Glossary term: Estrellas circumpolares
Description: En la mayoría de los lugares de la Tierra, el polo norte celeste o el polo sur celeste son visibles en el cielo a cierta distancia por encima del horizonte. Para un observador situado en uno de estos lugares, las estrellas parecen girar alrededor del polo celeste a medida que pasa el tiempo: cada estrella traza un círculo en el cielo, con el polo celeste —hacia el que apunta el eje de la Tierra— como centro. En los dos puntos donde el círculo cruza el horizonte del observador, uno al este y otro al oeste, la estrella en cuestión saldrá y se pondrá, respectivamente. En el caso de las estrellas que se encuentran lo suficientemente cerca del polo celeste, el círculo trazado quedará completamente por encima del horizonte. Nuestro observador nunca verá salir ni ponerse esas estrellas. Esas estrellas que nunca se ponen se denominan estrellas circumpolares.
Qué estrellas son circumpolares depende de la latitud geográfica del observador y de la declinación de la estrella; esta última es el ángulo entre la posición de la estrella y el ecuador celeste. En el hemisferio norte, una estrella es circumpolar si su declinación es mayor que 90° menos la latitud del observador. En el hemisferio sur, debemos tener en cuenta que tanto las latitudes meridionales de la Tierra como los valores de declinación meridional tienen signo negativo. Teniendo en cuenta estos signos, en el hemisferio sur, una estrella es circumpolar si su declinación es menor que –90° más el valor absoluto de la latitud del observador.
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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
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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In Other Languages
- Árabe: النجوم القطبية
- Alemán: Zirkumpolarsterne
- Inglés: Circumpolar Stars
- Francés: Étoiles circumpolaires
- Italiano: Stelle circumpolari
- Japonés: 周極星 (external link)
- Chino simplificado: 拱极星
- Chino tradicional: 拱極星
Related Media
Stone Star Circles, Startrails above Stonehenge, by Till Credner, Germany
Caption: Second place in the IAU OAE Astrophotography Contest, category Star trails.
Astronomy is one of the oldest (if not the oldest) of the sciences, and as such has connection to various cultures over millennia. This image in a way conveys this relationship by being contextualised in Stonehenge. There is much research into what astronomers call archeoastronomy sites, and how they connect to the sky (for example, seasons, phases of the moon and much more). Civilizations across time and from all over the world have their own views and interpretations of what they see in the sky, and this has been tied not only to culture but also to the people’s day-to-day and seasonal activities. The “concentric circles” which are often referred to as “star trails”, are the result of the apparent motion of the sky, which is in reality due to the rotation of the Earth on its axis. The small dot appearing towards the top center of the image is Polaris – The North or Pole Star. Polaris is only visible to observers in the Northern latitudes. The height of the Pole Star can be used to infer the observer’s actual latitude. Stonehenge is located at around 51° North. This image is taken from one of the most notable ancient sites in the world, brings us back in time, and makes us wonder about the stories told by the people that lived in that place many millennia ago.
Credit: Till Credner/IAU OAE
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Half day exposure to the north star, by Fabrizio Melandri, Italy
Caption: First place in the IAU OAE Astrophotography Contest, category Star trails.
This star trail image shows the apparent movement of the stars in the night sky, which results from the Earth’s rotation around its polar axis. The trees in the foreground serve as an anchor as we turn with the Earth. The bright white semi-circle in the center of the image is the North (Pole) star – Polaris, which is located very close to the North Celestial Pole. One way to imagine that the Earth is at center of hollow crystal sphere, and the stars are embedded on this sphere, as the Earth spins on its axis, an observer on Earth sees the stars rising and setting, following an arc, because the horizon prevents the observer from the full arc for stars that are further away from the Celestial Pole. The North Celestial Pole (and its opposite the South Celestial Pole) is essentially formed by extending the line of the Earth’s axis. Capturing this image requires the photographer to take a long exposure with the camera on a tripod and pointing towards the Pole Star (North Hemisphere). In the Southern Hemisphere there is no star as close as Polaris is to the Celestial Pole, so the position of the South Celestial Pole is found using the South Cross and Pointer Stars (Alpha and Beta Centauri). Although overall the image has a slight blue tint, it does capture the varying colours of stars, it is easy to distinguish between the higher temperature blue stars and the lower temperature of the whitish stars, and even lower temperature reddish stars. The reason for this variation in colour is because higher temperature stars emit more in shorter wavelengths (bluer), compared to lower temperature stars which emit in longer wavelengths (redder).
