The luminosity of the Milky Way Galaxy is about 3 × 10¹⁰ L_e. Suppose all of this luminosity is due to a black hole and accretion disk at the center of the galaxy that is assumed to be at its Eddington limit. What would this suggest the mass is of this black hole (in solar masses)? A)30,000 B)3 × 10⁵ C)10⁶ D)3 × 10¹⁰

Question

Quizplus · Accepted Answer

The Eddington luminosity limit is given by L_Edd = (4πGM*m_p*c)/σ_T where G is the gravitational constant, M is the mass of the black hole, m_p is the mass of a proton, c is the speed of light, and σ_T is the Thomson scattering cross section. Rearranging this equation to solve for the mass of the black hole, we get M = (L_Edd*σ_T)/(4πGM*m_p*c). Plugging in the given Eddington luminosity and solving for the mass gives M = 1.5 x 10^16 solar masses. Therefore, the best choice is C, 10^16 solar masses.

The Luminosity of the Milky Way Galaxy Is About 3