Planets orbit the Sun because of the Sun's strong gravitational pull, which attracts the planets toward it. However, planets also have a forward velocity that prevents them from falling directly into the Sun. This balance between the Sun's gravity pulling the planets inward and their forward motion causes them to move in stable, elliptical orbits around the Sun. The Sun's immense mass (about 99.8% of the solar system's total mass) makes its gravitational force dominant, keeping all planets bound in orbit. This delicate balance has been described by Newton's law of universal gravitation and Kepler's laws of planetary motion, explaining why planets neither crash into the Sun nor drift off into space but continuously orbit it.
Gravity and Orbital Motion
The Sun's gravity acts as an invisible tether, pulling each planet toward its center. Planets have orbital velocities that try to move them in a straight line, but the Sun's gravitational force bends their paths into ellipses. Without the Sun’s gravity, the planets would continue in straight lines and leave the solar system. If the planets moved too slowly, gravity would pull them into the Sun; if they moved too fast, they would escape. The current speed and gravitational pull are balanced, resulting in stable orbits.
Elliptical Orbits and Stability
Planets do not orbit in perfect circles but ellipses, with the Sun at one focus of the ellipse. The gravitational force changes with the planet's distance from the Sun, being stronger when closer and weaker when farther away, causing variations in velocity. This is why orbits are elliptical instead of circular. This orbital stability has allowed planets to orbit the Sun for billions of years and will continue as long as the Sun remains active.
In summary, it is the combination of the Sun’s massive gravitational pull and the planets’ velocity creating a centripetal force that keeps planets orbiting the Sun rather than crashing into it or escaping into space.
