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<span class="vector-toc-numb">2</span> <span>Terminology</span> </div> </a> <button aria-controls="toc-Terminology-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Terminology subsection</span> </button> <ul id="toc-Terminology-sublist" class="vector-toc-list"> <li id="toc-Etymology" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Etymology"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Etymology</span> </div> </a> <ul id="toc-Etymology-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Terminology_summary" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Terminology_summary"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Terminology summary</span> </div> </a> <ul id="toc-Terminology_summary-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Perihelion_and_aphelion" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Perihelion_and_aphelion"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Perihelion and aphelion</span> </div> </a> <button aria-controls="toc-Perihelion_and_aphelion-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Perihelion and aphelion subsection</span> </button> <ul id="toc-Perihelion_and_aphelion-sublist" class="vector-toc-list"> <li id="toc-Inner_planets_and_outer_planets" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Inner_planets_and_outer_planets"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Inner planets and outer planets</span> </div> </a> <ul id="toc-Inner_planets_and_outer_planets-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Lines_of_apsides" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Lines_of_apsides"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Lines of apsides</span> </div> </a> <ul id="toc-Lines_of_apsides-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Earth_perihelion_and_aphelion" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Earth_perihelion_and_aphelion"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Earth perihelion and aphelion</span> </div> </a> <ul id="toc-Earth_perihelion_and_aphelion-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Other_planets" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Other_planets"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.4</span> <span>Other planets</span> </div> </a> <ul id="toc-Other_planets-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Mathematical_formulae" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Mathematical_formulae"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Mathematical formulae</span> </div> </a> <ul id="toc-Mathematical_formulae-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Time_of_perihelion" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Time_of_perihelion"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Time of perihelion</span> </div> </a> <button aria-controls="toc-Time_of_perihelion-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Time of perihelion subsection</span> </button> <ul id="toc-Time_of_perihelion-sublist" class="vector-toc-list"> <li id="toc-Short_arcs" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Short_arcs"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Short arcs</span> </div> </a> <ul id="toc-Short_arcs-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Apsis</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 69 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-69" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">69 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Apside" title="Apside – Afrikaans" lang="af" hreflang="af" data-title="Apside" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-als mw-list-item"><a href="https://als.wikipedia.org/wiki/Apsis_(Astronomie)" title="Apsis (Astronomie) – Alemannic" lang="gsw" hreflang="gsw" data-title="Apsis (Astronomie)" data-language-autonym="Alemannisch" data-language-local-name="Alemannic" class="interlanguage-link-target"><span>Alemannisch</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%82%D8%A8%D8%A7" title="قبا – Arabic" lang="ar" hreflang="ar" data-title="قبا" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/%C3%81pside" title="Ápside – Asturian" lang="ast" hreflang="ast" data-title="Ápside" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-ban mw-list-item"><a href="https://ban.wikipedia.org/wiki/Apsis" title="Apsis – Balinese" lang="ban" hreflang="ban" data-title="Apsis" data-language-autonym="Basa Bali" data-language-local-name="Balinese" class="interlanguage-link-target"><span>Basa Bali</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%85%E0%A6%AA%E0%A6%A6%E0%A7%82%E0%A6%B0%E0%A6%AC%E0%A6%BF%E0%A6%A8%E0%A7%8D%E0%A6%A6%E0%A7%81" title="অপদূরবিন্দু – Bangla" lang="bn" hreflang="bn" data-title="অপদূরবিন্দু" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%90%D0%BF%D0%B0%D1%86%D1%8D%D0%BD%D1%82%D1%80_%D1%96_%D0%BF%D0%B5%D1%80%D1%8B%D1%86%D1%8D%D0%BD%D1%82%D1%80" title="Апацэнтр і перыцэнтр – Belarusian" lang="be" hreflang="be" data-title="Апацэнтр і перыцэнтр" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/%D0%9F%D1%8D%D1%80%D1%8B%D1%86%D1%8D%D0%BD%D1%82%D0%B0%D1%80_%D1%96_%D0%B0%D0%BF%D0%B0%D1%86%D1%8D%D0%BD%D1%82%D0%B0%D1%80" title="Пэрыцэнтар і апацэнтар – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="Пэрыцэнтар і апацэнтар" data-language-autonym="Беларуская (тарашкевіца)" data-language-local-name="Belarusian (Taraškievica orthography)" class="interlanguage-link-target"><span>Беларуская (тарашкевіца)</span></a></li><li class="interlanguage-link interwiki-bh mw-list-item"><a href="https://bh.wikipedia.org/wiki/%E0%A4%8F%E0%A4%AA%E0%A5%8D%E0%A4%B8%E0%A4%BF%E0%A4%B8" title="एप्सिस – Bhojpuri" lang="bh" hreflang="bh" data-title="एप्सिस" data-language-autonym="भोजपुरी" data-language-local-name="Bhojpuri" class="interlanguage-link-target"><span>भोजपुरी</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%90%D0%BF%D1%81%D0%B8%D0%B4%D0%B0_(%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D1%8F)" title="Апсида (астрономия) – Bulgarian" lang="bg" hreflang="bg" data-title="Апсида (астрономия)" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/%C3%80pside" title="Àpside – Catalan" lang="ca" hreflang="ca" data-title="Àpside" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Apsida_(astronomie)" title="Apsida (astronomie) – Czech" lang="cs" hreflang="cs" data-title="Apsida (astronomie)" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Apsis_(astronomi)" title="Apsis (astronomi) – Danish" lang="da" hreflang="da" data-title="Apsis (astronomi)" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Apsis_(Astronomie)" title="Apsis (Astronomie) – German" lang="de" hreflang="de" data-title="Apsis (Astronomie)" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Apsiid_(astronoomia)" title="Apsiid (astronoomia) – Estonian" lang="et" hreflang="et" data-title="Apsiid (astronoomia)" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/%C3%81pside" title="Ápside – Spanish" lang="es" hreflang="es" data-title="Ápside" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Apsido" title="Apsido – Esperanto" lang="eo" hreflang="eo" data-title="Apsido" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Apside" title="Apside – Basque" lang="eu" hreflang="eu" data-title="Apside" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%A7%D9%88%D8%AC_%D9%88_%D8%AD%D8%B6%DB%8C%D8%B6" title="اوج و حضیض – Persian" lang="fa" hreflang="fa" data-title="اوج و حضیض" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Apside" title="Apside – French" lang="fr" hreflang="fr" data-title="Apside" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-gv mw-list-item"><a href="https://gv.wikipedia.org/wiki/Apsis" title="Apsis – Manx" lang="gv" hreflang="gv" data-title="Apsis" data-language-autonym="Gaelg" data-language-local-name="Manx" class="interlanguage-link-target"><span>Gaelg</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Apse" title="Apse – Galician" lang="gl" hreflang="gl" data-title="Apse" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EC%9E%A5%EC%B6%95%EB%8B%A8" title="장축단 – Korean" lang="ko" hreflang="ko" data-title="장축단" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D4%B1%D5%BA%D5%B8%D5%AF%D5%A5%D5%B6%D5%BF%D6%80%D5%B8%D5%B6_%D6%87_%D5%BA%D5%A5%D6%80%D5%AB%D5%AF%D5%A5%D5%B6%D5%BF%D6%80%D5%B8%D5%B6" title="Ապոկենտրոն և պերիկենտրոն – Armenian" lang="hy" hreflang="hy" data-title="Ապոկենտրոն և պերիկենտրոն" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%AE%E0%A4%A8%E0%A5%8D%E0%A4%A6" title="मन्द – Hindi" lang="hi" hreflang="hi" data-title="मन्द" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Apsida_(astronomija)" title="Apsida (astronomija) – Croatian" lang="hr" hreflang="hr" data-title="Apsida (astronomija)" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-io mw-list-item"><a href="https://io.wikipedia.org/wiki/Apsido_(astronomio)" title="Apsido (astronomio) – Ido" lang="io" hreflang="io" data-title="Apsido (astronomio)" data-language-autonym="Ido" data-language-local-name="Ido" class="interlanguage-link-target"><span>Ido</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Apsis" title="Apsis – Indonesian" lang="id" hreflang="id" data-title="Apsis" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-is mw-list-item"><a href="https://is.wikipedia.org/wiki/N%C3%A1ndarsta%C3%B0a_og_fir%C3%B0sta%C3%B0a" title="Nándarstaða og firðstaða – Icelandic" lang="is" hreflang="is" data-title="Nándarstaða og firðstaða" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target"><span>Íslenska</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Apside" title="Apside – Italian" lang="it" hreflang="it" data-title="Apside" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%90%D7%A4%D7%A1%D7%99%D7%93" title="אפסיד – Hebrew" lang="he" hreflang="he" data-title="אפסיד" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%90%E1%83%9E%E1%83%9D%E1%83%AA%E1%83%94%E1%83%9C%E1%83%A2%E1%83%A0%E1%83%98_%E1%83%93%E1%83%90_%E1%83%9E%E1%83%94%E1%83%A0%E1%83%98%E1%83%AA%E1%83%94%E1%83%9C%E1%83%A2%E1%83%A0%E1%83%98" title="აპოცენტრი და პერიცენტრი – Georgian" lang="ka" hreflang="ka" data-title="აპოცენტრი და პერიცენტრი" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%90%D0%BF%D0%BE%D1%86%D0%B5%D0%BD%D1%82%D1%80_%D0%B6%D3%99%D0%BD%D0%B5_%D0%BF%D0%B5%D1%80%D0%B8%D1%86%D0%B5%D0%BD%D1%82%D1%80" title="Апоцентр және перицентр – Kazakh" lang="kk" hreflang="kk" data-title="Апоцентр және перицентр" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Apsis" title="Apsis – Latin" lang="la" hreflang="la" data-title="Apsis" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Aps%C4%ABda" title="Apsīda – Latvian" lang="lv" hreflang="lv" data-title="Apsīda" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Apsid%C4%97_(astronomija)" title="Apsidė (astronomija) – Lithuanian" lang="lt" hreflang="lt" data-title="Apsidė (astronomija)" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Apszispont" title="Apszispont – Hungarian" lang="hu" hreflang="hu" data-title="Apszispont" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%90%D0%BF%D1%81%D0%B8%D0%B4%D0%B0_(%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D1%98%D0%B0)" title="Апсида (астрономија) – Macedonian" lang="mk" hreflang="mk" data-title="Апсида (астрономија)" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%85%E0%B4%AA%E0%B4%B8%E0%B5%97%E0%B4%B0%E0%B4%82" title="അപസൗരം – Malayalam" lang="ml" hreflang="ml" data-title="അപസൗരം" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-mr mw-list-item"><a