Going Against the Flow around a Supermassive Black Hole
Arthur T Knackerbracket has found the following story:
At the center of a galaxy called NGC 1068, a supermassive black hole hides within a thick doughnut-shaped cloud of dust and gas. When astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) to study this cloud in more detail, they made an unexpected discovery that could explain why supermassive black holes grew so rapidly in the early Universe.
"Thanks to the spectacular resolution of ALMA, we measured the movement of gas in the inner orbits around the black hole," explains Violette Impellizzeri of the National Radio Astronomy Observatory (NRAO), working at ALMA in Chile and lead author on a paper published in the Astrophysical Journal. "Surprisingly, we found two disks of gas rotating in opposite directions."
Supermassive black holes already existed when the Universe was young -- just a billion years after the Big Bang. But how these extreme objects, whose masses are up to billions of times the mass of the Sun, had time to grow in such a relatively short timespan, is an outstanding question among astronomers. This new ALMA discovery could provide a clue. "Counter-rotating gas streams are unstable, which means that clouds fall into the black hole faster than they do in a disk with a single rotation direction," said Impellizzeri. "This could be a way in which a black hole can grow rapidly."
[...]Impellizzeri and her team used ALMA's superior zoom lens ability to observe the molecular gas around the black hole. Unexpectedly, they found two counter-rotating disks of gas. The inner disk spans 2-4 light-years and follows the rotation of the galaxy, whereas the outer disk (also known as the torus) spans 4-22 light-years and is rotating the opposite way.
"We did not expect to see this, because gas falling into a black hole would normally spin around it in only one direction," said Impellizzeri. "Something must have disturbed the flow, because it is impossible for a part of the disk to start rotating backward all on its own."
Journal Reference:
C. M. Violette Impellizzeri, Jack F. Gallimore, Stefi A. Baum, Moshe Elitzur, Richard Davies, Dieter Lutz, Roberto Maiolino, Alessandro Marconi, Robert Nikutta, Christopher P. O'Dea, Eleonora Sani. Counter-rotation and High-velocity Outflow in the Parsec-scale Molecular Torus of NGC 1068. The Astrophysical Journal, 2019; 884 (2): L28 DOI: 10.3847/2041-8213/ab3c64
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