Black hole jets may control star formation across entire galaxies: Study
Babushahi Bureau/PIB
New Delhi, September 25, 2026: A team of astronomers from India and the United States has identified a possible mechanism through which supermassive black holes at the centres of galaxies can influence vast reservoirs of gas surrounding them and potentially determine how actively their host galaxies form stars.
The study, involving researchers from the Raman Research Institute (RRI) and Arizona State University, found evidence that jets of extremely hot plasma launched by supermassive black holes can disturb and energise gas in the circumgalactic medium (CGM) — a huge, diffuse reservoir extending far beyond a galaxy’s visible disk.
The findings were published in The Astrophysical Journal Letters.
The CGM can extend to around 10–20 times the size of a galaxy and contains gas that can eventually cool and collapse to form new stars. Astronomers have long proposed that energy released by supermassive black holes could prevent this gas from cooling sufficiently, thereby limiting star formation. However, the precise mechanism has remained unclear.
The new study provides evidence that black hole jets may influence the CGM in a highly directional manner.
According to the researchers, when a jet first encounters the surrounding gas, it transfers energy to it, heating and ionising the gas. This can prevent the gas from cooling and clumping together to form stars.
The researchers searched for the characteristic glow produced by this energised gas. When measurements were averaged in all directions around the galaxies, they did not detect a significant signal. However, a strong signal emerged when they examined the regions aligned with the black hole jets.
“This told us that the jet was illuminating only the gas in its path, rather than affecting the gas equally in all directions,” said Namrata Roy, Assistant Professor in the Astronomy and Astrophysics Division at RRI and lead author of the study.
The strongest signal was detected at two locations: near the edge of the galaxy’s stellar disk, where the jet first encounters the CGM, and near the outer boundary of the CGM, where the slowing jet interacts with the surrounding gas again.
The researchers compared the process to the transfer of energy when a moving object strikes a hard surface. The energy deposited by the jet can heat and disturb the gas, making it less likely to collapse into the dense clouds required for star formation.
Supermassive black holes can be remarkably small compared with their host galaxies. While an individual black hole may be comparable in size to the Solar System, its influence can extend across a galaxy containing billions of stars and a vast surrounding gas reservoir.
The findings suggest that black holes may therefore influence the evolution of their host galaxies well beyond their immediate surroundings.
“The wider implication is that black holes can shape the lives of galaxies far beyond the small central region where they sit,” said Sanchayeeta Borthakur, Associate Professor at Arizona State University and a co-author of the study.
The researchers said the observations provide a new way of understanding how galaxies transition into less active, more passive systems by regulating the supply of gas available for future star formation.