In addition to the Sun and the nine planets, there are millions of other objects sailing through the Solar System.
Asteroids are miniature planets.
They are little lumps of rock and metal that circle the Sun. The largest asteroid has been named Ceres. Asteroids were formed billions of years ago. Scientists think that asteroids may have started out as small planets. Or, they may have been pieces of what tried to become a single large planet, but were kept from coming together because of Jupiter's strong gravity.