Although the scene depicting the transit of Arcturus puts the spaceship a bit close for comfort, the time it takes to cross from one side of Arcturus to the other side is too short in the movie which roughly times to about 25 seconds.

The space ship is travelling at ½ the speed of light which is 299,792/2 = 149,896 km/s. The diameter of Arcturus is 35,341,560 km. Therefore, the transit would take 35,341,560/149,896 = 235.773 seconds. That is about 3.93 minutes.

At the beginning of the movie, the spaceship rams into a bunch of floating space rocks.

I calculated the kinetic energy of 1-kilogram rock to see what damage would be done by smacking into it. There are several calculators on the Internet that makes that job easy.

The speed of light is 299,792,458 m/s

Half the speed of light is 149,896,229 m/s

According to the calculator found at

http://www.csgnetwork.com/kineticenergycalc.html

the kinetic energy of 1-kilogram rock would be

11234439734210220 Joules

According to the calculator found at

http://www.google.ca/#q=joules+to+tons+of+tnt

converting those Joules is equal to

2685095.5387691729702 tons of TNT

Therefore a 1 kg rock travelling at ½ the speed of light would explode with the force of 2.6 Megatons of TNT. That is a pretty big thermonuclear explosion. The amount of energy the shield would have to absorb for the scene in the movie would be astronomical for sure.