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Glossary Definition: Galilean Satellites - Windows to the Universe

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This composite of the Galilean Satellites shows images of the moons taken by the Galileo spacecraft, as well as details from the surfaces of the moons.
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NASA

Galilean Satellites

The Galilean satellites are the 4 major moons of Jupiter, Io, Europa, Ganymede, and Callisto. In this picture, Io, and Ioís surface, are shown on the left-most end, then Europa, and its surface, then Ganymede, then Callisto. Of Jupiterís 60 moons, these four are the biggest.

These moons were discovered by Galileo Galilei in 1610. Their discovery by Galileo was a key piece of evidence that the Earth was not the center of the Universe. Although Galileo initially thought they were stars, his continued observations over a couple of weeks showed that the objects remained near Jupiter. He was finally able to show that they were in orbit around Jupiter, thus proving that not all objects in the heavens orbited Earth.


Last modified September 18, 2003 by Roberta Johnson.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF