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Of the Solar System's eight planets and its nine most likely dwarf planets, six planets and seven dwarf planets are known to be orbited by at least 300 natural satellites, or moons. At least 19 of them are large enough to be gravitationally rounded; of these, all are covered by a crust of ice except for Earth's Moon and Jupiter's Io. [1]
Of the inner planets, Mercury and Venus have no natural satellites; Earth has one large natural satellite, known as the Moon; and Mars has two tiny natural satellites, Phobos and Deimos. The giant planets have extensive systems of natural satellites, including half a dozen comparable in size to Earth's Moon: the four Galilean moons , Saturn's ...
Perhaps inspired by Kepler (and quoting Kepler's third law of planetary motion), Jonathan Swift's satire Gulliver's Travels (1726) refers to two moons in Part 3, Chapter 3 (the "Voyage to Laputa"), in which Laputa's astronomers are described as having discovered two satellites of Mars orbiting at distances of 3 and 5 Martian diameters with ...
Mars has two relatively small (compared to Earth's) natural moons, Phobos (about 22 kilometres (14 mi) in diameter) and Deimos (about 12 kilometres (7.5 mi) in diameter), which orbit close to the planet. The origin of both moons is unclear, although a popular theory states that they were asteroids captured into Martian orbit.
Ganymede is the largest natural satellite in the Solar System at 5262.4 kilometers in diameter, which makes it larger than the planet Mercury – although only at about half of its mass [42] since Ganymede is an icy world.
The outer Solar System with the giant planets, their satellites, trojan asteroids and some minor planets. Jupiter. Rings of Jupiter; Complete list of Jupiter's natural satellites. Galilean moons. Io; Europa; Ganymede; Callisto; Jupiter trojans; Jupiter-crossing minor planets; Saturn. Rings of Saturn; Complete list of Saturn's natural satellites ...
Some dwarf planets, too, have satellites substantially less massive than the dwarf planets themselves. The most notable exception is the Pluto–Charon system. The Charon-to-Pluto mass ratio of 0.122 (≈ 1 ⁄ 8 ) is close enough to 1 that Pluto and Charon have frequently been described by many scientists as "double dwarf planets" ("double ...
Two small satellites were discovered around Haumea (which was at that time still designated 2003 EL 61) through observations using the W.M. Keck Observatory by a Caltech team in 2005. The outer and larger of the two satellites was discovered 26 January 2005, [ 2 ] and formally designated S/2005 (2003 EL 61 ) 1, though nicknamed " Rudolph " by ...