First extreme pairs spotted

A new piece has been added to the puzzle of gravitational waves, following the first ever detections of waves from a ‘mixed’ source – one where both a neutron star and a black hole collide.

Two such events were spotted back in January 2020 by the LIGO and Virgo gravitational wave observatories, but their origin was only recently confirmed.

It’s been theorised for decades that there are binary systems featuring a black hole and a neutron star, but none have been found within our Galaxy.

“These are our first robust detections of neutron-star–black-hole mergers. This important new source of gravitational waves could help us answer crucial questions about how, and where, neutron stars and black holes form in the cosmos,” says Prof Sheila Rowan, director of the University of Glasgow’s Institute for Gravitational Research and part of the LIGO collaboration.

The illustration here shows one of these mixed sources, a neutron star spiralling into a black hole.