> What they found was that the a value for our black hole is between 0.84 and 0.96, which means it’s rotating incredibly fast. At the upper range of the estimated rotation, it would be rotating at nearly the maximal rate. This is even higher than the spin parameter of the black hole in M87, where a is estimated to be between 0.89 and 0.91.<p>[0.84,0.96] and [0.89,0.91] are both centered on 0.90; strange to say that the former is higher, it's mostly just less well determined.