{"id":8249,"date":"2017-11-17T06:17:18","date_gmt":"2017-11-17T06:17:18","guid":{"rendered":"https:\/\/blogs.futura-sciences.com\/feldmann\/?p=8249"},"modified":"2017-11-28T17:43:09","modified_gmt":"2017-11-28T17:43:09","slug":"differences-entre-comete-etoile-filante","status":"publish","type":"post","link":"https:\/\/blogs.futura-sciences.com\/feldmann\/2017\/11\/17\/differences-entre-comete-etoile-filante\/","title":{"rendered":"Quelles diff\u00e9rences entre une com\u00e8te et une \u00e9toile filante ?"},"content":{"rendered":"

L’apparition d’une lueur dans le ciel nocturne donne souvent lieu \u00e0 des interpr\u00e9tations farfelues. Voici comment ne pas confondre com\u00e8te et \u00e9toile filante.\u00a0<\/strong><\/p>\n

“Soudain j’ai vu une com\u00e8te qui a travers\u00e9 le ciel devant moi en 3 secondes en allant de gauche \u00e0 droite”, “Une com\u00e8te s’est pr\u00e9sent\u00e9e alors que je regardais par la fen\u00eatre. Un flash comme un appareil photo tr\u00e8s puissant”<\/em>… Des t\u00e9moignages comme ceux-ci, on peut en entendre et en lire \u00e0\u00a0chaque apparition d’une brillante \u00e9toile filante.<\/p>\n

\"\"<\/a>
La com\u00e8te Hale-Bopp \u00e0 gauche et une \u00e9toile filante \u00e0 droite.<\/figcaption><\/figure>\n

Voici quelques explications pour ne plus confondre com\u00e8te et \u00e9toile filante :<\/p>\n

De quoi s’agit-il ?\u00a0<\/strong>Une com\u00e8te est un petit astre de quelques centaines de m\u00e8tres \u00e0 quelques kilom\u00e8tres de diam\u00e8tre constitu\u00e9 de gaz et de poussi\u00e8res qui circule dans le Syst\u00e8me solaire. Une \u00e9toile filante est une poussi\u00e8re ou une petite pierre qui se consume en traversant l’atmosph\u00e8re terrestre.<\/p>\n

Quelle est leur distance ? <\/strong>Une com\u00e8te s’approche au mieux \u00e0 plusieurs millions de kilom\u00e8tres de la Terre, alors qu’une \u00e9toile filante traverse notre atmosph\u00e8re \u00e0 quelques dizaines de kilom\u00e8tres au-dessus de nos t\u00eates.<\/p>\n

D’o\u00f9 vient leur lumi\u00e8re ?<\/strong> La com\u00e8te brille en r\u00e9fl\u00e9chissant la lumi\u00e8re du Soleil<\/a>. Son \u00e9clat (on parle de magnitude<\/a>) est rarement plus brillant que celui d’une plan\u00e8te comme Jupiter<\/a>. La derni\u00e8re grande com\u00e8te visible en France \u00e9tait Hale-Bopp<\/a> en 1997. Quant \u00e0 l’\u00e9toile filante elle devient lumineuse\u00a0car elle s’\u00e9chauffe tr\u00e8s fortement lors de sa travers\u00e9e de l’atmosph\u00e8re \u00e0 grande vitesse (plusieurs dizaines de kilom\u00e8tres par seconde). En g\u00e9n\u00e9ral les poussi\u00e8res spatiales qui se consument ont un \u00e9clat comparable \u00e0 celui des \u00e9toiles les plus brillantes (comme Sirius<\/a>) ; s’il s’agit d’un petit caillou sa combustion peut le rendre aussi brillant que la Pleine Lune<\/a> (on parle alors d’un bolide).<\/p>\n

Combien de temps peut-on les observer ?\u00a0<\/strong>La com\u00e8te, tr\u00e8s lointaine, se d\u00e9place lentement \u00e0 nos yeux ; on peut suivre son mouvement par rapport aux \u00e9toiles au fil des nuits. Le passage d’une \u00e9toile filante est extr\u00eamement bref, 2 ou 3 secondes au maximum.<\/p>\n

Peut-on en r\u00e9cup\u00e9rer un \u00e9chantillon ?\u00a0<\/strong>\u00c9tudier la composition d’une com\u00e8te n\u00e9cessite l’envoi de sondes spatiales (comme Rosetta<\/a>). Dans le cas des bolides, certains ne se d\u00e9sint\u00e8grent pas compl\u00e8tement dans l’atmosph\u00e8re et l’on peut en retrouver des fragments appel\u00e9s m\u00e9t\u00e9orites<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

L’apparition d’une lueur dans le ciel nocturne donne souvent lieu \u00e0 des interpr\u00e9tations farfelues. Voici comment ne pas confondre com\u00e8te et \u00e9toile filante.\u00a0 “Soudain j’ai vu une com\u00e8te qui a travers\u00e9 le ciel devant moi en 3 secondes en allant de gauche \u00e0 droite”, “Une com\u00e8te s’est pr\u00e9sent\u00e9e alors que je regardais par la fen\u00eatre. … Continuer la lecture de Quelles diff\u00e9rences entre une com\u00e8te et une \u00e9toile filante ?<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":8,"featured_media":8250,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_links_to":"","_links_to_target":""},"categories":[87],"tags":[554,93,296,650,471],"class_list":["post-8249","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-les-hommes-et-le-ciel","tag-bolide","tag-comete","tag-etoile-filante","tag-hale-bopp","tag-sonde-rosetta"],"yoast_head":"\nQuelles diff\u00e9rences entre une com\u00e8te et une \u00e9toile filante ?<\/title>\n<meta name=\"description\" content=\"L'apparition d'une lueur dans le ciel nocturne donne souvent lieu \u00e0 des interpr\u00e9tations farfelues. 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