Lighting

Hi,

I try to make a rotating earth with some buttons. It works fine. But I don't know to make the glow of the cities on "the dark side".
I think it should be done with a lightmap but i don't know how to do it.

Any ideas?

Thank you

Is this what you want?

Thank you for your answer,
more or less it is working.
But the glow is only visible on the light side. Is there a way to "flip" it?