Glossary term: Étoile
Description: Une étoile est une boule de plasma - des noyaux atomiques séparés de leurs électrons - maintenue par sa propre gravité et empêchée de s'effondrer par la pression interne résultant des processus de fusion nucléaire dans les régions centrales de l'étoile. Les astronomes, abusant légèrement de la terminologie physique, utilisent couramment les termes "gaz" et "plasma" de manière interchangeable, et se réfèrent donc également aux étoiles comme à des boules de gaz. Dans l'atmosphère d'une étoile, le plasma peut n'être que partiellement ionisé et (en fonction de la température de l'étoile) contenir quelques atomes.
L'étoile la plus proche de la Terre est le Soleil.
Dans un sens plus général, le mot "étoile" englobe les protoétoiles où la fusion nucléaire n'a pas encore commencé, ainsi que les vestiges stellaires tels que les étoiles à neutrons ou les naines blanches, qui sont deux possibilités (en fonction de la masse) de transformation des étoiles une fois qu'elles ont épuisé le combustible nécessaire à leur fusion nucléaire. Ces restes stellaires ne sont pas de simples boules de plasma : une naine blanche peut se cristalliser en un type de solide inhabituel après avoir été refroidie pendant des milliards d'années, et les étoiles à neutrons peuvent être comparées à de gigantesques noyaux atomiques.
Dans le cosmos, les étoiles se trouvent généralement à l'intérieur des galaxies, chaque étoile étant généralement accompagnée d'une ou plusieurs planètes. L'étude de la formation et de l'évolution des étoiles est un sous-domaine important de l'astrophysique.
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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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