You need to use a glow coming from the object itself as well as the light source.  If it is supposed to have a shape, like a flourescent bulb, then create a transparent object with a very bright glow, and a bright color.  Then through an aura on it in the effects menu for it.  This is how I create bright light sources.  Just remember the aura / glow is what will create the halo effect you want, whereas the anything glows on the object will create actual shadows.