http://breakthroughinitiatives.org/Initiative/3 http://www.spaceflightinsider.com/missions/stephen-hawking-r...

It says the probe would be able to get there in about 20 years, travelling at 20% the speed of light, that's around 37,200mps.

There's going to be a relativistic effect, I think 20 years from our perspective will be slightly shorter from the probes point of view?