Two gravitational wave events within 10 days: black holes have been discovered that eat neutron stars - "like Pac-Man"

The Laser Interferometer Gravitational Wave Observatory (LIGO) in the US and the Virago Gravitational Wave Observatory in Italy captured the gravitational waves from the death spiral and merger of a neutron star with a black hole, not once but twice. The findings were recently published in The Astrophysical Journal Letters

Scientists have discovered for the first time black holes that eat neutron stars, "like Pac-Man", in a discovery that documents the collision between the two most extreme and mysterious objects in the universe.

The Laser Interferometer Gravitational Wave Observatory (LIGO) in the US and the Virago Gravitational Wave Observatory in Italy captured the gravitational waves from the death spiral and merger of a neutron star with a black hole, not once but twice. The findings were recently published in The Astrophysical Journal Letters.

The researchers say their observations will help unravel some of the universe's most complex mysteries, including the building blocks of matter and the workings of space and time.

More than a thousand scientists participated in the world-first discoveries, with many of the leaders from Australia, including the Australian National University (ANU).

Research Professor Susan Scott of ANU's School of Physics Research in the Center for Gravitational Astrophysics, a co-author of the study, said the events occurred about a billion years ago but were so massive that we can still detect their gravitational waves today.

"These collisions shook the universe to its core and we detected the ripples they sent moving powerfully throughout the cosmos," she said.

"Every such collision is not just a meeting between two massive and dense objects. It's basically like Pac-Man, when a black star swallows its companion neutron star whole."

"These are amazing events and we have waited a very long time to witness them. So it's great to finally capture them."

One event involved a black hole with a mass nine times that of our sun and a neutron star with twice the mass of our sun. The other event involved a black hole with a mass about six times that of our Sun and a neutron star with a mass 1.5 times that of our Sun.

Professor Scott, who is also principal investigator at the ARC Center of Excellence for the Detection of Gravitational Waves (OzGrav), said the international team had previously captured many events involving two colliding black holes as well as two colliding neutron stars.

"We have now completed the last part of the suite with the first verified observations of gravitational waves from the collision of a black star and a neutron star," she said.

Dr Johannes Eichholz, from ANU's Center for Gravitational Astrophysics and co-researcher at OzGrav, said the two discoveries were originally made on 5 and 15 January 2020.

"Discoveries of this kind are very rare," he said.

"We discovered these events not once but twice within ten days."

"Like the ripples from these two events, felt a billion years later, these findings will have a major impact on our understanding of the universe for many years to come."

for the scientific article

More of the topic in Hayadan:

• What are gravitational waves?
• A new record in the measurement of an ultra-weak gravitational field
• Astronomers discovered a merger of a black hole and a neutron star, then another just ten days later
• Will gravitational waves be able to shed light on the expansion rate of the universe?