10 Hygiea

10 Hygiea is the fourth largest asteroid in the Solar System by volume and mass and is located in the asteroid belt. With somewhat oblong diameters of 350–500 km, and a mass estimated to be 2.9% of the total mass of the belt. It is the largest of the class of dark C-type asteroids with a carbonaceous surface.

Despite its size, due to its dark surface and larger-than-average distance from the Sun, it appears very dim when observed from Earth. For this reason several smaller asteroids were observed before Annibale de Gasparis discovered Hygiea on April 12, 1849. At most oppositions, Hygiea has a magnitude that is four orders lower than Vesta's, and observing it will require at least a 100 mm (4-inch) telescope, while at a perihelic opposition, it may be observable with 10x50 binoculars.