href="https://mr.wikipedia.org/wiki/%E0%A4%89%E0%A4%AA%E0%A4%A8%E0%A4%BE%E0%A4%AD%E0%A5%80_%E0%A4%AC%E0%A4%BF%E0%A4%82%E0%A4%A6%E0%A5%82" title="उपनाभी बिंदू – Marathi" lang="mr" hreflang="mr" data-title="उपनाभी बिंदू" data-language-autonym="मराठी" data-language-local-name="Marathi" class="interlanguage-link-target"><span>मराठी</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Apsis" title="Apsis – Malay" lang="ms" hreflang="ms" data-title="Apsis" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Apside" title="Apside – Dutch" lang="nl" hreflang="nl" data-title="Apside" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E8%BF%91%E7%82%B9%E3%83%BB%E9%81%A0%E7%82%B9" title="近点・遠点 – Japanese" lang="ja" hreflang="ja" data-title="近点・遠点" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Apsis_(astronomi)" title="Apsis (astronomi) – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Apsis (astronomi)" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Apsis_i_astronomi" title="Apsis i astronomi – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Apsis i astronomi" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-nds mw-list-item"><a href="https://nds.wikipedia.org/wiki/Apsis_(Astronomie)" title="Apsis (Astronomie) – Low German" lang="nds" hreflang="nds" data-title="Apsis (Astronomie)" data-language-autonym="Plattdüütsch" data-language-local-name="Low German" class="interlanguage-link-target"><span>Plattdüütsch</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Apsyda_(astronomia)" title="Apsyda (astronomia) – Polish" lang="pl" hreflang="pl" data-title="Apsyda (astronomia)" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Apside" title="Apside – Portuguese" lang="pt" hreflang="pt" data-title="Apside" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Apsid%C4%83" title="Apsidă – Romanian" lang="ro" hreflang="ro" data-title="Apsidă" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%90%D0%BF%D0%BE%D1%86%D0%B5%D0%BD%D1%82%D1%80_%D0%B8_%D0%BF%D0%B5%D1%80%D0%B8%D1%86%D0%B5%D0%BD%D1%82%D1%80" title="Апоцентр и перицентр – Russian" lang="ru" hreflang="ru" data-title="Апоцентр и перицентр" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-si mw-list-item"><a href="https://si.wikipedia.org/wiki/%E0%B6%AF%E0%B7%94%E0%B6%BB%E0%B7%8F%E0%B6%B1%E0%B7%8A%E0%B6%AD%E0%B7%92%E0%B6%9A%E0%B6%BA" title="දුරාන්තිකය – Sinhala" lang="si" hreflang="si" data-title="දුරාන්තිකය" data-language-autonym="සිංහල" data-language-local-name="Sinhala" class="interlanguage-link-target"><span>සිංහල</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Apsis" title="Apsis – Simple English" lang="en-simple" hreflang="en-simple" data-title="Apsis" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Apsida_(astron%C3%B3mia)" title="Apsida (astronómia) – Slovak" lang="sk" hreflang="sk" data-title="Apsida (astronómia)" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Apsidna_to%C4%8Dka" title="Apsidna točka – Slovenian" lang="sl" hreflang="sl" data-title="Apsidna točka" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-ckb mw-list-item"><a href="https://ckb.wikipedia.org/wiki/%D9%86%D8%B2%DB%8C%DA%A9%D8%AA%D8%B1%DB%8C%D9%86_%D9%88_%D8%AF%D9%88%D9%88%D8%B1%D8%AA%D8%B1%DB%8C%D9%86" title="نزیکترین و دوورترین – Central Kurdish" lang="ckb" hreflang="ckb" data-title="نزیکترین و دوورترین" data-language-autonym="کوردی" data-language-local-name="Central Kurdish" class="interlanguage-link-target"><span>کوردی</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/Apsida_(astronomija)" title="Apsida (astronomija) – Serbian" lang="sr" hreflang="sr" data-title="Apsida (astronomija)" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Apsida_(astronomija)" title="Apsida (astronomija) – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Apsida (astronomija)" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-su mw-list-item"><a href="https://su.wikipedia.org/wiki/Apsis" title="Apsis – Sundanese" lang="su" hreflang="su" data-title="Apsis" data-language-autonym="Sunda" data-language-local-name="Sundanese" class="interlanguage-link-target"><span>Sunda</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Apsidi_(t%C3%A4htitiede)" title="Apsidi (tähtitiede) – Finnish" lang="fi" hreflang="fi" data-title="Apsidi (tähtitiede)" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Apsis" title="Apsis – Swedish" lang="sv" hreflang="sv" data-title="Apsis" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%9A%E0%AF%81%E0%AE%B1%E0%AF%8D%E0%AE%B1%E0%AF%81%E0%AE%AA%E0%AF%8D%E0%AE%AA%E0%AE%BE%E0%AE%A4%E0%AF%88_%E0%AE%B5%E0%AF%80%E0%AE%9A%E0%AF%8D%E0%AE%9A%E0%AF%81" title="சுற்றுப்பாதை வீச்சு – Tamil" lang="ta" hreflang="ta" data-title="சுற்றுப்பாதை வீச்சு" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%88%E0%B8%B8%E0%B8%94%E0%B9%83%E0%B8%81%E0%B8%A5%E0%B9%89%E0%B9%81%E0%B8%A5%E0%B8%B0%E0%B9%84%E0%B8%81%E0%B8%A5%E0%B8%97%E0%B8%B5%E0%B9%88%E0%B8%AA%E0%B8%B8%E0%B8%94" title="จุดใกล้และไกลที่สุด – Thai" lang="th" hreflang="th" data-title="จุดใกล้และไกลที่สุด" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Apsis_(astronomi)" title="Apsis (astronomi) – Turkish" lang="tr" hreflang="tr" data-title="Apsis (astronomi)" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-tyv mw-list-item"><a href="https://tyv.wikipedia.org/wiki/%D0%90%D0%BF%D0%BE%D0%B3%D0%B5%D0%B9" title="Апогей – Tuvinian" lang="tyv" hreflang="tyv" data-title="Апогей" data-language-autonym="Тыва дыл" data-language-local-name="Tuvinian" class="interlanguage-link-target"><span>Тыва дыл</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%90%D0%BF%D1%81%D0%B8%D0%B4%D0%B8" title="Апсиди – Ukrainian" lang="uk" hreflang="uk" data-title="Апсиди" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/C%E1%BB%A7ng_%C4%91i%E1%BB%83m_qu%E1%BB%B9_%C4%91%E1%BA%A1o" title="Củng điểm quỹ đạo – Vietnamese" lang="vi" hreflang="vi" data-title="Củng điểm quỹ đạo" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%E6%8B%B1%E7%82%B9" title="拱点 – Wu" lang="wuu" hreflang="wuu" data-title="拱点" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target"><span>吴语</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E6%8B%B1%E9%BB%9E" title="拱點 – Cantonese" lang="yue" hreflang="yue" data-title="拱點" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E6%8B%B1%E9%BB%9E" title="拱點 – Chinese" lang="zh" hreflang="zh" data-title="拱點" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q83481#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit 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class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"><span class="mw-redirectedfrom">(Redirected from <a href="/w/index.php?title=Perihelion&redirect=no" class="mw-redirect" title="Perihelion">Perihelion</a>)</span></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Either of two extreme points in a celestial object's orbit</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Several terms redirect here. For other uses, see <a href="/wiki/Apogee_(disambiguation)" class="mw-disambig" title="Apogee (disambiguation)">Apogee (disambiguation)</a>, <a href="/wiki/Perigee_(disambiguation)" class="mw-disambig" title="Perigee (disambiguation)">Perigee (disambiguation)</a>, and <a href="/wiki/Apse_(disambiguation)" class="mw-disambig" title="Apse (disambiguation)">Apse (disambiguation)</a>.</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="/wiki/Apse" title="Apse">Apse</a> or <a href="/wiki/Aspis" title="Aspis">Aspis</a>.</div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-More_citations_needed plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This article <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Apsis" title="Special:EditPage/Apsis">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and removed.<br /><small><span class="plainlinks"><i>Find sources:</i> <a rel="nofollow" class="external text" href="https://www.google.com/search?as_eq=wikipedia&q=%22Apsis%22">"Apsis"</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22Apsis%22+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22Apsis%22&tbs=bkt:s&tbm=bks">newspapers</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?tbs=bks:1&q=%22Apsis%22+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22Apsis%22">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22Apsis%22&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">December 2020</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <p class="mw-empty-elt"> </p> <figure typeof="mw:File/Thumb"><a href="/w/index.php?title=File:Apogee_(PSF)_mul.svg&lang=zxx" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Apogee_%28PSF%29_mul.svg/langzxx-345px-Apogee_%28PSF%29_mul.svg.png" decoding="async" width="345" height="210" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Apogee_%28PSF%29_mul.svg/langzxx-518px-Apogee_%28PSF%29_mul.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Apogee_%28PSF%29_mul.svg/langzxx-690px-Apogee_%28PSF%29_mul.svg.png 2x" data-file-width="512" data-file-height="312" /></a><figcaption>The apsides refer to the farthest (2) and nearest (3) points reached by an orbiting <a href="/wiki/Planetary-mass_object" title="Planetary-mass object">planetary body</a> (2 and 3) with respect to a <a href="/wiki/Primary_body" title="Primary body">primary, or host, body</a> (1)</figcaption></figure> <p>An <b>apsis</b> (from <a href="/wiki/Ancient_Greek_language" class="mw-redirect" title="Ancient Greek language">Ancient Greek</a> <i> </i><span lang="grc"><a href="https://en.wiktionary.org/wiki/%E1%BC%81%CF%88%CE%AF%CF%82#Ancient_Greek" class="extiw" title="wikt:ἁψίς">ἁψίς</a></span><i> (<span title="Ancient Greek transliteration" lang="grc-Latn"><i>hapsís</i></span>)</i> <span class="gloss-quot">'</span><span class="gloss-text">arch, vault</span><span class="gloss-quot">'</span>; <abbr title="plural">pl.</abbr><span style="white-space:nowrap;"> <b>apsides</b></span> <span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="/ˈ/: primary stress follows">ˈ</span><span title="/æ/: 'a' in 'bad'">æ</span><span title="'p' in 'pie'">p</span><span title="'s' in 'sigh'">s</span><span title="/ɪ/: 'i' in 'kit'">ɪ</span><span title="/ˌ/: secondary stress follows">ˌ</span><span title="'d' in 'dye'">d</span><span title="/iː/: 'ee' in 'fleece'">iː</span><span title="'z' in 'zoom'">z</span></span>/</a></span></span> <a href="/wiki/Help:Pronunciation_respelling_key" title="Help:Pronunciation respelling key"><i title="English pronunciation respelling"><span style="font-size:90%">AP</span>-sih-deez</i></a>)<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> is the farthest or nearest point in the <a href="/wiki/Orbit" title="Orbit">orbit</a> of a <a href="/wiki/Planetary-mass_object" title="Planetary-mass object">planetary body</a> about its <a href="/wiki/Primary_body" title="Primary body">primary body</a>. The <b>line of apsides</b> (also called <b>apse line,</b> or <b>major axis of the orbit</b>) is the line connecting the two <a href="/wiki/Maximum_and_minimum" title="Maximum and minimum">extreme values</a>. </p><p>Apsides pretaining to orbits around different bodies have distinct names to differentiate themselves from other apsides. Apsides pertaining to <a href="/wiki/Geocentric_orbit" title="Geocentric orbit">geocentric orbits</a>, orbits around the <a href="/wiki/Earth" title="Earth">Earth</a>, are at the farthest point called the <i><b>apogee</b></i>, and at the nearest point the <i><b>perigee</b></i>, like with orbits of satellites and the Moon around Earth. Apsides pertaining to orbits around the <a href="/wiki/Sun" title="Sun">Sun</a> are named <i><b>aphelion</b></i> for the farthest and <i><b>perihelion</b></i> for the nearest point in a <a href="/wiki/Heliocentric_orbit" title="Heliocentric orbit">heliocentric orbit</a>.