Credit: Fabrizio Melandri/IAU OAE
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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 Reconocimiento 4.0 Internacional (CC BY 4.0) icons
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 Reconocimiento 4.0 Internacional (CC BY 4.0) icons
Big Dipper and Comet Neowise C2020 F3
Caption: Honorable mention in the 2023 IAU OAE Astrophotography Contest, category of Time-lapses of rotation of Big Dipper or Southern Cross.
This time-lapse documents the trajectory of the iconic Big Dipper across three frames taken in July 2020. Captured from three locations in Italy, Tre Cime di Lavaredo Auronzo di Cadore, Monte Rite, Cibiana di Cadore, and Casera Razzo, Vigo di Cadore, this visual odyssey showcases the captivating journey of the Big Dipper with the addition of trails of stars painting a celestial canvas. It not only traces the path of this renowned asterism but also features the rare appearance of comet Neowise C/2020 F3, an extraordinary event that graced our skies during July 2020.
Credit: Giorgia Hofer/IAU OAE (CC BY 4.0)
License: CC-BY-4.0 Creative Commons Reconocimiento 4.0 Internacional (CC BY 4.0) icons
Related Diagrams
Mapa de la constelación de Casiopea
Caption: La constelación de Casiopea junto con sus estrellas brillantes y las constelaciones que la rodean. Casiopea está rodeada por (en el sentido de las agujas del reloj desde arriba): Cefeo, Andrómeda, Perseo y Camelopardalis.
Casiopea es una constelación boreal visible desde todo el hemisferio norte y desde las regiones ecuatoriales del hemisferio sur. Es más visible por la noche a finales de otoño en el hemisferio norte y a finales de primavera en el hemisferio sur.
Los cúmulos estelares abiertos M52, M103, NGC 457 y NGC 663 se encuentran en esta constelación. Están marcados con círculos amarillos. Dos galaxias elípticas enanas, NGC 147 y NGC 185, se encuentran en la parte sur de la constelación. Están marcadas con elipses rojas y están ligadas gravitacionalmente a la galaxia de Andrómeda, que se encuentra al sur de la constelación de Andrómeda.
El eje-y de este diagrama está en grados de declinación con el norte hacia arriba y el eje-x está en horas de ascensión recta con el este a la izquierda. El tamaño de las estrellas marcadas aquí está relacionado con la magnitud aparente de la estrella, una medida de su brillo aparente. Los puntos más grandes representan estrellas más brillantes. Las letras griegas indican las estrellas más brillantes de la constelación. Están ordenadas según su brillo: la estrella más brillante se denomina alfa, la segunda más brillante beta, etc., aunque este orden no siempre se sigue con exactitud. Las líneas punteadas marcan los límites de las constelaciones según la UAI y las líneas verdes continuas marcan una de las formas habituales utilizadas para representar las figuras de las constelaciones. Ni los límites de las constelaciones ni las líneas que unen las estrellas aparecen en el cielo.
Credit: Adaptado por la Oficina de Astronomía para la Educación de la UAI a partir del original de UAI/Sky & Telescope
License: CC-BY-4.0 Creative Commons Reconocimiento 4.0 Internacional (CC BY 4.0) icons
Mapa de la Constelación de la Osa Menor
Caption: La constelación de la Osa Menor junto con sus estrellas brillantes y las constelaciones que la rodean. La Osa Menor está rodeada por (en el sentido de las agujas del reloj desde arriba): Cefeo, Camelopardalis y Draco. La Osa Menor destaca por su estrella más brillante, Polaris, que es la estrella del polo norte.
