{"id":823,"date":"2004-12-09T15:52:00","date_gmt":"2004-12-09T14:52:00","guid":{"rendered":"https:\/\/kids.esa.int\/space_velocity\/"},"modified":"2026-10-08T00:32:41","modified_gmt":"2026-10-07T22:32:41","slug":"space_velocity","status":"publish","type":"post","link":"https:\/\/kids.esa.int\/fr\/space_velocity\/","title":{"rendered":"Vitesse dans l\u2019espace"},"content":{"rendered":"
\n

Les objets qui tournent autour d\u2019une plan\u00e8te s\u2019appellent des satellites. Chaque tour complet effectu\u00e9 par un satellite autour de la plan\u00e8te s\u2019appelle une orbite.<\/p>\n<\/div>\n

Notre Terre a un satellite naturel \u2013 la Lune. Mais depuis octobre 1957 des milliers de satellites artificiels (fabriqu\u00e9s par l\u2019homme) ont \u00e9t\u00e9 plac\u00e9s en orbite autour de la Terre.<\/p>\n

Pour rester en orbite, un satellite doit se d\u00e9placer \u00e0 une vitesse tr\u00e8s \u00e9lev\u00e9e, qui d\u00e9pend de son altitude. Ainsi, en r\u00e8gle g\u00e9n\u00e9rale, pour une orbite circulaire \u00e0 une altitude de 300 km au-dessus de la surface de la Terre, une vitesse de 7,8 km\/s (28 000 km\/h) est n\u00e9cessaire. \u00c0 cette vitesse, le satellite effectuera une orbite compl\u00e8te autour de la Terre en 90 minutes.<\/p>\n

Les satellites doivent se d\u00e9placer \u00e0 cette vitesse pour compenser l\u2019attraction de la Terre. Vous pouvez imaginer quelqu\u2019un qui lance une balle de tennis ou de baseball. Plus la balle est lanc\u00e9e fort, plus elle ira loin avant de toucher le sol.<\/p>\n

Si un joueur parvenait \u00e0 lancer la balle avec suffisamment de force pour qu\u2019elle atteigne la vitesse n\u00e9cessaire, celle-ci entrerait en orbite. Elle ne retomberait jamais sur Terre. Lancez-la encore plus fort, de mani\u00e8re \u00e0 ce qu\u2019elle atteigne une vitesse de 11,2 km\/s (40 300 km\/h) \u2013 ce qu\u2019on appelle la \u2018 vitesse d\u2019\u00e9chappement \u2019 \u2013 et la balle quittera d\u00e9finitivement la Terre. Elle deviendra alors un \u2018 satellite \u2019 du Soleil.<\/p>","protected":false},"excerpt":{"rendered":"

Objects that travel around a planet are called satellites. Each complete journey a satellite makes around the planet is called an orbit. Our Earth has one natural satellite \u2013 the […]<\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"esa_banner_image":"https:\/\/www.esa.int\/var\/esa\/storage\/images\/esa_multimedia\/images\/2004\/12\/newton_s_cannon2\/17886950-2-eng-GB\/Newton_s_cannon.gif","esa_banner_description":"","esa_banner_credit":"ESA","esa_banner_licence":"ESA Standard Licence","esa_banner_detail_url":"https:\/\/www.esa.int\/ESA_Multimedia\/Images\/2004\/12\/Newton_s_cannon2","esa_external_url":"","esa_external_new_window":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":true},"categories":[10,65,40],"tags":[2],"panel":[],"language":[],"age":[],"duration":[],"resource_type":[],"audience":[],"wf_post_folders":[],"class_list":["post-823","post","type-post","status-publish","format-standard","hentry","category-learn","category-mission-control","category-technology","tag-background-article"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/posts\/823","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/comments?post=823"}],"version-history":[{"count":1,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/posts\/823\/revisions"}],"predecessor-version":[{"id":1966,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/posts\/823\/revisions\/1966"}],"wp:attachment":[{"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/media?parent=823"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/categories?post=823"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/tags?post=823"},{"taxonomy":"panel","embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/panel?post=823"},{"taxonomy":"language","embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/language?post=823"},{"taxonomy":"age","embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/age?post=823"},{"taxonomy":"duration","embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/duration?post=823"},{"taxonomy":"resource_type","embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/resource_type?post=823"},{"taxonomy":"audience","embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/audience?post=823"},{"taxonomy":"wf_post_folders","embeddable":true,"href":"https:\/\/kids.esa.int\/fr\/wp-json\/wp\/v2\/wf_post_folders?post=823"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}