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Terme du glossaire : Phase lunaire

Description : La phase lunaire fait référence à la position de la Lune dans son orbite autour de la Terre. Le changement de position de la Lune entraîne le changement de forme de la partie éclairée de la Lune visible depuis la Terre au cours d'un mois lunaire. Une moitié de la Lune est toujours, sauf lors des éclipses lunaires, éclairée par le Soleil. Sur Terre, nous voyons différentes parties de la Lune éclairées au fur et à mesure qu'elle se déplace sur son orbite autour de nous. Le mois lunaire commence et se termine à la même phase. À une phase de 0 degré, appelée "nouvelle lune", la Lune est la plus proche du Soleil. À cette phase, la face éclairée de la Lune est opposée à la Terre et la lune apparaît sombre. La taille de la partie éclairée de la Lune visible depuis la Terre augmente progressivement (premier croissant ou "waxing phase" en anglais) pour devenir un croissant. La phase du premier quartier (lorsque la moitié de la face de la lune visible semble être éclairée, c'est ce que l'on appelle communément la demi-lune - une moitié de la face visible correspond à un quart de la surface totale de la Lune) se produit à 90 degrés du point de départ. La partie éclairée de la Lune visible depuis la Terre continue d'augmenter, devenant gibbeuse (de forme convexe ou bombée). La pleine lune se produit à 180 degrés. Après ce point, la forme commence à diminuer progressivement (phase décroissante), ce qui donne une lune gibbeuse, la phase du dernier quartier (lorsque la moitié de la lune semble être éclairée, c'est ce que l'on appelle communément la demi-lune) à 270 degrés du point de départ, le croissant de lune, et se termine par une nouvelle lune à 360 degrés. Même si la moitié de la lune semble éclairée aux phases 90 et 270 degrés, ce sont les côtés opposés qui sont éclairés et visibles depuis la Terre.

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Statut du terme et de sa définition : La définition initiale de ce terme en anglais a été aprouvée par un·e spécialiste de la recherche en astronomie et un·e spécialiste de l’éducation
La traduction de ce terme et de sa définition n'ont pas encore été aprouvées

Le glossaire multilangue de l'OAE est un projet du Bureau de l'IAU de l'Astronomie pour l'Education (OAE) en collaboration avec le Bureau de l'IAU de diffusion de l'Astronomie (OAO). Les termes et définitions ont été choisis, écrits et relues grâce à un effort collectif de l'OAE, les Centres et les Noeuds de l'OAE, les Coordinateurs Nationaux de l'Astronomie pour l'Education de l'OAE(NAECs) et d'autres volontaires. La liste complète des crédits pour ce projet est disponible ici . Tous les termes du glossaire et leur définition sont déposés sous licence Creative Commons CC BY-4.0 et doivent être créditées au nom de "IAU OAE".

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Media associé


La Lune presque pleine avec des cratères, des hauts plateaux clairs et des plaines sombres

Pleine lune

Légende : L'image montre la lune presque pleine, observée avec un petit télescope et un appareil photo APRN.
Crédit : Luc Viatour Lien vers les crédits

License: CC-BY-SA-3.0 Creative Commons (CC) Attribution - Partage dans les Mêmes Conditions 3.0 non transposé Icônes


The moon appears as a large, bright disk. It has craters and light and dark patches. The lower half has more dark patches

Full Moon

Légende : The full moon imaged from the Southern Hemisphere (New Zealand). During this phase the moon's illuminated half is fully visible from Earth.
Crédit : Dave Young / dcysurfer Lien vers les crédits

License: CC-BY-2.0 Creative Commons (CC) Attribution 2.0 Générique Icônes


The left half of the moon is bright and the right half is dark.

First quarter moon

Légende : The first quarter moon photographed from New Zealand. As half of the moon's illuminated half is visible, this is phase is popularly know as half moon.
Crédit : Dave Young / dcysurfer Lien vers les crédits

License: CC-BY-2.0 Creative Commons (CC) Attribution 2.0 Générique Icônes


The right half of the moon is bright and the left half of the moon is dark

First quarter moon

Légende : The first quarter moon photographed from the Northern Hemisphere (USA). At this phase half of the moon's illuminated half is visible. This phase is popularly known as half moon.
Crédit : Stephen Rahn Lien vers les crédits

License: CC0 CC0 1.0 universel (CC0 1.0) Transfert dans le Domaine Public Icônes


The moon appears as a disk. The left half of the moon is bright but the right half is dark.

