Oops, sorry.  Let me clarify.  I just happened to be searching for atmospheric stuff when I stumbled across the tutorials, there is no atmospheric way to do it that I know of.  HOWEVER, an ambient surface WILL cast light onto other surfaces when rendering with IDL.  With no other surfaces in the scene it will not show any light except for what directly hits the "lense".  There was a good thread on that not long ago.

That second, larger ball for the halo sounds familiar, I think that was the gist of what I had seen before.  As far as I know, that is the only way to get a halo effect.

By the way, for those working with pre-Poser 8 versions you can still have one object illuminate another by putting a gather node on the reflective property of the target object.  There was a really good thread about that, too, just a bit longer ago.  FYI it is a complete beast to render like that, though.

Miss Nancy, I'm curious to know what "in pre-poser 9" means :)