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== Discovery and naming ==

== Discovery and naming ==

[[Galileo Galilei]] observed Jupiter beginning on January 7, 1610, with his famous telescope. He at first thought he had discovered three stars near Jupiter, but on the next night those "stars" seemed to have moved. (Those "stars" were actually Io, [[Europa]], and [[Callisto]].) He continued to observe Jupiter and its companion "stars" for seven days, during which time a fourth "star" ([[Ganymede]]) appeared and all four of these objects appeared to move with Jupiter. Finally he concluded that these objects were not stars at all, but satellites of Jupiter. This was the first direct observation that provided evidence for [[Nicolaus Copernicus]]'s heliocentric model of the solar system.<ref name=disc/>

[[Galileo Galilei]] observed Jupiter beginning on January 7, 1610, with his famous telescope. He at first thought he had discovered three stars near Jupiter, but on the next night those "stars" seemed to have moved. (Those "stars" were actually Io, [[Europa (moon)|Europa]], and [[Callisto]].) He continued to observe Jupiter and its companion "stars" for seven days, during which time a fourth "star" ([[Ganymede]]) appeared and all four of these objects appeared to move with Jupiter. Finally he concluded that these objects were not stars at all, but satellites of Jupiter. This was the first direct observation that provided evidence for [[Nicolaus Copernicus]]'s heliocentric model of the solar system.<ref name=disc/>

[[Simon Marius]] claimed to observe Jupiter and these satellites independently of Galileo and beginning five weeks earlier. However, he did not ''publish'' his findings, while Galileo published his. Furthermore, Galileo's notes were more reliable and extensive than those of Marius, which is why Ganymede and the three other satellites he observed ([[Io]], [[Europa]], and [[Callisto]]) are called the Galilean satellites and not the Galilean-Marian satellites.<ref name=disc/>

[[Simon Marius]] claimed to observe Jupiter and these satellites independently of Galileo and beginning five weeks earlier. However, he did not ''publish'' his findings, while Galileo published his. Furthermore, Galileo's notes were more reliable and extensive than those of Marius, which is why Ganymede and the three other satellites he observed ([[Io]], [[Europa]], and [[Callisto]]) are called the Galilean satellites and not the Galilean-Marian satellites.<ref name=disc/>