{"id":492,"date":"2021-06-28T14:46:08","date_gmt":"2021-06-28T12:46:08","guid":{"rendered":"https:\/\/graphonautedelespace.fr\/?p=492"},"modified":"2021-06-28T14:46:08","modified_gmt":"2021-06-28T12:46:08","slug":"episode-4-la-seconde-vie-du-telescope-spatial-spitzer","status":"publish","type":"post","link":"https:\/\/graphonautedelespace.fr\/?p=492","title":{"rendered":"[EPISODE 4] La seconde vie du t\u00e9lescope spatial Spitzer"},"content":{"rendered":"

[et_pb_section fb_built=”1″ _builder_version=”4.8.2″ background_color=”#FFFFFF” background_enable_image=”off” custom_margin=”|||” custom_padding=”0px|||||”][et_pb_row _builder_version=”4.8.2″ _module_preset=”default” positioning=”none” position_origin_r=”top_right” z_index=”0″ width=”100%” max_width=”1902px” custom_padding=”0px|||||”][et_pb_column type=”4_4″ _builder_version=”4.8.2″ _module_preset=”default”][et_pb_image src=”https:\/\/web.archive.org\/web\/20181214004530im_\/http:\/\/scenario-terre.space\/wp-content\/uploads\/2018\/01\/banniere-S4-fb.jpg” title_text=”bannie\u0300re-S0-fbVF” force_fullwidth=”on” _builder_version=”4.8.2″ _module_preset=”default” min_height__hover_enabled=”on|desktop”][\/et_pb_image][\/et_pb_column][\/et_pb_row][et_pb_row admin_label=”Ligne” _builder_version=”4.8.2″ _module_preset=”default”][et_pb_column type=”4_4″ _builder_version=”4.8.2″ _module_preset=”default”][et_pb_blurb title=”%91EPISODE 4%93 Exoplan\u00e8tes : le remake ?” use_icon=”on” font_icon=”%%103%%” icon_color=”rgba(0,0,0,0.61)” use_circle=”on” circle_color=”rgba(0,0,0,0.16)” use_icon_font_size=”on” icon_font_size=”30px” _builder_version=”4.8.2″ _module_preset=”default” header_font=”Trebuchet|300|||||||” text_orientation=”center”][\/et_pb_blurb][et_pb_text _builder_version=”4.8.2″ _module_preset=”default” text_font=”Trebuchet||||||||” text_text_color=”#FFFFFF” header_font=”Nasalization||||||||” header_text_align=”center” header_text_color=”#ffffff” header_font_size=”50px” text_orientation=”center”]<\/p>\n

La seconde vie du t\u00e9lescope spatial Spitzer ?
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[\/et_pb_text][et_pb_divider color=”#000000″ _builder_version=”4.8.2″ _module_preset=”default” width=”21%” module_alignment=”center”][\/et_pb_divider][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.8.2″ _module_preset=”default”][et_pb_column type=”4_4″ _builder_version=”4.8.2″ _module_preset=”default”][et_pb_text _builder_version=”4.8.2″ _module_preset=”default” text_font=”Trebuchet||||||||”]<\/p>\n

Lanc\u00e9 en 2003, le t\u00e9lescope spatial Spitzer de la NASA a cartographi\u00e9 les sources de rayonnement infrarouge de l\u2019univers : milieu interstellaire des galaxies, naissance des \u00e9toiles, impact des trous noirs supermassifs \u2026 Cette mission s\u2019est termin\u00e9e en 2009, faute d\u2019h\u00e9lium liquide maintenant les d\u00e9tecteurs \u00e0 basse temp\u00e9rature. Depuis Spitzer continue ses op\u00e9rations dans une nouvelle phase dite \u00ab\u00a0warm mission\u00a0\u00bb.<\/strong><\/p>\n

Les instruments de mesure de l\u2019astronomie infrarouge sont maintenus \u00e0 tr\u00e8s basse temp\u00e9rature pour optimiser leur sensibilit\u00e9 et leur capacit\u00e9 de d\u00e9tection des sources cosmiques de tr\u00e8s faible intensit\u00e9. L\u2019instrument \u00e0 basse temp\u00e9rature \u00e9met peu de chaleur, c\u2019est-\u00e0-dire peu de lumi\u00e8re infrarouge qui est une source de lumi\u00e8re parasite. L\u2019infrarouge est un domaine \u00e9lectromagn\u00e9tique vaste : il va d\u2019une longueur d\u2019onde de 1 \u00b5m (infrarouge proche) \u00e0 environ 100 \u00b5m (infrarouge lointain). Puisque tout corps caract\u00e9ris\u00e9 par une temp\u00e9rature de surface \u00e9met de la lumi\u00e8re, l\u2019infrarouge correspond \u00e0 des sources d\u2019\u00e9mission ayant une temp\u00e9rature entre -250\u00b0C et 1000\u00b0C environ. L\u2019infrarouge n\u2019est pas donc n\u00e9cessairement une signature du \u00ab\u00a0chaud\u00a0\u00bb, il peut aussi tracer des objets tr\u00e8s froids.<\/p>\n

Pour assurer le refroidissement, les instruments de Spitzer sont mis en contact avec de l\u2019h\u00e9lium liquide \u00e0 2 Kelvins, soit -271\u00b0C. L\u2019h\u00e9lium monte l\u00e9g\u00e8rement en temp\u00e9rature, s\u2019\u00e9vapore et emporte avec lui l\u2019exc\u00e8s de chaleur des instruments\u2026puis il est \u00e9vacu\u00e9 dans l\u2019espace. Une fois l\u2019h\u00e9lium liquide consomm\u00e9, les instruments montent en temp\u00e9rature et la d\u00e9tection de sources faibles devient impossible. Elles sont noy\u00e9es dans la lumi\u00e8re parasite des instruments.<\/p>\n

[\/et_pb_text][et_pb_image src=”https:\/\/scenarioterre.files.wordpress.com\/2017\/09\/cryostat.jpg” _builder_version=”4.8.2″ _module_preset=”default” hover_enabled=”0″ sticky_enabled=”0″][\/et_pb_image][et_pb_text _builder_version=”4.8.2″ _module_preset=”default” hover_enabled=”0″ sticky_enabled=”0″]<\/p>\n

Vue du satellite Spitzer comprenant un tube \u00e0 l\u2019int\u00e9rieur duquel est plac\u00e9 le miroir parabolique concentrant la lumi\u00e8re vers un miroir secondaire, puis vers les instruments. C\u2019est le t\u00e9lescope. La zone en bleu est le \u00ab cryostat \u00bb, un thermos renfermant les instruments et le r\u00e9servoir d\u2019h\u00e9lium liquide. (c) NASA.<\/em><\/p>\n

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N\u00e9anmoins certaines sources astronomiques sont suffisamment fortes pour demeurer \u00ab d\u00e9tectables \u00bb par des instruments non refroidi cryog\u00e9niquement. Ces instruments sont tout de m\u00eame refroidis passivement dans l\u2019espace autour de 80-100 K. Parmi ces objets d\u00e9tectables figurent les \u00e9toiles et le passage devant elle d\u2019un cort\u00e8ge de plan\u00e8tes\u2026<\/p>\n

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par Vincent Minier<\/p>\n

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