{"id":2362,"date":"2015-03-31T04:56:29","date_gmt":"2015-03-31T04:56:29","guid":{"rendered":"https:\/\/blogs.futura-sciences.com\/feldmann\/?p=2362"},"modified":"2015-04-10T05:05:18","modified_gmt":"2015-04-10T05:05:18","slug":"astuce-comment-reperer-la-celebre-etoile-polaire","status":"publish","type":"post","link":"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/03\/31\/astuce-comment-reperer-la-celebre-etoile-polaire\/","title":{"rendered":"Astuce : comment rep\u00e9rer la c\u00e9l\u00e8bre \u00e9toile polaire"},"content":{"rendered":"

Alpha Ursae Minoris<\/em>, l’\u00e9toile la plus brillante (magnitude 2) de la constellation de la Petite Ourse, est l\u2019\u00e9toile polaire\u00a0; cela signifie qu’elle est actuellement l’\u00e9toile la plus proche du p\u00f4le nord c\u00e9leste, point par lequel passe l’axe imaginaire de rotation de la Terre<\/a>.<\/p>\n

\"rotation\"<\/a><\/p>\n

Au cours de la nuit vous aurez l’impression que toute la vo\u00fbte c\u00e9leste tourne autour de l’\u00e9toile polaire (image ci-dessus) ; ce mouvement de la sph\u00e8re c\u00e9leste n’est qu’apparent puisque c’est en r\u00e9alit\u00e9 la Terre qui tourne.<\/p>\n

Pour rep\u00e9rer l’\u00e9toile polaire, un astre tr\u00e8s important pour les hommes depuis longtemps (en particulier pour les marins de l’h\u00e9misph\u00e8re nord), il vous faut dans un premier temps localiser la constellation de la Grande Ourse<\/a>, un ast\u00e9risme de sept \u00e9toiles qui ressemble beaucoup \u00e0 une casserole.<\/p>\n

Rep\u00e9rez les deux \u00e9toiles les plus \u00e9loign\u00e9es du “manche” de la casserole, Merak et Dubhe (la plus brillante des deux). En tra\u00e7ant une ligne imaginaire entre Merak et Dubhe et en reportant 5 fois la distance entre ces deux \u00e9toiles, vous arrivez \u00e0 l\u2019\u00e9toile polaire.<\/p>\n

\"polaire\"<\/a><\/p>\n

Comme la direction de l’axe de rotation de la Terre change lentement (c’est ce qu’on appelle la pr\u00e9cession des \u00e9quinoxes), Alpha Ursae Minoris<\/em> n’a pas toujours jou\u00e9 le r\u00f4le de l’\u00e9toile polaire. Il y a 12 000 ans le p\u00f4le nord c\u00e9leste se trouvait \u00e0 quelques degr\u00e9s seulement de Vega, la plus brillante \u00e9toile de la constellation de la Lyre, une des trois balises c\u00e9lestes qui forment le triangle d’\u00e9t\u00e9<\/a>.<\/p>\n

Notez enfin que dans l’h\u00e9misph\u00e8re sud c’est actuellement l’\u00e9toile Beta Hydri<\/em> (constellation de l’Hydre M\u00e2le) qui fait office d’\u00e9toile polaire.<\/p>\n","protected":false},"excerpt":{"rendered":"

