High Quality Content by WIKIPEDIA articles! 153 Hilda is a large asteroid in the outer main belt, with a diameter of 170 km. Because it is composed of primitive carbonaceous materials, it has a very dark surface. It was discovered by Johann Palisa on November 2, 1875 from the Austrian Naval Observatory at Pula. The name was chosen by the astronomer Theodor von Oppolzer, who named it after one of his daughters.