Active Supermassive Black Holes May Be Engines of Star Formation, Not Just Destruction, Study Suggests

At the heart of some galaxies lie extremely bright spots—far too luminous to be lit by stars alone. Each glowing core outshines the rest of its galaxy combined, thanks to a supermassive black hole that’s devouring matter, pushing out jets and winds, and driving emissions of every type of electromagnetic radiation, from radio waves to gamma rays. Our galaxy’s own supermassive black hole is quieter.

But studying these bright regions, called active galactic nuclei (AGNs), that are sprinkled across the cosmos can teach astronomers about how stars and galaxies form—and possibly shed light on our Milky Way. Active galactic nuclei “are extreme physics laboratories,” says Niel Brandt, an astrophysicist at Penn State. They are sites where powerful gravity plays out, cloaked in high-temperature plasma.

Perhaps most importantly, they include supermassive black holes, which are thought to play a role in cosmic evolution. Their findings, published September 14 in the Astrophysical Journal, suggest that these active regions might promote star formation—contrary to what astronomers have long thought. But a supermassive black hole ejects jets and waves, which can heat up the surrounding gas—so, it seemed likely that these active cores of galaxies might squash the chance of forming stars.

A black hole consistently pulls matter in with its intense gravity, creating a hot, bright, spinning disk of debris around it known as an accretion disk. At an active galactic nucleus, magnetic fields eject some of this material in the form of jets or winds, which can travel far beyond the host galaxy. To find out what’s happening around super-bright AGNs, the team focused on nearby galaxies, because they could get high-resolution views of their centers using the Very Large Telescope in Chile and the Chandra X-Ray Observatory that’s orbiting Earth.

Detailed theoretical models, built by the researchers, offered predictions for black hole behavior that they could compare with their observations. In the end, they found a common pattern across the nine AGN-containing galaxies. The team identified areas of star formation—shaped like rings or arcs—around each of the AGNs, all located somewhere between 2,600 and 19,600 light-years from the center of their galaxies.

Due to their immense gravity, black holes are known for accreting, or pulling in, material. That process could be thought to “take over all the gas” that might otherwise help form stars, she adds. The team also mapped out the charged gas coming from the black holes.