Asteroid 6478 Gault. NASA/ESA Hubble Space Telescope iamge of the gradual self-destruction of asteroid 6478 Gault. The ejected dusty material has formed two long, thin, comet-like tails. The longer tail stretches more than 800,000 kilometres and is roughly 4,800 kilometres wide. The shorter tail is about a quarter as long. The material is being ejected due to the spin of the asteroid. Large grains (about the size of sand particles) are close to the object and the smallest grains (about the size of flour grains) are the farthest away because they are being pushed faster by pressure from sunlight.