2025 News 2025: UMass Dartmouth faculty involved in discovery of the largest-ever black hole merger

UMassD faculty help LIGO uncover signal that upends black hole formation theories

Scientists at the Laser Interferometer Gravitational-Wave Observatory (LIGO), including UMass Dartmouth Assistant Professors Sarah Caudill (physics) and Vijay Varma (data science & mathematics) recently detected the largest ever merger of colliding black holes, a discovery that has major implications for researchers' understanding of how such bodies grow in the universe.

The event, known as GW231123, produced a rapidly spinning black hole approximately 225 times the mass of our Sun. The enormous mass and extremely high spin rate push the limits of Einstein's theory of general relativity and gravitational-wave detection technology. Extracting accurate information from the signal required the use of models that account for the intricate dynamics of highly spinning black holes.

Caudill is part of LIGO's search team that makes initial detections and is one of the primary developers of the GstLAL software used to find gravitational-wave signals buried in data.

"GW231123 really challenged our search methods. It sits on the edge of what we are able to detect and required a deeper look with more refined analyses to correctly model the noise," said Caudill. "Discoveries like this one remind us that we should continue to widen our search horizons and rethink our analysis methods because we never know what new doors will open."

"At UMass Dartmouth, students can join one of the world's largest gravitational-wave research teams ... By blending physics, computational mathematics, and machine learning, our interdisciplinary group is driving the next wave of discoveries in both ground- and space-based gravitational-wave astronomy."

Varma, who co-developed one of the main models used to interpret the discovery alongside Associate Professor Scott Field, contributed to the paper's scientific analysis. The modeling technique Numerical Relativity Surrogate (referenced in the paper as NRSur), was developed in part at UMass Dartmouth and was crucial for understanding the properties of the new black hole.

"GW231123 is a landmark observation not just for understanding black hole growth, but also because this is the first time we are seeing clear disagreements between different gravitational wave models used to analyze the signal," said Varma. "The LIGO detectors have become so good that they are posing a challenge for our theoretical models. Our group's focus is on developing even better models using machine learning methods. Such models will be needed to extract black hole astrophysics from future observations."

Opportunities for UMassD students

This milestone builds on UMass Dartmouth's growing reputation in gravitational wave and data science research. The university is a full member of the Laser Interferometer Space Antenna (LISA) Consortium—the next generation space-based gravitational wave observatory—and continues to attract talented graduate students from around the world to STEM OPT programs in data science, engineering, and physics.

Field, Varma, and two graduate students found the first ever evidence of a fast-moving black hole in 2022 while observing data from LIGO machines. In 2023, PhD student Tousif Islam was the lead author on a study that identified the second-fastest black hole ever observed at the time—GW191109, now considered the third-fastest.

"At UMass Dartmouth, students can join one of the world's largest gravitational-wave research teams—second in Massachusetts only to MIT—working side-by-side with faculty on NSF-funded projects," said Field. "We're engaged with LIGO, LISA, and the Simulating eXtreme Spacetimes (SXS) collaboration, tackling everything from waveform modeling and black hole merger simulations to data analysis and astrophysical interpretation.

"By blending physics, computational mathematics, and machine learning, our interdisciplinary group is driving the next wave of discoveries in both ground- and space-based gravitational-wave astronomy."

The paper is still in preprint and currently undergoing a peer review process.