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Four new gravitational waves detected

Press Trust of India  |  Washington 

Scientists have made four new detections of -- in the fabric of space and time -- emanating from separate black hole mergers.

So far the US-based LIGO and Europe-based gravitational-wave detectors have recorded from a total of 10 black hole mergers and one merger of neutron stars.

The new events are known as GW170729, GW170809, GW170818, and GW170823, in reference to the dates they were detected.

GW170729, detected in the second observing run on July 29, 2017, is the most massive and distant gravitational-wave source ever observed.

In this coalescence, which happened roughly 5 billion years ago, an of almost five solar masses was converted into gravitational radiation, researchers said.

From September 12, 2015, to January 19, 2016, during the first LIGO observing run since undergoing upgrades in a program called Advanced LIGO, from three mergers were detected.

The second observing run, which lasted from November 30, 2016, to August 25, 2017, yielded one binary neutron star merger and seven additional mergers, including the four new gravitational-wave events being reported now.

GW170814 was the first merger measured by the three-detector network, and allowed for the first tests of gravitational-wave polarization (analogous to light polarization).

The event GW170817, detected three days after GW170814, represented the first time that gravitational waves were ever observed from the merger of a binary neutron star system.

What is more, this collision was seen in gravitational waves and light, marking an exciting new chapter in multi-messenger astronomy, in which cosmic objects are observed simultaneously in different forms of

One of the new events, GW170818, which was detected by the global network formed by the LIGO and observatories, was very precisely pinpointed in the sky.

The position of the binary black holes, located 2.5 billion light-years from Earth, was identified in the sky with a precision of 39 square degrees.

That makes it the next best localised gravitational-wave source after the GW170817 neutron star merger.

"The release of four additional binary black hole mergers further informs us of the nature of the population of these in the universe and better constrains the event rate for these types of events," said Albert Lazzarini, of the at in the US.

"The next observing run, starting in Spring 2019, should yield many more gravitational-wave candidates, and the science the community can accomplish will grow accordingly," said David Shoemaker, for the LIGO Scientific Collaboration.

The scientific papers describing the findings, which are being initially published on the arXiv repository of electronic preprints, present detailed information in the form of a catalogue of all the gravitational wave detections and candidate events of the two observing runs.

Almost all black holes formed from stars are lighter than 45 times the mass of the Sun, researchers said.

Thanks to more advanced and better calibration of the instruments, the accuracy of the astrophysical parameters of the previously announced events increased considerably.

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)

First Published: Tue, December 04 2018. 11:35 IST
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