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Glossary term: 天極

Description: 南北兩天極被定義為地球自轉軸與天球的交點。

在地球的北極,北天極總是在正上方;而在地球的南極,南天極總是在正上方。由於地球自轉,北半球的天空似乎圍繞著北天極旋轉,而南半球的天空似乎圍繞著南天極旋轉。北天極的赤緯為+90度,而南天極的赤緯為-90度。

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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".

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北斗七星逐漸向左側地平線下方移動,而右側則有一顆彗星在天空中升起。

北斗七星和新智彗星 C2020 F3

Caption: 這段延時攝影記錄了2020年7月拍攝的三幀畫面中標誌性的北斗七星的軌跡。影像在意大利的三個地點拍攝:拉瓦雷多三峰(Tre Cime di Lavaredo)奧隆佐迪卡多雷、裡特山(Monte Rite)奇比亞納迪卡多雷,以及拉佐牧場(Casera Razzo)維戈迪卡多雷。這場視覺奧德賽展示了北斗七星的迷人軌跡,並在夜空中繪製出天體畫卷。它不僅描繪了這個著名星群的軌跡,還捕捉到2020年7月照亮天空的罕見新智彗星 C/2020 F3 這一非凡的天文事件,為我們的夜空增添了光彩。
Credit: 喬爾賈·霍弗/國際天文學聯合會教育辦公室 (CC BY 4.0)

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繁星劃出的數百條小弧線以地平線附近的一個點為中心形成同心圓。一棵樹矗立在前景中。

博特爾四級光汙染下的南半球星軌

Caption: 這張令人歎為觀止的照片是 2020 年 6 月 25 日在印度尼西亞西爪哇庫寧安省西里穆斯市凌加梅卡村的晴朗夜空下拍攝的,照片中的星軌掠過南半球的天際。星軌是地球自轉所導致的恆星表觀運動,當長時間跟蹤時,就會產生這些令人著迷的光弧。因為這張照片是在赤道附近拍攝的,所以恆星所圍繞旋轉的點(南天極)靠近地平線。攝影師使用智能手機上的星軌功能,在較長時間內拍攝了一系列圖像,並將它們疊加在一起。前景引人注目的大樹增添了畫面的深度,使上方天體的運動與地面的靜止形成了鮮明對比,同時也遮掩了周圍的一些光汙染。世界不同地區的夜空景色各異,令人驚嘆,使人們意識到保護各地黑暗天空的重要性。
Credit: Slamat Riyadi/IAU OAE (CC BY 4.0)

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The Milky Way appears as a diagonal stripe bottom left to top right. It becomes more horizontal as the video progresses.

Southern Sky Over La Silla

Caption: This video shows the Milky Way’s sprawling brilliance across the celestial expanse. Among the stars’ grand theatre, the Southern Cross constellation claims its place in the scene, distinguished by its distinctive cross shape as seen in the top of this video and slightly to the right just over the Milky Way, slowly disappearing as the video progresses. This celestial marker, a prominent feature in the southern hemisphere, holds cultural and navigational significance, having served as a navigational guidepost for centuries. Accompanying the Milky Way’s grandeur are the two Magellanic clouds, celestial companions seen dancing in the distant sky. The Carina Nebula adds its ethereal glow to the cosmic panorama, painting a radiant hue against the darkness. In the midst of this celestial ballet, a gentle green hue envelops the atmosphere, a phenomenon known as airglow, adding a touch of subtle luminescence to the night sky. The terrestrial also makes an appearance, with planes flying overhead and vehicles driving between observatory buildings. This time-lapse, taken from the La Silla Observatory in Chile, is a window to the captivating dance of stars, offering a glimpse into the awe-inspiring beauty of our galaxy and the celestial landmarks that grace the southern sky.
Credit: José Rodrigues/IAU OAE (CC BY 4.0)

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The Southern Cross points out the South Celestial Pole, around which the sky appears to rotate

