LEXINGTON, Ky. — An international research team led by the Université de Montréal and including a University of Kentucky astronomer has solved a decades-old puzzle about how supermassive black holes continue to gain mass despite releasing enormous amounts of energy into space.

The findings, published in the Astrophysical Journal Letters, offer the clearest evidence yet of a self-sustaining cycle in which cooling gas flows inward to feed black holes while powerful jets push material outward.

Gary Ferland, a professor of astronomy at UK's College of Arts and Sciences, contributed critical computational tools to the research. He used Cloudy, a sophisticated spectral simulation code he developed at the university more than 45 years ago, to interpret data from NASA's James Webb Space Telescope observing the galaxy NGC 4696 at the center of the Centaurus Cluster, approximately 145 million light-years from Earth.

"The James Webb Space Telescope observes light from gas and dust under conditions that could never be studied before," Ferland said in a statement. "JWST includes superb spectrometers that reveal the physical conditions, motions and chemical composition of gas in unprecedented detail."

The researchers found a rotating disk of gas surrounding the black hole connected to larger streams of infalling material extending throughout the galaxy. Gas flows along these filaments toward the disk and ultimately toward the black hole itself, the observations revealed.

For decades, astronomers have been puzzled by an apparent paradox: active supermassive black holes release tremendous energy through jets that heat surrounding gas, a process that in theory should cut off their fuel supply. The new observations suggest that heated gas can cool, condense into long filaments and flow back inward, creating a self-regulating cycle that continually replenishes the black hole.

"Our observations reveal how cool streams of gas can feed the black hole despite the energy it releases, helping explain how galaxies and their central black holes evolve together," Ferland said.

Ferland's Cloudy code, which he began developing at Cambridge University in 1978, is used by astronomers worldwide to interpret light from astronomical objects. The open-source software has become one of the most widely used tools in astrophysics, cited in hundreds of research papers annually.

Ferland is now conducting follow-up research using Cloudy to analyze the detailed spectrum collected by the James Webb Space Telescope and investigate the physical conditions of gas surrounding the black hole. Two additional papers analyzing emission lines from elements such as carbon, oxygen and nitrogen are currently underway.

"JWST allowed us to watch gas flowing into the rotating disk around the black hole for the first time," Ferland said. "We are much closer to understanding how supermassive black holes regulate the evolution of galaxies."