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Earth's two apsides are the farthest point, <i>aphelion</i>, and the nearest point, <i>perihelion</i>, of its orbit around the host Sun. The terms <i>aphelion</i> and <i>perihelion</i> apply in the same way to the orbits of <a href="/wiki/Jupiter" title="Jupiter">Jupiter</a> and the other <a href="/wiki/Planet" title="Planet">planets</a>, the <a href="/wiki/Comet" title="Comet">comets</a>, and the <a href="/wiki/Asteroid" title="Asteroid">asteroids</a> of the <a href="/wiki/Solar_System" title="Solar System">Solar System</a>. </p> <style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol 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style="padding-bottom:0.85em;"><span typeof="mw:File"><a href="/wiki/File:Orbit_mechanics_icon.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Orbit_mechanics_icon.svg/60px-Orbit_mechanics_icon.svg.png" decoding="async" width="60" height="60" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Orbit_mechanics_icon.svg/90px-Orbit_mechanics_icon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/cc/Orbit_mechanics_icon.svg/120px-Orbit_mechanics_icon.svg.png 2x" data-file-width="48" data-file-height="48" /></a></span></td></tr><tr><th class="sidebar-heading" style="padding-bottom:0.55em;"> <div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Orbital_mechanics" title="Orbital mechanics"><span style="font-size:110%;">Orbital mechanics</span></a></div></th></tr><tr><td class="sidebar-content hlist"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)"><a href="/wiki/Orbital_elements" title="Orbital elements">Orbital elements</a></div><div class="sidebar-list-content mw-collapsible-content plainlist" style="padding-top:0;"> <ul><li><a class="mw-selflink selflink">Apsis</a></li> <li><a href="/wiki/Argument_of_periapsis" title="Argument of periapsis">Argument of periapsis</a></li> <li><a href="/wiki/Orbital_eccentricity" title="Orbital eccentricity">Eccentricity</a></li> <li><a href="/wiki/Orbital_inclination" title="Orbital inclination">Inclination</a></li> <li><a href="/wiki/Mean_anomaly" title="Mean anomaly">Mean anomaly</a></li> <li><a href="/wiki/Orbital_node" title="Orbital node">Orbital nodes</a></li> <li><a href="/wiki/Semi-major_and_semi-minor_axes" title="Semi-major and semi-minor axes">Semi-major axis</a></li> <li><a href="/wiki/True_anomaly" title="True anomaly">True anomaly</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content hlist"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Types of <a href="/wiki/Two-body_problem" title="Two-body problem">two-body orbits</a> by <br />eccentricity</div><div class="sidebar-list-content mw-collapsible-content plainlist" style="padding-top:0;"> <ul><li><a href="/wiki/Circular_orbit" title="Circular orbit">Circular orbit</a></li> <li><a href="/wiki/Elliptic_orbit" title="Elliptic orbit">Elliptic orbit</a></li></ul> <div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Transfer_orbit" title="Transfer orbit">Transfer orbit</a> <div class="hlist" style="font-size:90%"><ul><li>(<a href="/wiki/Hohmann_transfer_orbit" title="Hohmann transfer orbit">Hohmann transfer orbit</a></li><li><a href="/wiki/Bi-elliptic_transfer" title="Bi-elliptic transfer">Bi-elliptic transfer orbit</a>)</li></ul></div></div> <ul><li><a href="/wiki/Parabolic_trajectory" title="Parabolic trajectory">Parabolic orbit</a></li> <li><a href="/wiki/Hyperbolic_trajectory" title="Hyperbolic trajectory">Hyperbolic orbit</a></li> <li><a href="/wiki/Radial_trajectory" title="Radial trajectory">Radial orbit</a></li> <li><a href="/wiki/Orbital_decay" title="Orbital decay">Decaying orbit</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content hlist"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Equations</div><div class="sidebar-list-content mw-collapsible-content plainlist" style="padding-top:0;"> <ul><li><a href="/wiki/Dynamical_friction" title="Dynamical friction">Dynamical friction</a></li> <li><a href="/wiki/Escape_velocity" title="Escape velocity">Escape velocity</a></li> <li><a href="/wiki/Kepler%27s_equation" title="Kepler's equation">Kepler's equation</a></li> <li><a href="/wiki/Kepler%27s_laws_of_planetary_motion" title="Kepler's laws of planetary motion">Kepler's laws of planetary motion</a></li> <li><a href="/wiki/Orbital_period" title="Orbital period">Orbital period</a></li> <li><a href="/wiki/Orbital_speed" title="Orbital speed">Orbital velocity</a></li> <li><a href="/wiki/Surface_gravity" title="Surface gravity">Surface gravity</a></li> <li><a href="/wiki/Specific_orbital_energy" title="Specific orbital energy">Specific orbital energy</a></li> <li><a href="/wiki/Vis-viva_equation" title="Vis-viva equation">Vis-viva equation</a></li></ul></div></div></td> </tr><tr><th class="sidebar-heading" style="padding-bottom:0.55em;"> <div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Celestial_mechanics" title="Celestial mechanics"><span style="font-size:110%;">Celestial mechanics</span></a></div></th></tr><tr><td class="sidebar-content hlist"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Gravitational influences</div><div class="sidebar-list-content mw-collapsible-content plainlist" style="padding-top:0;"> <ul><li><a href="/wiki/Barycenter" class="mw-redirect" title="Barycenter">Barycenter</a></li> <li><a href="/wiki/Hill_sphere" title="Hill sphere">Hill sphere</a></li> <li><a href="/wiki/Perturbation_(astronomy)" title="Perturbation (astronomy)">Perturbations</a></li> <li><a href="/wiki/Sphere_of_influence_(astrodynamics)" title="Sphere of influence (astrodynamics)">Sphere of influence</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content hlist"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)"><a href="/wiki/N-body_problem" title="N-body problem">N-body orbits</a></div><div class="sidebar-list-content mw-collapsible-content plainlist" style="padding-top:0;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Lagrange_point" title="Lagrange point">Lagrangian points</a> <div class="hlist" style="font-size:90%"><ul><li>(<a href="/wiki/Halo_orbit" title="Halo orbit">Halo orbits</a>)</li></ul></div></div> <ul><li><a href="/wiki/Lissajous_orbit" title="Lissajous orbit">Lissajous orbits</a></li> <li><a href="/wiki/Lyapunov_stability" title="Lyapunov stability">Lyapunov orbits</a></li></ul></div></div></td> </tr><tr><th class="sidebar-heading" style="padding-bottom:0.55em;"> <div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Aerospace_engineering" title="Aerospace engineering"><span style="font-size:110%;">Engineering and efficiency</span></a></div></th></tr><tr><td class="sidebar-content hlist"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Preflight engineering</div><div class="sidebar-list-content mw-collapsible-content plainlist" style="padding-top:0;"> <ul><li><a href="/wiki/Mass_ratio" title="Mass ratio">Mass ratio</a></li> <li><a href="/wiki/Payload_fraction" title="Payload fraction">Payload fraction</a></li> <li><a href="/wiki/Propellant_mass_fraction" title="Propellant mass fraction">Propellant mass fraction</a></li> <li><a href="/wiki/Tsiolkovsky_rocket_equation" title="Tsiolkovsky rocket equation">Tsiolkovsky rocket equation</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content hlist"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Efficiency measures</div><div class="sidebar-list-content mw-collapsible-content plainlist" style="padding-top:0;"> <ul><li><a href="/wiki/Gravity_assist" title="Gravity assist">Gravity assist</a></li> <li><a href="/wiki/Oberth_effect" title="Oberth effect">Oberth effect</a></li></ul></div></div></td> </tr><tr><td class="sidebar-content hlist"> <div class="sidebar-list mw-collapsible mw-collapsed"><div class="sidebar-list-title" style="color: var(--color-base)">Propulsive maneuvers</div><div class="sidebar-list-content mw-collapsible-content plainlist" style="padding-top:0;"> <ul><li><a href="/wiki/Orbital_maneuver" title="Orbital maneuver">Orbital maneuver</a></li> <li><a href="/wiki/Orbit_insertion" title="Orbit insertion">Orbit insertion</a></li></ul></div></div></td> </tr><tr><td class="sidebar-navbar"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Astrodynamics" title="Template:Astrodynamics"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Astrodynamics" title="Template talk:Astrodynamics"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Astrodynamics" title="Special:EditPage/Template:Astrodynamics"><abbr title="Edit this template">e</abbr></a></li></ul></div></td></tr></tbody></table> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="General_description">General description</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=1" title="Edit section: General description"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Periapsis_apoapsis.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/a0/Periapsis_apoapsis.png/250px-Periapsis_apoapsis.png" decoding="async" width="250" height="281" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/a0/Periapsis_apoapsis.png/375px-Periapsis_apoapsis.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/a0/Periapsis_apoapsis.png/500px-Periapsis_apoapsis.png 2x" data-file-width="567" data-file-height="637" /></a><figcaption>The two-body system of interacting <a href="/wiki/Elliptic_orbit" title="Elliptic orbit">elliptic orbits</a>: The smaller, satellite body (blue) orbits the <a href="/wiki/Primary_(astronomy)" class="mw-redirect" title="Primary (astronomy)">primary body</a> (yellow); both are in elliptic orbits around their <a href="/wiki/Center_of_mass" title="Center of mass">common center of mass</a> (or <a href="/wiki/Barycenter" class="mw-redirect" title="Barycenter">barycenter</a>), (red +).<br /> ∗Periapsis and apoapsis as distances: the smallest and largest distances between the orbiter and its host body.</figcaption></figure> <p>There are two apsides in any <a href="/wiki/Elliptic_orbit" title="Elliptic orbit">elliptic orbit</a>. The name for each apsis is created from the prefixes <i>ap-</i>, <i>apo-</i> (from <i> </i>ἀπ(ό)<i>, (ap(o)-)</i> <span class="gloss-quot">'</span><span class="gloss-text">away from</span><span class="gloss-quot">'</span>) for the farthest or <i>peri-</i> (from <i> </i>περί<i> (peri-)</i> <span class="gloss-quot">'</span><span class="gloss-text">near</span><span class="gloss-quot">'</span>) for the closest point to the <a href="/wiki/Primary_body" title="Primary body">primary body</a>, with a suffix that describes the primary body. The suffix for Earth is <i>-gee</i>, so the apsides' names are <i>apogee</i> and <i>perigee</i>. For the Sun, the suffix is <i>-helion</i>, so the names are <i>aphelion</i> and <i>perihelion</i>. </p><p>According to <a href="/wiki/Newton%27s_laws_of_motion" title="Newton's laws of motion">Newton's laws of motion</a>, all periodic orbits are ellipses. The barycenter of the two bodies may lie well within the bigger body—e.g., the Earth–Moon barycenter is about 75% of the way from Earth's center to its surface.