Supermassive black holes that have a retrograde spin might produce more ferocious jets of gas, a new theory suggests.
Black holes seem to defy our comprehension and be contrary to conventional understanding, so perhaps it is not entirely surprising that to find that supermassive black holes that have a retrograde or backwards spin might be more powerful and produce more ferocious jets of gas. While this new finding goes against what astronomers had thought for decades, it also helps solve a mystery why some black holes have no jets at all.
Powerful jets stream out from the accretion disks that spin around many supermassive black holes. The black holes can spin either in the same direction as the disks, called prograde black holes, or against the flow – the retrograde black holes. For decades, astronomers thought that the faster the spin of the black hole, the more powerful the jet. But there were problems with this "spin paradigm" model. For example, some prograde black holes had been found with no jets.
Theoretical astrophysicist David Garofalo and his colleagues have been studying the motion of black holes for years, and in previous papers, they proposed that the backward, or retrograde, black holes spew the most powerful jets, while the prograde black holes have weaker or no jets.