The centre of the Milky Way is populated with so-called super-massive black holes. In most of the papers and books about black holes at the centre of galaxies, the mass is said to be gigantic. In this paper, we will see how to calculate the mass of these super-massive black holes out of observational data, by using the Maxwell Analogy for Gravitation, and we see how to make the difference between real physical mass and apparent (fictive) mass. We discover that so-called ‘super-massive black holes’ do not have huge masses at all but that they have an apparent mass that can be thousands times the real mass. This suggests that the energy of such black-holes could decrease very fast in relative terms.
Keywords: black hole, horizon, spinning star, super-massive black hole, gravity, gravitomagnetism, gyrotation, orbital velocity, angular momentum