ALMA Telescope Spotted A Rotating Dusty ‘Gas Doughnut’ Around An Active Supermassive Black Hole

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Scientists discovered a rotating dusty gas torus with a donut-shaped structure around an active supermassive black hole in a distant galaxy known as M77. Astronomers have been talking about this “gas doughnut” since decades ago, yet its visibility has been confirmed using the powerful Atacama Large Millimeter/submillimeter Array (ALMA) for the first time now.

The discovery published in the Astrophysical Journal could help the scientists understand the co-evolution of supermassive black holes and their host galaxies. The compact doughnut gas structure has a radius of about 20 light-years at the center of galaxy M77, which is located approximately 47 million light-years away of the southern constellation Cetus the Whale. The scientists also found that the compact structure is spinning around the black hole, according to Earth Sky.

Masatoshi Imanishi, the lead author of the study from the National Astronomical Observatory of Japan (NAOJ), said that to interpret different observational features of AGNs, astronomers have assumed rotating donut-like structures of the dusty gas around active supermassive black holes. He described it as the unified model of AGN, which refers to “active galactic nucleus.”

On the other hand, the dusty, gaseous donut is very tiny in appearance. And with the help of the high resolution of ALMA, they could now directly see the structure, added Imanishi.


As noted in the press release of ALMA Observatory, in the central region of M77 or AGN, the matter is falling toward the core of the supermassive black hole and ejecting an intense light. The AGNs have a substantial impact on the surrounding environment. With this effect, they could be significant objects in unraveling the mystery of the co-evolution of galaxies and black holes.


Moreover, scientists examined the microwave emission from hydrogen cyanide molecules (HCN) together with the form ions (HC)+). These specific particles eject microwaves only in dense gas, and as regularly observed, the carbon monoxide (CO) discharges microwaves under various conditions.

The scientists also assumed that the torus around the AGN is very dense. The torus has asymmetry and its rotation does not follow the black hole’s gravity. It has a highly random motion, which indicates that the AGN could have a violent past such as merging with the small galaxy. However, knowing the rotation of torus could be a significant insight in discerning the co-evolution of black holes and their galaxies.