Galilean moon Callisto The Galilean moons are the four moons of Jupiter discovered by Galileo Galilei. By far the largest of the many moons of Jupiter, they are visible even in a low-power telescope. In fact, if the observing conditions are perfect, it is just possible to see Callisto, the outermost, with the unaided eye. They were first observed by Galileo on January 7, 1610. Galileo observed the moons' motion over several days and realized that they were in orbit around Jupiter. This discovery supported the heliocentric theory of Nicolaus Copernicus and showed that not everything revolves around the Earth. Galileo first called his discovery the Cosmica Sidera, in honour of Cosimo II dé Medici (1590–1621), grand-duke of Tuscany from 1609, whose patronage Galileo wanted to secure. At the grand-duke's suggestion, Galileo changed the name to Medicea Sidera ("Médici stars"), because the Médici were four brothers. The discovery was announced in the Sidereus Nuncius ("Starry Messenger"), published in Venice in March 1610, less than two months after the first observations. Amongst the other names that were put forward, there is Principharus, Victipharus, Cosmipharus and Ferdinandipharus, for each of the four Médici brothers, proposed by Giovanni Battista Hodierna, a disciple of Galileo and author of the first ephemerides (Medicaeorum Ephemerides, 1656). Johannes Hevelius called them the Circulatores Jovis or Jovis Comites, and Jacques Ozanam called them Gardes or Satellites (from the Latin satelles, satellitis: escort). It would be the names proposed by Simon Marius (Simon Mayer), who pretended to have discovered the moons at the same time as Galileo, that would eventually prevail: Io, Europa, Ganymede and Callisto, published in his Mundus Jovialis in 1614. Galileo steadfastly refused to use Marius' names and invented as a result the numbering scheme that is still used nowadays, in parallel with proper moon names. The numbers run from Jupiter outward, thus I, II, III and IV for Io, Europa, Ganymede and Callisto respectively. Galileo used this system in his notebooks but never actually published it. The Galilean moons are, in order from closest to Jupiter to farthest away: See also: Jupiter's natural satellites Most Popular Articles: Music    Musical Instruments    Guitar    Classical Music    History    Music Definition    Country Music    Rock Music    Pop Music    Hip Hop    Rap    DJ    Video Games    Casino Games    Poker    Blackjack    Casinos    Real Estate    Loan    Auction    eBay    Marketing    Search Engine Optimization    File Sharing    MP3    Music Industry    Kazaa    Internet    Supermodel    Fashion    Fashion Designers    Erotica    Modeling    Clothing    Boots    Shoes    Diamond Engagement Rings    Diamond    Rugs    Gospel Music    Affiliate    E-Commerce    Radio This article is licensed under the GNU Free Documentation License at http://www.gnu.org/copyleft/fdl.html You may copy and modify it as long as the entire work (including additions) remains under this license. You must provide a link to http://www.gnu.org/copyleft/fdl.html To view or edit this article at Wikipedia go to http://www.wikipedia.org/wiki/Galilean_moon