https://www.sciencealert.com/new-ligo-virgo-gravitational-waves-neutron-stars-space-news-sept-2017

A massive international team made history in 2016 when they announced that, for the first time ever, they’d confirmed the existence of gravitational waves – ripples in the fabric of spacetime from the collision of two black holes.

Now gravitational wave astronomy has taken a leap forward with the detection of of a collision between two black holes using not two detectors, but three – vastly improving the accuracy, by a factor of about 10, with which astronomers can pinpoint the source of the waves.

The collision, in a galaxy about 1.8 billion light-years from the Milky Way, occurred between two black holes with masses about 31 and 25 times the mass of our Sun. The single black hole that resulted from this collision is about 53 times the mass of the Sun.

It’s the first observation taken using three detectors, and the first for the updated Advanced Virgo detector in Italy, in collaboration with LIGO’s two detectors in Livingston, Louisiana, and Hanford, Washington, both in the US.

The first detected ripples in the fabric of spacetime were gravitational shockwaves caused by two black holes colliding. It was a huge deal – confirmation of the last remaining major prediction by Einstein in his theory of general relativity.

Just as radio telescopy was able to detect objects and events in the universe invisible to optical telescopes, gravitational wave astronomy is becoming a new way to discover things we didn’t even know existed.

Since its first 2016 announcement, LIGO made two more gravitational wave detections from black hole collisions. This new announcement marks the fourth.

Advanced Virgo joined LIGO for an observation run on 1 August, its first time observing. The detection was made on 14 August.

It also marks the first time that scientists have been able to measure the polarisation of the gravitational waves, or the way they distort spacetime in three dimensions.