HEL (This is for Astronomy i put physics cuz that’s the closest thing) Which of the following BEST describes the gravitational binding of galaxies?
A) They are arranged from smallest to largest.
B) There is no certain arrangement.
C) They are found in clumps called clusters or superclusters.
D) They often violently collide because of their absence of gravity.

Two identical stars with mass m orbit around their center of mass. each orbit is circular and has radius r, so that the two stars are always on opposite sides of the circle. (a) find the gravitational force of one star on the other. (b) find the orbital speed of each star and the period of the orbit. (c) how much energy would be required to separate the two stars to infinity?