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How did Isaac Newton explain why planets orbit the Sun?

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Illustration showing the eight planets of the solar system in order from the Sun-Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune-depicted to scale by size, with labeled diameters in miles and kilometers. The Sun is partially visible on the left for comparison. — Solar system The planets (in comparative size) in order of distance from the Sun.

Isaac Newton explained planetary orbits by applying his laws of motion and his law of universal gravitation to celestial bodies.12

According to Newton’s first law, an object in motion tends to continue in a straight line unless acted upon by an external force. Newton recognized that because planets move in curved paths rather than straight lines, a continuous force must be acting upon them to pull them toward the Sun. He identified this force as gravity, the same force that causes objects to fall on Earth.1234

By mathematically analyzing Kepler’s laws of planetary motion, Newton determined that this gravitational force must vary inversely with the square of the distance between the planet and the Sun. This inward centripetal force constantly diverts the planet from its inertial, straight-line path, effectively keeping it in a stable orbit. Through this synthesis, Newton successfully unified terrestrial and celestial mechanics under a single set of physical laws.1234