{"id":3388,"date":"2015-08-12T07:24:47","date_gmt":"2015-08-12T07:24:47","guid":{"rendered":"https:\/\/blogs.futura-sciences.com\/feldmann\/?p=3388"},"modified":"2015-08-25T05:08:22","modified_gmt":"2015-08-25T05:08:22","slug":"decouverte-dun-anneau-de-galaxies-geant","status":"publish","type":"post","link":"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/08\/12\/decouverte-dun-anneau-de-galaxies-geant\/","title":{"rendered":"D\u00e9couverte d&#8217;un anneau de galaxies g\u00e9ant"},"content":{"rendered":"<p><strong>En traquant les sursauts gamma, des astronomes ont d\u00e9couvert un immense anneau de galaxies dont le diam\u00e8tre avoisine 5 milliards d&#8217;ann\u00e9es-lumi\u00e8re.<\/strong><\/p>\n<p>D\u00e9tect\u00e9s accidentellement par des satellites militaires \u00e0 la fin des ann\u00e9es 1960, les <a href=\"http:\/\/www.futura-sciences.com\/magazines\/espace\/infos\/actu\/d\/sursaut-gamma-derriere-sursaut-gamma-long-cachait-magnetar-59041\/\" target=\"_blank\">sursauts gamma<\/a> (en anglais\u00a0<em>gamma-ray bursts<\/em> ou GRB) constituent les \u00e9v\u00e9nements les plus \u00e9nerg\u00e9tiques connus dans l&#8217;Univers (apr\u00e8s le <a href=\"http:\/\/www.futura-sciences.com\/magazines\/espace\/infos\/dico\/d\/univers-big-bang-858\/\" target=\"_blank\">Big-Bang<\/a>), lib\u00e9rant autant d&#8217;\u00e9nergie en quelques secondes que le <a href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/08\/09\/ar-2396-une-nouvelle-tache-solaire-geante\/\" target=\"_blank\">Soleil <\/a>ne le fera tout au long de son existence (10 milliards d&#8217;ann\u00e9es).<\/p>\n<p>Ces sursauts gamma sont \u00e9mis lors de l&#8217;effondrement d&#8217;\u00e9toiles massives dans des <a href=\"http:\/\/www.futura-sciences.com\/magazines\/espace\/infos\/dico\/d\/univers-trou-noir-62\/\" target=\"_blank\">trous noirs<\/a>. Leur \u00e9norme luminosit\u00e9 permet aux <a href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2014\/12\/14\/lumiere-rouge-les-astronomes\/\" target=\"_blank\">astronomes <\/a>de cartographier l&#8217;emplacement des galaxies lointaines \u00e0 l&#8217;aide d&#8217;instruments dans l&#8217;espace comme <a href=\"http:\/\/swift.gsfc.nasa.gov\/index.html\" target=\"_blank\">Swift<\/a>, ou au sol (en utilisant par exemple les antennes du <a href=\"http:\/\/www.vla.nrao.edu\/\" target=\"_blank\">VLA <\/a>au Nouveau-Mexique).<\/p>\n<p><a href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2015\/08\/gamma2.jpg\" rel=\"lightbox[3388]\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-3389\" src=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2015\/08\/gamma2-450x219.jpg\" alt=\"gamma2\" width=\"450\" height=\"219\" srcset=\"https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2015\/08\/gamma2-450x219.jpg 450w, https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2015\/08\/gamma2-1024x498.jpg 1024w, https:\/\/blogs.futura-sciences.com\/feldmann\/wp-content\/uploads\/sites\/9\/2015\/08\/gamma2.jpg 1168w\" sizes=\"auto, (max-width: 450px) 100vw, 450px\" \/><\/a><\/p>\n<p>Comme le rapporte un papier de la <em><a href=\"http:\/\/www.ras.org.uk\/news-and-press\/2693-5-billion-light-years-across-the-largest-feature-in-the-universe\" target=\"_blank\">Royal Astronomical Society<\/a><\/em>, une \u00e9quipe am\u00e9ricano-hongroise dirig\u00e9e par le professeur Lajos Balazs (<a href=\"http:\/\/www.konkoly.hu\/general.shtml\" target=\"_blank\">Observatoire de Budapest<\/a>) a d\u00e9couvert plusieurs sursauts gamma a environ 7 milliards d&#8217;ann\u00e9es-lumi\u00e8re inscrits dans un cercle de 36\u00b0 dans le ciel, plus de 70 fois le diam\u00e8tre apparent de la <a href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/07\/10\/pleine-lune-le-2-juillet-derriere-le-temple-de-poseidon\/\" target=\"_blank\">Pleine Lune<\/a> !