4.243 light years

The Breakthrough Initiatives project proposes some ambitious plans to transform humanity into a starfaring species. Most exciting to me is Project Starshot, which suggests that we could get a fleet of nanocraft to Alpha Centauri (a little over 4 light years away) and beam back images to Earth a mere 20 years after launch. 

Now comes news that our closest galactic neighbor, Proxima Centauri, harbors what is called an "earth-like planet," meaning it shares some superficial characteristics with our world. In other ways, the planet is radically unlike ours - it's tidally locked, in a much tighter orbit around a red dwarf star, and bombarded by radiation. But it's just 4.243 light years from home, and it might have liquid water and an atmosphere.

As soon as someone gets that multi-billion dollar kickstarter going, I'm in.