Question

Why is the distance between stars are expressed in light years?

Answer 1

We already know that stars are millions of kilometres away from the earth. It is definitely not easy to express such huge number in small units like metre or even Kilometre. So the distance of stars from the earth is expressed in time taken by light to travel in one year. Known as Light years. 

Hope this helps :)

Answer 2

Star are at a distance between of millions of kilometers from the earth thus these large distances are expressed in light year. One light year distance travelled by the light in one year.

One light year is equal to 9.46 × 10^12km.