The force that keeps planets in orbit around the Sun is gravity. According to Isaac Newton's law of universal gravitation, every mass attracts every other mass. The Sun, having a massive gravitational pull due to its substantial mass, exerts a force on the planets, pulling them toward it. Simultaneously, the planets are moving forward in their orbits due to their velocity, creating a balance between the gravitational pull of the Sun and the planets' inertia. This dynamic interaction results in elliptical orbits, a concept that was later refined by Johannes Kepler in his laws of planetary motion.