{"id":8073,"date":"2017-07-13T08:07:38","date_gmt":"2017-07-13T08:07:38","guid":{"rendered":"https:\/\/blogs.futura-sciences.com\/feldmann\/?p=8073"},"modified":"2017-08-02T12:38:39","modified_gmt":"2017-08-02T12:38:39","slug":"eblm-j0555-57ab-etoile-pas-plus-grosse-saturne","status":"publish","type":"post","link":"https:\/\/blogs.futura-sciences.com\/feldmann\/2017\/07\/13\/eblm-j0555-57ab-etoile-pas-plus-grosse-saturne\/","title":{"rendered":"EBLM J0555-57Ab, une \u00e9toile pas plus grosse que Saturne"},"content":{"rendered":"

Des astronomes ont d\u00e9couvert une \u00e9toile de la taille de Saturne, ce qui en fait la plus petite connue \u00e0 ce jour. Elle r\u00e9pond au doux nom de\u00a0EBLM J0555-57Ab.<\/strong><\/p>\n

Nous savons tous qu’une \u00e9toile est une boule massive et lumineuse de plasma li\u00e9e par sa propre gravit\u00e9. Pour que la temp\u00e9rature de son c\u0153ur puisse atteindre plusieurs millions de degr\u00e9s, condition indispensable pour amorcer la r\u00e9action de fusion nucl\u00e9aire qui \u00a0va permettre la transformation de l’h\u00e9lium en hydrog\u00e8ne, l’\u00e9toile doit donc imp\u00e9rativement avoir un diam\u00e8tre et une densit\u00e9 cons\u00e9quents.<\/p>\n

\"\"<\/a><\/p>\n

Pour m\u00e9moire le diam\u00e8tre de notre Soleil<\/a> est 107 fois plus important que celui de la Terre et 11 fois plus important que celui de Saturne<\/a>, et notre \u00e9toile a une taille bien modeste quand on la compare \u00e0 la plupart de ses voisines dans la Voie lact\u00e9e<\/a>.<\/p>\n

En utilisant WASP<\/a> (Wide Angle Search for Planets<\/em>), un r\u00e9seau de t\u00e9lescopes robotis\u00e9s qui surveillent les transits d’\u00e9ventuelles exoplan\u00e8tes<\/a> devant des \u00e9toiles, des astronomes<\/a> ont d’abord d\u00e9couvert un petit astre tournant autour d’une \u00e9toile, EBLM J0555-57, situ\u00e9e \u00e0 600 ann\u00e9es-lumi\u00e8re de la Terre.<\/p>\n

Pensant qu’il s’agissait d’une exoplan\u00e8te de plus, ils ont mesur\u00e9 son diam\u00e8tre (qui est \u00e9quivalent \u00e0 celui de Saturne) puis ont cherch\u00e9 \u00e0 \u00e9valuer sa masse. Surprise, l’astre en question (surnomm\u00e9 EBLM J0555-57Ab) pr\u00e9sente une masse qui est beaucoup trop importante pour une exoplan\u00e8te de cette taille : environ 8% de la masse du Soleil, ce qui pour un astre de la taille de EBLM J0555-57Ab permet en th\u00e9orie l’amorce d’une r\u00e9action de fusion nucl\u00e9aire.<\/p>\n

L’astre en question est sans doute une petite naine rouge hyperdense et ultrafroide, tout comme sa cousine tr\u00e8s m\u00e9diatis\u00e9e Trappist-1<\/a>, l\u00e9g\u00e8rement plus grosse et connue pour les 7 exoplan\u00e8tes qui gravitent autour. Bien qu’on estime qu’elles repr\u00e9sentent pr\u00e8s de 20% des \u00e9toiles les plus proches de nous, les naines rouges sont tr\u00e8s difficiles \u00e0 d\u00e9tecter en raison de leur faible \u00e9clat. Elles int\u00e9ressent pourtant beaucoup les astronomes car c’est autour de ces petites \u00e9toiles que pourraient se trouver des exoplan\u00e8tes\u00a0potentiellement habitables.<\/p>\n","protected":false},"excerpt":{"rendered":"

Des astronomes ont d\u00e9couvert une \u00e9toile de la taille de Saturne, ce qui en fait la plus petite connue \u00e0 ce jour. Elle r\u00e9pond au doux nom de\u00a0EBLM J0555-57Ab. Nous savons tous qu’une \u00e9toile est une boule massive et lumineuse de plasma li\u00e9e par sa propre gravit\u00e9. Pour que la temp\u00e9rature de son c\u0153ur puisse … Continuer la lecture de EBLM J0555-57Ab, une \u00e9toile pas plus grosse que Saturne<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":8,"featured_media":8074,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_links_to":"","_links_to_target":""},"categories":[84],"tags":[2285,2283,110,1307,136,97,828,2284,166,1100],"class_list":["post-8073","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-ciel-etoile","tag-eblm-j0555-57","tag-eblm-j0555-57ab","tag-exoplanete","tag-naine-rouge","tag-saturne","tag-soleil","tag-transit","tag-trappist-1","tag-voie-lactee","tag-wasp"],"yoast_head":"\nEBLM J0555-57Ab, une \u00e9toile pas plus grosse que Saturne<\/title>\n<meta name=\"description\" content=\"Des astronomes ont d\u00e9couvert une \u00e9toile de la taille de Saturne, ce qui en fait la plus petite connue \u00e0 ce jour. 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