The largest asteroid is named Ceres and has a diameter of 579 miles. The smallest detected asteroids have diameters of several hundred feet. Together with comets and meteroids, asteroids make up the minor bodies of the solar system. They are the left over planetessimals from the formation of the solar system. The vast gravitational pull of Jupiter is thought to have stopped the members of the asteroid belt from forming a planet.
Some asteroids travel in eccentric, elliptical orbits which cross the orbit of the Earth.
These are known as Earth crossing asteroids. For purposes of cataloging they are numbered sequentially as they are discovered. A star, which can be inferred to be a member of a binary star system, because the gravitational influence of its unseen companion causes it to oscillate about a mean position. See illustration . This is the mean radius of the Earth's orbit around the Sun.