When Jake wakes up from cryo, the med tech tells everyone that they have been under for 5 years, 9 months and 22 days, witch is something like 5.81 years.
So that means that you would have to have an average speed of 4.37/5.81 = 0.752 times the speed off light to get there in 5.81 years. The ISV does not even have that high cruising speed and it still needs to accelerate and deaccelerate.
The only solution that make all things fit is that the people was not put in to cryo sleep until they had already left(witch seams wierd, why wait a year before going in to cryo sleep ). Or that it is a movie and the movie Alpha Centauri is way closer than ours.