What role does the Sun play in keeping planets in orbit?

The Sun's gravitational pull keeps the planets in their respective orbits around it.

The Sun, being the largest object in our solar system, has a significant gravitational force. This force is what keeps the planets, including Earth, in a stable orbit around it. The concept of gravity was first explained by Sir Isaac Newton, who stated that every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres. This is known as Newton's law of universal gravitation.

In the context of our solar system, the Sun's mass is so large that its gravitational pull is strong enough to keep the planets in orbit around it. The planets move in elliptical orbits, with the Sun at one of the two foci of the ellipse. This motion is a balance between the forward motion of the planet (its inertia) and the inward pull of the Sun's gravity. If there were no gravity, the planets would move in a straight line off into space. But because of the Sun's gravity, they are pulled towards the Sun. However, because they are also moving forward, they don't fall into the Sun but instead keep moving around it.

This delicate balance between inertia and gravity is what creates the stable orbits we observe. The speed of a planet's orbit depends on its distance from the Sun; planets closer to the Sun orbit faster than those further away. This is because the gravitational pull is stronger the closer objects are to each other.

In summary, the Sun's gravitational pull is the key factor that keeps the planets in their orbits, maintaining the structure of our solar system. Without it, the planets would not be held in their paths and would drift off into space.