Like this? I used a cube and sphere for a quick render, but you can see the effect (no postwork) I'll post a screenshot of the Atmosphere node setting for this render.

There are only three things you need to do this... spotlight, backdrop, and atmosphere settings. The spotlight here had an angle start of 20 degrees, angle end of 30 degrees.

Hope it helps.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)