Physics: Asteroid Kepler's Law?

I don't know the specific answer without complex math which I can't be bothered to do now. What I do know is no object orbiting a star has ever been found with an escape velocity of 0. This make your asteroid impossible as it requires an escape velocity of 0 for inert rocks to fly off the surface. So in a nutshell T would have to be.. I guess less than 100 m or so.. something impossible to observe from earth at any rate.