{"id":509,"date":"2004-11-16T10:36:00","date_gmt":"2004-11-16T09:36:00","guid":{"rendered":"https:\/\/kids.esa.int\/asteroids_the_minor_planets\/"},"modified":"2026-10-08T00:29:02","modified_gmt":"2026-10-07T22:29:02","slug":"asteroids_the_minor_planets","status":"publish","type":"post","link":"https:\/\/kids.esa.int\/fi\/asteroids_the_minor_planets\/","title":{"rendered":"Asteroidit \u2013 pienplaneetat"},"content":{"rendered":"<div class=\"lede\">\n<p>Asteroidit ovat pieni\u00e4, kivisi\u00e4 taivaankappaleita, jotka ovat j\u00e4\u00e4neet j\u00e4ljelle planeettojen muodostumisesta 4,5 miljardia vuotta sitten. Niit\u00e4 kutsutaan usein \u2018pienplaneetoiksi\u2019.<\/p>\n<\/div>\n<p>N\u00e4it\u00e4 kivenpalasia arvioidaan olevan miljardeja. Suurin osa niist\u00e4 sijaitsee donitsinmuotoisessa \u2018p\u00e4\u00e4vy\u00f6hykkeess\u00e4\u2019 Marsin ja Jupiterin kiertoratojen v\u00e4liss\u00e4. T\u00e4m\u00e4n p\u00e4\u00e4vy\u00f6hykkeen sis\u00e4reunalla asteroidit kiert\u00e4v\u00e4t Aurinkoa noin kolmessa vuodessa. P\u00e4\u00e4vy\u00f6hykkeen ulkorajan l\u00e4hell\u00e4 olevilla asteroideilla kiertorata kest\u00e4\u00e4 kaksi kertaa niin kauan.<\/p>\n<p>Sana \u2018asteroidi\u2019 tarkoittaa \u2018t\u00e4htim\u00e4ist\u00e4\u2019. Ne saivat t\u00e4m\u00e4n nimen, koska ne n\u00e4kyv\u00e4t useimmissa kaukoputkissa vain valopistein\u00e4. 1900-luvun alkupuolella t\u00e4htitieteilij\u00e4t kutsuivat niit\u00e4 \u2018taivaan tuholaisiksi\u2019. Niit\u00e4 n\u00e4kyi niin paljon, ett\u00e4 ne pilasivat kaukaisten galaksien ja sumujen valokuvia.<\/p>\n<p>Asteroideista suurin, Ceres, l\u00f6ydettiin ensimm\u00e4isen\u00e4. Sen l\u00f6ysi Giuseppi Piazzi Palermosta, Sisiliasta, 1. tammikuuta 1801.<\/p>\n<p>Wilhelm Olbers l\u00f6ysi toisen pienen planeetan \u2013 Pallasin \u2013 vuonna 1802. Sen j\u00e4lkeen l\u00f6ydettiin Juno (1804) ja Vesta (1807). Vuodesta 1847 l\u00e4htien ei ole kulunut yht\u00e4\u00e4n vuotta ilman, ett\u00e4 olisi l\u00f6ydetty v\u00e4hint\u00e4\u00e4n yksi asteroidi.<\/p>\n<nav class=\"related\" aria-label=\"Aiheeseen liittyv\u00e4t\">\n<h2 class=\"related__heading\">Aiheeseen liittyv\u00e4t<\/h2>\n<div class=\"grid related__grid\">\n<div class=\"grid-item\">\n<article class=\"card focuson agency\"><a class=\"card__link\" href=\"\/fi\/asteroider_de_smaa_planeter\/\"><\/p>\n<figure class=\"thumbnail\"><span class=\"dimmer\"><\/span><\/figure>\n<header class=\"entry\">\n<h3 class=\"heading\">Tanska<\/h3>\n<\/header>\n<p><\/a><\/article>\n<\/div>\n<div class=\"grid-item\">\n<article class=\"card focuson agency\"><a class=\"card__link\" href=\"\/fi\/planetoiden_-_de_kleine_planeten\/\"><\/p>\n<figure class=\"thumbnail\"><span class=\"dimmer\"><\/span><\/figure>\n<header class=\"entry\">\n<h3 class=\"heading\">hollanti<\/h3>\n<\/header>\n<p><\/a><\/article>\n<\/div>\n<div class=\"grid-item\">\n<article class=\"card focuson agency\"><a class=\"card__link\" href=\"\/fi\/asteroiden_-_die_kleinplaneten\/\"><\/p>\n<figure class=\"thumbnail\"><span class=\"dimmer\"><\/span><\/figure>\n<header class=\"entry\">\n<h3 class=\"heading\">saksa<\/h3>\n<\/header>\n<p><\/a><\/article>\n<\/div>\n<div class=\"grid-item\">\n<article class=\"card focuson agency\"><a class=\"card__link\" href=\"\/fi\/asteroider_de_smaa_planetene\/\"><\/p>\n<figure