{"id":51856,"date":"2025-12-19T18:16:08","date_gmt":"2025-12-19T18:16:08","guid":{"rendered":"https:\/\/www.africa-press.net\/benin\/politique\/collisions-de-planetesimaux-autour-de-fomalhaut-a"},"modified":"2025-12-19T18:16:08","modified_gmt":"2025-12-19T18:16:08","slug":"collisions-de-planetesimaux-autour-de-fomalhaut-a","status":"publish","type":"post","link":"https:\/\/www.africa-press.net\/benin\/toutes-les-actualites\/collisions-de-planetesimaux-autour-de-fomalhaut-a","title":{"rendered":"Collisions de Plan\u00e9t\u00e9simaux Autour de Fomalhaut A"},"content":{"rendered":"

Africa-Press – Benin. <\/strong> <\/span>La vie des jeunes plane\u0300tes n’est pas un long fleuve tranquille. L’expe\u0301rience de notre syste\u0300me solaire montre que les plane\u0300tes en formation ou tout juste forme\u0301es subissent parfois de cataclysmiques collisions. Ainsi, la Terre a-t-elle e\u0301te\u0301 frappe\u0301e dans sa prime jeunesse par un corps de la taille de Mars. Cela a donne\u0301 la Lune. Pour la premie\u0300re fois, des astronomes ont pu e\u0302tre les \u00ab\u00a0te\u0301moins\u00a0\u00bb de cette jeunesse tumultueuse dans un autre syste\u0300me que le no\u0302tre: Fomalhaut A, situe\u0301e a\u0300 25 anne\u0301es-lumie\u0300re de nous, la tre\u0300s proche banlieue a\u0300 l\u2019e\u0301chelle de l\u2019Univers. Fomalhaut A est la plus brillante des trois e\u0301toiles composant le syste\u0300me de Fomalhaut, dans la constellation du Poisson austral.<\/p>\n

Elle est entoure\u0301e d\u2019un vaste disque de de\u0301bris et de poussie\u0300res, a\u0302ge\u0301e de quelques centaines de millions d\u2019anne\u0301es. Une e\u0301quipe internationale d\u2019astrophysiciens, mene\u0301e par Paul Kalas, astronome a\u0300 Berkeley (Universite\u0301 de Californie), a retrouve\u0301 la trace de deux collisions entre plane\u0301te\u0301simaux sous la forme de nuages de de\u0301bris exceptionnellement lumineux, apparus puis disparus dans la vaste ceinture de poussie\u0300res qui entoure l\u2019e\u0301toile. Ce re\u0301sultat a e\u0301te\u0301 publie\u0301 le 18 de\u0301cembre 2025 dans la revue Science.<\/p>\n

Une plane\u0300te qui disparai\u0302t<\/b><\/p>\n

Cette de\u0301couverte doit tout au cher vieux te\u0301lescope Hubble, toujours vaillant en de\u0301pit de ses 35 ans. C\u2019est lui qui a permis, gra\u0302ce a\u0300 un suivi e\u0301tale\u0301 sur pre\u0300s de vingt ans, de repe\u0301rer puis de caracte\u0301riser des points lumineux fugitifs autour de Fomalhaut A. Le premier est de\u0301tecte\u0301 en 2008, et il est d\u2019abord interpre\u0301te\u0301 comme une plane\u0300te re\u0301fle\u0301chissant la lumie\u0300re de son e\u0301toile. Ainsi nai\u0302t Fomalhaut Ab. Mais des observations re\u0301alise\u0301es au de\u0301but des anne\u0301es 2010 montrent que la luminosite\u0301 de la plane\u0300te de\u0301croit rapidement… Et en 2014, elle semble bel et bien avoir disparu. A tel point que des astronomes, en 2020, e\u0301mettent l’hypothe\u0300se que l’e\u0301ve\u0301nement de 2008 e\u0301tait une collision entre deux plane\u0301te\u0301simaux.<\/p>\n

