Glossary term: 伽利略卫星
Description: 伽利略卫星是围绕木星运行的四颗最大、最明亮的卫星：木卫一（Io, 艾奥）、木卫二（Europa, 欧罗巴）、木卫三（Ganymede, 加尼美得）和木卫四（Callisto, 卡利斯托）。离木星最近的是木卫一，它有数百座活火山。木卫一火山爆发的主要原因是受到木星引力潮汐效应的 "揉捏"。木卫二的整个表面都被冰覆盖着。据信，冰层下是液态水海洋，是太阳系除地球外能够孕育生命的最佳候选者之一。木卫三是太阳系中体积最大的卫星，也是质量最大的，是月球质量的两倍。木卫四的大小几乎与水星完全一致，但质量只有水星的三分之一。
这四颗伽利略卫星是伽利略-伽利莱（Galileo Galilei）于 1610 年发现的，是伽利莱使用望远镜进行天文观测的开创性活动中的若干发现之一。伽利莱通过记录发现，随着时间的推移，四颗卫星围绕木星运行，就像一个微型太阳系。这清楚地表明，天体可以围绕地球以外的中心运行；这一观测结果在科学界对太阳系的认知转变过程中发挥了重要作用，从以地球为中心（地心说）转为以太阳为中心（日心说）。
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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
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Credit: Vishal Sharma/IAU OAE
License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons
木卫影片2，Nicolas Hurez，Paul-Antoine Matrangolo，和Carl Pennypacker，美国
Credit: Nicolas Hurez，Paul-Antoine Matrangolo 和 Carl Pennypacker/IAU OAE
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木星、木卫一及其阴影，作者：Ralf Burkart，德国
Credit: Ralf Burkart/IAU OAE
License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons
木卫一（伊奥）
Credit: 美国宇航局/JPL/亚利桑那大学 credit link
License: PD Public Domain icons
Europa
Credit: NASA/JPL/DLR
License: PD Public Domain icons