class=\"thumbnail\"><span class=\"dimmer\"><\/span><\/figure>\n<header class=\"entry\">\n<h3 class=\"heading\">norja<\/h3>\n<\/header>\n<p><\/a><\/article>\n<\/div>\n<div class=\"grid-item\">\n<article class=\"card focuson agency\"><a class=\"card__link\" href=\"\/fi\/asteroidy_czyli_planetoidy\/\"><\/p>\n<figure class=\"thumbnail\"><span class=\"dimmer\"><\/span><\/figure>\n<header class=\"entry\">\n<h3 class=\"heading\">puola<\/h3>\n<\/header>\n<p><\/a><\/article>\n<\/div>\n<div class=\"grid-item\">\n<article class=\"card focuson agency\"><a class=\"card__link\" href=\"\/fi\/asteroider_smaaplaneterna\/\"><\/p>\n<figure class=\"thumbnail\"><span class=\"dimmer\"><\/span><\/figure>\n<header class=\"entry\">\n<h3 class=\"heading\">ruotsi<\/h3>\n<\/header>\n<p><\/a><\/article>\n<\/div>\n<\/div>\n<\/nav>","protected":false},"excerpt":{"rendered":"<p>Asteroids are small, rocky bodies that have been left over from the formation of the planets 4.5 billion years ago. They are often known as &#8216;minor planets&#8217;. There are thought [&hellip;]<\/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\/2001\/07\/asteroid_243_ida_and_its_newly_discovered_moon_dactyl2\/17863270-3-eng-GB\/Asteroid_243_Ida_and_its_newly_discovered_moon_Dactyl.jpg","esa_banner_description":"Asteroid 243 Ida and its newly discovered moon, Dactyl","esa_banner_credit":"NASA","esa_banner_licence":"ESA Standard Licence","esa_banner_detail_url":"https:\/\/www.esa.int\/ESA_Multimedia\/Images\/2001\/07\/Asteroid_243_Ida_and_its_newly_discovered_moon_Dactyl2","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":[46,10,11],"tags":[2],"panel":[],"language":[],"age":[],"duration":[],"resource_type":[],"audience":[],"wf_post_folders":[],"class_list":["post-509","post","type-post","status-publish","format-standard","hentry","category-comets-and-meteors","category-learn","category-our-universe","tag-background-article"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts\/509","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/comments?post=509"}],"version-history":[{"count":1,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts\/509\/revisions"}],"predecessor-version":[{"id":1652,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/posts\/509\/revisions\/1652"}],"wp:attachment":[{"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/media?parent=509"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/categories?post=509"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/tags?post=509"},{"taxonomy":"panel","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/panel?post=509"},{"taxonomy":"language","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/language?post=509"},{"taxonomy":"age","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/age?post=509"},{"taxonomy":"duration","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/duration?post=509"},{"taxonomy":"resource_type","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/resource_type?post=509"},{"taxonomy":"audience","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/audience?post=509"},{"taxonomy":"wf_post_folders","embeddable":true,"href":"https:\/\/kids.esa.int\/fi\/wp-json\/wp\/v2\/wf_post_folders?post=509"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}