La Osa Menor es visible desde todo el hemisferio norte y algunas partes de la constelación desde las regiones ecuatoriales del hemisferio sur. También es circumpolar para las regiones templadas y árticas del hemisferio norte. Polaris, situada muy cerca del polo norte celeste, es circumpolar para todo el hemisferio norte. La constelación es más visible por la noche en verano en el hemisferio norte y en invierno en el hemisferio sur.
Este diagrama muestra una zona alrededor del polo norte celeste. Aquí convergen las líneas de ascensión recta constante. Los valores de ascensión recta (en horas) de estas líneas están marcados en el eje-x encima y debajo del diagrama. Algunas de las líneas de declinación constante (en grados) están marcadas en el eje-y. El tamaño de las estrellas marcadas aquí está relacionado con la magnitud aparente de la estrella, una medida de su brillo aparente. Los puntos más grandes representan estrellas más brillantes. Las letras griegas indican las estrellas más brillantes de la constelación. Están ordenadas según su brillo: la estrella más brillante se denomina alfa, la segunda más brillante beta, etc., aunque este orden no siempre se sigue con exactitud. Las líneas punteadas marcan los límites de las constelaciones según la UAI y las líneas verdes continuas marcan una de las formas habituales utilizadas para representar las figuras de las constelaciones. Ni los límites de las constelaciones ni las líneas que unen las estrellas aparecen en el cielo.
Credit: Adaptado por la Oficina de Astronomía para la Educación de la UAI a partir del original de UAI/Sky & Telescope
License: CC-BY-4.0 Creative Commons Reconocimiento 4.0 Internacional (CC BY 4.0) icons
Mapa de la Constelación de la Osa Mayor
Caption: La constelación de la Osa Mayor junto con sus estrellas brillantes y las constelaciones que la rodean. La Osa Mayor está rodeada por (en el sentido de las agujas del reloj desde arriba): Draco, Camelopardalis, Lynx, Leo Menor, Leo, Coma Berenices, Canes Venatici y Bootes. La Osa Mayor es famosa por su distintivo asterismo, a menudo conocido en inglés como Big Dipper (Osa Mayor) o Plough (Arado). Este distintivo asterismo septentrional recibe una gran variedad de nombres de culturas de todo el mundo. Mientras que la mayoría de las constelaciones y asterismos están formados por estrellas no relacionadas que aparecen juntas en el cielo de forma aleatoria, cinco de las estrellas de la Osa Mayor forman parte de la Asociación Estelar de la Osa Mayor, un grupo de estrellas que se mueven juntas por el espacio y que probablemente se formaron en el mismo lugar hace 300 millones de años. Las dos estrellas del extremo derecho de la Osa Mayor en este diagrama forman un par de estrellas puntero que pueden utilizarse para localizar a Polaris, la estrella polar del norte que se encuentra en la constelación de la Osa Menor.
La Osa Mayor es una constelación boreal y es visible desde las regiones septentrionales y ecuatoriales. Algunas partes de la constelación son visibles desde todas las regiones del hemisferio sur, excepto las más antárticas, pero no todas las regiones templadas del hemisferio sur pueden ver toda la Osa Mayor. Por el contrario, la Osa Mayor y gran parte del resto de la constelación son circumpolares en las regiones árticas y en muchas regiones templadas del hemisferio norte. La Osa Mayor es más visible al atardecer en primavera en el hemisferio norte y en otoño en el hemisferio sur.
