28 a binary system consists of two stars ofequal mass morbiting each in a circular orbit under the infhuence of gravitational forces. the period ofthe orbit is

i dont understand how to approach this question. (28)A binary system consists of two stars ofequal mass morbiting each in a circular orbit under the infhuence of gravitational forces. The period ofthe orbit is T. Att=0, the motion is stopped and the stars are allowed to fall towards each other. After what time t, expressed in terms oft do they collide ? The following integral may be useful (x=r), J () 42 (a) 2