Black holes have been detected eating neutron stars "like Pac-Man" - a first-time discovery.

Astrophysicists spotted two instances of this violent cosmic event using the Advanced LIGO and Virgo gravitational wave detectors.

Previous gravitational wave detections have spotted black holes colliding, and neutron stars merging.

However, this is the first time scientists have detected a collision from one of each.

Gravitational waves are produced when celestial objects collide and the energy created causes ripples in the fabric of space-time which travel all the way to the detectors on Earth.

More than 1,000 scientists were involved with the world-first detections, with many from Australia, including the Australian National University, leading the way.

Professor Susan Scott said the events occurred about a billion years ago but were so massive we are still able to see their gravitational waves today.

She explained: "These collisions have shaken the universe to its core and we've detected the ripples they have sent hurtling through the cosmos.

"Each collision isn't just the coming together of two massive and dense objects.

"It's really like Pac-Man, with a black hole swallowing its companion neutron star whole."

On 5 January last year, 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.

They 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.

But on 15 January a second signal was again coming from the final orbits and smashing together of another neutron star and black hole pair.

Researchers from Cardiff University, who form part of the LIGO Scientific Collaboration, helped to analyse both events, unpicking the gravitational wave signals and painting a picture of how the extreme collisions played out.

Since the first direct detection of gravitational waves in 2015, astronomers have predicted that this type of system could exist, but without any compelling observational evidence.

The findings, published in The Astrophysical Journal Letters, provide new clues about how black holes and neutron stars form.