The asteroid belt (or the “main belt”) is the region between the orbit of Mars and the orbit of Jupiter—about 150 to 500 million miles (240 to 800 million kilometers) away from the Sun. The vast majority of known asteroids orbit in this belt. The main belt itself is divided into thinner belts, separated by object-free zones called Kirkwood Gaps. The gaps are named after the American astronomer Daniel Kirkwood (1814–1895), who first discovered them.