The precise frequencies are determined by the mass of the...

The precise frequencies are determined by the mass of the black hole and also by how fast it spins. Those measurements -- mass and spin -- have been difficult to obtain. Fortunately, we already have an estimate of the mass of this black hole. By understanding the behavior of matter so close to the black hole's edge, we can now begin to determine the spin and thus, for the first time, completely describe the black hole.