From TheBestLinks.com
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 just right, it is barely 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 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 Hodierna, a disciple of Galileo and author of the first ephemerides (Medicaeorum Ephemerides, 1656).
Hevelius called them the Circulatores Jovis or Jovis Comites, and 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:
| Name
| Diameter (km)
| Mass (kg)
| Mean orbital
radius (km)
| Orbital period
|
| Io
| 3643
| 8.93×1022
| 421,800
| 1.77 days
|
| Europa
| 3122
| 4.8×1022
| 671,100
| 3.55 days
|
| Ganymede
| 5262
| 1.48×1023
| 1,070,400
| 7.16 days
|
| Callisto
| 4821
| 1.08×1023
| 1,882,700
| 16.69 days
|
See also: Jupiter's natural satellites
de:Galileische Monde
fr:Lune galiléenne
it:Lune galileiane
hu:Galilei-holdak
ja:ガリレオ衛星
pl:Galileuszowe księżyce Jowisza
Related links
Top visited
0 of
0 links
[no links posted yet]
>> place link >>
Discussion
Last posted
0 of
0 messages
[no messages posted yet]
>> post message >>
Watch
You can
add this article to your own "watchlist" and receive e-mail notification about all changes in this page.