Last quarter moon

Légende : This shows the last quarter moon photographed from the Northern Hemisphere (USA). During this phase half of the moon's illuminated half is visible. This phase is popularly known as half moon.
Crédit : Stephen Rahn Lien vers les crédits

License: CC0 CC0 1.0 universel (CC0 1.0) Transfert dans le Domaine Public Icônes

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Diagrammes associés


The Moon begins as dark, an illuminated portion grows from the left. Then once fully illuminated a dark portion grows from the left

Lunar Phase Northern Hemisphere

Légende : The phases of the Moon when viewed from the Northern Hemisphere. Here north is up and east is left. The Moon orbits the Earth every 29.5 days. It is tidally locked to the Earth meaning its rotation period is the same as its orbital period and the same side of the Moon always faces the Earth. At any particular time, half of the Moon is illuminated by the Sun and half is in shadow. Over the course of the Moon’s orbit around the Earth every part of the Moon is illuminated for half of the orbit and is in shadow for the other half of the orbit. When the Moon sits between the Earth and the Sun its illuminated half faces away from the Earth and we only see the half that is in shadow. This phase of the Moon is known as new moon. As the Moon moves in its orbit, a small but growing sliver of the illuminated half of the Moon begins to be seen from the Earth. This illuminated sliver appears on the western side of the Moon’s face when viewed from Earth. This phase is known as waxing crescent moon. By a quarter of the way through the Moon’s orbit around the Earth the Moon appears 90° away from the Sun and half of the Moon’s illuminated half points toward the Earth. This phase is known as first quarter moon. As the orbit continues more than half of the Moon seen from Earth is now illuminated with a dark crescent. This phase is known as waxing gibbous moon. Once we reach the halfway point in the Moon’s orbit round the Earth the Moon is now on the opposite side of the Earth from the Sun and we see all of the Moon’s illuminated half. As the whole of the side of the Moon that faces the Earth is now illuminated this is referred to as full moon. For the remaining half of the Moon’s orbit the half of the moon that faces the Earth begins to move into shadow. Hence the illuminated portion of the Moon that we see from Earth begins to shrink or wane. The western edge of the face of the Moon when viewed from Earth begins to appear dark and this grows through subsequent phases. The phases are repeated in reverse order: waning gibbous, third quarter, waning crescent and finally back to new moon. Note the surface features of the Moon are illustrative and do not accurately represent the Moon’s true surface.
Crédit : Aneta Margraf/IAU OAE

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


The Moon begins as dark, an illuminated portion grows from the right. Then once fully illuminated a dark portion grows from the right

Lunar Phase Southern Hemisphere

Légende : The phases of the Moon when viewed from the Southern Hemisphere. Here north is up and west is left The Moon orbits the Earth every 29.5 days. It is tidally locked to the Earth meaning its rotation period is the same as its orbital period and the same side of the Moon always faces the Earth. At any particular time, half of the Moon is illuminated by the Sun and half is in shadow. Over the course of the Moon’s orbit around the Earth every part of the Moon is illuminated for half of the orbit and is in shadow for the other half of the orbit. When the Moon sits between the Earth and the Sun its illuminated half faces away from the Earth and we only see the half that is in shadow. This phase of the Moon is known as new moon. As the Moon moves in its orbit, a small but growing sliver of the illuminated half of the Moon begins to be seen from the Earth. This illuminated sliver appears on the western side of the Moon’s face when viewed from Earth. This phase is known as waxing crescent moon. By a quarter of the way through the Moon’s orbit around the Earth the Moon appears 90° away from the Sun and half of the Moon’s illuminated half points toward the Earth. This phase is known as first quarter moon. As the orbit continues more than half of the Moon seen from Earth is now illuminated with a dark crescent. This phase is known as waxing gibbous moon. Once we reach the halfway point in the Moon’s orbit round the Earth the Moon is now on the opposite side of the Earth from the Sun and we see all of the Moon’s illuminated half. As the whole of the side of the Moon that faces the Earth is now illuminated this is referred to as full moon. For the remaining half of the Moon’s orbit the half of the moon that faces the Earth begins to move into shadow. Hence the illuminated portion of the Moon that we see from Earth begins to shrink or wane. The western edge of the face of the Moon when viewed from Earth begins to appear dark and this grows through subsequent phases. The phases are repeated in reverse order: waning gibbous, third quarter, waning crescent and finally back to new moon. Note the surface features of the Moon are illustrative and do not accurately represent the Moon’s true surface.
Crédit : Aneta Margraf/IAU OAE

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


The Moon begins as dark, an illuminated portion grows from the top. Then once fully illuminated a dark portion grows from the top

