{"id":95,"date":"2014-01-31T17:06:27","date_gmt":"2014-01-31T17:06:27","guid":{"rendered":"http:\/\/expositions.obspm.fr\/lacaille\/?page_id=95"},"modified":"2014-03-24T15:55:07","modified_gmt":"2014-03-24T15:55:07","slug":"cataloguer-les-etoiles","status":"publish","type":"page","link":"http:\/\/expositions.obspm.fr\/lacaille\/cataloguer-les-etoiles\/","title":{"rendered":"Cataloguer les \u00e9toiles"},"content":{"rendered":"<h3><span style=\"color: #059fd9;\">Vers 150 apr\u00e8s J.-C., Ptol\u00e9m\u00e9e publie dans son <em>Almageste<\/em> un catalogue de 1022 \u00e9toiles, dont 700 observ\u00e9es pr\u00e9c\u00e9demment par Hipparque.<\/span><\/h3>\n<p>La pr\u00e9cision sur leur position est 10\u2019 (soit 1\/3 du diam\u00e8tre apparent du Soleil). Tycho Brah\u00e9 obtient 2\u2019 \u00e0 la fin du XVIe si\u00e8cle, puis Hevelius 1\u2019 en 1690. C\u2019est la limite de ce qui est possible \u00e0 l\u2019\u0153il nu. Gr\u00e2ce aux lunettes, Flamsteed atteint 15\u2019\u2019 en 1725.<\/p>\n<p>La Caille obtient une pr\u00e9cision bien meilleure, de l\u2019ordre de 4\u2019\u2019. Il est le premier \u00e0 tenir compte de l\u2019aberration\u00a0 et de la nutation, d\u00e9couvertes par Bradley respectivement en 1728 et 1748, qui affectent fortement la position apparente des \u00e9toiles. John Bird et Jesse Ramsden construisent ensuite de grands instruments encore plus pr\u00e9cis, qui donnent la seconde de degr\u00e9 d\u00e8s la fin du XVIIIe si\u00e8cle.<\/p>\n<p>La photographie permet un nouveau bond en avant\u00a0 en permettant les observations de masse. Un astronome du Cap, David Gill, associ\u00e9 au hollandais Jacobus Kapteyn, atteint 1\u2019\u2019 pour 450 000 \u00e9toiles de l\u2019h\u00e9misph\u00e8re sud dans le <em>Cape Durchmusterung<\/em> (1900). Les observations ult\u00e9rieures porteront la pr\u00e9cision \u00e0 0,13\u2019\u2019.<\/p>\n<p>L\u2019observation spatiale marque une nouvelle \u00e9tape : la pr\u00e9cision des mesures du satellite HIPPARCOS d\u00e9passe 0,001\u2019\u2019 pour 118 000 \u00e9toiles, et on attend du satellite GAIA une pr\u00e9cision de quelques millioni\u00e8mes de seconde de degr\u00e9 pour un milliard d\u2019\u00e9toiles : voir l&rsquo;exposition Gaia \u00e0 l&rsquo;\u00e9tage sup\u00e9rieur.<\/p>\n<div id=\"attachment_222\" style=\"width: 160px\" class=\"wp-caption alignleft\"><a href=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo1.jpg\"><img aria-describedby=\"caption-attachment-222\" loading=\"lazy\" class=\"size-thumbnail wp-image-222 \" alt=\"Portrait de Tycho Brahe par Brookes Warwick, 1881 .\" src=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo1-150x150.jpg\" width=\"150\" height=\"150\" srcset=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo1-150x150.jpg 150w, http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo1-200x200.jpg 200w\" sizes=\"(max-width: 150px) 100vw, 150px\" \/><\/a><p id=\"caption-attachment-222\" class=\"wp-caption-text\"><\/p>\n<div id=\"legendes\">Portrait de Tycho Brahe par Brookes Warwick, 1881 .