Vesta is the second largest object in the Asteroids Belt and the third largest in size, with a main diameter of about 530 kilometers and an estimated mass of 9% of whole asteroids belt. It is thought to have lost about 1% of its mass in an impact produced just under a billion years ago and many fragments of this impact have collided with Earth, constituting a rich source of information on the asteroid. Vesta is the brightest asteroid and the only one sometimes visible to the naked eye as a sixth magnitude star. Its orbit intersects with that of Ceres, such that its farthest point in its orbit in the Sun is farther than the nearest point in the orbit of Ceres. It was discovered in 1807 by Heinrich Olbers. It was visited by the Dawn probe between July 2011 and May 2012.