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> If, compared to the larger mass, the smaller mass is negligible (e.g., for satellites), then the <a href="/wiki/Orbital_elements" title="Orbital elements">orbital parameters</a> are independent of the smaller mass. </p><p>When used as a suffix—that is, <i>-apsis</i>—the term can refer to the two distances from the primary body to the orbiting body when the latter is located: 1) at the <i>periapsis</i> point, or 2) at the <i>apoapsis</i> point (compare both graphics, second figure). The line of apsides denotes the distance of the line that joins the nearest and farthest points across an orbit; it also refers simply to the extreme range of an object orbiting a host body (see top figure; see third figure). </p><p>In <a href="/wiki/Orbital_mechanics" title="Orbital mechanics">orbital mechanics</a>, the apsides technically refer to the distance measured between the <a href="/wiki/Barycenter" class="mw-redirect" title="Barycenter">barycenter</a> of the 2-body system and the center of mass of the orbiting body. However, in the case of a <a href="/wiki/Spacecraft" title="Spacecraft">spacecraft</a>, the terms are commonly used to refer to the orbital <a href="/wiki/Altitude" title="Altitude">altitude</a> of the spacecraft above the surface of the central body (assuming a constant, standard reference radius). </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Angular_Parameters_of_Elliptical_Orbit.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1d/Angular_Parameters_of_Elliptical_Orbit.png/250px-Angular_Parameters_of_Elliptical_Orbit.png" decoding="async" width="250" height="250" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1d/Angular_Parameters_of_Elliptical_Orbit.png/375px-Angular_Parameters_of_Elliptical_Orbit.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1d/Angular_Parameters_of_Elliptical_Orbit.png/500px-Angular_Parameters_of_Elliptical_Orbit.png 2x" data-file-width="1200" data-file-height="1200" /></a><figcaption><a href="/wiki/Kepler_orbit" title="Kepler orbit">Keplerian</a> <a href="/wiki/Orbital_elements" title="Orbital elements">orbital elements</a>: point <i>G</i>, the nearest point of approach of an orbiting body, is the pericenter (also periapsis) of an orbit; point <i>H</i>, the farthest point of the orbiting body, is the apocenter (also apoapsis) of the orbit; and the red line between them is the line of apsides.</figcaption></figure> <div class="mw-heading mw-heading2"><h2 id="Terminology">Terminology</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=2" title="Edit section: Terminology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The words "pericenter" and "apocenter" are often seen, although periapsis/apoapsis are preferred in technical usage. </p> <ul><li>For generic situations where the primary is not specified, the terms <i>pericenter</i> and <i>apocenter</i> are used for naming the extreme points of orbits (see table, top figure); <i>periapsis</i> and <i>apoapsis</i> (or <i>apapsis</i>) are equivalent alternatives, but these terms also frequently refer to distances—that is, the smallest and largest distances between the orbiter and its host body (see second figure).</li> <li>For a body orbiting the <a href="/wiki/Sun" title="Sun">Sun</a>, the point of least distance is the <i>perihelion</i> (<span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="/ˌ/: secondary stress follows">ˌ</span><span title="'p' in 'pie'">p</span><span title="/ɛr/: 'err' in 'merry'">ɛr</span><span title="/ɪ/: 'i' in 'kit'">ɪ</span><span title="/ˈ/: primary stress follows">ˈ</span><span title="'h' in 'hi'">h</span><span title="/iː/: 'ee' in 'fleece'">iː</span><span title="'l' in 'lie'">l</span><span title="/i/: 'y' in 'happy'">i</span><span title="/ə/: 'a' in 'about'">ə</span><span title="'n' in 'nigh'">n</span></span>/</a></span></span>), and the point of greatest distance is the <i>aphelion</i> (<span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="/æ/: 'a' in 'bad'">æ</span><span title="'p' in 'pie'">p</span><span title="/ˈ/: primary stress follows">ˈ</span><span title="'h' in 'hi'">h</span><span title="/iː/: 'ee' in 'fleece'">iː</span><span title="'l' in 'lie'">l</span><span title="/i/: 'y' in 'happy'">i</span><span title="/ə/: 'a' in 'about'">ə</span><span title="'n' in 'nigh'">n</span></span>/</a></span></span>);<sup id="cite_ref-Sun_5-0" class="reference"><a href="#cite_note-Sun-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> when discussing orbits around other stars the terms become <i>periastron</i> and <i>apastron</i>.</li> <li>When discussing a satellite of <a href="/wiki/Earth" title="Earth">Earth</a>, including the <a href="/wiki/Moon" title="Moon">Moon</a>, the point of least distance is the <i>perigee</i> (<span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="/ˈ/: primary stress follows">ˈ</span><span title="'p' in 'pie'">p</span><span title="/ɛr/: 'err' in 'merry'">ɛr</span><span title="/ɪ/: 'i' in 'kit'">ɪ</span><span title="/dʒ/: 'j' in 'jam'">dʒ</span><span title="/iː/: 'ee' in 'fleece'">iː</span></span>/</a></span></span>), and of greatest distance, the <i>apogee</i> (from <a href="/wiki/Ancient_Greek" title="Ancient Greek">Ancient Greek</a>: Γῆ (<i>Gē</i>), "land" or "earth").<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup></li> <li>For objects in <a href="/wiki/Lunar_orbit" title="Lunar orbit">lunar orbit</a>, the point of least distance are called the <i>pericynthion</i> (<span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="/ˌ/: secondary stress follows">ˌ</span><span title="'p' in 'pie'">p</span><span title="/ɛr/: 'err' in 'merry'">ɛr</span><span title="/ɪ/: 'i' in 'kit'">ɪ</span><span title="/ˈ/: primary stress follows">ˈ</span><span title="'s' in 'sigh'">s</span><span title="/ɪ/: 'i' in 'kit'">ɪ</span><span title="'n' in 'nigh'">n</span><span title="/θ/: 'th' in 'thigh'">θ</span><span title="/i/: 'y' in 'happy'">i</span><span title="/ə/: 'a' in 'about'">ə</span><span title="'n' in 'nigh'">n</span></span>/</a></span></span>) and the greatest distance the <i>apocynthion</i> (<span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="/ˌ/: secondary stress follows">ˌ</span><span title="/æ/: 'a' in 'bad'">æ</span><span title="'p' in 'pie'">p</span><span title="/ə/: 'a' in 'about'">ə</span><span title="/ˈ/: primary stress follows">ˈ</span><span title="'s' in 'sigh'">s</span><span title="/ɪ/: 'i' in 'kit'">ɪ</span><span title="'n' in 'nigh'">n</span><span title="/θ/: 'th' in 'thigh'">θ</span><span title="/i/: 'y' in 'happy'">i</span><span title="/ə/: 'a' in 'about'">ə</span><span title="'n' in 'nigh'">n</span></span>/</a></span></span>). The terms <i>perilune</i> and <i>apolune</i>, as well as <i>periselene</i> and <i>aposelene</i> are also used.<sup id="cite_ref-nasaglossary_7-0" class="reference"><a href="#cite_note-nasaglossary-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Since the Moon has no natural satellites this only applies to man-made objects.</li></ul> <div class="mw-heading mw-heading3"><h3 id="Etymology">Etymology</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=3" title="Edit section: Etymology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The words <i>perihelion</i> and <i>aphelion</i> were coined by <a href="/wiki/Johannes_Kepler" title="Johannes Kepler">Johannes Kepler</a><sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> to describe the orbital motions of the planets around the Sun. The words are formed from the prefixes <i>peri-</i> (Greek: <i>περί</i>, near) and <i>apo-</i> (Greek: <i>ἀπό</i>, away from), affixed to the Greek word for the Sun, (<i>ἥλιος</i>, or <i>hēlíos</i>).<sup id="cite_ref-Sun_5-1" class="reference"><a href="#cite_note-Sun-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>Various related terms are used for other <a href="/wiki/Celestial_body" class="mw-redirect" title="Celestial body">celestial objects</a>. The suffixes <i>-gee</i>, <i>-helion</i>, <i>-astron</i> and <i>-galacticon</i> are frequently used in the astronomical literature when referring to the Earth, Sun, stars, and the <a href="/wiki/Galactic_Center" title="Galactic Center">Galactic Center</a> respectively. The suffix <i>-jove</i> is occasionally used for Jupiter, but <i>-saturnium</i> has very rarely been used in the last 50 years for Saturn. The <i>-gee</i> form is also used as a generic closest-approach-to "any planet" term—instead of applying it only to Earth. </p><p>During the <a href="/wiki/Apollo_program" title="Apollo program">Apollo program</a>, the terms <i>pericynthion</i> and <i>apocynthion</i> were used when referring to <a href="/wiki/Lunar_orbit" title="Lunar orbit">orbiting the Moon</a>; they reference Cynthia, an alternative name for the Greek Moon goddess <a href="/wiki/Artemis" title="Artemis">Artemis</a>.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> More recently, during the <a href="/wiki/Artemis_program" title="Artemis program">Artemis program</a>, the terms <i>perilune</i> and <i>apolune</i> have been used.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>Regarding black holes, the term peribothron was first used in a 1976 paper by J. Frank and M. J. Rees,<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> who credit W. R. Stoeger for suggesting creating a term using the greek word for pit: "bothron". </p><p>The terms <i>perimelasma</i> and <i>apomelasma</i> (from a Greek root) were used by physicist and science-fiction author <a href="/wiki/Geoffrey_A._Landis" title="Geoffrey A. Landis">Geoffrey A. Landis</a> in a story published in 1998,<sup id="cite_ref-Asimov's_12-0" class="reference"><a href="#cite_note-Asimov's-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> thus appearing before <i>perinigricon</i> and <i>aponigricon</i> (from Latin) in the scientific literature in 2002.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Terminology_summary">Terminology summary</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=4" title="Edit section: Terminology summary"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The suffixes shown below may be added to prefixes <i>peri-</i> or <i>apo-</i> to form unique names of apsides for the orbiting bodies of the indicated host/<a href="/wiki/Primary_(astronomy)" class="mw-redirect" title="Primary (astronomy)">(primary)</a> system. However, only for the Earth, Moon and Sun systems are the unique suffixes commonly used. <a href="/wiki/Exoplanet" title="Exoplanet">Exoplanet</a> studies commonly use <i>-astron</i>, but typically, for other host systems the generic suffix, <i>-apsis</i>, is used instead.