have achieved hydrostatic equilibrium, but, uniquely for a large moon, has a retrograde orbit, suggesting it was a dwarf planet that was captured. Neptune also has seven known inner regular satellites, and six outer irregular satellites. Pluto, a dwarf planet, has five moons. Its largest moon Charon, named after the ferryman who took souls across the River Styx, is more than half as large as Pluto itself, and large enough to orbit a point outside Pluto's surface. In effect, each orbits the other, forming a binary system informally referred to as a double-dwarf-planet. Pluto's four other moons, Nix, Hydra, Kerberos and Styx are far smaller and orbit the Pluto–Charon system. Among the other dwarf planets, has no known moons. It is 90 percent certain that Ceres has no moons larger than 1 km in size, assuming that they would have the same albedo as Ceres itself. has one large known moon, Dysnomia. Accurately determining its size is difficult: one indicative estimate of its radius is . Two objects were named as dwarf planets, under the expectation that they would prove to be so (though this remains uncertain). has two moons, Hiʻiaka and Namaka, of radii ~195 and ~100 km, respectively. has one moon, discovered in April 2016. A number of other objects in the Kuiper belt and scattered disk may turn out to be dwarf planets. , , , and are generally agreed to be dwarf planets among astronomers, and all but Sedna are known to have moons. A number of other smaller objects, such as , , and , also have moons, although their dwarf planethood is more doubtful. This list includes all objects with best estimated diameter above 700 km, including whose satellite has not been seen since its initial discovery. , 365 asteroid moons and 128 trans-Neptunian moons (including those of Pluto and the other dwarf planets) had been discovered. {| class="wikitable" style="text-align: center;" |+Summary – number of moons |- ! width=120 | Planet ! width=70 | Mercury ! width=70 | Venus ! width=70 | Earth ! width=70 | Mars ! width=110 | Jupiter ! width=110 | Saturn ! width=70 | Uranus ! width=110 | Neptune |- | Number of moons | 0 | 0 | 1 | 2 | 95 (+45 unconfirmed) | 83 (+83 unconfirmed) | 27 | 14 (+1 unconfirmed) |} {| class="wikitable" style="text-align: center;" |- ! width=120 | (Possible) dwarf ! width=70 |