A planet of mass m orbits a star of mass m, where m< 1) The gravitational force between the planet and the star is equal to the centripetal force acting on the planet.
2) The radius of the orbit is directly proportional to the mass of the planet.
3) The period of the orbit is inversely proportional to the mass of the planet.
4) The period of the orbit is directly proportional to the radius of the orbit.