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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]
It is slightly more massive than the second most massive moon, Saturn's satellite Titan, and is more than twice as massive as the Earth's Moon. It is larger than the planet Mercury, which has a diameter of 4,880 kilometres (3,030 mi) but is only 45 percent of Mercury's mass. Ganymede is the ninth-largest object in the solar system, but the ...
The four outer planets, called giant planets or Jovian planets, collectively make up 99% of the mass orbiting the Sun. [h] All four giant planets have multiple moons and a ring system, although only Saturn's rings are easily observed from Earth. [91]
Jupiter has surpassed Saturn with the record for the planet with the most moons in our solar system. The gas giant has a total of 92 confirmed moons, according to new observations by astronomers.
The distinction between a satellite and a classical planet was not recognized until after the heliocentric model of the Solar System was established. When in 1610 Galileo discovered the first satellites of another planet (the four Galilean moons of Jupiter), he referred to them as "four planets flying around the star of Jupiter at unequal intervals and periods with wonderful swiftness."
They are planetary-mass moons and among the largest objects in the Solar System. All four, along with Titan, Triton, and Earth's Moon, are larger than any of the Solar System's dwarf planets. The largest, Ganymede, is the largest moon in the Solar System and surpasses the planet Mercury in size (though not mass). Callisto is only slightly ...
Oldest, largest and most massive planet in the Solar System; [239] this planet hosts 95 known moons including the Galilean moons. Reported for reference. For smaller exoplanets, see the list of smallest exoplanets or other lists of exoplanets. For exoplanets with milestones, see the list of exoplanet extremes and list of exoplanet firsts.
A planet usually has at least around 10,000 times the mass of any natural satellites that orbit it, with a correspondingly much larger diameter. [3] The Earth–Moon system is a unique exception in the Solar System; at 3,474 kilometres (2,158 miles) across, the Moon is 0.273 times the diameter of Earth and about 1 ⁄ 80 of its mass. [4]