Alpha Ursae Minoris, l’\u00e9toile la plus brillante (magnitude 2) de la constellation de la Petite Ourse, est l\u2019\u00e9toile polaire\u00a0; cela signifie qu’elle est actuellement l’\u00e9toile la plus proche du p\u00f4le nord c\u00e9leste, point par lequel passe l’axe imaginaire de rotation de la Terre. Au cours de la nuit vous aurez l’impression que toute la vo\u00fbte … Continuer la lecture de Astuce : comment rep\u00e9rer la c\u00e9l\u00e8bre \u00e9toile polaire<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":8,"featured_media":2364,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_links_to":"","_links_to_target":""},"categories":[84],"tags":[930,931,936,456,99,934,98,933,932,312,935,100],"class_list":["post-2362","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-ciel-etoile","tag-alpha-ursae-minoris","tag-asterisme","tag-beta-hydri","tag-constellation-de-la-grande-ourse","tag-constellation-de-la-petite-ourse","tag-dubhe","tag-etoile-polaire","tag-merak","tag-pole-nord-celeste","tag-precession-des-equinoxes","tag-triangle-dete","tag-vega"],"yoast_head":"\nAstuce : comment rep\u00e9rer la c\u00e9l\u00e8bre \u00e9toile polaire<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/03\/31\/astuce-comment-reperer-la-celebre-etoile-polaire\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Astuce : comment rep\u00e9rer la c\u00e9l\u00e8bre \u00e9toile polaire\" \/>\n<meta property=\"og:description\" content=\"Alpha Ursae Minoris, l’\u00e9toile la plus brillante (magnitude 2) de la constellation de la Petite Ourse, est l\u2019\u00e9toile polaire\u00a0; cela signifie qu’elle est actuellement l’\u00e9toile la plus proche du p\u00f4le nord c\u00e9leste, point par lequel passe l’axe imaginaire de rotation de la Terre. Au cours de la nuit vous aurez l’impression que toute la vo\u00fbte … Continuer la lecture de Astuce : comment rep\u00e9rer la c\u00e9l\u00e8bre \u00e9toile polaire →\" \/>\n<meta property=\"og:url\" content=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/03\/31\/astuce-comment-reperer-la-celebre-etoile-polaire\/\" \/>\n<meta property=\"og:site_name\" content=\"CIELMANIA : le blog de Jean-Baptiste FELDMANN, photographe du ciel\" \/>\n<meta property=\"article:published_time\" content=\"2015-03-31T04:56:29+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2015-04-10T05:05:18+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2015\/03\/rotation.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"1198\" \/>\n\t<meta property=\"og:image:height\" content=\"899\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"Jean-Baptiste FELDMANN\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u00c9crit par\" \/>\n\t<meta name=\"twitter:data1\" content=\"Jean-Baptiste FELDMANN\" \/>\n\t<meta name=\"twitter:label2\" content=\"Dur\u00e9e de lecture estim\u00e9e\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/03\/31\/astuce-comment-reperer-la-celebre-etoile-polaire\/\",\"url\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/03\/31\/astuce-comment-reperer-la-celebre-etoile-polaire\/\",\"name\":\"Astuce : comment rep\u00e9rer la c\u00e9l\u00e8bre \u00e9toile polaire\",\"isPartOf\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/03\/31\/astuce-comment-reperer-la-celebre-etoile-polaire\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/03\/31\/astuce-comment-reperer-la-celebre-etoile-polaire\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2015\/03\/rotation.jpg\",\"datePublished\":\"2015-03-31T04:56:29+00:00\",\"dateModified\":\"2015-04-10T05:05:18+00:00\",\"author\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/#\/schema\/person\/62b391b709c307783237b759b62731ea\"},\"inLanguage\":\"fr-FR\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/03\/31\/astuce-comment-reperer-la-celebre-etoile-polaire\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"fr-FR\",\"@id\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/03\/31\/astuce-comment-reperer-la-celebre-etoile-polaire\/#primaryimage\",\"url\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2015\/03\/rotation.jpg\",\"contentUrl\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2015\/03\/rotation.jpg\",\"width\":1198,\"height\":899,\"caption\":\"Astuce : comment rep\u00e9rer la c\u00e9l\u00e8bre \u00e9toile polaire\"},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/#website\",\"url\":\"https:\/\/blogs.futura-sciences.com\/feldmann\/\",\"name\":\"CIELMANIA : le blog de Jean-Baptiste FELDMANN, photographe du ciel\",\"description\":\""J'ai en moi un besoin terrible. 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