Light behaves strangely in space. The gravitation lens effect produces this strange behavior.

According to Einstein's General Theory of Relativity, an object that has mass (or weight, so to speak) will cause space-time to bend around it. Objects with extremely high mass will cause the surrounding space-time to bend even more. When such an object exists in outer space, light passing near it will travel along the curve it creates in space. By nature, light travels in a straight line, but when it encounters such an object in space-time, it bends much like it does when passing through a convex lens, hence the term gravitational lens effect.