Testing the extent of an ergosphere.

Is it possible from earth to measure the extent of a spinning black holes ergosphere. Does the frame dragging effect have a visible signature for us here on earth, or is it only something observed by objects within the ergosphere?

By knowing the shape of a spinning black holes ergosphere, and using it as an already complete part in Kerr's solution for Einsteins Field Equations, could we reverse engineer the mathematics and adjust the equation accordingly? Or would it rather just alter another part of the solution? If instead it exactly matched Kerr's solution, would this tell us anything else?

Could we be confident enough in our other measurements of the BH to get any certain results? It seems to me that IF the BH has angular momentum > 0 AND Kerr's solution is correct THEN the ergosphere must be an elipsoid. Any other shape, even with uncertainty of mass or angular momentum, would tell us the solution is wrong.

Edited January 6, 201610 yr by Sorcerer