{"id":40780,"date":"2026-08-29T14:31:00","date_gmt":"2026-08-29T12:31:00","guid":{"rendered":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/?p=40780"},"modified":"2026-08-29T14:35:08","modified_gmt":"2026-08-29T12:35:08","slug":"entretien-roser-pello-les-quasars-ont-peut-etre-eu-un-role-plus-important-dans-la-reionisation","status":"publish","type":"post","link":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/2026\/08\/29\/entretien-roser-pello-les-quasars-ont-peut-etre-eu-un-role-plus-important-dans-la-reionisation\/","title":{"rendered":"[Entretien] Roser Pello : \u00ab&nbsp;Les quasars ont peut-\u00eatre eu un r\u00f4le plus important dans la r\u00e9ionisation&nbsp;\u00bb"},"content":{"rendered":"<div class=\"paragraph\">\n<p><b>La Marseillaise :<\/b><b> Euclid a d\u00e9couvert 12 nouveaux quasars pr\u00e9sents 770<\/b><b>\u00a0<\/b><b>millions d\u2019ann\u00e9es apr\u00e8s le Big Bang \u2013soit tr\u00e8s t\u00f4t apr\u00e8s la formation de l\u2019Univers. Que va-t-on \u00e9tudier \u00e0 leur sujet ?<\/b><\/p>\n<p><b>Roser Pello : <\/b>Une des premi\u00e8res choses que les astrophysiciens voudront \u00e9tudier est leur contribution \u00e0 la r\u00e9ionisation de l\u2019Univers. Car ces quasars se trouvent dans cette p\u00e9riode qui se termine environ un milliard d\u2019ann\u00e9es apr\u00e8s le Big Bang. Sa date de d\u00e9but n\u2019est pas claire. Elle intervient apr\u00e8s les \u00ab\u00a0\u00e2ges sombres\u00a0\u00bb\u00a0: quand l\u2019Univers \u00e9tait compos\u00e9 essentiellement de mati\u00e8re sombre, d\u2019atomes d\u2019hydrog\u00e8ne et d\u2019h\u00e9lium, sans \u00e9toile ni galaxie pour l\u2019\u00e9clairer. La r\u00e9ionisation se produit justement apr\u00e8s la formation des premi\u00e8res \u00e9toiles, galaxies et quasars qui, via les photons \u00e9mis, font retourner l\u2019hydrog\u00e8ne sous sa forme d\u2019ion.<\/p>\n<p><b>Qu\u2019imaginait-on du r\u00f4le des quasars dans cette r\u00e9ionisation ?<\/b><\/p>\n<p><b>R.P.<\/b><b>\u00a0<\/b><b>:<\/b> On le pensait anecdotique par rapport \u00e0 celui des premi\u00e8res \u00e9toiles et galaxies \u2013petites mais nombreuses\u2013 consid\u00e9r\u00e9es comme les principales contributrices. Mais si nous commen\u00e7ons \u00e0 trouver beaucoup de quasars \u00e0 cette \u00e9poque, cela signifie peut-\u00eatre que leur r\u00f4le est plus important que nous le pensions.<\/p>\n<p><b>Comment va-t-on faire ? <\/b><\/p>\n<p><b>R.P.<\/b><b>\u00a0<\/b><b>:<\/b> Il faut construire une fonction de luminosit\u00e9\u00a0: d\u00e9terminer, pour chaque tranche d\u2019Univers \u00e0 mesure qu\u2019on se rapproche du Big Bang, combien de quasars on trouve pour telle ou telle luminosit\u00e9. Cela permettra de d\u00e9finir le potentiel ionisant de cette population de quasars et de le comparer \u00e0 celui des \u00e9toiles et des galaxies.<\/p>\n<p><b><span class=\"mln_small-caps_mln\">Propos recueillis par X.B.<\/span><\/b><\/p>\n<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"La Marseillaise : Euclid a d&eacute;couvert 12 nouveaux quasars pr&eacute;sents 770&nbsp;millions d&rsquo;ann&eacute;es apr&egrave;s le Big Bang &ndash;soit tr&egrave;s t&ocirc;t apr&egrave;s la formation de l&rsquo;Univers. Que va-t-on &#8230;","protected":false},"author":1,"featured_media":40781,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[20],"tags":[224,3444,10,343,5484,16,1058,353,2603,988,2001],"news-destination":[],"news-source":[475],"is_homepage":[],"ta_other":[],"class_list":["post-40780","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-societe","tag-astronomie","tag-astrophysique","tag-bouches-du-rhone","tag-entretien","tag-galaxie","tag-marseille","tag-science","tag-sciences","tag-univers","tag-week-end","tag-weekend","news-source-website"],"_links":{"self":[{"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/posts\/40780","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/comments?post=40780"}],"version-history":[{"count":1,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/posts\/40780\/revisions"}],"predecessor-version":[{"id":40782,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/posts\/40780\/revisions\/40782"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/media\/40781"}],"wp:attachment":[{"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/media?parent=40780"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/categories?post=40780"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/tags?post=40780"},{"taxonomy":"news-destination","embeddable":true,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/news-destination?post=40780"},{"taxonomy":"news-source","embeddable":true,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/news-source?post=40780"},{"taxonomy":"is_homepage","embeddable":true,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/is_homepage?post=40780"},{"taxonomy":"ta_other","embeddable":true,"href":"https:\/\/euapp01.newsmemory.com\/lamarseillaise\/news\/wp-json\/wp\/v2\/ta_other?post=40780"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}