Our solar system is a vast place, with lots of mostly empty space between planets. But out there are comets, asteroids and more rocky, frozen objects (including dwarf planets) yet to be discovered in the Kuiper Belt and Oort Cloud.
The solar system is made up of the sun and everything that orbits around it, including planets, moons, asteroids, comets and meteoroids. It extends from the sun, called Sol by the ancient Romans, and goes past the four inner planets, through the Asteroid Belt to the four gas giants and on to the disk-shaped Kuiper Belt and far beyond to the giant, spherical Oort Cloud and the teardrop-shaped heliopause. Scientists estimate that the edge of the solar system is about 9 billion miles (15 billion kilometers) from the sun.
For millennia, astronomers have followed points of light that seemed to move among the stars. The ancient Greeks named these planets, meaning "wanderers." Mercury, Venus, Mars, Jupiter and Saturn were known in antiquity, and the invention of the telescope added the Asteroid Belt, Uranus, Neptune, Pluto and many of these worlds' moons. The dawn of the space age saw dozens of probes launched to explore our system, an adventure that continues today. The discovery of Eris kicked off a rash of new discoveries of dwarf planets.