Glossary term: 行星

Description: 根據國際天文學聯合會的定義，行星是指圍繞恆星或恆星殘餘物運行的天體，其體積足夠大，在自身引力作用下接近圓形，但質量不足以使其內核發生熱核聚變。它還必須足夠大，其引力才能將靠近恆星軌道的其他天體移走。因此，它們是寒冷的天體（與恆星相比），只能通過反射恆星的光在可見光波段發光，但它們也會在紅外波段發光。在太陽系中，有八顆行星圍繞太陽運行。行星基本上可能是岩石天體，比如內行星--水星、金星、地球和火星；也可能是主要由液態和氣態物質組成的天體，有一個小的固態核心，比如外行星--木星、土星、天王星和海王星。太陽系之外的行星被稱為太陽系外行星，簡稱系外行星。

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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

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

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

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 姓名標示 4.0 國際 (CC BY 4.0) icons

水星

Caption: 這張圖像是由信使號探測器（英文縮寫：MESSENGER，意譯為“水星表面、空間環境、環境化學與測距“）獲取的水星表面拼接圖像的合成圖。信使號由美國宇航局於2004年發射，並在2011年至2015年間對水星進行了探索。
Credit: 美國國家航空航天局/約翰霍普金斯大學應用物理實驗室/華盛頓卡內基研究所 credit link