The black hole in the galaxy M87 has a mass of about 3 billion solar masses. Let us assume that most of that mass flowed into the black hole through an acretion disk that radiated 10% of the mass-energy passing through it. (a) In that case, what would be the total amount of energy radiated by the accretion disk during the history of the black hole? (b) What would be the average luminosity (in solar luminosities) of the accretion disk, if it that energy over a period of 10 billion years? (c) How does that average huminosity compare with the luminosity of the Milky Way?
