Astronomers at New Mexico State University, the Nicolaus Copernicus Astronomical Center, and Manhattan Community College propose that the dust-rich torus surrounding an active galactic nucleus (AGN)—a galaxy’s energetic core powered by a supermassive black hole supply—behaves much like a protoplanetary disk that produces planets around young stars.
Mishra others. They suggest that AGN dust Tori harbors the largest planetary population in the universe. Image credit: ESO.
“Planets form in disks of gas and dust surrounding young stars,” said New Mexico State University astrophysicist Vladimir Lyra and his colleagues.
“However, an additional attractive environment for planet formation has emerged: the disk surrounding the AGN.”
“In recent years, important similarities have been shown between physical processes within circumstellar disks and within AGN disks.”
“These analogies suggest that the mechanisms traditionally associated with planet formation may also operate in the more extreme environment of a disk around a supermassive black hole.”
Using computer modeling of strongly magnetized AGN disks, the researchers found that dust particles ranging from a few nanometers to a few millimeters in diameter drifting from the interstellar medium can clump together, triggering a process called streaming instability.
This mechanism concentrates dust into dense filaments that collapse under their own gravity, seeding objects ranging from Earth-mass objects to super-Jupiters and, in some cases, objects above the hydrogen combustion limit, the threshold at which an object becomes massive enough to become a star.
Scientists estimate that such a disk could contain tens of millions of planetary-mass objects, with pebble accretion and gas accretion driving continued growth over the approximately 1 million to 10 million year lifetime of an AGN episode.
“We have discovered objects that are 1,000 times more massive than Earth but are made of pure dust,” Dr Lyra said.
“Not only that, but some of these objects approach the mass of the Sun.”
“We came up with the hypothesis that a low-mass black hole orbiting a disk around a supermassive black hole would behave in the same way that planetary embryos and protoplanets behave around the sun.”
“They will move, change their orbits, collide with other protoplanets and create larger ones.”
“This is a completely different way to form massive black holes than any other method in the universe.”
“We have refined this idea into a full-fledged theory, known as the ‘AGN channel,’ and we are accumulating convincing observational evidence.”
This growth could push some objects in the AGN disk past their hydrogen burning limit, making this mechanism a new pathway for star formation.
“This is the first mechanism of star formation that we have discovered,” Dr Lyra said.
“Stars usually form by something called gravitational collapse. It’s top-down. You form gas. You have a big cloud of gas, but it’s too dense, so it collapses under its own weight. Usually it starts with something big, and then it collapses to form a star.”
“Our mechanism is the opposite: it forms from the bottom up. First the building blocks form, then the gas accumulates, and then there’s a boom and a star forms.”
These newly formed stars could themselves collapse into black holes, potentially merging with massive black holes that could be detected by future gravitational-wave observatories such as ESA’s Laser Interferometer Space Antenna (LISA), scheduled to launch in the mid-2030s.
“These black holes are huge,” says Dr. Bhupendra Mishra of Santa Fe Preparatory School.
“They are hundreds or thousands of times larger than the Sun, and as they begin to move toward the center, they also produce gravitational wave signals that will likely be detected by LISA.”
of study will appear in astrophysical journal.
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Bhupendra Mishra others. 2026. Active galactic nucleus Tori: potential birthplace of millions of planets. APJ 1005, 99;doi: 10.3847/1538-4357/ae6f0b
Source: www.sci.news
