A new study proposes that the dusty regions surrounding active supermassive black holes could be fertile grounds for planet formation. Based on computer modeling, researchers argue that these environments may host millions of planets and perhaps the largest planetary populations in the universe.
The idea challenges the traditional image of supermassive black holes as purely destructive objects. While these cosmic giants are known for consuming surrounding matter, the new research suggests that conditions in their outer disks may allow dust to gather and grow into planetary bodies on a remarkable scale.
Supermassive black holes occupy the centers of most large galaxies. During active phases, they accrete gas and dust from their surroundings, creating what astronomers call active galactic nuclei, or AGNs.
Planet formation is usually associated with young stars. In conventional models, planets emerge within rotating disks of gas and dust, where particles gradually stick together and form larger structures. The new study examines whether a similar process could occur much farther from the central black hole, within the dusty outer regions of AGN disks.
A Familiar Environment In An Unexpected Place
The research centers on the outer edges of AGN disks, known as dust tori. According to the paper Active Galactic Nucleus Tori: Potential Birthplace to Millions of Planets, these regions possess temperatures and physical conditions comparable to those found in planet-forming disks around young stars.
That resemblance led the researchers to investigate whether dust in AGN tori could survive long enough to begin the process of planetary growth. If grains of dust remain stable, they can collide and accumulate into progressively larger bodies, a mechanism already associated with planet formation elsewhere in the universe.
To test the idea, Barry McKernan of the City University of New York and his colleagues developed a computer model of a magnetized black hole disk. The model incorporated data on temperatures and gases present within the outer ring of the AGN environment.
The team then calculated several key factors linked to planetary development, including the rate at which dust could clump together and the likely sizes of resulting objects. As stated by the researchers, the calculations indicate that planets can indeed form within these dusty structures surrounding active supermassive black holes.
A Recipe for Rapid Planet Formation
The study also explored what happens after the first planetary bodies appear. Researchers estimated how much additional gas and dust these objects could accrete over periods lasting millions of years.
Their findings suggest that the AGN environment may allow planets to grow more rapidly than those forming around ordinary stars. Dense concentrations of material, combined with the influence of the surrounding gravitational environment, could provide a substantial reservoir for continued growth. The paper explained that some of these worlds could become much larger than Earth and may even exceed Jupiter in size. The authors emphasize the scale of the process, writing that:
“Our approximate model suggests that AGN dust tori host the largest populations of planets in the universe.”
The statement reflects one of the study’s central conclusions: if the proposed mechanism operates as modeled, active galactic nuclei could contain enormous numbers of planets forming simultaneously within their dusty outer regions.
Tracing the Journey from Planets to Stars
The researchers also identified a possible pathway extending beyond planet formation. Some objects may continue accreting material until they reach stellar masses. As stated in the paper:
“Vigorous accretion can occur, leading to objects with stellar masses—defining a core accretion channel for star formation.”
In this scenario, bodies that begin forming through processes associated with planets could ultimately become stars after accumulating enough matter. The team additionally predicts the possible formation of unusual massive objects composed largely of dust. These bodies would differ from planets observed around ordinary stars and would represent a class of objects not currently known in conventional planetary systems.
The work remains theoretical and awaits observational confirmation. As Bhupendra Mishra and colleagues noted, direct evidence will be needed to determine whether AGN dust tori truly function as planetary nurseries.
