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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Related Media

木星的自转，作者 Vishal Sharma，印度

Caption: 2021 年国际天文学联合会 (IAU) 天文教育办公室 (OAE) 天体摄影比赛，伽利略卫星类第三名：《木星的自转》，作者 Vishal Sharma，来自印度。这幅延时摄影作品精美地展示了木星的自转，以及画面右侧经过的两颗伽利略卫星。木星自转一圈只需不到 10 个小时，我们可以看到大红斑从左向右移动。在这短短的时间内，两颗卫星明显沿着它们的轨道前进了一段距离。这张照片是 2020 年在印度北部拍摄的。
Credit: Vishal Sharma/IAU OAE

License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons

The planet Jupiter, seen here as a bright disk, is orbited by the four Galilean moons, seen here as bright dots

Jupiter Moons Movie2, by Nicolas Hurez, Paul-Antoine Matrangolo, and Carl Pennypacker, United States of America

Caption: Second place in the 2021 IAU OAE Astrophotography Contest, category Galilean moons. This sequence shows the orbit of the four Galilean moons around the planet Jupiter. Almost two entire orbits of the innermost moon, Io, can be seen, with the other moons (Europa and Ganymede, but in particular Callisto) being further away, orbiting noticeably slower. The images were obtained in 2018 with the Las Cumbres Global Observatory at different locations on Earth, allowing a continuous sequence of images over approximately half a week without gaps during the day. With clear skies and over the course of several nights, the motion of the Galilean moons can also be observed with binoculars (ideally steady your elbows on a surface).
Credit: Nicolas Hurez, Paul-Antoine Matrangolo and Carl Pennypacker/IAU OAE

License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons

Jupiter with coloured horizontal bands of clouds. The shadow of the moon Io is seen as a dark circle in the top left

Jupiter, Io and its shadow, by Ralf Burkart, Germany

Caption: First place in the 2021 IAU OAE Astrophotography Contest, category Galilean moons. This time-lapse of Jupiter taken in 2017 from Germany beautifully illustrates the transit of one of the Galilean moons, Io, in front of Jupiter. As this is simply a moon casting a shadow on a planet it is equivalent to a lunar eclipse on Earth observed from further away. While the shadow of the moon is clearly visible from the beginning, it might be difficult to spot the moon itself against the background of the beautiful atmospheric bands of Jupiter the first time the video is seen. Watching it repeatedly allows appreciating the rapid motion and rotation in this fantastic observation.
Credit: Ralf Burkart/IAU OAE

License: CC-BY-4.0 Creative Commons 署名 4.0 国际 (CC BY 4.0) icons

伊奥卫星

Caption: 美国国家航空航天局的伽利略号航天器于1999年7月3日获得了木星卫星木卫一的最高分辨率图像。木卫一是伽利略-伽利雷 1610 年发现的四颗卫星之一。木卫一的颜色源于硫化物，是大量火山活动存在的证据。木星和邻近卫星的潮汐力是木卫一火山活动的原因。
Credit: 美国宇航局/JPL/亚利桑那大学 credit link

License: PD Public Domain icons

Europa

Caption: This image taken by NASA's Galileo space probe in September 1996 shows Jupiter's ice-covered satellite, Europa, in approximate natural color. Long, dark lines are fractures in the crust, some of which are more than 3,000 kilometers (1,850 miles) long. The bright feature containing a central dark spot in the lower third of the image is a young impact crater some 50 kilometers (31 miles) in diameter. Europa is about 3,160 kilometers (1,950 miles) in diameter, or about the size of Earth's moon.
Credit: NASA/JPL/DLR

License: PD Public Domain icons

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