Order of the moons by size

After the Sun, the Moon is the second brightest object in our sky. However, our moon is not the only moon in the solar system, nor is it the largest by a long shot! Following the order of the moons by size, you would begin with Jupiter’s Ganymede. It has a diameter of 5279km, and is so large that it has its own magnetic field and its bigger then Mercury and Pluto.

Titan, one of the moons orbiting planets like Saturn, is the second largest moon, measuring 5149km wide. Callisto, which orbits Jupiter, is the next largest moon, measuring 4821km across. Jupiter has some of the largest moons in the solar system in its orbit – Io and Europa are 3643km and 3122km across, respectively. Earth’s own moon is 3475km in radius while Neptune’s Triton is 2707km across.

The order of moons by size under 2000km radius is as follows: Saturn’s Rhea and Iapetus (1530km and1470km), Charon of Pluto (1205km), Dione and Tethys, both of Saturn, and 1120km and 1070km in radius, respectively. Moons whose radius is below 1000km in radius include Titania, which goes around Uranus (788.9km), Enceladus of Saturn (500km), Proteus of Neptune (420km), Mimas of Saturn (400km) and Nereid of Neptune (338km).

Jupiter has some of the largest moons in the solar system in its orbit, but it also has some of the smallest – the four small moons in the inner groups are all less than 200km in diameter. There are a number of moons orbiting planets under 200km in diameter: Larissa and Galatea of Neptune are 194km and 176km, respectively. The dwarf planet Haumea has a moon, Hi’iaka, measuring 155km across. Despina of Neptune is slightly smaller at 150km across. Eris is a dwarf planet with one known moon, Dysnomia. Dysnomia’s exact radius is unknown, but is thought to be about 100km.

Moons can range from the enormous to the relatively smaller, such as Nix of Pluto (88km) and Namaka of Haumea (85km). Thalassa of Neptune is slightly smaller at 82km in diameter. Hydra of Pluto is much smaller at 72km in diameter, but it’s bigger than Naiad, Halimede, Neso Sao, Laomedeia, and Psamathe of Neptune, which are 66km, 62km 60km 44km, 42km and 38km in radius, respectively. The smallest moons in the solar system are Saturn’s Pan (19km wide), and Phobos and Deimos of Mars, which are 11.1km and 11km in diameter respectively.