31 NOLL. 2003
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1610: On 13 January 1610, Galileo Galilei discovered Callisto, the fourth satellite of Jupiter.
Galileo originally called the Jupiter's moons the 'Medicean planets', after the Medici family and referred to the individual moons numerically as I, II, III and IV. Galileo's naming system was used for a couple of centuries.
It wouldn't be until the mid 1800s that the names of the Galilean moons, Io, Europa, Ganymede and Callisto were officially adopted, after it became apparent that naming moons by number would be very confusing as new additional moons were being discovered.
It is now known that Callisto is larger than the planet Mercury, and composed mostly of water and water ice with large quantities of ice exposed on the surface.
Modh meán
11 January
1787: On 11 January 1787, Sir William Herschel discovered Titania, the first moon of Uranus. Six years earlier, he had discovered the planet.
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Liostáil lenár nuachtlitir chun an nuacht is déanaí, nuashonruithe misin, agus léargas eisiach a fháil go díreach i do bhosca isteach. Bí ar an gcéad duine a bheidh ar an eolas faoinár dtionscadail agus ár ndul chun cinn atá le teacht.