I mean, I’m sure there’s a statistic that someone can look up but as many people as are on the planet, I feel like there would always be someone within shouting distance if not closer. I guess it really depends on how fast the earth is moving and what the frame of reference is.
It’s been a while since I’ve done long exposure photography and composites, but my recollection is that excessive noise is a symptom of long exposure and high ISO, and stacking multiple shorter exposures into a composite will significantly reduce the noise of the final photo.