An astronaut travels to a star system 4.5 ly away at a speed of 0. Assume that the time needed to accelerate and decelerate is negligible.

An astronaut travels to a star system 4.5 ly away at a speed of 0.9c. Assume that the time needed to accelerate and decelerate is negligible. 1 lightyear (ly) is the distance light travels in 1 year moving at 3 x 108 m/s. How long does the journey take according to the astronaut?