Detection of the Most Massive Black Hole Merger to Date

LSU physicists work to improve astrophysical sensitivity of LIGO detectors for advanced discoveries.

The LIGO-Virgo-KAGRA (LVK) Collaboration has detected the merger of the most massive black holes ever observed with gravitational waves, using the US National Science Foundation-funded (NSF) LIGO Hanford and Livingston Observatories. The merger produced a final black hole more than 225 times the mass of our Sun. The signal, designated GW231123, was observed during the fourth observing run (O4) of the LVK network.

The two black holes that merged were approximately 100 and 140 times the mass of the Sun. In addition to their high masses they are also rapidly spinning, making this a uniquely challenging signal to interpret and suggesting the possibility of a complex formation history.

“As we are now approaching a decade of observations after the first detection of gravitational waves in 2015, the LIGO instruments keep delivering surprises, like the mergers of these large black holes,” said Louisiana State University Boyd Professor Gabriela González, LIGO Scientific Collaboration Spokesperson 2011-2017. “Scientists in Louisiana and worldwide, including our group at LSU, work hard on improving the astrophysical sensitivity of the detectors, and it pays off. There will be much more to come this year!”

To date, approximately 300 black-hole mergers have been observed through gravitational waves, including candidates identified in the ongoing O4 run. Until now the most massive confirmed black-hole binary was the source of GW190521, with a much smaller total mass of “only” 140 times that of the sun.

Gravitational-wave detectors such as LIGO in the United States, Virgo in Italy, and KAGRA in Japan are designed to measure minute distortions in spacetime caused by violent cosmic events like black hole mergers.

“GW231123, in my opinion, is one of the most spectacular events we've ever detected,” said LSU PhD Candidate Zach Yarbrough. “The two initial black holes were both over 100 times more massive than our sun, and the final black hole that they merged to create is an astonishing 225 times more massive than our sun, or about 75 million times more massive than the Earth.”

The LIGO Livingston observatory is located on LSU property, and LSU faculty, students and research staff are major contributors to the 15-nation international LIGO Science Collaboration, or LSC.

“This is the most massive event ever observed by the LVK Collaboration!” Yarbrough said “ I am incredibly lucky to be a graduate student in LSU’s Experimental Gravity group and part of the LVK during such an exciting time. Since joining in Fall 2022, I’ve seen over 200 detections, and GW231123 stands out as a true highlight. None of this would be possible without the contributions of Dr. González, past and present LSU faculty and student researchers, and the global LVK team — there has truly never been a better time to be a Gravitational Wave researcher and I'm grateful every day for the opportunity to do this work.”

LSU’s investment in gravitational-wave detection spans more than five decades, and is among the longest of the institutions contributing to the discoveries. LSU faculty, students and scholars have had leading roles in the development of several generations of gravitational wave detectors, in their commissioning and operation as well as the collaborations formed.

LSU’s pioneering role in this science began in 1970 with the arrival of William Hamilton, now professor emeritus, who along with Physics Professor Warren Johnson, built and operated previous-generation cryogenic bar gravitational wave detectors on the Baton Rouge campus for many years. Currently, LSU Professor Thomas Corbitt focuses his research on advanced quantum metrology techniques for a future detector. These examples of LSU faculty involvement represent more than 55 years of cutting-edge research, with state and institutional commitment, and long-standing multimillion dollar support from NSF producing educational opportunities for students and postdoctoral researchers, several of whom have gone on to professorial appointments around the world.

“Looking ahead, we have to find ways to make detectors even more sensitive, so that we can observe other types of events that are not as loud as black holes colliding,” said Corbitt. “The discrete, or quantum, nature of the light used in the measurement limits the sensitivity, but we are developing methods to manipulate this noise source in order to improve future detectors.”

LSU’s campus is located 25 miles from LIGO Livingston in Baton Rouge. LSU has about 1,600 faculty; 31,000 students; and is classified by the Carnegie Foundation as "Doctoral/Research Universities-Extensive." LSU is the only research university in the US located close enough for students and faculty to engage in daily interactions with a LIGO observatory. LSU faculty and administrators, including the late Chancellor Emeritus James Wharton, led the effort to bring LIGO to Louisiana, and the university owns the land on which LIGO is operated.

 

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Mimi LaValle

LSU Physics & Astronomy

225-439-5633

mlavall@lsu.edu