What is a solar system?
A solar system is a star and all the objects that orbit it, including planets, moons, asteroids, comets and dust. Our solar system has the Sun, eight planets and many smaller bodies.
Our solar system formed about 4.6 billion years ago from a spinning cloud of gas and dust. Most of the material collapsed into the center to form the Sun, which contains more than 99.8 percent of the solar system's mass. The rest formed a disk that clumped together into planets, moons and smaller objects.
The inner solar system has four rocky planets: Mercury, Venus, Earth and Mars. Beyond the asteroid belt are the four giant planets: Jupiter, Saturn, Uranus and Neptune. Farther out lie the Kuiper Belt, home to dwarf planets like Pluto, and the distant Oort Cloud of icy comets.
Other solar systems
Astronomers have discovered thousands of planetary systems around other stars. Some have several planets, and some include giant planets orbiting very close to their stars, unlike ours. The term solar system technically refers to ours, because Sol is the Latin name for the Sun.
Did You Know?
Our solar system orbits the center of the Milky Way galaxy, taking about 230 million years to complete one orbit.