En la parte norte de esta constelación aparecen dos galaxias destacadas, la galaxia espiral M81, y M82, una posible galaxia espiral cuya estructura es difícil de observar desde la Tierra, ya que aparece de canto. Ambas se muestran aquí como elipses rojas. La nebulosa planetaria M97 (la nebulosa del Búho) se encuentra en el centro de la constelación y está marcada con un círculo verde superpuesto a un signo de más.
El eje-y de este diagrama está en grados de declinación con el norte hacia arriba y el eje-x está en horas de ascensión recta con el este a la izquierda. El tamaño de las estrellas marcadas aquí está relacionado con la magnitud aparente de la estrella, una medida de su brillo aparente. Los puntos más grandes representan estrellas más brillantes. Las letras griegas indican las estrellas más brillantes de la constelación. Están ordenadas según su brillo: la estrella más brillante se denomina alfa, la segunda más brillante beta, etc., aunque este orden no siempre se sigue con exactitud. Las líneas punteadas marcan los límites de las constelaciones según la UAI y las líneas verdes continuas marcan una de las formas habituales utilizadas para representar las figuras de las constelaciones. Ni los límites de las constelaciones ni las líneas que unen las estrellas aparecen en el cielo.
Credit: Adaptado por la Oficina de Astronomía para la Educación de la UAI a partir del original de UAI/Sky & Telescope
License: CC-BY-4.0 Creative Commons Reconocimiento 4.0 Internacional (CC BY 4.0) icons
Apus Constellation Map
Caption: The constellation Apus with its bright stars and surrounding constellations. Apus is surrounded by (going clockwise from the top): Triangulum Australe, Circinus, Musca, Chamaeleon, Octans, Pavo and Ara.
Apus is a southern constellation lying close to the south celestial pole. As such it is visible at some point in the year from the entire southern hemisphere but is only visible from the most equatorial regions of the northern hemisphere. Apus is circumpolar for all temperate and antarctic regions of the southern hemisphere. It is most visible in the evenings in the northern hemisphere summer and southern hemisphere autumn.
The globular cluster NGC 6101 can be found in Apus. It is marked here with a yellow circle with a plus symbol superimposed on it.
This diagram maps an area around the south celestial pole. Here lines of constant right ascension converge. The right ascension values (in hours) of these lines are marked on the x-axis above and below the diagram. Lines of constant declination (in degrees) are marked on the y-axis. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the lines joining the stars appear on the sky.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope
License: CC-BY-4.0 Creative Commons Reconocimiento 4.0 Internacional (CC BY 4.0) icons
Auriga Constellation Map
Caption: The constellation Auriga with its bright stars and surrounding constellations. Auriga is surrounded by (going clockwise from the top): Camelopardalis, Perseus, Taurus, Gemini and Lynx. Capella, the brightest star in Auriga, is the sixth brightest star in the night sky.
As a northern constellation, Auriga is visible from the whole of the northern hemisphere at some point in the year. The whole of the constellation is visible to equatorial regions of the southern hemisphere with parts of it visible to temperate southern regions. The whole constellation is circumpolar from arctic regions. The constellation is best viewed in the evening in the late northern hemisphere winter and late southern hemisphere summer.
Auriga lies in the plane of the Milky Way and thus hosts a number of open clusters. Of these M36, M37 and M38 are marked on this diagram with yellow circles. IC 405, also known as the flaming star nebula, is marked here with a green square.
The y-axis of this diagram is in degrees of declination with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. The blue line at the bottom of the diagram marks the ecliptic. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Credit: Adapted by the IAU Office of Astronomy for Education from the original by the IAU and Sky & Telescope
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Related Activities
Navigation in the Ancient Mediterranean and Beyond
astroEDU educational activity (links to astroEDU website) Description: Learn the ancient skill of Celestial Navigation
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Tags:
History
, Geography
, Celestial navigation
Age Ranges:
14-16
, 16-19
Education Level:
Middle School
, Secondary
Areas of Learning:
Discussion Groups
, 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
, Using mathematics and computational thinking
