The luminosity a body would have to have for the force generated by radiation pressure to exceed the gravitational force. The force due to radiation pressure is given by

(1)

where L is the luminosity, is the Thomson cross section, r is the radius, and c is the speed of light, and the gravitational force is

(2)

where G is the gravitational constant, M is the mass of the body, and m is the mass of a particle. Equating (2) and (1) gives

(3)