Vesta was the fourth asteroid to be discovered, in 1807. It is one lf the largest asteroids, but still only 512 km in diameter. It traces a slow path around the sky, orbiting the Sun once every 3.63 years. It is relatvely bright when its orbit brings it closest to the earth. When these images were taken, it was about magnitude 6, which means it could be barely seen with the naked eye under ideally dark skies. It is easy to spot in binoculars if you have a map of its path across the sky.
Vesta appears as a bright ball here simply because its image is overexposed; it is actually to small to see its shape at this magnification. To show Vesta's movement relative to the background stars in the constellation Leo, two sets of images were taken through a telescope about 90 minutes apart (roll over the image to see the movement).