Our solar system consists of our star, the Sun, and everything bound to it by gravity – the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; dwarf planets such as Pluto; dozens of moons; and millions of asteroids, comets, and meteoroids. It is held together by the gravitational pull of the Sun, which is nearly 1,000 times more massive than all the planets put together. The solar system was probably formed from a huge cloud of interstellar gas and dust that contracted under the force of its own gravity five billion years ago. Beyond our own solar system, we have discovered thousands of planetary systems orbiting other stars in the Milky Way.
