The moon is a solid natural object that orbits around a planet. It is a planet’s natural satellite. No definite scientific explanation has satisfactorily answered the question of how moons came into existence, although there are several theories. The Earth’s Moon was thought to be the only moon but after the invention of the telescope, other moons on other planets were discovered. Each planet has one or more moons except Mercury and Venus and the dwarf planet Ceres. Jupiter has 79 moons the highest number in the solar system. Technological advancements have made it possible for man to discover and even go on expeditions to the moon. Jupiter’s Ganymede is the largest moon in our solar system. Ganymede is a satellite of Jupiter (Jupiter III), is the largest and most massive of the Solar System’s moons. The ninth largest object in the Solar System, it is the largest without a substantial atmosphere. It has a diameter of 5,268 km (3,273 mi) and is 8% larger than the planet Mercury, although only 45% as massive. Possessing a metallic core, it has the lowest moment of inertia factor of any solid body in the Solar System and is the only moon known to have a magnetic field. Outward from Jupiter, it is the seventh satellite and the third of the Galilean moons, the first group of objects discovered orbiting another planet. Ganymede orbits Jupiter in roughly seven days and is in a 1:2:4 orbital resonance with the moons Europa and Io, respectively. Ganymede is the name the biggest moon in our Solar System.
Ganymede is the largest of Jupiter’s 79 moons as well as by far the largest moon in the solar system. Ganymede orbits around Jupiter with a diameter of 5,262 kilometers. It is bigger in size than the smallest planet Mercury and would have easily been classified as a planet if it was orbiting the sun. It has its own magnetic field. Its discovery was made by Galileo Galilei the Italian astronomer on January 7, 1610. The satellite orbits around Jupiter at a distance of 1,0700,400 km and takes 7.1 days to complete one orbit. The surface of Ganymede has two types of terrains. It consists of lighter, younger areas and a darker cratered region. The planet’s atmosphere is thin and has oxygen contained in dispersed molecules. Water ice and rocky material make up the planet, and it thought to have underground oceans. The name is derived from a prince in Greek mythology.
Ganymede is composed of approximately equal amounts of silicate rock and water ice. It is a fully differentiated body with an iron-rich, liquid core, and an internal ocean that may contain more water than all of Earth’s oceans combined. Its surface is composed of two main types of terrain. Dark regions, saturated with impact craters and dated to four billion years ago, cover about a third of the satellite. Lighter regions, crosscut by extensive grooves and ridges and only slightly less ancient, cover the remainder. The cause of the light terrain’s disrupted geology is not fully known, but was likely the result of tectonic activity due to tidal heating.
Ganymede’s magnetic field is probably created by convection within its liquid iron core. The meager magnetic field is buried within Jupiter’s much larger magnetic field and would show only as a local perturbation of the field lines. The satellite has a thin oxygen atmosphere that includes O, O2, and possibly O3 (ozone). Atomic hydrogen is a minor atmospheric constituent. Whether the satellite has an ionosphere associated with its atmosphere is unresolved.
Chinese astronomical records report that in 365 BC, Gan De detected what might have been a moon of Jupiter, probably Ganymede, with the naked eye. However, Gan De reported the color of the companion as reddish, which is puzzling since the moons are too faint for their color to be perceived with the naked eye. Shi Shen and Gan De together made fairly accurate observations of the five major planets.
On January 7, 1610, Galileo Galilei observed what he thought were three stars near Jupiter, including what turned out to be Ganymede, Callisto, and one body that turned out to be the combined light from Io and Europa; the next night he noticed that they had moved. On January 13, he saw all four at once for the first time, but had seen each of the moons before this date at least once. By January 15, Galileo came to the conclusion that the stars were actually bodies orbiting Jupiter. He claimed the right to name the moons; he considered “Cosmian Stars” and settled on “Medicean Stars”
The French astronomer Nicolas-Claude Fabri de Peiresc suggested individual names from the Medici family for the moons, but his proposal was not taken up. Simon Marius, who had originally claimed to have found the Galilean satellites, tried to name the moons the “Saturn of Jupiter”, the “Jupiter of Jupiter” (this was Ganymede), the “Venus of Jupiter”, and the “Mercury of Jupiter”, another nomenclature that never caught on.
Other Large Moons
Other big moons and the planets they orbit in include, the Earth’s Moon (3,475km), Jupiter’s Europa (3,122km), Neptune’s Triton (2,707km), Uranus’s Titania (1,578km), Saturn’s Rhea (1,529km) and Uranus’s Oberon (1,523km). Most of the observations on these moons are done from the ground. Improved technology has helped scientists send man-made satellites to revolve around the solar system and enable the discovery of more information on these moons.
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