En 2023, lorsque l’e\u0301quipe de Paul Kalas pointe Hubble vers Fomalhaut, surprise: les astronomes voient apparai\u0302tre un second point lumineux, a\u0300 un autre endroit de la ceinture de poussie\u0300res. Baptise\u0301 Fomalhaut cs2 (pour \u00ab\u00a0collision source\u00a0\u00bb), il pre\u0301sente des caracte\u0301ristiques e\u0301tonnamment similaires a\u0300 celles observe\u0301es pour le premier objet, pre\u0300s de vingt ans plus to\u0302t. Me\u0302me e\u0301clat, distance a\u0300 l\u2019e\u0301toile comparable, me\u0302me comportement transitoire: une apparition soudaine suivie d\u2019une dispersion progressive. Tout indique qu\u2019il s\u2019agit, la\u0300 encore, du nuage de de\u0301bris laisse\u0301 par un choc entre plane\u0301te\u0301simaux. Le syste\u0300me aurait ainsi connu deux collisions spectaculaires en 20 ans…<\/p>\n

Un syste\u0300me solaire qui scintille<\/b><\/p>\n

Cette double observation est d\u2019autant plus remarquable que \u00ab\u00a0la the\u0301orie sugge\u0300re qu\u2019on ne devrait observer qu\u2019une collision tous les 100 000 ans, voire a\u0300 des intervalles encore plus longs. Or ici, en vingt ans, nous en avons vu deux, souligne dans un communique\u0301 Paul Kalas. Si l\u2019on pouvait projeter un film des 3 000 dernie\u0300res anne\u0301es, acce\u0301le\u0301re\u0301 de sorte que chaque anne\u0301e ne dure qu\u2019une fraction de seconde, on verrait une multitude d\u2019e\u0301clairs: le syste\u0300me plane\u0301taire de Fomalhaut scintillerait.\u00a0\u00bb<\/p>\n

Les astronomes n\u2019ont pas l\u2019intention de quitter ce syste\u0300me des yeux. Ils comptent de\u0301sormais suivre l\u2019e\u0301volution de Fomalhaut cs2 a\u0300 l\u2019aide du te\u0301lescope spatial James Webb, dont les instruments infrarouges permettront d\u2019aller plus loin que Hubble. En analysant la couleur et la structure de ce nuage de de\u0301bris, les chercheurs espe\u0300rent de\u0301terminer la taille et la composition des grains de poussie\u0300re, et peut-e\u0302tre me\u0302me de\u0301tecter la pre\u0301sence d\u2019eau ou de glace. Autant d\u2019indices pre\u0301cieux pour mieux comprendre la nature des corps qui s\u2019entrechoquent et, plus largement, les me\u0301canismes a\u0300 l\u2019\u0153uvre dans la formation des plane\u0300tes.<\/p>\n

Retrouvez plus d\u2019actualit\u00e9s et d\u2019analyses sur Benin<\/span> sur le site Africa Press<\/span> <\/p>\n","protected":false},"excerpt":{"rendered":"

Africa-Press – Benin. La vie des jeunes plane\u0300tes n’est pas un long fleuve tranquille. L’expe\u0301rience de notre syste\u0300me solaire montre que les plane\u0300tes en formation ou tout juste forme\u0301es subissent parfois de cataclysmiques collisions. Ainsi, la Terre a-t-elle e\u0301te\u0301 frappe\u0301e dans sa prime jeunesse par un corps de la taille de Mars. Cela a donne\u0301 […]<\/p>\n","protected":false},"author":82,"featured_media":51855,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22,10],"tags":[46],"class_list":["post-51856","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-divers","category-toutes-les-actualites","tag-benin-2"],"yoast_head":"\nCollisions de Plan\u00e9t\u00e9simaux Autour de Fomalhaut A - B\u00e9nin<\/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:\/\/www.africa-press.net\/benin\/politique\/collisions-de-planetesimaux-autour-de-fomalhaut-a\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Collisions de Plan\u00e9t\u00e9simaux Autour de Fomalhaut A\" \/>\n<meta property=\"og:description\" content=\"Africa-Press – Benin. La vie des jeunes plane\u0300tes n’est pas un long fleuve tranquille. L’expe\u0301rience de notre syste\u0300me solaire montre que les plane\u0300tes en formation ou tout juste forme\u0301es subissent parfois de cataclysmiques collisions. Ainsi, la Terre a-t-elle e\u0301te\u0301 frappe\u0301e dans sa prime jeunesse par un corps de la taille de Mars. 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