Loading...

Glossary term: 北極星

Description: 北極星是距離北天極最近的亮星(1度以內)。它的正式名稱是小熊座α星,通常被稱為北極星,在中國也叫勾陳一、北辰、宸極。北天球的所有恆星都似乎圍繞著它旋轉,因此它是進行導航和天體測量的絕佳固定點。它的地平高度可以提供觀測地點的大致緯度。不過,由於地球自轉軸的進動,北極星在天球上的位置正在慢慢發生變化,因此再過幾個世紀,北極星就不再能指示北天極的位置了。

北極星是一個由三合星系統。主星是一顆黃超巨星,被命名為北極星Aa;伴星是一顆較小的主序星,被命名為北極星Ab。它們在非常近的軌道上相互繞轉運行。這對恆星還有一顆較大的伴星——北極星B,它是一顆主序星,在2400個天文單位的距離上運行,軌道週期約為29.3年。北極星B可以用普通望遠鏡分辨出來。哈勃太空望遠鏡能夠分辨出北極星三合星系統的所有三個成員。北極星的視星等會有波動,這是因為北極星Aa是一個仙王座變星。北極星系統距離地球約447光年。

See this term in other languages

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


The ladle-shaped Big Dipper with the orange star Arcturus to its left. Right is the diffuse disk-shaped Andromeda galaxy

Dreamlike Starry Sky and Airglow

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   This spectacular image shows a range of prominent constellations visible in the night sky over the desert of inner Mongolia, taken in August 2019. The yellowish star in the bottom left side is Arcturus, one of the brightest stars in the night sky, and the brightest in the constellation Boötes. The handle of the Big Dipper points towards this bright star and the Dipper is also visible above Boötes. The Northern Dipper (Bei Dou) is a traditional Chinese constellation. It is considered a chariot in which the Judges for Nobility are sitting. Arcturus is considered a single-star asterism, named the Horn, which forms part of the Chinese super-constellation for the spring, the Azure Dragon of the East. The front of the Northern Dipper points towards the star at the top of the photograph which is now called Polaris, the northern Pole Star. In ancient China, there was no bright star at the pole, so the stars in the nearest vicinity of the pole were considered to belong to the emperor and his family in the constellation the Purple Forbidden Palace. At least as early as mediaeval times, Polaris was considered part of the constellation of the Great Emperor of Heaven. Corona Borealis is also visible in the top right corner of this image, although not in its completeness. It is called the Coiled Thong in China. With its characteristic semi-circular shape, this is one of the smaller constellations of the 88 modern ones, but also can be traced back at least three or four millennia through the Roman “Crown”, the Greek wedding “Wreath”, and the Babylonian “Asterism of Dignity”. The modern name literally means “Northern Crown” in Latin. At the upper-right edge of the image, we find the part of the modern constellation Cassiopeia that is considered the Flying Corridor and an Auxiliary Road in ancient China. The W-shape of Cassiopeia is cut off by the edge of the photograph but the constellations to its south and southeast, Andromeda and Perseus, are clearly recognisable. Prominently we see the Andromeda galaxy, the most distant object that is visible to the unaided eye. It is located at the outermost outliers of the band of the Milky Way, which could explain why it has not been mentioned explicitly in ancient star catalogues, as it was mistakenly thought to be part of the Milky Way. The photograph also shows clearly reddish parts of the Milky Way that don’t appear bright to the naked eye, and also open clusters that are formed from the same molecular cloud, i.e., groups of stars with similar ages. This region is part of many big and small asterisms in traditional Chinese uranology.
Credit: Likai Lin/IAU OAE

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


The Big Dipper, seven bright stars shaped like a ladle, viewed in 4 seasons, each time at a different angle

Big Dipper in Four Seasons

Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   As Earth moves around the Sun, the positions of the stars in the night sky appear to change over the course of the year. This is well exemplified in this mosaic, with images taken in all four seasons throughout 2020 in the region of Veneto, Italy, showing the apparent motion of the Ursa Minor and Ursa Major constellations. Ursa Minor, the Little Bear, is a constellation of the northern hemisphere, and it contains the northern celestial pole, in our current epoch marked by a bright star called Polaris or the Pole Star. For centuries Polaris has been used for navigation in the northern hemisphere, as it has been almost at the exact pole position for roughly 200 years. In the Middle Ages and antiquity, there was no pole star; the celestial north pole lay in a dark region and the Greeks considered the “Little She-Bear” as a companion of the “Great She-Bear”, which is more easily recognizable. The brightest stars of these constellations were alternatively also considered as chariots by the Greeks, as written in Aratus’s famous didactic poem from the 3rd century before the common era. The most famous asterism in Ursa Major, composed of seven stars, has different names across the (northern) world. While considered as a chariot by the Greeks, it is “The Northern Dipper” in China, and “The Seven Oxen” for the ancient Romans. It was also the navigational purpose that led to the name The Great She-Bear, Ursa Major; for the Greeks, travelling towards the direction of the horizon above which Ursa Major appears meant moving towards the land of the bears (northern Europe). An animal is clearly recognizable when taking into account all the fainter stars in the vicinity of the seven bright ones. They considered it a female bear because Greek mythology connects this animal with the nymph Callisto, whose story describes the initiation rituals for women. In the top left, we see an image taken on a spring evening, while the image below shows the same portion of the sky on a summer evening. Going counterclockwise, we see the sky during autumn in the bottom right image, while the top right finally shows this portion of the sky in the winter. Note that the relative positions of Ursa Minor and the Big Dipper don’t change, but all stars appear to be moved in a circle around Polaris. This star pointing due north lies at the point where Earth’s rotational axis intersects the celestial sphere. The shift of constellations throughout the year is therefore a globe-clock or a globe-calendar, used by ancient civilizations to measure the year, and to predict the changes of seasons. It helps to establish, for instance, the best time for sowing and sailing as winds change with the seasons.
Credit: Giorgia Hofer/IAU OAE

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


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)

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


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)

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


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)

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


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)

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


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)

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

Related Activities


Navigating with the Kamal – Northern Hemisphere

Navigating with the Kamal – Northern Hemisphere

astroEDU educational activity (links to astroEDU website)
Description: How did Arabian sailors navigate at sea?

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

Tags: History , Geography , Coordinates , Celestial navigation , Arabia , Kamal
Age Ranges: 14-16 , 16-19
Education Level: Middle School , Secondary
Areas of Learning: Modelling , Social Research
Costs: Low Cost
Duration: 1 hour 30 mins
Group Size: Group
Skills: Analysing and interpreting data , Asking questions , Communicating information , Developing and using models , Planning and carrying out investigations