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Glossary term: Ciel

Description: Le ciel est ce que nous voyons lorsque nous sommes à l'extérieur, notre vue n'étant encombrée par aucune structure sur Terre, regardant vers le haut ou au moins plus haut que l'horizon qui marque la limite de ce que nous pouvons voir de la Terre et des structures terrestres. La nuit, lorsque le ciel est dégagé, nous pouvons voir des planètes lointaines, des étoiles et même quelques galaxies (la galaxie d'Andromède dans l'hémisphère nord et les nuages de Magellan dans l'hémisphère sud). Le scintillement des étoiles prouve que nous regardons encore à travers les gaz de l'atmosphère terrestre. Pendant la journée, la lumière du soleil dispersée par les molécules d'air fait briller le ciel d'une couleur bleue, bloquant notre vue sur le cosmos. Les nuages ou le brouillard qui couvrent le ciel nous empêchent également d'observer les objets astronomiques.

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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

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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L'arc de la Voie Lactée au-dessus de quelques arbres. Deux petites galaxies sont visibles dans la partie inférieure de l'image.

Voie Lactée Au-dessus de l'Arbre à Carquois

Caption: Cette photographie époustouflante a été prise le 17 juin 2023, près de Keetmanshoop, en Namibie, à l'aide d'un smartphone. Dominant le ciel nocturne, l'arc majestueux de la Voie Lactée crée un pont céleste à travers les cieux. L'image capture une série d'objets astronomiques remarquables : le Grand et le Petit Nuage de Magellan, vus vers le bas de l'image et apparaissant comme des nuages flous ; Antarès, vu vers le haut à gauche de l'image ; et la nébuleuse du sac de charbon désignée par divers noms par les cultures indigènes du monde entier), vue verticalement au-dessus du Grand Nuage de Magellan. Sur cette toile de fond astrale, les arbres, qui sont en fait des aloès succulents originaires d'Afrique australe, ajoutent une touche à la beauté unique de la Terre. Historiquement, ces plantes étaient appelées "arbres à carquois" parce que des groupes d'indigènes locaux utilisaient leurs branches creuses pour contenir des fléchettes. Le paysage serein de la Namibie, combiné à l'éclat des étoiles de l'hémisphère sud, offre un aperçu de la majesté de notre univers.
Credit: Jianfeng Dai/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


Four dish-shaped telescopes point at the sky with the arc of the Milky Way overhead.

Milky Way Over H.E.S.S Observatory

Caption: The darkness of the skies at H.E.S.S Observatory reveal the seemingly innumerable stars that make up the Milky Way galaxy, making it challenging to discern the constellations as seen taken with a smartphone from Namibia in June 2023. The stars Alpha and Beta Centauri are visible bottom left of the image just about the tower. The orange-hued star visible just above and to the right of the left H.E.S.S telescope is Antares, a red-giant star that is part of the constellation Scorpius.
Credit: Jianfeng Dai/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


The Big Dipper drifts lower towards the horizon on the left, on the right a comet rises in the sky.

Big Dipper and Comet Neowise C2020 F3

Caption: 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 Attribution 4.0 International (CC BY 4.0) icons


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)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons

The Office of Astronomy for Education is hosted by the Haus der Astronomie on the campus of the Max Planck Institute for Astronomy in Heidelberg. The Office of Astronomy for Education is an office of the International Astronomical Union, with substantial funding from the Klaus Tschira Foundation and the Carl Zeiss Foundation. The Shaw-IAU Workshops on Astronomy for Education
are funded by the Shaw Prize Foundation.