Unless it's in a perfect vacuum with absolute zero gravity then nothing will go straight.
From
http://www.findarticles.com/p/articles/mi_m1134/is_n1_v106/ai_19318730
"The action of a gravitational lens is not restricted to visible light. If light takes the shortest distance through space-time between two points (which it does), and if space-time itself is curved (which it is), then the path of light will curve along with it, regardless of whether the light is composed of gamma rays, X-rays, ultraviolet, infrared, microwaves, or radio waves. And, most importantly, the cosmic stuff that causes the bending can be made of absolutely anything, as long as it contains enough mass to curve space-time measurably in its vicinity."
"There are no straight lines in nature, only areas of color one against another." - Monet