Perhaps not a total fix, but some ideas in hopefully a helpful direction.
I doubt the noise is camera noise at 100 or 200 ISO, if you are completely filling the frame of the D5000. My D5500 is newer, but I'm almost sure it couldn't be that much noisier than mine.
It is, btw, just about fixable in Photoshop, pic at the end of a quick 'fix' attempt.
To fix ...