Vesta asteroid. Satellite image of the asteroid Vesta (4 Vesta). Vesta orbits the Sun between the orbits of Mars and Jupiter at an average distance of 353 million kilometres. It is the second largest asteroid, having a diameter of about 538 kilometres. Under favourable conditions, it is the only asteroid visible to the naked eye. Imaged by NASA's Dawn spacecraft, on 16th July 2011, from a distance of about 15,000 kilometres away.