Lunar Phase Equator

Légende : The phases of the Moon when viewed from the Equator. Here west is up, north is left and east is down. The Moon orbits the Earth every 29.5 days. It is tidally locked to the Earth meaning its rotation period is the same as its orbital period and the same side of the Moon always faces the Earth. At any particular time, half of the Moon is illuminated by the Sun and half is in shadow. Over the course of the Moon’s orbit around the Earth every part of the Moon is illuminated for half of the orbit and is in shadow for the other half of the orbit. When the Moon sits between the Earth and the Sun its illuminated half faces away from the Earth and we only see the half that is in shadow. This phase of the Moon is known as new moon. As the Moon moves in its orbit, a small but growing sliver of the illuminated half of the Moon begins to be seen from the Earth. This illuminated sliver appears on the western side of the Moon’s face when viewed from Earth. This phase is known as waxing crescent moon. By a quarter of the way through the Moon’s orbit around the Earth the Moon appears 90° away from the Sun and half of the Moon’s illuminated half points toward the Earth. This phase is known as first quarter moon. As the orbit continues more than half of the Moon seen from Earth is now illuminated with a dark crescent. This phase is known as waxing gibbous moon. Once we reach the halfway point in the Moon’s orbit round the Earth the Moon is now on the opposite side of the Earth from the Sun and we see all of the Moon’s illuminated half. As the whole of the side of the Moon that faces the Earth is now illuminated this is referred to as full moon. For the remaining half of the Moon’s orbit the half of the moon that faces the Earth begins to move into shadow. Hence the illuminated portion of the Moon that we see from Earth begins to shrink or wane. The western edge of the face of the Moon when viewed from Earth begins to appear dark and this grows through subsequent phases. The phases are repeated in reverse order: waning gibbous, third quarter, waning crescent and finally back to new moon. The perspective for this diagram is with west up, north left and east down. When the moon is viewed looking west, for example viewing the waxing crescent just after sunset, the view of the Moon would be rotated by 180°. Note the surface features of the Moon are illustrative and do not accurately represent the Moon’s true surface.
Crédit : Aneta Margraf/IAU OAE

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


The Moon lies between the Sun and Earth casts a small shadow and large partial shadow

Total Solar Eclipse

Légende : This not to scale diagram shows what happens during a total solar eclipse. The Moon orbits the Earth, but its orbit is slightly tilted with respect to the Earth’s orbit around the Sun. During the new moon lunar phase, the Moon lies between the Earth and the Sun, but due to the Moon’s tilted orbit around the Earth, the Moon normally lies above or below the Sun at this point. However twice a year the Moon’s orbit lines up in such a way that the Moon can lie in a direct line between the Earth and Sun. During this time a solar eclipse can occur. The Moon is about 400 times smaller than the Sun, but is 400 times closer to the Earth than the Sun. Hence the Sun and Moon have approximately the same angular size when viewed from the Earth. This means that it is possible for the Moon to completely cover the Sun when viewed from Earth. This is known as a total solar eclipse. Here we see a schematic of such and eclipse. The Moon casts a shadow on the Earth known as the umbra. This is a roughly circular shadow a few hundred kilometres across. Any region within the umbra will see the Moon completely cover the Sun and thus will experience a total solar eclipse. Outside of the umbra there are regions where the Moon will cover part of the Sun. This partial shadow is known as the penumbra. Regions in the penumbra will experience a partial solar eclipse. An eclipse is a dynamic event with the Moon moving in its orbit and the Earth rotating. Hence the umbra and penumbra move across the Earth’s surface. The path the umbra takes across the Earth is known as the path of totality. Let’s consider one particular region that lies in the path of totality. Except in rare cases where an eclipse begins at sunrise, a region that experiences totality will first see the Moon cover part of the Sun and gradually move across Sun until it is totally covered. From outside the Earth this would appear as the penumbra moving over this particular region followed by the umbra moving over this region. Once the Moon moves so that it no longer completely covers the Sun, totality ends and the umbra moves away from this particular region. The Moon will continue to uncover the Sun until (unless the Sun sets before the end of the eclipse) the Sun is completely uncovered. From outside the Earth this would appear as the umbra moving away from our particular region and the edge of the penumbra approaching and eventually passing over the region. Outside of the path or totality there is a much broader region that will lie in the penumbra but will be missed by the umbra. Such regions will not experience a total solar eclipse during this event, only a partial solar eclipse.
Crédit : Aneta Margraf/IAU OAE

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

Le Bureau de l'astronomie pour l'éducation est hébergé par la Maison de l'astronomie sur le campus de l'Institut Max Planck d'astronomie à Heidelberg. Le Bureau de l'astronomie pour l'éducation est un bureau de l'Union Astronomique Internationale, avec un financement important des Fondations Klaus Tschira et Carl Zeiss. Les colloques Shaw-IAU sur l'astronomie pour l'éducation sont financés par la Fondation Shaw Prize.