Proxima Centauri, V645 Cen, is our closest stellar neighbor, at 4.2 Light years.
1 Light Year is:
exactly 9,460,730,472,580.8 km (about 9.5 Trillion Km)
about 5,878,625,373,183.608 miles (about 5.9 Trillion miles)
So a Proxima Centauri is about :
39.9 trillion km --- that's 39,900,000,000,000 km
24.78 trillion miles --- 24,780,000,000,000 miles
in 21 days (as pointed out in the link) the probe moved about 6 million miles-9.66 million km
so 285,714 miles per day --- 460,000 km/day ..
A vessel, fully stocked and capable of supporting a crew for the whole duration, bound for Proxima Centauri, moving at the speed that the Juno probe is currently, would arrive at Proxima Centauri in:
about 86,739,130 days --- or 237,641.45 YEARS
So in conclusion: Warp Drive, or we are not going anywhere
Also, "Modern man" has been dated to be as old as nearly 200,000 years for it's whole complete (up to today) cycle to have been completed.
A journey as long as the one to Proxima Centauri shown above could show that a another whole evolutionary cycle could occur. The travelers would be something not at all human by modern definition, and neither would the residents still on the Earth.
We're "Boldly Going"... it makes me smile to see this kind of thing. It puts us just one little step closer to the dream of actually venturing to the stars. Well done Nasa and everyone involved in the project.