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup><sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability"><span title="Reference is simply one example of the use of -apsis for an orbit around Mars (January 2019)">failed verification</span></a></i>]</sup> </p> <table class="wikitable"> <caption>Host objects in the Solar System with named/nameable apsides </caption> <tbody><tr> <th><a href="/wiki/Astronomical_object" title="Astronomical object">Astronomical<br />host object</a> </th> <th>Suffix </th> <th>Origin<br />of the name </th></tr> <tr> <td><a href="/wiki/Sun" title="Sun">Sun</a> </td> <td><span class="nowrap">-helion</span> </td> <td><a href="/wiki/Helios" title="Helios">Helios</a> </td></tr> <tr> <td><a href="/wiki/Mercury_(planet)" title="Mercury (planet)">Mercury</a> </td> <td><span class="nowrap">-hermion</span> </td> <td><a href="/wiki/Hermes" title="Hermes">Hermes</a> </td></tr> <tr> <td><a href="/wiki/Venus" title="Venus">Venus</a> </td> <td><span class="nowrap">-cythe</span>-cytherion </td> <td><a href="/wiki/Cytherean" title="Cytherean">Cytherean</a> </td></tr> <tr> <td><a href="/wiki/Earth" title="Earth">Earth</a> </td> <td><span class="nowrap">-gee</span> </td> <td><a href="/wiki/Gaia_(mythology)" class="mw-redirect" title="Gaia (mythology)">Gaia</a> </td></tr> <tr> <td><a href="/wiki/Moon" title="Moon">Moon</a> </td> <td><span class="nowrap">-lune</span><sup id="cite_ref-nasaglossary_7-1" class="reference"><a href="#cite_note-nasaglossary-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><br /><span class="nowrap">-cynthion</span><br /><span class="nowrap">-selene</span><sup id="cite_ref-nasaglossary_7-2" class="reference"><a href="#cite_note-nasaglossary-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </td> <td><a href="/wiki/Luna_(goddess)" title="Luna (goddess)">Luna</a><br /><a href="/wiki/Artemis" title="Artemis">Cynthia</a><br /><a href="/wiki/Selene" title="Selene">Selene</a> </td></tr> <tr> <td><a href="/wiki/Mars" title="Mars">Mars</a> </td> <td><span class="nowrap">-areion</span> </td> <td><a href="/wiki/Ares" title="Ares">Ares</a> </td></tr> <tr> <td><a href="/wiki/Ceres_(dwarf_planet)" title="Ceres (dwarf planet)">Ceres</a> </td> <td><span class="nowrap">-demeter</span><sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </td> <td><a href="/wiki/Demeter" title="Demeter">Demeter</a> </td></tr> <tr> <td><a href="/wiki/Jupiter" title="Jupiter">Jupiter</a> </td> <td><span class="nowrap">-jove</span> </td> <td><a href="/wiki/Zeus" title="Zeus">Zeus</a><br /><a href="/wiki/Jupiter" title="Jupiter">Jupiter</a> </td></tr> <tr> <td><a href="/wiki/Saturn" title="Saturn">Saturn</a> </td> <td><span class="nowrap">-chron</span><sup id="cite_ref-nasaglossary_7-3" class="reference"><a href="#cite_note-nasaglossary-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><br /><span class="nowrap">-kronos</span><br /><span class="nowrap">-saturnium</span><br /><span class="nowrap">-krone</span><sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </td> <td><a href="/wiki/Cronus" title="Cronus">Cronos</a><br /><a href="/wiki/Saturn" title="Saturn">Saturn</a> </td></tr> <tr> <td><a href="/wiki/Uranus" title="Uranus">Uranus</a> </td> <td><span class="nowrap">-uranion</span> </td> <td><a href="/wiki/Uranus" title="Uranus">Uranus</a> </td></tr> <tr> <td><a href="/wiki/Neptune" title="Neptune">Neptune</a> </td> <td><span class="nowrap">-poseideum</span><sup id="cite_ref-McKevitt_Bulla_Dixon_Criscola_2021_17-0" class="reference"><a href="#cite_note-McKevitt_Bulla_Dixon_Criscola_2021-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup><br /><span class="nowrap">-poseidion</span> </td> <td><a href="/wiki/Poseidon" title="Poseidon">Poseidon</a> </td></tr></tbody></table> <table class="wikitable"> <caption>Other host objects with named/nameable apsides </caption> <tbody><tr> <th>Astronomical<br /> host object </th> <th>Suffix </th> <th>Origin<br />of the name </th></tr> <tr> <td><a href="/wiki/Star" title="Star">Star</a> </td> <td>-astron </td> <td><a href="/wiki/Ad_astra_(phrase)" class="mw-redirect" title="Ad astra (phrase)">Lat: astra</a>; <i>stars</i> </td></tr> <tr> <td><a href="/wiki/Galaxy" title="Galaxy">Galaxy</a> </td> <td>-galacticon </td> <td>Gr: <a href="/wiki/Galaxy" title="Galaxy">galaxias; <i>galaxy</i></a> </td></tr> <tr> <td><a href="/wiki/Barycenter" class="mw-redirect" title="Barycenter">Barycenter</a> </td> <td>-center<br />-focus<br />-apsis </td> <td> </td></tr> <tr> <td><a href="/wiki/Black_hole" title="Black hole">Black hole</a> </td> <td>-melasma<br />-bothron<br />-nigricon </td> <td>Gr: melos; <i>black</i><br />Gr: <a href="/wiki/Bothros" title="Bothros">bothros</a>; <i>hole</i><br />Lat: <span title="Latin-language text"><i lang="la">niger</i></span>; <i>black</i> </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="Perihelion_and_aphelion">Perihelion and aphelion</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=5" title="Edit section: Perihelion and aphelion"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">"Perihelion" redirects here. For other uses, see <a href="/wiki/Perihelion_(disambiguation)" class="mw-disambig" title="Perihelion (disambiguation)">Perihelion (disambiguation)</a>.</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">"Aphelion" redirects here. For other uses, see <a href="/wiki/Aphelion_(disambiguation)" class="mw-disambig" title="Aphelion (disambiguation)">Aphelion (disambiguation)</a>.</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Perihelion-Aphelion.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/94/Perihelion-Aphelion.svg/220px-Perihelion-Aphelion.svg.png" decoding="async" width="220" height="194" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/94/Perihelion-Aphelion.svg/330px-Perihelion-Aphelion.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/94/Perihelion-Aphelion.svg/440px-Perihelion-Aphelion.svg.png 2x" data-file-width="486" data-file-height="428" /></a><figcaption>Diagram of a body's direct <a href="/wiki/Orbit" title="Orbit">orbit</a> around the <a href="/wiki/Sun" title="Sun">Sun</a> with its nearest (perihelion) and farthest (aphelion) points</figcaption></figure> <p>The perihelion (q) and aphelion (Q) are the nearest and farthest points respectively of a body's direct <a href="/wiki/Orbit" title="Orbit">orbit</a> around the <a href="/wiki/Sun" title="Sun">Sun</a>. </p><p>Comparing <a href="/wiki/Osculating_elements" class="mw-redirect" title="Osculating elements">osculating elements</a> at a specific <a href="/wiki/Epoch_(astronomy)" title="Epoch (astronomy)">epoch</a> to those at a different epoch will generate differences. The time-of-perihelion-passage as one of six osculating elements is not an exact prediction (other than for a generic <a href="/wiki/Two-body_problem" title="Two-body problem">two-body model</a>) of the actual minimum distance to the Sun using the <a href="/wiki/N-body_problem" title="N-body problem">full dynamical model</a>. Precise predictions of perihelion passage require <a href="/wiki/Numerical_integration" title="Numerical integration">numerical integration</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Inner_planets_and_outer_planets">Inner planets and outer planets</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=6" title="Edit section: Inner planets and outer planets"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The two images below show the orbits, <a href="/wiki/Orbital_node" title="Orbital node">orbital nodes</a>, and positions of perihelion (q) and aphelion (Q) for the planets of the Solar System<sup id="cite_ref-:0_18-0" class="reference"><a href="#cite_note-:0-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> as seen from above the northern pole of <a href="/wiki/Ecliptic" title="Ecliptic">Earth's ecliptic plane</a>, which is <a href="/wiki/Coplanar" class="mw-redirect" title="Coplanar">coplanar</a> with <a href="/wiki/Orbital_plane_(astronomy)" class="mw-redirect" title="Orbital plane (astronomy)">Earth's orbital plane</a>. The planets travel counterclockwise around the Sun and for each planet, the blue part of their orbit travels north of the ecliptic plane, the pink part travels south, and dots mark perihelion (green) and aphelion (orange). </p><p>The first image (below-left) features the <i>inner</i> planets, situated outward from the Sun as Mercury, Venus, Earth, and Mars. The <i>reference</i> Earth-orbit is colored yellow and represents the <a href="/wiki/Orbital_plane_(astronomy)" class="mw-redirect" title="Orbital plane (astronomy)">orbital plane of reference</a>. At the time of vernal equinox, the Earth is at the bottom of the figure. The second image (below-right) shows the <i>outer</i> planets, being Jupiter, Saturn, Uranus, and Neptune. </p><p>The orbital nodes are the two end points of the <a href="/wiki/Orbital_node#Node_distinction" title="Orbital node">"line of nodes"</a> where a planet's tilted orbit intersects the plane of reference;<sup id="cite_ref-darlinglon_19-0" class="reference"><a href="#cite_note-darlinglon-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> here they may be 'seen' as the points where the blue section of an orbit meets the pink. </p> <ul class="gallery mw-gallery-traditional skin-invert-image"> <li class="gallerybox" style="width: 335px"> <div class="thumb" style="width: 330px; height: 330px;"><span typeof="mw:File"><a href="/wiki/File:Inner_Planet_Orbits_02.svg" class="mw-file-description" title="The perihelion (green) and aphelion (orange) points of the inner planets of the Solar System"><img alt="The perihelion (green) and aphelion (orange) points of the inner planets of the Solar System" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Inner_Planet_Orbits_02.svg/300px-Inner_Planet_Orbits_02.svg.png" decoding="async" width="300" height="300" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Inner_Planet_Orbits_02.svg/450px-Inner_Planet_Orbits_02.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b1/Inner_Planet_Orbits_02.svg/600px-Inner_Planet_Orbits_02.svg.png 2x" data-file-width="600" data-file-height="600" /></a></span></div> <div class="gallerytext">The perihelion (green) and aphelion (orange) points of the <a href="/wiki/Inner_planets" class="mw-redirect" title="Inner planets">inner planets</a> of the Solar System</div> </li> <li class="gallerybox" style="width: 335px"> <div class="thumb" style="width: 330px; height: 330px;"><span typeof="mw:File"><a href="/wiki/File:Outer_Planet_Orbits_02.svg" class="mw-file-description" title="The perihelion (green) and aphelion (orange) points of the outer planets of the Solar System"><img alt="The perihelion (green) and aphelion (orange) points of the outer planets of the Solar System" src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f1/Outer_Planet_Orbits_02.svg/300px-Outer_Planet_Orbits_02.svg.png" decoding="async" width="300" height="300" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f1/Outer_Planet_Orbits_02.svg/450px-Outer_Planet_Orbits_02.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f1/Outer_Planet_Orbits_02.svg/600px-Outer_Planet_Orbits_02.svg.png 2x" data-file-width="600" data-file-height="600" /></a></span></div> <div class="gallerytext">The perihelion (green) and aphelion (orange) points of the <a href="/wiki/Outer_planets" class="mw-redirect" title="Outer planets">outer planets</a> of the Solar System</div> </li> </ul> <div class="mw-heading mw-heading3"><h3 id="Lines_of_apsides">Lines of apsides</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=7" title="Edit section: Lines of apsides"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The chart shows the extreme range—from the closest approach (perihelion) to farthest point (aphelion)—of several orbiting <a href="/wiki/Celestial_bodies" class="mw-redirect" title="Celestial bodies">celestial bodies</a> of the <a href="/wiki/Solar_System" title="Solar System">Solar System</a>: the planets, the known dwarf planets, including <a href="/wiki/Ceres_(dwarf_planet)" title="Ceres (dwarf planet)">Ceres</a>, and <a href="/wiki/Halley%27s_Comet" title="Halley's Comet">Halley's Comet</a>. The length of the horizontal bars correspond to the extreme range of the orbit of the indicated body around the Sun. These extreme distances (between perihelion and aphelion) are <i>the lines of apsides</i> of the orbits of various objects around a host body. </p> <div class="thumb" style="width:auto; margin: 0 auto; overflow:hidden;"> <div class="thumbinner"> <div class="timeline-wrapper"><map name="timeline_cc0jl2xbbj7tdx7c6e1sxyxu74q3uio"><area