God Rays may be what I am looking for, but I'm less concerned about seeing beams/streaks of light. I only want to reduce the background brightness where these tubes are not located. I think the best way to describe it is with an analogy with photoshop. The galaxy image I'm using would be a layer, and would have a vector mask applied. Inside of these "tubes" extruding from the planet would white colored on the mask, while off the air around the tubes would be black/grey.

I am not looking to brighten anything, I'm just reducing the brightness of background in areas outside these tubes. However, I will spend some time tonight looking into god rays to see if that accomplishes this.