Final answer:
Traveling to a galaxy with 1/5 of Earth's gravity would decrease Luke Star killer's weight, but not his mass.
Step-by-step explanation:
The effect of traveling to a galaxy with 1/5 of Earth's gravity on Luke Star killer's weight and mass can be determined using the equation for gravitational force: F = (G * m1 * m2) / r^2 (where F is the force of gravity, G is the gravitational constant, m1 and m2 are the masses of the two objects, and r is the distance between them).
In this case, since Luke Star killer wants to travel to a galaxy with 1/5 of Earth's gravity, the force of gravity acting on him would be approximately 1/5 of what he experiences on Earth.
Therefore, his weight would be approximately 1/5 of his weight on Earth, but his mass would remain the same.