<\/p>\n<p><!--more-->Selon le professeur Balazs il y a une infime probabilit\u00e9 (1 sur 20 000) que la distribution de ces sursauts gamma soit le fruit du hasard ; ils font tr\u00e8s certainement partie d&#8217;un anneau g\u00e9ant de <a href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/04\/23\/les-galaxies-de-la-chaine-de-markarian\/\" target=\"_blank\">galaxies <\/a>dont le diam\u00e8tre estim\u00e9 est de l&#8217;ordre de 5 milliards d&#8217;ann\u00e9es-lumi\u00e8re.<\/p>\n\n<!-- iframe plugin v.5.1 wordpress.org\/plugins\/iframe\/ -->\n<iframe loading=\"lazy\" frameborder=\"0\" width=\"480\" height=\"270\" src=\"\/\/www.dailymotion.com\/embed\/video\/x26zvmx\" 0=\"allowfullscreen\" scrolling=\"yes\" class=\"iframe-class\"><\/iframe>\n\n<p style=\"text-align: center\"><strong>En vid\u00e9o : les secrets de la mission Planck<\/strong><\/p>\n<p>Si l&#8217;existence de cet anneau g\u00e9ant se confirme, les astrophysiciens pourraient \u00eatre amen\u00e9s \u00e0 remettre en cause l&#8217;homog\u00e9n\u00e9it\u00e9 de l&#8217;Univers telle qu&#8217;elle semblait se dessiner \u00e0 travers les r\u00e9sultats de la mission europ\u00e9enne <a href=\"http:\/\/www.esa.int\/Our_Activities\/Space_Science\/Planck\" target=\"_blank\">Planck<\/a>. En effet, selon le principe cosmologique, l&#8217;Univers devrait \u00eatre uniforme, avec une\u00a0limite th\u00e9orique de 1,2 milliard d&#8217;ann\u00e9es-lumi\u00e8re pour les plus grandes structures.<\/p>\n<!-- AddThis Advanced Settings generic via filter on the_content --><!-- AddThis Share Buttons generic via filter on the_content -->","protected":false},"excerpt":{"rendered":"<p>En traquant les sursauts gamma, des astronomes ont d\u00e9couvert un immense anneau de galaxies dont le diam\u00e8tre avoisine 5 milliards d&#8217;ann\u00e9es-lumi\u00e8re. D\u00e9tect\u00e9s accidentellement par des satellites militaires \u00e0 la fin des ann\u00e9es 1960, les sursauts gamma (en anglais\u00a0gamma-ray bursts ou GRB) constituent les \u00e9v\u00e9nements les plus \u00e9nerg\u00e9tiques connus dans l&#8217;Univers (apr\u00e8s le Big-Bang), lib\u00e9rant autant &hellip; <a href=\"https:\/\/blogs.futura-sciences.com\/feldmann\/2015\/08\/12\/decouverte-dun-anneau-de-galaxies-geant\/\" class=\"more-link\">Continuer la lecture de <span class=\"screen-reader-text\">D\u00e9couverte d&#8217;un anneau de galaxies g\u00e9ant<\/span>  <span class=\"meta-nav\">&rarr;<\/span><\/a><!-- AddThis Advanced Settings generic via filter on get_the_excerpt --><!-- AddThis Share Buttons generic via filter on get_the_excerpt --><\/p>\n","protected":false},"author":8,"featured_media":3390,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_links_to":"","_links_to_target":""},"categories":[509],"tags":[89,112,1204,1202,1206,1205,1203,398],"class_list":["post-3388","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-actualites","tag-etoile","tag-galaxie","tag-grb","tag-lajos-balazs","tag-planck","tag-royal-astronomical-society","tag-sursaut-gamma","tag-trou-noir"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v24.1 - 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