<\/p>\n<div id=\"credits\">\u00a9 Antonin Geoffroy \/ Observatoire de Paris<\/div>\n<\/div>\n<p><\/p><\/div>\n<div id=\"attachment_223\" style=\"width: 160px\" class=\"wp-caption alignleft\"><a href=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo2.jpg\"><img aria-describedby=\"caption-attachment-223\" loading=\"lazy\" class=\"size-thumbnail wp-image-223 \" alt=\"Portrait de David Gill\" src=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo2-150x150.jpg\" width=\"150\" height=\"150\" srcset=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo2-150x150.jpg 150w, http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo2-200x200.jpg 200w\" sizes=\"(max-width: 150px) 100vw, 150px\" \/><\/a><p id=\"caption-attachment-223\" class=\"wp-caption-text\">Portrait de David Gill<\/p><\/div>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<br \/>\n&nbsp;<\/p>\n<div id=\"attachment_224\" style=\"width: 160px\" class=\"wp-caption alignleft\"><a href=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo3.jpg\"><img aria-describedby=\"caption-attachment-224\" loading=\"lazy\" class=\"size-thumbnail wp-image-224 \" alt=\"Le satellite astrom\u00e9trique europ\u00e9en HIPPARCOS aux essais avant son lancement, 1989.\" src=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo3-150x150.jpg\" width=\"150\" height=\"150\" srcset=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo3-150x150.jpg 150w, http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo3-200x200.jpg 200w\" sizes=\"(max-width: 150px) 100vw, 150px\" \/><\/a><p id=\"caption-attachment-224\" class=\"wp-caption-text\"><\/p>\n<div id=\"legendes\">Le satellite astrom\u00e9trique europ\u00e9en HIPPARCOS aux essais avant son lancement, 1989. <\/p>\n<div id=\"credits\">Photo : Agence Spatiale Europ\u00e9enne.<\/div>\n<\/div>\n<p><\/p><\/div>\n<div id=\"attachment_225\" style=\"width: 160px\" class=\"wp-caption alignleft\"><a href=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo4.jpg\"><img aria-describedby=\"caption-attachment-225\" loading=\"lazy\" class=\"size-thumbnail wp-image-225  \" alt=\"Le satellite astrom\u00e9trique GAIA, vue de principe.\" src=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo4-150x150.jpg\" width=\"150\" height=\"150\" srcset=\"http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo4-150x150.jpg 150w, http:\/\/expositions.obspm.fr\/lacaille\/wp-content\/uploads\/2014\/01\/expo10-photo4-200x200.jpg 200w\" sizes=\"(max-width: 150px) 100vw, 150px\" \/><\/a><p id=\"caption-attachment-225\" class=\"wp-caption-text\"><\/p>\n<div id=\"legendes\">Le satellite astrom\u00e9trique GAIA, vue de principe.<\/p>\n<div id=\"credits\">Photo : Agence Spatiale Europ\u00e9enne.<\/div>\n<\/div>\n<p><\/p><\/div>\n\n","protected":false},"excerpt":{"rendered":"<p>Vers 150 apr\u00e8s J.-C., Ptol\u00e9m\u00e9e publie dans son Almageste un catalogue de 1022 \u00e9toiles, dont 700 observ\u00e9es pr\u00e9c\u00e9demment par Hipparque. La pr\u00e9cision sur leur &hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"open","ping_status":"open","template":"","meta":[],"_links":{"self":[{"href":"http:\/\/expositions.obspm.fr\/lacaille\/wp-json\/wp\/v2\/pages\/95"}],"collection":[{"href":"http:\/\/expositions.obspm.fr\/lacaille\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/expositions.obspm.fr\/lacaille\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/expositions.obspm.fr\/lacaille\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/expositions.obspm.fr\/lacaille\/wp-json\/wp\/v2\/comments?post=95"}],"version-history":[{"count":19,"href":"http:\/\/expositions.obspm.fr\/lacaille\/wp-json\/wp\/v2\/pages\/95\/revisions"}],"predecessor-version":[{"id":544,"href":"http:\/\/expositions.obspm.fr\/lacaille\/wp-json\/wp\/v2\/pages\/95\/revisions\/544"}],"wp:attachment":[{"href":"http:\/\/expositions.obspm.fr\/lacaille\/wp-json\/wp\/v2\/media?parent=95"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}