shape="rect" href="/wiki/Astronomical_unit" coords="1440,-8,1512,16" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Astronomical_unit" coords="1285,-8,1357,16" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Astronomical_unit" coords="1131,-8,1202,16" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Astronomical_unit" coords="976,-8,1048,16" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Astronomical_unit" coords="821,-8,893,16" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Astronomical_unit" coords="667,-8,738,16" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Astronomical_unit" coords="512,-8,584,16" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Astronomical_unit" coords="357,-8,429,16" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Astronomical_unit" coords="203,-8,274,16" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Astronomical_unit" coords="66,-8,124,16" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Halley%27s_Comet" coords="341,64,472,88" title="Halley's Comet" alt="Halley's Comet" /><area shape="rect" href="/wiki/Sun" coords="67,160,125,184" title="Sun" alt="Sun" /><area shape="rect" href="/wiki/Eris_(dwarf_planet)" coords="867,144,932,168" title="Eris (dwarf planet)" alt="Eris (dwarf planet)" /><area shape="rect" href="/wiki/Makemake_(dwarf_planet)" coords="766,124,858,148" title="Makemake (dwarf planet)" alt="Makemake (dwarf planet)" /><area shape="rect" href="/wiki/Haumea_(dwarf_planet)" coords="730,104,808,128" title="Haumea (dwarf planet)" alt="Haumea (dwarf planet)" /><area shape="rect" href="/wiki/Pluto" coords="675,84,747,108" title="Pluto" alt="Pluto" /><area shape="rect" href="/wiki/Ceres_(dwarf_planet)" coords="107,104,179,128" title="Ceres (dwarf planet)" alt="Ceres (dwarf planet)" /><area shape="rect" href="/wiki/Neptune" coords="530,20,615,44" title="Neptune" alt="Neptune" /><area shape="rect" href="/wiki/Uranus" coords="361,20,440,44" title="Uranus" alt="Uranus" /><area shape="rect" href="/wiki/Saturn" coords="212,20,290,44" title="Saturn" alt="Saturn" /><area shape="rect" href="/wiki/Jupiter" coords="145,20,230,44" title="Jupiter" alt="Jupiter" /><area shape="rect" href="/wiki/Mars" coords="88,45,153,69" title="Mars" alt="Mars" /><area shape="rect" href="/wiki/Earth" coords="80,32,152,56" title="Earth" alt="Earth" /><area shape="rect" href="/wiki/Venus" coords="76,19,147,43" title="Venus" alt="Venus" /><area shape="rect" href="/wiki/Mercury_(planet)" coords="70,6,155,30" title="Mercury (planet)" alt="Mercury (planet)" /><area shape="rect" href="/wiki/Astronomical_unit" coords="-4,5,108,25" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Astronomical_unit" coords="-4,-5,97,15" title="Astronomical unit" alt="Astronomical unit" /><area shape="rect" href="/wiki/Dwarf_planet" coords="0,121,80,111" title="Dwarf planet" alt="Dwarf planet" /><area shape="rect" href="/wiki/Dwarf_planet" coords="0,101,80,91" title="Dwarf planet" alt="Dwarf planet" /><area shape="rect" href="/wiki/Comet" coords="0,61,80,51" title="Comet" alt="Comet" /><area shape="rect" href="/wiki/Planet" coords="0,21,80,11" title="Planet" alt="Planet" /></map><img usemap="#timeline_cc0jl2xbbj7tdx7c6e1sxyxu74q3uio" src="//upload.wikimedia.org/wikipedia/en/timeline/cc0jl2xbbj7tdx7c6e1sxyxu74q3uio.png" /></div> <div class="thumbcaption"> <p>Distances of selected bodies of the <a href="/wiki/Solar_System" title="Solar System">Solar System</a> from the Sun. The left and right edges of each bar correspond to the <a href="/wiki/Perihelion" class="mw-redirect" title="Perihelion">perihelion</a> and <a href="/wiki/Aphelion" class="mw-redirect" title="Aphelion">aphelion</a> of the body, respectively, hence long bars denote high <a href="/wiki/Orbital_eccentricity" title="Orbital eccentricity">orbital eccentricity</a>. The radius of the Sun is 0.7 million km, and the radius of Jupiter (the largest planet) is 0.07 million km, both too small to resolve on this image. </p> </div></div></div> <div class="mw-heading mw-heading3"><h3 id="Earth_perihelion_and_aphelion">Earth perihelion and aphelion</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=8" title="Edit section: Earth perihelion and aphelion"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Currently, the Earth reaches perihelion in early January, approximately 14 days after the <a href="/wiki/December_solstice" title="December solstice">December solstice</a>. At perihelion, the Earth's center is about <span class="nowrap"><span data-sort-value="6999983290000000000♠"></span>0.983<span style="margin-left:.25em;">29</span></span> <a href="/wiki/Astronomical_unit" title="Astronomical unit">astronomical units</a> (AU) or 147,098,070 km (91,402,500 mi) from the Sun's center. In contrast, the Earth reaches aphelion currently in early July, approximately 14 days after the <a href="/wiki/June_solstice" title="June solstice">June solstice</a>. The aphelion distance between the Earth's and Sun's centers is currently about <span class="nowrap"><span data-sort-value="7011152097651119397♠"></span>1.016<span style="margin-left:.25em;">71</span> AU</span> or 152,097,700 km (94,509,100 mi). </p><p>The dates of perihelion and aphelion change over time due to precession and other orbital factors, which follow cyclical patterns known as <a href="/wiki/Milankovitch_cycles" title="Milankovitch cycles">Milankovitch cycles</a>. In the short term, such dates can vary up to 2 days from one year to another.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> This significant variation is due to the presence of the Moon: while the Earth–Moon <a href="/wiki/Barycenter" class="mw-redirect" title="Barycenter">barycenter</a> is moving on a stable orbit around the Sun, the position of the Earth's center which is on average about 4,700 kilometres (2,900 mi) from the barycenter, could be shifted in any direction from it—and this affects the timing of the actual closest approach between the Sun's and the Earth's centers (which in turn defines the timing of perihelion in a given year).<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p><p>Because of the increased distance at aphelion, only 93.55% of the radiation from the Sun falls on a given area of Earth's surface as does at perihelion, but this does not account for the <a href="/wiki/Season" title="Season">seasons</a>, which result instead from the <a href="/wiki/Axial_tilt" title="Axial tilt">tilt of Earth's axis</a> of 23.4° away from perpendicular to the plane of Earth's orbit.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> Indeed, at both perihelion and aphelion it is <a href="/wiki/Summer" title="Summer">summer</a> in one hemisphere while it is <a href="/wiki/Winter" title="Winter">winter</a> in the other one. Winter falls on the hemisphere where sunlight strikes least directly, and summer falls where sunlight strikes most directly, regardless of the Earth's distance from the Sun. </p><p>In the northern hemisphere, summer occurs at the same time as aphelion, when solar radiation is lowest. Despite this, summers in the northern hemisphere are on average 2.3 °C (4 °F) warmer than in the southern hemisphere, because the northern hemisphere contains larger land masses, which are easier to heat than the seas.<sup id="cite_ref-Earth_at_Aphelion_23-0" class="reference"><a href="#cite_note-Earth_at_Aphelion-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p><p>Perihelion and aphelion do however have an indirect effect on the seasons: because Earth's <a href="/wiki/Orbital_speed" title="Orbital speed">orbital speed</a> is minimum at aphelion and maximum at perihelion, the planet takes longer to orbit from June solstice to September equinox than it does from December solstice to March equinox. Therefore, summer in the northern hemisphere lasts slightly longer (93 days) than summer in the southern hemisphere (89 days).<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p><p>Astronomers commonly express the timing of perihelion relative to the <a href="/wiki/First_Point_of_Aries" class="mw-redirect" title="First Point of Aries">First Point of Aries</a> not in terms of days and hours, but rather as an angle of orbital displacement, the so-called <a href="/wiki/Longitude_of_the_periapsis" class="mw-redirect" title="Longitude of the periapsis">longitude of the periapsis</a> (also called longitude of the pericenter). For the orbit of the Earth, this is called the <i>longitude of perihelion</i>, and in 2000 it was about 282.895°; by 2010, this had advanced by a small fraction of a degree to about 283.067°,<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> i.e. a mean increase of 62" per year. </p><p>For the orbit of the Earth around the Sun, the time of apsis is often expressed in terms of a time relative to seasons, since this determines the contribution of the elliptical orbit to seasonal variations. The variation of the seasons is primarily controlled by the annual cycle of the elevation angle of the Sun, which is a result of the tilt of the axis of the Earth measured from the <a href="/wiki/Plane_of_the_ecliptic" class="mw-redirect" title="Plane of the ecliptic">plane of the ecliptic</a>. The Earth's <a href="/wiki/Orbital_eccentricity" title="Orbital eccentricity">eccentricity</a> and other orbital elements are not constant, but vary slowly due to the perturbing effects of the planets and other objects in the solar system (Milankovitch cycles). </p><p>On a very long time scale, the dates of the perihelion and of the aphelion progress through the seasons, and they make one complete cycle in 22,000 to 26,000 years. There is a corresponding movement of the position of the stars as seen from Earth, called the <a href="/wiki/Apsidal_precession" title="Apsidal precession">apsidal precession</a>. (This is closely related to the <a href="/wiki/Axial_precession_(astronomy)" class="mw-redirect" title="Axial precession (astronomy)">precession of the axes</a>.) The dates and times of the perihelions and aphelions for several past and future years are listed in the following table:<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> </p> <table class="wikitable" style="margin-left:auto; margin-right:auto;"> <tbody><tr> <th rowspan="2" width="50">Year </th> <th colspan="2">Perihelion </th> <th colspan="2">Aphelion </th></tr> <tr> <th width="95">Date</th> <th width="80">Time (<a href="/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">UT</a>) </th> <th width="95">Date</th> <th width="80">Time (<a href="/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">UT</a>) </th></tr> <tr> <th>2010 </th> <td>January 3</td> <td>00:09 </td> <td>July 6</td> <td>11:30 </td></tr> <tr> <th>2011 </th> <td>January 3</td> <td>18:32 </td> <td>July 4</td> <td>14:54 </td></tr> <tr> <th>2012 </th> <td>January 5</td> <td>00:32 </td> <td>July 5</td> <td>03:32 </td></tr> <tr> <th>2013 </th> <td>January 2</td> <td>04:38 </td> <td>July 5</td> <td>14:44 </td></tr> <tr> <th>2014 </th> <td>January 4</td> <td>11:59 </td> <td>July 4</td> <td>00:13 </td></tr> <tr> <th>2015 </th> <td>January 4</td> <td>06:36 </td> <td>July 6</td> <td>19:40 </td></tr> <tr> <th>2016 </th> <td>January 2</td> <td>22:49 </td> <td>July 4</td> <td>16:24 </td></tr> <tr> <th>2017 </th> <td>January 4</td> <td>14:18 </td> <td>July 3</td> <td>20:11 </td></tr> <tr> <th>2018 </th> <td>January 3</td> <td>05:35 </td> <td>July 6</td> <td>16:47 </td></tr> <tr> <th>2019 </th> <td>January 3</td> <td>05:20 </td> <td>July 4</td> <td>22:11 </td></tr> <tr> <th>2020 </th> <td>January 5</td> <td>07:48 </td> <td>July 4</td> <td>11:35 </td></tr> <tr> <th>2021 </th> <td>January 2 </td> <td>13:51 </td> <td>July 5 </td> <td>22:27 </td></tr> <tr> <th>2022 </th> <td>January 4 </td> <td>06:55 </td> <td>July 4 </td> <td>07:11 </td></tr> <tr> <th>2023 </th> <td>January 4 </td> <td>16:17 </td> <td>July 6 </td> <td>20:07 </td></tr> <tr> <th>2024 </th> <td>January 3 </td> <td>00:39 </td> <td>July 5 </td> <td>05:06 </td></tr> <tr> <th>2025 </th> <td>January 4 </td> <td>13:28 </td> <td>July 3 </td> <td>19:55 </td></tr> <tr> <th>2026 </th> <td>January 3 </td> <td>17:16 </td> <td>July 6 </td> <td>17:31 </td></tr> <tr> <th>2027 </th> <td>January 3 </td> <td>02:33 </td> <td>July 5 </td> <td>05:06 </td></tr> <tr> <th>2028 </th> <td>January 5 </td> <td>12:28 </td> <td>July 3 </td> <td>22:18 </td></tr> <tr> <th>2029 </th> <td>January 2 </td> <td>18:13 </td> <td>July 6 </td> <td>05:12 </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="Other_planets">Other planets</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=9" title="Edit section: Other planets"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The following table shows the distances of the <a href="/wiki/Planet" title="Planet">planets</a> and <a href="/wiki/Dwarf_planet" title="Dwarf planet">dwarf planets</a> from the Sun at their perihelion and aphelion.