The donut-shaped ring surrounding many supermassive black holes tells researchers how fast the space object is feeding and may change the black hole’s view of Earth. Image credits: ESA/NASA, the AVO project and Paolo Padovani
Researchers are using X-ray telescopes and a new data analysis technique to describe space objects.
Black holes with different light signatures, previously thought to be the same objects viewed from different angles, are actually at different stages of the life cycle, according to a study led by Dartmouth scientists.
This new research on black holes, known as “active galactic nuclei” or AGNs, says it definitely shows the need to revise the widely held “unified model of AGN,” which characterizes supermassive black holes as all having the same properties .
The study provides answers to a troubling space mystery and should allow researchers to create more accurate models of how the Universe evolved and how black holes form. It was released on July 15 in The Astrophysical Journal,
“These objects have puzzled researchers for over half a century,” said Tonima Tasnim Ananna, the paper’s lead author and postdoctoral researcher at Dartmouth. “Over time we have made many assumptions about the physics of these objects. Now we know that the properties of eclipsed black holes differ significantly from the properties of less eclipsed AGNs.”
Tonima Tasnim Ananna, postdoctoral fellow at Dartmouth College. Credit: Robert Gil/Dartmouth College
Supermassive black holes are believed to be at the center of almost all large galaxies, including our own, the
” data-gt-translate-attributes=”[{” attribute=””>Milky Way. The gravitationally powerful objects devour galactic gas, dust, and stars, and they can become heavier than small galaxies.
For decades, astronomers have been interested in the light signatures of active galactic nuclei, a type of supermassive 
Tonima Tasnim Ananna, a postdoctoral research associate at Dartmouth College, and Ryan Hickox, professor of physics and astronomy. Credit: Robert Gill/Dartmouth College
“This provides support for the idea that the torus structures around black holes are not all the same,” said Ryan Hickox, professor of physics and astronomy and a co-author of the study. “There is a relationship between the structure and how it is growing.”
The result shows that the amount of dust and gas surrounding an AGN is directly related to how much it is feeding, confirming that there are differences beyond orientation between different populations of AGNs. When a black hole is accreting at a high rate, the energy blows away dust and gas. As a result, it is more likely to be unobscured and appear brighter. Conversely, a less active AGN is surrounded by a denser torus and appears fainter.
“In the past, it was uncertain how the obscured AGN population varied from their more easily observable, unobscured counterparts,” said Ananna. “This new research definitively shows a fundamental difference between the two populations that goes beyond viewing angle.”
The study stems from a decade-long analysis of nearby AGNs detected by Swift-BAT, a high-energy
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