Scientists have for the first time detected black holes eating neutron stars, “like Pac Man,” in a discovery documenting the collision of the two most extreme and enigmatic objects in the Universe.
The Laser Interferometer Gravitational-Wave Observatory (LIGOThe Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory supported by the National Science Foundation and operated by Caltech and MIT. It’s designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. It’s multi-kilometer-scale gravitational wave detectors use laser interferometry to measure the minute ripples in space-time caused by passing gravitational waves. It consists of two widely separated interferometers within the United States—one in Hanford, Washington and the other in Livingston, Louisiana.”>LIGO) in the US and the Virgo gravitational-wave observatory in Italy have captured the gravitational wavesGravitational waves are distortions or ripples in the fabric of space and time. They were first detected in 2015 by the Advanced LIGO detectors and are produced by catastrophic events such as colliding black holes, supernovae, or merging neutron stars.”>gravitational waves from the death spiral and merger of a neutron starA neutron star is the collapsed core of a large (between 10 and 29 solar masses) star. Neutron stars are the smallest and densest stars known to exist. Though neutron stars typically have a radius on the order of just 10 – 20 kilometers (6 – 12 miles), they can have masses of about 1.3 – 2.5 that of the Sun.”>neutron star with a black holeA black hole is a place in space where the pull of gravity is so strong not even light can escape it. Astronomers classify black holes into three categories by size: miniature, stellar, and supermassive black holes. Miniature black holes could have a mass smaller than our Sun and supermassive black holes could have a mass equivalent to billions of our Sun.”>black hole, not once but twice. The findings were published recently in The Astrophysical Journal Letters.
The researchers say their observations will help unlock some of the most complex mysteries of the Universe, including the building blocks of matter and the workings of space and time.
More than 1,000 scientists were involved with the world-first detections, with many from Australia, including The Australian National UniversityFounded in 1946, the Australian National University (ANU) is a national research university located in Canberra, the capital of Australia. Its main campus in Acton encompasses seven teaching and research colleges, in addition to several national academies and institutes.”>Australian National University, leading the way.
Distinguished Professor Susan Scott, a co-author on the study based at the ANU Research School of Physics in the Centre for Gravitational Astrophysics, said the events occurred about a billion years ago but were so massive that we are still able to observe their gravitational waves today.
“These collisions have shaken the Universe to its core and we’ve detected the ripples they have sent hurtling through the cosmos,” she said.
“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.
“These are remarkable events and we have waited a very long time to witness them. So it’s incredible to finally capture them.”
One event included a black hole with a mass nine times bigger than our own sun and a neutron star with two times our sun’s mass. The other event included a black hole with about six times the mass of our sun and a neutron star with 1.5 times its mass.
Professor Scott, also a Chief Investigator at the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), said the international team had previously captured many events involving two black holes colliding as well as two neutron stars smashing together.
“Now, we’ve completed the last piece of the puzzle with the first confirmed observations of gravitational waves from a black hole and a neutron star colliding,” she said.
Dr. Johannes Eichholz, from the ANU Centre for Gravitational Astrophysics and an Associate Investigator with OzGrav, said the two detections were originally made on January 5 and 15, 2020.
“These kind of detections are incredibly rare,” he said.
“We haven’t detected these events once — but twice and within 10 days of each other.
“Like the ripples from these two events, which have been felt a billion years later, these findings will have a profound impact on our understanding of the Universe for many years to come.”
Reference: “Observation of Gravitational Waves from Two Neutron Star–Black Hole Coalescences” by R. Abbott, T. D. Abbott, S. Abraham, F. Acernese, K. Ackley, A. Adams, C. Adams, R. X. Adhikari, V. B. Adya, C. Affeldt, et. al., 29 June 2021, The Astrophysical Journal Letters.