New study suggests some supermassive black holes may be smaller than previously thought

A distant supermassive black hole may be smaller than previously thought, a finding that could reshape how scientists view the growth of these cosmic giants in the universe’s youth. In a galaxy about 12 billion light-years from Earth, researchers measured the black hole at its core to be roughly 800 million solar masses — about one-tenth the mass earlier estimates had implied. The result challenges long-standing methods used to weigh black holes in the distant, early universe and suggests a need to revisit models of cosmic evolution.

To reach that conclusion, the team employed GRAVITY+, a cutting-edge instrument that combines light from four telescopes at the European Southern Observatory’s Paranal Observatory to act as a single telescope about 100 meters across. By tracking the precise position and motion of gas orbiting near the black hole, scientists can infer the black hole’s mass with far greater accuracy than previous approaches that relied on indirect relations calibrated in the nearby universe. The researchers describe their method as directly measuring the black hole’s influence on surrounding gas rather than inferring mass from local scaling relations.

Co-author Professor Seb Hoenig of the University of Southampton said the findings indicate that the techniques historically used to weigh these objects may not be reliable in the early universe. Our results suggest the methods to weigh these black holes used previously are just not working reliably in the early universe. It could lead to a re-evaluation of our models of cosmic evolution.

By focusing on a quasar—an extremely bright and distant black hole—the team could test whether local relations hold when the universe was much younger. The results imply that some seemingly gigantic black holes might have appeared larger because of observational effects rather than actual mass. Dr. Taro Shimizu of the Max-Planck Institute for Extraterrestrial Physics explained that GRAVITY+’s capability to integrate light from multiple telescopes enables highly precise measurements of gas motion near the event horizon. By determining both the location and speed of the gas, the team can directly weigh the black hole.

The analysis also showed that the black hole was consuming gas at a rate faster than previously thought. An intense outflow of gas, traveling at about 6,200 miles per second (10,000 km/s), was detected emanating from the core. The researchers say this radiation-driven wind could have biased earlier measurements, making the black hole seem larger than it truly is when only indirect indicators were used. Dr. Richard Davies, a co-author from the Max-Planck Institute for Extraterrestrial Physics, noted that the prior estimates were based on relationships calibrated in the local universe, which may not apply to the early cosmos. He added that while the black hole remains enormous by any measure, the discrepancy highlights how measurement methods can shape our understanding of black hole demographics in the early universe.

If other distant supermassive black holes prove to be smaller than previously thought, scientists may need to rethink how rapidly galaxies and their central black holes grew in the universe’s first few billion years. The study’s authors emphasize the importance of applying independent mass measurements to distant SMBHs and incorporating flexible models that account for possible differences in early cosmic conditions. The findings, published in Astronomy & Astrophysics, contribute to an ongoing reevaluation of black hole growth mechanisms and their role in shaping galaxy evolution.

Black holes form when massive stars collapse or through direct collapse of gas clouds, followed by accretion of surrounding material. In the modern universe, supermassive black holes sit at the centers of most large galaxies and are thought to co-evolve with their hosts. Yet questions remain about how so many grew to enormous sizes so quickly after the Big Bang. The new measurements underscore the need for continued use of advanced observational tools, like GRAVITY+, to probe the physics of black holes in the distant, formative epochs of the cosmos.