  The evolution of a supermassive black hole in the center of galaxy is
considered. We analyze the kinetic equation describing relaxation processes
associated with stellar encounters. The initial distribution function of stars
is assumed to be isothermal, and it changes in accordance with consumption of
stars by the black hole. We calculate the consumption rate and obtain the law
of growth of supermassive black hole, i.e. the dependence of the black hole
mass on time and on the velocity dispersion of stars. The obtained values of
mean black hole mass and mean rate of stars consumption by a black hole are in
reasonable agreement with observational data.
