A space colony ship about the size of a baseball field is carrying 20,000 colonists in deep hibernation to a planet far-far away, when suddenly the computer awakens all of the colonists.
The captain looks at the computer report and sees that a nearby phenomenon has interfered with the warp-drive and it has to be jettisoned before it explodes. They must proceed to their target planet at sub-light speed.
Their sub-light engines have already accelerated the ship to its maximum velocity of 150,000 meters per second (half the speed of light). Their destination is 3 parsecs away.
How many years (from an outsider's perspective), will it take the colony ship to reach its destination?