Blender+Cycles. A touch of vignette in GIMP.
See full resolution: http://wipup.org/updates/view/542/
VERY nice modelling and composition, it looks fantastic! My only crit is that the overall scene might benefit if the planet was less blurred.
Hey look! It’s mvortex! =D
I tend to agree with mvortex on the planet, though I think maybe it might be the effect you were going for? Sci-fi concept art is purposefully vague on a lot of detail, usually preferring to use brush-y strokes instead to give the illusion of detail. If that’s the feel you were going for, then the blurry planet actually looks pretty good. =)
Keep up the great work!
Dan
Thanks mvortex and JDaniels!
Originally the planet wasn’t blurred, but it was added as otherwise the depth of field seemed unnatural. As a space elevator, the structure was meant to be “shooting” out of the earth, so I thought the blur would be a good idea. But then again, perhaps not given your comments 
You should post your two works together, I think so.
Very good work!
looks cool
if camera is focused on elevator, and planet is blurred, stars should be defocused too…or not?