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Gases around black holes form dynamic fountains, not rigid donuts

Georgina Torbet
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Recent research performed using observations from the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile and computer simulations is shedding light on the nature of black holes. The ALMA was used to observe supermassive black holes, and in particular the ring of gas that surrounds them. It was previously thought that these rings of gas formed a donut-type shape, with the black hole in the middle. But now it seems that the gases around the black hole are in constant circulation, forming a shape more like a water fountain than a donut.

Supermassive black holes are commonly found at the center of galaxies, providing a point around which other stars rotate. Researchers from the National Astronomical Observatory of Japan (NAOJ) wanted to know more about how matter moves around these black holes, and whether it falls into the black hole or builds up around the event horizon. To study this, they looked to the Circinus Galaxy, about 14 million light-years away from us, and observed a supermassive black hole located there.

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The NAOJ team tested what was happening around the black hole by producing a computer simulation of how gases would fall towards a black hole, then comparing this simulation to the data from the Circinus Galaxy. They found that the gases did not form the expected rigid donut shape, but in fact formed a more dynamic structure which starts when colder gas falls towards the black hole, then this gas warms as it approaches the black hole, and some of this warmed gas is then expelled outwards away from the disk. This expelled gas then falls back towards the disk and the cycle begins again.

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Artist’s impression of the gas motion around the supermassive black hole in the center of the Circinus Galaxy. The three gaseous components form the long-theorized “donut” structure: (1) a disk of infalling dense cold molecular gas, (2) outflowing hot atomic gas, and (3) gas returning to the disk. NAOJ

This finding shows that we were wrong to assume that the gases around black holes form a rigid donut structure, which could have a profound effect on our understanding of black holes in general. “Based on this discovery, we need to rewrite the astronomy textbooks,” said Takuma Izumi, a researcher at the National Astronomical Observatory of Japan (NAOJ).

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