Two similar stars, each encompass a mass and radius equivalent to that of our sun (M = 2 x 1029 kg and R = 7 x 108 m), are initially at rest in the outer space. Their initial separation is similar as the distance between our sun and the earth, D = 1.5 x 1011 m. Their gravitational interaction causes the stars to be pulled toward one other. Determine the speed of the stars just before they collide.