A pair of distant cosmic black hole mergers, measured just one month apart, is improving how scientists understand the formation and evolution of the most violent deep-space collisions in the universe.
Data collected from the events, detected in October and November of 2024, validates with unprecedented accuracy fundamental laws of physics that were predicted more than 100 years ago by Albert Einstein.
Analysis of the gravitational waves generated by the mergers, led by the international LIGO-Virgo-KAGRA Collaboration and published in The Astrophysical Journal Letters, also rules out certain exotic particles proposed by new theories of physics, tightening the search for unknown elementary particles.
Co-author Dr Fabio Antonini from the Gravity Exploration Institute at Cardiff University said: "In this study, we are trying to answer fundamental questions about how black holes form, grow, and interact.
"Most are thought to form when massive stars collapse, but recent observations suggest some may form in stellar clusters from earlier black hole mergers—through a process called hierarchical merging."
By studying these two new events, we aimed to determine whether 'second-generation' black holes truly exist - a discovery that could reveal how stars evolve and how stellar clusters and galaxies take shape across the Universe.
Gravity Exploration Institute
Astronomy Group
Cardiff Hub for Astrophysics Research and Technology
Gravitational waves are ripples in space-time that result from cataclysmic events in deep space, with the strongest waves produced by the collision of black holes.
GW241011, the first merger analysed in the study, occurred approximately 700 million light years away and resulted from the collision of two black holes weighing around 20 and 6 times the mass of the sun.
The larger of the two merging black holes in GW241011 is one of the fastest rotating black holes observed to date.
GW241011 allowed us to test Einstein's theory of general relativity with unprecedented precision, confirming that black holes behave exactly as predicted even under some of the most extreme conditions in the universe.
Almost one month later, GW241110 was detected around 2.4 billion light years away and involved the merger of black holes about 17 and 8 times the mass of the sun.
While most observed black holes spin in the same direction as their orbit, the primary black hole of GW241110 was noted to be spinning in a direction opposite to its orbit – a first of its kind.
Together, the detection of GW241011 and GW241110 highlight the remarkable progress of gravitational-wave astronomy in uncovering the properties of merging black holes, the authors claim.
"GW241011 and GW241110 are some of the most novel events among the several hundred that the LIGO-Virgo-KAGRA network has observed since the very first direct detection in September 2015," said Professor Stephen Fairhurst, the LIGO Scientific Collaboration spokesperson based at Cardiff University."
With both events having one black hole which is both significantly more massive than the other and rapidly spinning, they provide tantalising evidence that these black holes were formed from previous black hole mergers.
Gravity Exploration Institute
Gravitational waves were first predicted by Albert Einstein as part of his general theory of relativity in 1916, but their presence – though proven in the 1970s – wasn't directly observed by scientists until just 10 years ago, when the LIGO observatory confirmed detection of the waves as the result of a black hole merger.
Today, LIGO-Virgo-KAGRA is a worldwide network of advanced gravitational-wave detectors and is in the midst of its fourth observing run, O4. The current run started in late May 2023 and is expected to continue through mid-November of this year. To date, approximately 300 black hole mergers have been observed through gravitational waves, including candidates identified in the ongoing O4 run.
As an experimentalist, it's always exciting to see how the work my colleagues and I put into make the gravitational wave detectors better and better truly does lead to these fantastic new discoveries about our universe.
"Planned upgrades to the LIGO, Virgo, and KAGRA detectors will enable further observations of similar systems, enabling us to better understand both the fundamental physics governing these black hole binaries and the astrophysical mechanisms that lead to their formation," added Professor Fairhurst.
The paper, 'GW241011 and GW241110: Exploring Binary Formation and Fundamental Physics with Asymmetric, High-Spin Black Hole Coalescences' is published in The Astrophysical Journal Letters .
