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Terme du glossaire : Amas globulaire

Description : Un amas globulaire est un groupe d'étoiles, de forme sphérique, massif et très dense, lié par la gravitation et stable depuis des milliards d'années. Dans la Voie lactée, les amas globulaires ne sont constitués que d'étoiles très anciennes (en général, leur âge est compris entre 11 et 13 milliards d'années). Les amas globulaires comptent parmi les objets les plus anciens de la Voie lactée. Dans la plupart des amas globulaires, les étoiles qui les composent se sont toutes formées à peu près en même temps, bien que quelques amas globulaires montrent des signes de générations multiples d'étoiles. La Voie lactée compte environ 160 amas globulaires (la plupart résidant dans son halo), tandis que les galaxies elliptiques géantes peuvent en compter plusieurs milliers.

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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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Media associé


Un amas d'étoiles de différentes couleurs. Les étoiles sont fortement concentrées au centre de l'image.

Étoiles dans les amas globulaires près du cœur de la Voie lactée

Légende : Cette image du télescope spatial Hubble présente une vue de l'intérieur de l'amas globulaire Terzan 9, composé de millions d'étoiles et situé près du cœur de notre galaxie, la Voie lactée. Cet amas globulaire se trouve dans le bulbe central de la galaxie, au milieu de la poussière interstellaire, qui masque la lumière de ces amas d'étoiles. Cette image est une combinaison de la lumière observée dans les parties visible et infrarouge du spectre électromagnétique. L'imagerie multi-longueur d'onde de la couleur et de la luminosité des étoiles permet de déterminer leur âge et, par conséquent, l'âge de l'amas d'étoiles parent.
Crédit : ESA/Hubble & NASA, R. Cohen Lien vers les crédits

License: PD Domaine Public Icônes

Diagrammes associés


Scorpius appears as a letter T joined to a letter J. The ecliptic runs ESE to WNW and clips one arm of the T

Scorpius Constellation Map

Légende : The constellation Scorpius (often commonly called Scorpio) along with its bright stars and surrounding constellations. Scorpius is surrounded by (going clockwise from the top) Ophiuchus, Serpens Caput, Libra, Lupus, Norma, Ara, Corona Australis and Sagittarius. Scorpius’s brightest star Antares appears in the heart of the constellation with the famous tail of Scoprius in the south-east (lower left). Scorpius lies on the ecliptic (shown here as a blue line), this is the path the Sun appears to take across the sky over the course of a year. The Sun only spends a short amount of time in late November in Scorpius. The other planets of the Solar System can often be found in Scorpius. Scorpius lies south of the celestial equator. The whole constellation is not visible from the most arctic regions of the world with parts of Scorpius obscured for observers in northern parts of Asia, Europe and North America. Scorpius is most visible in the evenings in the northern hemisphere summer and southern hemisphere winter. The yellow circles mark the positions of the open clusters M6, M7 & NGC 6231 while the yellow circles with plus signs superimposed on them mark the globular clusters M4 and M80. 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 circle around Antares indicates that it is a variable star. 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 marks the ecliptic, the path the Sun appears to travel across the sky over the course of one year. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Crédit : Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

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


Sagittarius is shaped like a teapot pouring tea south west. The ecliptic runs WSW to ENE at the top of the constellation

Sagittarius Constellation Map

Légende : The constellation Sagittarius along with its bright stars and surrounding constellations. Sagittarius is surrounded by (going clockwise from the top) Aquila, Scutum, Serpens Cauda, Ophiuchus, Scorpius, Corona Australis, Telescopium, Microscopium and Capricornus. The brighter stars in Sagittarius form a distinctive teapot shape. Sagittarius lies on the ecliptic (shown here as a blue line), this is the path the Sun appears to take across the sky over the course of a year. The Sun is in Sagittarius from mid December to mid January. The other planets of the Solar System can often be found in Sagittarius. Sagittarius lies south of the celestial equator. The famous teapot asterism is visible for all but the most arctic regions of the world but the most southerly parts of the constellation are not visible in northern parts of Asia, Europe and North America. Sagittarius is most visible in the evenings in the northern hemisphere summer and southern hemisphere winter. The supermassive black hole Sagittarius A* which lies at the center of our Milky Way Galaxy is sits on the western (here right-hand) edge of Sagittarius. Due to it covering an area at the center of our Galaxy, Sagittarius is home to many star clusters including open clusters (marked here with yellow circles) and globular clusters (marked here with yellow circles with + signs superimposed on them). Three nebulae are also marked here with green squares. 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. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Crédit : Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

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


Le Capricorne se présente comme un triangle isocèle orienté vers le bas. L'écliptique passe par le centre, de l'OSO à l'ENE.

