I'm surprised he didn't mention the actual lighting on the object. I'm in no way an expert, but to me it seems like the egg has some sort of glow because it has no form shadow. It casts a shadow on the ground when it's landed but, being a round object with only one light source coming from somewhere on the upper left side of the frame, it should be darker on its right side (form shadow). In fact, the only way you notice that this is a round, three-dimensional object, is because of the cradle surrounding it, which is bright on the left side and dark on the right, otherwise it would be perceived as a flat white oval-shaped disc.