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Cardiff Uni researchers play 'crucial role' in detecting black hole and neutron star merger

Artist's impression of a neutron star falling into a black hole (Image: Carl Knox, OzGrav/Swinburne)

Scientists have, for the first time, picked up the ripples in space-time caused by the collision of a neutron star and a black hole.

Two instances of this violent cosmic event have been detected using the Advanced LIGO and Virgo gravitational wave detectors, details of which were published in Astrophysical Journal Letters.

Though previous gravitational wave detections have spotted black holes colliding, and neutron stars merging, this is the first time that scientists have detected a collision from one of each.

Gravitational waves are produced when celestial objects collide and the ensuing energy creates ripples in the fabric of space-time which travel all the way to the detectors we have here on Earth.

On January 5 2020, the Advanced LIGO (ALIGO) detector in Louisiana in the US and the Advanced Virgo detector in Italy observed gravitational waves from this entirely new type of astronomical system.

The detectors picked up the final throes of the death spiral between a neutron star and a black hole as they circled ever closer and merged together.

Remarkably, on January 15, a second signal was picked up by Virgo and both ALIGO detectors – in Louisiana and Washington state – again coming from the final orbits and smashing together of another neutron star and black hole pair.

Cardiff University

Researchers from Cardiff University, who form part of the LIGO Scientific Collaboration, played a crucial role in the data analysis of both events, unpicking the gravitational wave signals and painting a picture of how the extreme collisions played out.

This involved generating millions of possible gravitational waves and matching them to the observed data to determine the properties of the objects that produced the signals in the first place, such as their masses and their location in the sky.

From the data they were able to infer that the first signal, dubbed GW200105, was caused by a 9-solar mass black hole colliding with a 1.9-solar mass neutron star.

Dr Vivien Raymond, from Cardiff University’s Gravity Exploration Institute, said: “After the detections of black holes merging together, and neutron stars merging together, we finally have the final piece of the puzzle: black holes swallowing neutron stars whole. This observation really completes our picture of the densest objects in the universe and their diet.”



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