<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> </p> <table class="wikitable sortable" style="margin-left:auto; margin-right:auto;"> <tbody><tr> <th class="unsortable">Type of body</th> <th>Body</th> <th class="unsortable">Distance from Sun at perihelion</th> <th class="unsortable">Distance from Sun at aphelion</th> <th>difference (%)</th> <th><a href="/wiki/Insolation" class="mw-redirect" title="Insolation">insolation</a><br />difference (%) </th></tr> <tr> <td rowspan="8">Planet </td> <td><span data-sort-value="1 !"><a href="/wiki/Mercury_(planet)" title="Mercury (planet)">Mercury</a></span></td> <td>46,001,009 km (28,583,702 mi)</td> <td>69,817,445 km (43,382,549 mi)</td> <td>34%</td> <td>57% </td></tr> <tr> <td><span data-sort-value="2 !"><a href="/wiki/Venus" title="Venus">Venus</a></span></td> <td>107,476,170 km (66,782,600 mi)</td> <td>108,942,780 km (67,693,910 mi)</td> <td>1.3%</td> <td>2.8% </td></tr> <tr> <td><span data-sort-value="3 !"><a href="/wiki/Earth" title="Earth">Earth</a></span></td> <td>147,098,291 km (91,402,640 mi)</td> <td>152,098,233 km (94,509,460 mi)</td> <td>3.3%</td> <td>6.5% </td></tr> <tr> <td><span data-sort-value="4 !"><a href="/wiki/Mars" title="Mars">Mars</a></span></td> <td>206,655,215 km (128,409,597 mi)</td> <td>249,232,432 km (154,865,853 mi)</td> <td>17%</td> <td>31% </td></tr> <tr> <td><span data-sort-value="5 !"><a href="/wiki/Jupiter" title="Jupiter">Jupiter</a></span></td> <td>740,679,835 km (460,237,112 mi)</td> <td>816,001,807 km (507,040,016 mi)</td> <td>9.2%</td> <td>18% </td></tr> <tr> <td><span data-sort-value="6 !"><a href="/wiki/Saturn" title="Saturn">Saturn</a></span></td> <td>1,349,823,615 km (838,741,509 mi)</td> <td>1,503,509,229 km (934,237,322 mi)</td> <td>10%</td> <td>19% </td></tr> <tr> <td><span data-sort-value="7 !"><a href="/wiki/Uranus" title="Uranus">Uranus</a></span></td> <td>2,734,998,229 km (1.699449110<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>3,006,318,143 km (1.868039489<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>9.0%</td> <td>17% </td></tr> <tr> <td><span data-sort-value="8 !"><a href="/wiki/Neptune" title="Neptune">Neptune</a></span></td> <td>4,459,753,056 km (2.771162073<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>4,537,039,826 km (2.819185846<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>1.7%</td> <td>3.4% </td></tr> <tr> <td rowspan="5">Dwarf planet </td> <td><span data-sort-value="9 !"><a href="/wiki/Ceres_(dwarf_planet)" title="Ceres (dwarf planet)">Ceres</a></span></td> <td>380,951,528 km (236,712,305 mi)</td> <td>446,428,973 km (277,398,103 mi)</td> <td>15%</td> <td>27% </td></tr> <tr> <td><span data-sort-value="10 !"><a href="/wiki/Pluto" title="Pluto">Pluto</a></span></td> <td>4,436,756,954 km (2.756872958<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>7,376,124,302 km (4.583311152<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>40%</td> <td>64% </td></tr> <tr> <td><span data-sort-value="11 !"><a href="/wiki/Haumea_(dwarf_planet)" class="mw-redirect" title="Haumea (dwarf planet)">Haumea</a></span></td> <td>5,157,623,774 km (3.204798834<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>7,706,399,149 km (4.788534427<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>33%</td> <td>55% </td></tr> <tr> <td><span data-sort-value="12 !"><a href="/wiki/Makemake_(dwarf_planet)" class="mw-redirect" title="Makemake (dwarf planet)">Makemake</a></span></td> <td>5,671,928,586 km (3.524373028<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>7,894,762,625 km (4.905578065<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>28%</td> <td>48% </td></tr> <tr> <td><span data-sort-value="13 !"><a href="/wiki/Eris_(dwarf_planet)" title="Eris (dwarf planet)">Eris</a></span></td> <td>5,765,732,799 km (3.582660263<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>14,594,512,904 km (9.068609883<span style="margin:0 .15em 0 .25em">×</span>10<sup>9</sup> mi)</td> <td>60%</td> <td>84% </td></tr></tbody></table> <div class="mw-heading mw-heading2"><h2 id="Mathematical_formulae">Mathematical formulae</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=10" title="Edit section: Mathematical formulae"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>These <a href="/wiki/Formula" title="Formula">formulae</a> characterize the pericenter and apocenter of an orbit: </p> <dl><dt>Pericenter</dt> <dd>Maximum speed, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle v_{\text{per}}={\sqrt {\frac {(1+e)\mu }{(1-e)a}}}\,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>per</mtext> </mrow> </msub> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <mfrac> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>e</mi> <mo stretchy="false">)</mo> <mi>μ</mi> </mrow> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>−</mo> <mi>e</mi> <mo stretchy="false">)</mo> <mi>a</mi> </mrow> </mfrac> </msqrt> </mrow> <mspace width="thinmathspace"></mspace> </mstyle> </mrow> <annotation encoding="application/x-tex">{\textstyle v_{\text{per}}={\sqrt {\frac {(1+e)\mu }{(1-e)a}}}\,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/88f258a76779781e8fbbde3f8f4426d1f1cf4810" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:15.431ex; height:6.343ex;" alt="{\textstyle v_{\text{per}}={\sqrt {\frac {(1+e)\mu }{(1-e)a}}}\,}" /></span>, at minimum (pericenter) distance, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle r_{\text{per}}=(1-e)a}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>per</mtext> </mrow> </msub> <mo>=</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>−</mo> <mi>e</mi> <mo stretchy="false">)</mo> <mi>a</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\textstyle r_{\text{per}}=(1-e)a}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f32b1f5d8a14ce2ea8b8cc8b8f7da5139e299410" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:14.793ex; height:3.009ex;" alt="{\textstyle r_{\text{per}}=(1-e)a}" /></span>.</dd> <dt>Apocenter</dt> <dd>Minimum speed, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle v_{\text{ap}}={\sqrt {\frac {(1-e)\mu }{(1+e)a}}}\,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <msub> <mi>v</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>ap</mtext> </mrow> </msub> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <mfrac> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>−</mo> <mi>e</mi> <mo stretchy="false">)</mo> <mi>μ</mi> </mrow> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>e</mi> <mo stretchy="false">)</mo> <mi>a</mi> </mrow> </mfrac> </msqrt> </mrow> <mspace width="thinmathspace"></mspace> </mstyle> </mrow> <annotation encoding="application/x-tex">{\textstyle v_{\text{ap}}={\sqrt {\frac {(1-e)\mu }{(1+e)a}}}\,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/55d6417052779b0bffbf04e23d5ead50dd1b8456" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:14.878ex; height:6.343ex;" alt="{\textstyle v_{\text{ap}}={\sqrt {\frac {(1-e)\mu }{(1+e)a}}}\,}" /></span>, at maximum (apocenter) distance, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle r_{\text{ap}}=(1+e)a}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>ap</mtext> </mrow> </msub> <mo>=</mo> <mo stretchy="false">(</mo> <mn>1</mn> <mo>+</mo> <mi>e</mi> <mo stretchy="false">)</mo> <mi>a</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\textstyle r_{\text{ap}}=(1+e)a}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/77eb6f3ff6c7035fb4eeb96d86e078f0cf5cce31" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:14.241ex; height:3.009ex;" alt="{\textstyle r_{\text{ap}}=(1+e)a}" /></span>.</dd></dl> <p>While, in accordance with <a href="/wiki/Kepler%27s_laws_of_planetary_motion" title="Kepler's laws of planetary motion">Kepler's laws of planetary motion</a> (based on the conservation of <a href="/wiki/Angular_momentum" title="Angular momentum">angular momentum</a>) and the conservation of energy, these two quantities are constant for a given orbit: </p> <dl><dt><a href="/wiki/Specific_relative_angular_momentum" class="mw-redirect" title="Specific relative angular momentum">Specific relative angular momentum</a></dt> <dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle h={\sqrt {\left(1-e^{2}\right)\mu a}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>h</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <mrow> <mo>(</mo> <mrow> <mn>1</mn> <mo>−</mo> <msup> <mi>e</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mrow> <mo>)</mo> </mrow> <mi>μ</mi> <mi>a</mi> </msqrt> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle h={\sqrt {\left(1-e^{2}\right)\mu a}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7091ebb873ea5effa0f170847158553cfa854b85" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:18.05ex; height:4.843ex;" alt="{\displaystyle h={\sqrt {\left(1-e^{2}\right)\mu a}}}" /></span></dd> <dt><a href="/wiki/Specific_orbital_energy" title="Specific orbital energy">Specific orbital energy</a></dt> <dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \varepsilon =-{\frac {\mu }{2a}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>ε</mi> <mo>=</mo> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>μ</mi> <mrow> <mn>2</mn> <mi>a</mi> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \varepsilon =-{\frac {\mu }{2a}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/82b2540426831a23225bb6291fcaedf2034222ff" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:9.218ex; height:4.843ex;" alt="{\displaystyle \varepsilon =-{\frac {\mu }{2a}}}" /></span></dd></dl> <p>where: </p> <ul><li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle r_{\text{ap}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>ap</mtext> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\textstyle r_{\text{ap}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/59f77ed0d789bee9e478728b5041980b94b9e957" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:3.017ex; height:2.343ex;" alt="{\textstyle r_{\text{ap}}}" /></span> is the distance from the apocenter to the primary focus</li> <li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle r_{\text{per}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>per</mtext> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\textstyle r_{\text{per}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3f89c39229458a3b2c1df1e085744b0b7441aeba" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:3.569ex; height:2.343ex;" alt="{\textstyle