Glossary term: 外行星

Description: 在太陽系中，外行星包括木星、土星、天王星和海王星。它們的軌道都在小行星帶之外，並且所有這些行星都是所謂的巨行星，它們的大氣層非常厚，主要由氫氣構成。這使得它們在物理上與內行星截然不同，內行星都是相對較小的岩質天體，大氣層相對稀薄。

對於太陽以外的恆星，其周圍的行星並不一定分為具有類似特徵的內行星群和外行星群--我們知道有許多恆星的近軌道上至少有一顆氣態巨行星，即 "熱木星"。

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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

This is an automated transliteration of the simplified Chinese translation of this term

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Related Media

木星的自轉，作者 Vishal Sharma，印度

Caption: 2021 年國際天文學聯合會 (IAU) 天文教育辦公室 (OAE) 天體攝影比賽，伽利略衛星類第三名：《木星的自轉》，作者 Vishal Sharma，來自印度。這幅延時攝影作品精美地展示了木星的自轉，以及畫面右側經過的兩顆伽利略衛星。木星自轉一圈只需不到 10 個小時，我們可以看到大紅斑從左向右移動。在這短短的時間內，兩顆衛星明顯沿著它們的軌道前進了一段距離。這張照片是 2020 年在印度北部拍攝的。
Credit: Vishal Sharma/IAU OAE

License: CC-BY-4.0 Creative Commons 姓名標示 4.0 國際 (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 姓名標示 4.0 國際 (CC BY 4.0) icons

木星、木衛一及其陰影，作者：Ralf Burkart，德國

Caption: 2021 年國際天文學聯合會 OAE 天體攝影比賽伽利略衛星類第一名。這幅木星的延時攝影是於2017 年從德國拍攝的，作品精美地展示了伽利略衛星之一木衛一在木星前的凌星現象。由於這只是衛星在行星上投下影子，因此相當於從更遠的地方觀測地球上的月食。雖然衛星的影子從一開始就清晰可見，但在木星美麗的大氣帶背景下，第一次觀看視頻時可能很難發現衛星本身。反復觀看可以欣賞到這一奇妙的快速運動和旋轉過程。
Credit: Ralf Burkart/IAU OAE

License: CC-BY-4.0 Creative Commons 姓名標示 4.0 國際 (CC BY 4.0) icons

木星

Caption: 這是 2014 年 4 月 21 日利用哈勃的寬視場相機3號 (WFC3) 拍攝的木星全盤視圖。它展示了明顯的大紅斑，一個巨大的氣旋。木星表面覆蓋著雲帶，其顏色來自氨等氣體和其他化合物。
Credit: 美國國家航空航天局、歐空局和 A. Simon（戈達德太空飛行中心） credit link

License: CC-BY-4.0 Creative Commons 姓名標示 4.0 國際 (CC BY 4.0) icons

土星

Caption: NASA/ESA 哈勃太空望遠鏡的寬視場相機3號於 2019 年 6 月 20 日觀測到土星，當時這顆行星距離地球約 13.6 億公里，是今年距離地球最近的行星。圖像顯示了土星表面的彩色氣體條帶以及由冰和岩石物質組成的突出星環。
Credit: 美國國家航空航天局、歐空局、A. Simon（戈達德太空飛行中心）和 M.H. Wong（加州大學伯克利分校） credit link

License: CC-BY-4.0 Creative Commons 姓名標示 4.0 國際 (CC BY 4.0) icons

Uranus showing a uniformly greenish-blue coloured appearance

Uranus in natural colours

Caption: This is an image of the planet Uranus taken by the spacecraft Voyager 2 in 1986. Its appearance is close to what the naked eye would see. The greenish-blue colour indicates an atmosphere containing methane.
Credit: NASA/JPL-Caltech credit link

License: PD Public Domain icons

天王星與星環

Caption: NASA/ESA 哈勃太空望遠鏡的 ACS/HRC 相機於 2005 年 8 月觀測到天王星。天王星表面有白色的雲層和明亮的極區。天王星週圍的星環很窄，包含從微小塵埃顆粒到數米大小的巨石的岩石物質。
Credit: 美國國家航空航天局、歐洲航天局和 M. Showalter（SETI 研究所） credit link

License: PD Public Domain icons

Neptune

Caption: Voyager 2 Narrow Angle Camera image of Neptune taken in August 1989. The Great Dark Spot, flanked by cirrus clouds, is at center. A smaller dark storm, Dark Spot Jr., is rotating into view at bottom left. Additionally, a patch of white cirrus clouds to its north, named "Scooter" for its rapid motion relative to other features, is visible.
Credit: NASA / JPL / Voyager-ISS / Justin Cowart credit link

License: PD Public Domain icons

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