{"id":829,"date":"2026-09-01T16:38:31","date_gmt":"2026-09-01T15:38:31","guid":{"rendered":"https:\/\/sites-lira.obspm.fr\/pierre-lena\/?p=829"},"modified":"2026-09-13T20:55:29","modified_gmt":"2026-09-13T19:55:29","slug":"250-ans-des-etats-unis-damerique","status":"publish","type":"post","link":"https:\/\/sites-lira.obspm.fr\/pierre-lena\/2026\/09\/01\/250-ans-des-etats-unis-damerique\/","title":{"rendered":"250 ans des \u00c9tats-Unis d’Am\u00e9rique"},"content":{"rendered":"\n

L’Acad\u00e9mie des sciences <\/strong>(France) et la National Academy of Sciences<\/strong> (\u00c9tats-Unis) ont c\u00e9l\u00e9br\u00e9 conjointement deux si\u00e8cles et demi de coop\u00e9rations scientifiques multiples, en Mai 2026 \u00e0 Paris, en pr\u00e9sence d’un nombreux public dans l’Auditorium de l’Institut de France.<\/p>\n\n\n\n

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Avec Etienne Ghys, Secr\u00e9taire perp\u00e9tuel, nous avons r\u00e9alis\u00e9 l’un des 21 podcasts publi\u00e9s et diffus\u00e9s \u00e0 cette occasion. Au dessus du Mont Wilson, des \u00e9toiles<\/em> …<\/a>, est enregistr\u00e9 sous la Grande Lunette de l’Observatoire de Paris \u00e0 Meudon. Le Mont Wilson est une modeste montagne dominant la ville de Los Angeles (Californie). Depuis le d\u00e9but du 20e si\u00e8cle, l’installation de t\u00e9lescopes y conduisit \u00e0 de multiples coop\u00e9rations entre astronomes de France et des \u00c9tats-Unis. C’est le site o\u00f9 fut mesur\u00e9 pour la premi\u00e8re fois par Albert Michelson le diam\u00e8tre d’une \u00e9toile (B\u00e9telgeuse, dans la constellation d’Orion) selon l’id\u00e9e propos\u00e9e par le Fran\u00e7ais Hippolyte Fizeau. Aujourd’hui les astronomes des deux pays coop\u00e8rent sur l’interf\u00e9rom\u00e8tre CHARA et observent de minuscules d\u00e9tails sur les \u00e9toiles.<\/p>\n\n\n\n

Cette image<\/a> de l’\u00e9toile B\u00e9telgeuse est due \u00e0 Miguel Montarg\u00e8s (LESIA\/Observatoire de Paris-PSL) et ses collaborateurs. Obtenue en 2021 avec le Very Large Telescope de l’ESO, elle montre la surface de l’\u00e9toile, gr\u00e2ce aux techniques interf\u00e9rom\u00e9triques de Fizeau\/Michelson\/Labeyrie. <\/h2>\n<\/div><\/div>\n\n\n\n
\n

En 1910, le passage au Mt. Wilson du c\u00e9l\u00e8bre opticien fran\u00e7ais Henri Chr\u00e9tien, marqua George Ritchey, ing\u00e9nieur cr\u00e9ateur du t\u00e9lescope Hooker de 250 cm, alors le plus grand du monde. Vers 1920, Ritchey vint s’installer \u00e0 Paris, et leur collaboration conduisit au sch\u00e9ma optique, dit Ritchey-Chr\u00e9tien. Il garantit une image de qualit\u00e9 dans un grand champ de vue. D\u00e9sormais presque tous les grands t\u00e9lescopes au monde seront construits sur ce sch\u00e9ma, dont r\u00e9cemment le James Webb Space Telescope. <\/p>\n\n\n\n

La fuite des galaxies, caus\u00e9e par l\u00a0\u00bbexpansion de l’univers ainsi d\u00e9couverte, fut mise en \u00e9vidence avec le t\u00e9lescope Hooker en 1929, par l’astronome Edwin Hubble. <\/p>\n\n\n\n

Dans la nuit du 13 septembre 1920, Albert Michelson & Francis Pease mesurent, au Mont Wilson et pour la premi\u00e8re fois, le diam\u00e8tre d’une \u00e9toile. Image du t\u00e9lescope Hooker avec sa configuration interf\u00e9rom\u00e9trique, o\u00f9 la position des observateurs est indiqu\u00e9e (Image due \u00e0 l’obligeance de Harold McAlister\/Projet CHARA). <\/h2>\n<\/div>
\"\"<\/a><\/figure><\/div>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

L’Acad\u00e9mie des sciences (France) et la National Academy of Sciences (\u00c9tats-Unis) ont c\u00e9l\u00e9br\u00e9 conjointement deux si\u00e8cles et demi de coop\u00e9rations scientifiques multiples, en Mai 2026 \u00e0 Paris, en pr\u00e9sence d’un nombreux public dans l’Auditorium de l’Institut de France. Avec Etienne … Continuer la lecture →<\/span><\/a><\/p>\n","protected":false},"author":25,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12],"tags":[],"class_list":["post-829","post","type-post","status-publish","format-standard","hentry","category-non-classe-fr"],"yoast_head":"\n250 ans des \u00c9tats-Unis d'Am\u00e9rique - Pierre L\u00e9na<\/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:\/\/sites-lira.obspm.fr\/pierre-lena\/2026\/09\/01\/250-ans-des-etats-unis-damerique\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"250 ans des \u00c9tats-Unis d'Am\u00e9rique - Pierre L\u00e9na\" \/>\n<meta property=\"og:description\" content=\"L’Acad\u00e9mie des sciences (France) et la National Academy of Sciences (\u00c9tats-Unis) ont c\u00e9l\u00e9br\u00e9 conjointement deux si\u00e8cles et demi de coop\u00e9rations scientifiques multiples, en Mai 2026 \u00e0 Paris, en pr\u00e9sence d’un nombreux public dans l’Auditorium de l’Institut de France. 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