Mean diameter in the context of "Dione (moon)"

Vesta (minor-planet designation: 4 Vesta) is one of the largest objects in the asteroid belt, with a mean diameter of 525 kilometres (326 mi). It was discovered by the German astronomer Heinrich Wilhelm Matthias Olbers on 29 March 1807 and is named after Vesta, the virgin goddess of home and hearth from Roman mythology.

Vesta is thought to be the second-largest asteroid, both by mass and by volume, after the dwarf planet Ceres. Measurements give it a nominal volume only slightly larger than that of Pallas (about 5% greater), but it is 25% to 30% more massive. It constitutes an estimated 9% of the mass of the asteroid belt. Vesta is the only known remaining rocky protoplanet of the kind that formed the terrestrial planets. Numerous fragments of Vesta were ejected by collisions one and two billion years ago that left two enormous craters occupying much of Vesta's southern hemisphere. Debris from these events has fallen to Earth as howardite–eucrite–diogenite (HED) meteorites, which have been a rich source of information about Vesta.

10 Hygiea is a large asteroid located in the outer main asteroid belt between the orbits of Mars and Jupiter. It was the tenth known asteroid, discovered on 12 April 1849 by Italian astronomer Annibale de Gasparis at the Astronomical Observatory of Capodimonte in Naples, Italy. It was named after Hygieia, the Greek goddess of health. It is the fourth-largest main-belt asteroid by both volume and mass, with a mean diameter of 433 km (269 mi) and a mass constituting 3% of the main asteroid belt's total mass.

Hygiea has a nearly spherical shape, with two known craters about 100 and 180 km (62 and 112 mi) in diameter. Because of its shape and large size, some researchers consider Hygiea a possible dwarf planet. Hygiea has a dark, carbonaceous surface consisting of hydrated and ammoniated silicate minerals, with carbonates and water ice. Hygiea's subsurface likely contains a large fraction of water ice. These characteristics make Hygiea very similar to the main-belt dwarf planet Ceres, which suggests the two objects have similar origins and evolutionary histories.

Phoebe (/ˈfiːbi/ FEE-bee) is the most massive irregular satellite of Saturn with a mean diameter of 213 km (132 mi). It was discovered by William Henry Pickering on 18 March 1899 from photographic plates that had been taken by DeLisle Stewart starting on 16 August 1898 at the Boyden Station of the Carmen Alto Observatory near Arequipa, Peru. It was the first natural satellite to be discovered photographically.

Phoebe was the first target encountered upon the arrival of the Cassini spacecraft in the Saturn system in 2004, and is thus unusually well-studied for an irregular moon of its size. Cassini's trajectory to Saturn and time of arrival were chosen to permit this flyby. After the encounter and its insertion into orbit, Cassini did not go much beyond the orbit of Iapetus.

This is a list of Jupiter trojans that lie in the Greek camp, an elongated curved region around the leading Lagrangian point (L₄), 60° ahead of Jupiter in its orbit.

All the asteroids at Jupiter's L₄ point have names corresponding to participants on the Greek side of the Trojan War, except for 624 Hektor, which was named before this naming convention was instituted. Correspondingly, 617 Patroclus is a Greek-named asteroid at the "Trojan" (L₅) Lagrangian point. In 2018, at its 30th General Assembly in Vienna, the International Astronomical Union amended this naming convention, allowing Jupiter trojans with an H larger than 12 (that is, a mean diameter smaller than approximately 22 kilometers, for an assumed albedo of 0.057) to be named after Olympic athletes, as the number of known Jupiter trojans, currently more than 10,000, far exceeds the number of available names of heroes from the Trojan War in Greek mythology.

This is a list of Jupiter trojans that lie in the Trojan camp, an elongated curved region around the trailing L₅ Lagrangian point, 60° behind Jupiter in its orbit.

All the asteroids at the trailing L₅ point have names corresponding to participants on the Trojan side of the Trojan War, except for 617 Patroclus, which was named before this naming convention was instituted. Correspondingly, 624 Hektor is a Trojan-named asteroid at the "Greek" (L₄) Lagrangian point. In 2018, at its 30th General Assembly in Vienna, the International Astronomical Union amended this naming convention, allowing for Jupiter trojans with H larger than 12 (that is, a mean diameter smaller than approximately 22 kilometers, for an assumed albedo of 0.057) to be named after Olympic athletes, as the number of known Jupiter trojans, currently more than 10,000, far exceeds the number of available names of heroes from the Trojan War in Greek mythology.

Mimas is the seventh-largest natural satellite of Saturn. With a mean diameter of 396.4 kilometres or 246.3 miles, Mimas is the smallest astronomical body known to be roughly rounded in shape due to its own gravity. Mimas's low density, 1.15 g/cm, indicates that it is composed mostly of water ice with only a small amount of rock, and study of Mimas's motion suggests that it may have a liquid ocean beneath its surface ice. The surface of Mimas is heavily cratered and shows little signs of recent geological activity. A notable feature of Mimas's surface is Herschel, one of the largest craters relative to the size of the parent body in the Solar System. Herschel measures 139 kilometres (86 miles) across, about one-third of Mimas's mean diameter, and formed from an extremely energetic impact event. The crater's name is derived from the discoverer of Mimas, William Herschel, in 1789. The moon's presence has created one of the largest 'gaps' in Saturn's ring, named the Cassini Division, due to orbital resonance destabilising the particles' orbit there.