Why are planetary perturbations usually small in the solar system?

In celestial mechanics, planetary perturbations in our solar system are generally small because the Sun contains the vast majority of the system's total mass.1

While Kepler’s laws describe the motion of a planet as an ellipse when considering only the gravitational interaction between two bodies, the actual motion of any planet is influenced by the gravitational pull of other planets. Because the combined mass of all the planets is only about one-thousandth of the Sun's mass, the gravitational force exerted by the Sun remains the dominant influence on each planet's trajectory.21

Consequently, the deviations from a perfect elliptical orbit—known as perturbations—remain minor. These small forces cause the orbital parameters of a planet to vary slowly over time, allowing astronomers to treat the actual path as an osculating ellipse that serves as a highly accurate approximation of the planet's motion.324