The four largest satellites of Jupiter, namely Io, Europa, Ganymede, and Callisto, which were discovered by Galileo in 1610. All four are easily visible in binoculars and small telescopes, and would be bright enough to be visible with the naked eye were it not for the glare of Jupiter. Some keen-sighted people have claimed to be able to see them without optical aid.
http://photojournal.jpl.nasa.gov/catalog/PIA00601
The four largest moons of Jupiter (Io, Europa, Callisto, and Ganymede). The moons were seen through a telescope for the first time by the Italian astronomer Galileo Galilei in 1610. The largest Galilean satellite is Ganymede with a diameter (5 262 km) similar in size to that of the planet Mercury.
http://solarviews.com/eng/galdisc.htm Article documenting Galileo Galilei's discovery of Jupiter's four largest satellites, now known as the Galilean satellites. There are pictures (and translations) of original manuscripts as well as modern Voyager views.
The four classical satellites Io, Europa, Ganymede, and Callisto (in order outwards from Jupiter) which were discovered in 1610 by Galileo. The observation that they orbited a body other than the Earth was fatal to the Ptolemaic cosmology. Ganymede (radius 2638 km) is the largest satellite in the solar system, larger than both Mercury and Pluto. Europa (radius 1536 km), the smallest of the four, is a little smaller than the Moon (radius 1738 km). They occupy equatorial orbits. There is a regular decrease in density from Io (3550 kg/m3) to Callisto (1830 kg/m3), Callisto preserving one of the most heavily cratered surfaces of any satellite.
- flexor
- flexprice
- flexural basin
- flexural isostasy
- flexural rigidity
- flexural slip
- flexure
- flexus
- flicker
- flickering
- flicker noise
- flies
- flight
- flight control
- flight control system
- flight data file
- flight deck
- flight from money
- flight model
- flight path
- flight plan
- flight recorder
- flight simulator
- flight suit
- flight system