Carte de la constellation du Capricorne

Légende : La constellation du Capricorne (communément appelée Capricorne) inclut ses étoiles brillantes et les constellations environnantes. Le Capricorne est entouré (dans le sens des aiguilles d'une montre à partir du haut) du Verseau, de l'Aigle, du Sagittaire, de Microscope et du Poisson Austral. Le Capricorne se trouve sur l'écliptique (représenté ici par une ligne bleue), c'est-à-dire la trajectoire que le Soleil semble suivre dans le ciel au cours d'une année. Le Soleil se trouve dans le Capricorne de la mi-janvier à la mi-février. Les autres planètes du système solaire se trouvent souvent dans le Capricorne. Le Capricorne se trouve juste au sud de l'équateur céleste et est visible pour tous les observateurs situés au sud du cercle polaire arctique. Le Capricorne est surtout visible le soir, en automne dans l'hémisphère nord et au printemps dans l'hémisphère sud. Au sud-est (en bas à gauche sur ce diagramme) de la constellation se trouve l'amas globulaire M30 (représenté ici par un cercle jaune sur lequel est superposé un signe plus). L'axe des y de ce diagramme est en degrés de déclinaison avec le nord en haut et l'axe des x est en heures d'ascension droite avec l'est à gauche. La taille des étoiles marquées ici correspond à la magnitude apparente de l'étoile, une mesure de sa luminosité apparente. Les points les plus gros représentent les étoiles les plus brillantes. Les lettres grecques indiquent les étoiles les plus brillantes de la constellation. Elles sont classées par ordre de luminosité, l'étoile la plus brillante étant étiquetée alpha, la deuxième plus brillante bêta, etc., bien que cet ordre ne soit pas toujours respecté à la lettre. Les lignes pointillées marquent les limites des constellations selon l'UAI et les lignes vertes pleines marquent l'une des formes couramment utilisées pour représenter les figures des constellations. Ni les limites des constellations, ni les lignes reliant les étoiles n'apparaissent sur le ciel.
Crédit : Adapté par le Bureau de l'astronomie pour l'éducation de l'AIU à partir de l'original de l'AIU/Sky & Telescope

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


Aquarius appears as a sprawling series of connected lines. The ecliptic runs through its center from WSW to ENE.

Aquarius Constellation Map

Légende : The constellation Aquarius along with its bright stars and surrounding constellations. Aquarius is surrounded by (going clockwise from the top) Pegasus, Equuleus, Aquila, Capricornus, Piscis Austrinus, Sculptor, Cetus and Pisces. Aquarius lies on the ecliptic (shown here as a blue line), this is the path the Sun appears to take across the sky over the course of a year. The Sun is in Aquarius from mid February to mid March. The other planets of the Solar System can often be found in Aquarius. Aquarius spans the celestial equator and is thus visible at some time in the year from all of planet Earth. In the most arctic or antarctic regions of the world, some parts of the constellation may not be visible. Aquarius is most visible in the evenings in the northern hemisphere autumn and southern hemisphere spring. The yellow circles with plus symbols superimposed on them mark the globular clusters M2 and M72. The green circles superimposed on plus symbols mark the planetary nebulae NGC 7293 (the Helix Nebula) and NGC 7002 (the Saturn Nebula). M73 (marked with an x symbol) is a coincident grouping of stars previously erroneously classified as an open cluster. 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. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Crédit : Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

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


Ophiuchus appears as a headless stick figure

Ophiuchus Constellation Map

Légende : The constellation Ophiuchus along with its bright stars and its surrounding constellations. Ophiuchus is surrounded by (going clockwise from the top): Hercules, Serpens Caput, Scorpius, Sagittarius and Serpens Cauda. Ophiuchus is not part of the traditional twelve zodiac constellations but it lies on the ecliptic (shown here as a blue line), this is the path the Sun appears to take across the sky over the course of a year. The Sun is in Ophiuchus from late November to mid December. The other planets of the Solar System can often be found in Ophiuchus. Ophiuchus spans the celestial equator and thus part of the constellation is visible across the whole of the earth at some point in the year. However during the time it is most visible in the evenings (the southern hemisphere winter and northern hemisphere summer) much of the arctic is in perpetual daylight making the stars in the constellation impossible to see. The whole constellation is visible from equatorial and temperate regions of both hemispheres. As Ophiuchus lies close to the galactic center it contains many globular clusters such as M9, M10, M12, M14, M19, M62, and M107. These are marked as yellow circles with plus symbols superimposed. 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. Neither the constellation boundaries, nor the line marking the ecliptic, nor the lines joining the stars appear on the sky.
Crédit : Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

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

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