![]() ![]() Thus, several generations of Galilean-mass satellites may have been in Jupiter's early history. However, only 2% of the proto-disk mass of Jupiter is required to explain the existing satellites. Simulations suggest that, while the disk had a relatively high mass at any given moment, over time a substantial fraction (several tens of a percent) of the mass of Jupiter captured from the solar nebula was passed through it. They may be the remnants of a score of Galilean-mass satellites that formed early in Jupiter's history. Jupiter's regular satellites are believed to have formed from a circumplanetary disk, a ring of accreting gas and solid debris analogous to a protoplanetary disk. Those smaller than Europa are not visible at this scale, and combined would only be visible at 100× magnification. Origin and evolution The relative masses of the Jovian moons. Orbital periods range from seven hours (taking less time than Jupiter does to rotate around its axis), to almost three Earth years. Their orbital shapes range from nearly perfectly circular to highly eccentric and inclined, and many revolve in the direction opposite to Jupiter's rotation ( retrograde motion). All other Jovian moons are less than 250 kilometres (160 mi) in diameter, with most barely exceeding 5 kilometres (3.1 mi). The four Galileans are all over 3,100 kilometres (1,900 mi) in diameter the largest Galilean, Ganymede, is the ninth largest object in the Solar System, after the Sun and seven of the planets, Ganymede being larger than Mercury. ![]() The physical and orbital characteristics of the moons vary widely. From left to right, in order of increasing distance from Jupiter: Io Europa Ganymede Callisto. Of the 87 known irregular moons of Jupiter, 38 of them have not yet been officially named.Ĭharacteristics The Galilean moons. Jupiter is expected to have about 100 irregular moons larger than 1 km (0.6 mi) in diameter, plus around 500 more smaller retrograde moons down to diameters of 0.8 km (0.5 mi). The largest of these moons were likely asteroids that were captured from solar orbits by Jupiter before impacts with other small bodies shattered them into many kilometer-sized fragments, forming collisional families of moons sharing similar orbits. The remainder of Jupiter's moons are outer irregular satellites whose prograde and retrograde orbits are much farther from Jupiter and have high inclinations and eccentricities. The other four regular satellites, known as the inner moons, are much smaller and closer to Jupiter these serve as sources of the dust that makes up Jupiter's rings. The Galilean satellites are nearly spherical in shape due to their planetary mass, and are just massive enough that they would be considered major planets if they were in direct orbit around the Sun. Of Jupiter's moons, eight are regular satellites with prograde and nearly circular orbits that are not greatly inclined with respect to Jupiter's equatorial plane. The Galilean moons are by far the largest and most massive objects to orbit Jupiter, with the remaining 91 known moons and the rings together composing just 0.003% of the total orbiting mass. Much more recently, beginning in 1892, dozens of far smaller Jovian moons have been detected and have received the names of lovers (or other sexual partners) or daughters of the Roman god Jupiter or his Greek equivalent Zeus. The most massive of the moons are the four Galilean moons: Io, Europa, Ganymede, and Callisto, which were independently discovered in 1610 by Galileo Galilei and Simon Marius and were the first objects found to orbit a body that was neither Earth nor the Sun. All together, Jupiter's moons form a satellite system called the Jovian system. ![]() This number does not include a number of meter-sized moonlets thought to be shed from the inner moons, nor hundreds of possible kilometer-sized outer irregular moons that were only briefly captured by telescopes. There are 95 moons of Jupiter with confirmed orbits as of 23 March 2023. ![]() For other uses, see Moons of Jupiter (disambiguation).Ī montage of Jupiter and its four largest moons (distance and sizes not to scale) ![]()
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