Physicists confirm two cases of “elusive” black hole/neutron star mergers

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Ars Technica 29 June, 2021 - 07:00am 37 views

Scientists catch 1st glimpse of a black hole swallowing a neutron star

Space.com 29 June, 2021 - 07:02am

"These were not events where the black holes munched on the neutron stars like the Cookie Monster and flung bits and pieces about," one physicist said.

Now, researchers say they have done just that, observing the unique ripples in space-time caused by such a collision.

"With this new discovery of neutron star-black hole mergers outside our galaxy, we have found the missing type of binary," Astrid Lamberts, a CNRS researcher at Observatoire de la Côte d'Azur in France, said in a statement. "We can finally begin to understand how many of these systems exist, how often they merge, and why we have not yet seen examples in the Milky Way."

GW200105 wasn't detected as definitively, but scientists suspect it was a merger between a black hole about nine times the mass of the sun and a neutron star about twice as massive as the sun about 550 million and 1.3 billion light-years away.

However, the scientists do suspect that at least for these particular mergers, there was no light signal to see.

Given the two January 2020 observations, scientists now predict that one merger between a black hole and a neutron star occurs once per month within one billion light-years of Earth.

The two new collision observations aren't enough to determine what's going on, but scientists do hope that eventually, gravitational wave detections will solve the puzzle.

The twin LIGO detectors, Virgo and KAGRA are all undergoing preparations for the partnership's fourth observing run, which is scheduled to begin next summer. Scientists say that work could see the partnership detecting one gravitational wave signal every day, opening scientists to immensely more information about what is taking place across the cosmos, as in these dramatic mergers.

The results are described in a paper published on June 29 in the journal The Astrophysical Journal Letters.

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