An astronaut travels to a star system 4.5 ly away at a speed of 0.9c. Suppose that the time needed to accelerate and decelerate is negligible. The journey take according to Mission Control on earth takes 5 years. And the journey takes2.2 years according to the astronaut
How much time (s) elapses among the launch and the arrival of the first radio message from the astronaut saying that she has arrived? Express your answer using two important figures.