Astronomers can measure the masses of black holes in a relatively straightforward way by watching how matter moves in their vicinity (including other black holes) under the influence of their gravitational fields.

The charges of black holes are thought to be insignificant when positive and negative infalling charges are balanced in number. The spins of black holes are difficult to determine; typically they are determined by interpreting the X-ray emission from the hot inner edge of the accretion disk around the black hole. The spin is quantified by a number between zero and one, and black hole spins have been measured with results ranging from a few tenths to close to the one.



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