Beautiful Night in the Atacama Desert

Caption: Taken from San Pedro de Atacama, Chile, in June 2023, this time-lapse reveals the celestial ballet that unfolds as the Southern Cross takes its majestic journey across the sky, pointing the way to the South Celestial Pole around which the sky rotates, until it gracefully sets. The star-studded canvas showcases the grandeur of the Milky Way, adorned by the rotating Large and Small Magellanic Clouds swirling around the Southern Celestial Pole. The prominent constellations of Crux, Centaurus, Scorpius, and the former Argo Navis (Carina, Puppis, Vela) are also visible. The spectacle begins just after nightfall, capturing the radiant descent of Canopus, a beacon about to dip below the horizon. Throughout the sequence, there is a subtle presence of passing aeroplanes, fleeting headlights of cars, drifting clouds, and the ethereal airglow. At a stunning moment, a vivid meteor streaked across the sky, a breathtaking fireball briefly igniting the right lower corner around the 41st second mark. As the sequence progresses, the rising moon elegantly illuminates the landscape, casting its glow upon an ancient tree trunk resting on the dry, dusty grounds of the Salar de Atacama. This captivating journey through the night skies concludes before the break of dawn, offering a glimpse into the celestial marvels that are woven into the nocturnal tapestry of San Pedro de Atacama.
Credit: Uwe Reichert/IAU OAE (CC BY 4.0)

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The dish of a radio telescope rotates as the Big Dipper moves in the sky behind.

The Big Dipper with the Sardinia Radio Telescope SRT

Caption: This time-lapse captures the movement of the stars alongside the majestic 64-metre Sardinia Radio Telescope (SRT) from the National Institute of Astrophysics (INAF), with special attention to the renowned Big Dipper against the backdrop of the celestial sphere. The camera pans as the famous asterism sinks in the sky while planes fly past and the radio telescope rotates. The harmonious interplay between the stellar pathways and the colossal dish of the radio telescope creates a mesmerising visual ode to the cosmic ballet taken in September 2019.
Credit: Antonio Finazzi/IAU OAE (CC BY 4.0)

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The Big Dipper sinks in the sky with the handle sweeping out a larger circle than the bowl of the asterism.

Big Dipper Over the Mono Lake

Caption: The Big Dipper asterism gracefully moves above the otherworldly tufa formations of Mono Lake, California. The time-lapse captures the Big Dipper’s movement across the northern horizon until its inferior conjunction. At Mono Lake’s latitude (+38°), the stars of the Big Dipper remain circumpolar, except for Alkaid. The North Star sits 38° above the horizon, just outside the field of view in the top right. The lunar illumination bathes the landscape in a soft glow, gradually fading as the Moon sets, cloaking the scene in darkness.
Credit: Fabrizio Melandri/IAU OAE (CC BY 4.0)

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Timelapses of rotating skies behind trees, telescopes, mountains and observatories

The Rotating Planet

Caption: A cosmic journey unfolds across continents in this time-lapse video which captures both iconic constellations from diverse corners of the world. Starting in China, the Big Dipper graces the night sky, a steadfast guide embedded in cultural narratives. Its luminance marks the beginning of this celestial odyssey. The two pointer stars on the end of the Big Dipper point to the North Star (Polaris) which appears to remain stationary as the sky rotates. From Nepal’s lofty peaks, the Big Dipper’s familiarity persists, a reliable fixture in the shifting panorama of the rotating planet. Moving to Chile, the Southern Cross adorns the firmament, emblematic of the southern skies. Frames from Chile showcase this constellation accompanied by the Milky Way Galaxy. In Namibia, a telescope from the H.E.S.S. Observatory appears in the video. Later, nestled beneath sheltering trees, the Big Dipper persists in its celestial prominence, appearing against a canvas of stars. Using varied techniques — fisheye lenses, static cameras, and Earth's movement-tracking — each frame unveils the Cross’s grandeur against diverse landscapes. These sequences — marked by star trails and Earth’s rotation—highlight the enduring presence of the Big Dipper and Southern Cross, bridging cultures and celestial beauty across hemispheres.
Credit: Jianfeng Dai/IAU OAE (CC BY 4.0)

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A traditional Chinese building. Above the streaks of stars form a circular pattern around the north star.

Star Trails of the Forbidden City

Caption: Beneath the celestial ballet of star trails that weave their way across the night sky, the Beijing Forbidden City stands as a testament to ancient celestial connections in this image captured in March 2022. Designed with a cosmic alignment in mind, the palace echoes the orientation of the North Star, also known as Polaris, a celestial anchor that has long guided navigators and symbolised steadiness in the sky. It was believed that the Emperor embodied the earthly representation of this pole star, bridging the realms between heaven and earth. In this harmonious one-hour exposure captured with a smartphone, the streaks of stars trace their nightly journey across the firmament, converging toward the North Star, reflecting the precision of both architectural design and celestial paths.
Credit: Stephanie Ziyi Ye/IAU OAE (CC BY 4.0)

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