

Rodiano Bonacci
Dicembre 6, 2018

A team of scientists formed by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) in the USA and the Australian National University (ANU) in Canberra have detected the gravitational waves that resulted from the biggest collision of black holes ever observed. 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.

Gravitational waves carry information about their origins and about the nature of gravity that can not otherwise be obtained.

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 and candidate events of the two observing runs as well as describing the characteristics of the merging black hole population. In the coalescence, that happened nearly 9 billion years ago, an equivalent energy of nearly five solar masses has been converted into gravitational radiation.

Another event GW170818 not highlighted by mass or distance. That makes it the next best localized gravitational-wave source after the GW170817 neutron star merger. The second run, from November 30, 2016, to August 25, 2017, produced seven more binary black-hole mergers (including the four just announced) and a binary neutron-star merger, supported by a simultaneous gamma-ray burst and signals in the rest of the electromagnetic spectrum.

Thanks to the LIGO and Virgo detectors, scientists on Earth can now capture these signals, which lets them study the collisions and objects involved.

'This event also had black holes spinning the fastest of all mergers observed so far.

"In only one year, LIGO and VIRGO together have significantly advanced gravitational-wave science, and the rate of disclosure recommends the most staggering discoveries are yet to come", Denise Caldwell, the director of the National Science Foundation's Division of Physics said in an announcement. As LIGO grows more sensitive, even more are on the way.

"The new catalog is another proof of the exemplary global collaboration of the gravitational wave community and an asset for the forthcoming runs and upgrades" adds EGO Director Stavros Katsanevas.

While listening to gravitational waves, we usually use memorized sounds called templates. 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.

Professor Susan Scott, who is Leader of the General Relativity Theory and Data Analysis Group at ANU, said the team discovered the four collisions by re-analyzing data from Advanced LIGO's first two observing runs.

'We can't see these events any other way except through gravitational waves, as they don't emit light or radio waves. because they're black holes, ' she said.

"Gravitational waves give us unprecedented insight into the population and properties of black holes", Chris Pankow, an astrophysicist at Northwestern University, said in a statement - for example, that most black holes formed by stars encompass less than 45 suns' worth of material.

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