On January 7, 1610, Italian astronomer Galileo Galilei wrote a letter describing his discovery of three moons orbiting Jupiter with a recently upgraded telescope. He discovered a fourth moon within the next two weeks, and the four are called the Galilean Moons. They are named Io, Callisto, Europa, and Ganymede.
Sources:
http://en.wikipedia.org/wiki/Galilean_moon
http://en.wikipedia.org/wiki/Galileo_Galilei
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Fact of the Day
On January 7, 1610, Galileo Galilei announced his discovery of three moons with a telescope he designed. These three plus one more he discovered later are now called the Galilean Moons.
On January 7, 1610, Galileo Galilei announced his discovery of three moons with a telescope he designed. These three plus one more he discovered later are now called the Galilean Moons.