r_{\text{per}}}" /></span> is the distance from the pericenter to the primary focus</li> <li><i>a</i> is the <a href="/wiki/Semi-major_axis" class="mw-redirect" title="Semi-major axis">semi-major axis</a>: <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle a={\frac {r_{\text{per}}+r_{\text{ap}}}{2}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>a</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>per</mtext> </mrow> </msub> <mo>+</mo> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>ap</mtext> </mrow> </msub> </mrow> <mn>2</mn> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle a={\frac {r_{\text{per}}+r_{\text{ap}}}{2}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4129cae6c00273c42685411ad07f547adc98347e" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:14.591ex; height:5.343ex;" alt="{\displaystyle a={\frac {r_{\text{per}}+r_{\text{ap}}}{2}}}" /></span></dd></dl></li> <li><i>μ</i> is the <a href="/wiki/Standard_gravitational_parameter" title="Standard gravitational parameter">standard gravitational parameter</a></li> <li><i>e</i> is the <a href="/wiki/Orbital_eccentricity" title="Orbital eccentricity">eccentricity</a>, defined as <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle e={\frac {r_{\text{ap}}-r_{\text{per}}}{r_{\text{ap}}+r_{\text{per}}}}=1-{\frac {2}{{\frac {r_{\text{ap}}}{r_{\text{per}}}}+1}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>e</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>ap</mtext> </mrow> </msub> <mo>−</mo> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>per</mtext> </mrow> </msub> </mrow> <mrow> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>ap</mtext> </mrow> </msub> <mo>+</mo> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>per</mtext> </mrow> </msub> </mrow> </mfrac> </mrow> <mo>=</mo> <mn>1</mn> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>2</mn> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>ap</mtext> </mrow> </msub> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>per</mtext> </mrow> </msub> </mfrac> </mrow> <mo>+</mo> <mn>1</mn> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle e={\frac {r_{\text{ap}}-r_{\text{per}}}{r_{\text{ap}}+r_{\text{per}}}}=1-{\frac {2}{{\frac {r_{\text{ap}}}{r_{\text{per}}}}+1}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a95b0f32e743d2ac2f04c088cdb517d5a46f3091" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -3.838ex; width:29.985ex; height:7.343ex;" alt="{\displaystyle e={\frac {r_{\text{ap}}-r_{\text{per}}}{r_{\text{ap}}+r_{\text{per}}}}=1-{\frac {2}{{\frac {r_{\text{ap}}}{r_{\text{per}}}}+1}}}" /></span></dd></dl></li></ul> <p>Note that for conversion from heights above the surface to distances between an orbit and its primary, the radius of the central body has to be added, and conversely. </p><p>The <a href="/wiki/Arithmetic_mean" title="Arithmetic mean">arithmetic mean</a> of the two limiting distances is the length of the semi-major axis <i>a</i>. The <a href="/wiki/Geometric_mean" title="Geometric mean">geometric mean</a> of the two distances is the length of the <a href="/wiki/Semi-minor_axis" class="mw-redirect" title="Semi-minor axis">semi-minor axis</a> <i>b</i>. </p><p>The geometric mean of the two limiting speeds is </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\sqrt {-2\varepsilon }}={\sqrt {\frac {\mu }{a}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <mo>−</mo> <mn>2</mn> <mi>ε</mi> </msqrt> </mrow> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <mfrac> <mi>μ</mi> <mi>a</mi> </mfrac> </msqrt> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\sqrt {-2\varepsilon }}={\sqrt {\frac {\mu }{a}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2dba469e21d7807410a198414ab3fd861eedc068" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:13.65ex; height:6.176ex;" alt="{\displaystyle {\sqrt {-2\varepsilon }}={\sqrt {\frac {\mu }{a}}}}" /></span></dd></dl> <p>which is the speed of a body in a circular orbit whose radius is <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle a}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>a</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle a}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ffd2487510aa438433a2579450ab2b3d557e5edc" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.23ex; height:1.676ex;" alt="{\displaystyle a}" /></span>. </p> <div class="mw-heading mw-heading2"><h2 id="Time_of_perihelion">Time of perihelion</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=11" title="Edit section: Time of perihelion"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Orbital_elements" title="Orbital elements">Orbital elements</a> such as the <i>time of perihelion passage</i> are defined at the <a href="/wiki/Epoch_(astronomy)" title="Epoch (astronomy)">epoch</a> chosen using an unperturbed <a href="/wiki/Two-body_problem" title="Two-body problem">two-body solution</a> that does not account for the <a href="/wiki/N-body_problem" title="N-body problem">n-body problem</a>. To get an accurate time of perihelion passage you need to use an epoch close to the perihelion passage. For example, using an epoch of 1996, <a href="/wiki/Comet_Hale%E2%80%93Bopp" title="Comet Hale–Bopp">Comet Hale–Bopp</a> shows perihelion on 1 April 1997.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> Using an epoch of 2008 shows a less accurate perihelion date of 30 March 1997.<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Short-period_comet" class="mw-redirect" title="Short-period comet">Short-period comets</a> can be even more sensitive to the epoch selected. Using an epoch of 2005 shows <a href="/wiki/101P/Chernykh" title="101P/Chernykh">101P/Chernykh</a> coming to perihelion on 25 December 2005,<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> but using an epoch of 2012 produces a less accurate unperturbed perihelion date of 20 January 2006.<sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </p><p><span class="anchor" id="12P"></span> </p> <table class="wikitable sortable" style="text-align: center; font-size: 0.9em;"> <caption><a href="/wiki/Two-body_problem" title="Two-body problem">Two body</a> solution vs <a href="/wiki/N-body_problem" title="N-body problem">n-body</a> solution for <a href="/wiki/12P/Pons%E2%80%93Brooks" title="12P/Pons–Brooks">12P/Pons–Brooks</a> time of perihelion passage </caption> <tbody><tr> <th><a href="/wiki/Epoch_(astronomy)" title="Epoch (astronomy)">Epoch</a> </th> <th><a href="#Time_of_perihelion">Date of perihelion (tp)</a> </th></tr> <tr> <td><a rel="nofollow" class="external text" href="https://archive.today/20220623124113/https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html%23/?sstr=12P&view=OPC">2010</a></td> <td>2024-Apr-19.892 </td></tr> <tr> <td><a href="/wiki/N-body_problem" title="N-body problem">n-body</a><sup id="cite_ref-Horizons2024_32-0" class="reference"><a href="#cite_note-Horizons2024-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup></td> <td>2024-Apr-21.139 </td></tr> <tr> <td><a rel="nofollow" class="external text" href="https://archive.today/20230211111847/https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html%23/?sstr=12P&view=OPC">2018</a></td> <td>2024-Apr-23.069 </td></tr></tbody></table> <p><a href="/wiki/Numerical_integration" title="Numerical integration">Numerical integration</a> shows <a href="/wiki/Dwarf_planet" title="Dwarf planet">dwarf planet</a> <a href="/wiki/Eris_(dwarf_planet)" title="Eris (dwarf planet)">Eris</a> will come to perihelion around December 2257.<sup id="cite_ref-Eris_33-0" class="reference"><a href="#cite_note-Eris-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> Using an epoch of 2021, which is 236 years early, less accurately shows Eris coming to perihelion in 2260.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/4_Vesta" title="4 Vesta">4 Vesta</a> came to perihelion on 26 December 2021,<sup id="cite_ref-Horizons2021_35-0" class="reference"><a href="#cite_note-Horizons2021-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> but using a two-body solution at an epoch of July 2021 less accurately shows Vesta came to perihelion on 25 December 2021.<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Short_arcs">Short arcs</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=12" title="Edit section: Short arcs"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Trans-Neptunian_object" title="Trans-Neptunian object">Trans-Neptunian objects</a> discovered when 80+ AU from the Sun need dozens of observations over multiple years to well constrain their orbits because they move very slowly against the background stars. Due to statistics of small numbers, trans-Neptunian objects such as <span class="nowrap"><a href="/wiki/2015_TH367" title="2015 TH367">2015 TH<span style="position: relative; top: 0.3em;"><span style="font-size:80%;">367</span></span></a></span> when it had only 8 observations over an <a href="/wiki/Observation_arc" title="Observation arc">observation arc</a> of 1 year that have not or will not come to perihelion for roughly 100 years can have a <a href="/wiki/68%E2%80%9395%E2%80%9399.7_rule" title="68–95–99.7 rule">1-sigma</a> uncertainty of 77.3 years (28,220 days) in the perihelion date.<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=13" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Distance_of_closest_approach" title="Distance of closest approach">Distance of closest approach</a></li> <li><a href="/wiki/Eccentric_anomaly" title="Eccentric anomaly">Eccentric anomaly</a></li> <li><a href="/wiki/Flyby_(spaceflight)" title="Flyby (spaceflight)">Flyby (spaceflight)</a></li> <li><a href="/wiki/Hyperbolic_trajectory#Closest_approach" title="Hyperbolic trajectory">Hyperbolic trajectory § Closest approach</a></li> <li><a href="/wiki/Mean_anomaly" title="Mean anomaly">Mean anomaly</a></li> <li><a href="/wiki/Perifocal_coordinate_system" title="Perifocal coordinate system">Perifocal coordinate system</a></li> <li><a href="/wiki/True_anomaly" title="True anomaly">True anomaly</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=14" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation encyclopaedia cs1"><a rel="nofollow" class="external text" href="https://www.dictionary.com/browse/apsis">"apsis"</a>. <i><a href="/wiki/Dictionary.com" title="Dictionary.com">Dictionary.com Unabridged</a></i> (Online). n.d.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=apsis&rft.btitle=Dictionary.com+Unabridged&rft_id=https%3A%2F%2Fwww.dictionary.com%2Fbrowse%2Fapsis&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="Reference-AHD-apsis" class="citation encyclopaedia cs1"><a rel="nofollow" class="external text" href="https://www.ahdictionary.com/word/search.html?q=apsis">"apsis"</a>. <i><a href="/wiki/The_American_Heritage_Dictionary_of_the_English_Language" title="The American Heritage Dictionary of the English Language">The American Heritage Dictionary of the English Language</a></i> (5th ed.). HarperCollins.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=apsis&rft.btitle=The+American+Heritage+Dictionary+of+the+English+Language&rft.edition=5th&rft.pub=HarperCollins&rft_id=https%3A%2F%2Fwww.ahdictionary.com%2Fword%2Fsearch.html%3Fq%3Dapsis&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFJoe_Rao2023" class="citation web cs1">Joe Rao (July 6, 2023). <a rel="nofollow" class="external text" href="https://www.space.com/earth-farthest-from-sun-aphelion-july-2023">"Happy Aphelion Day! Earth is at its farthest from the sun for 2023 today"</a>. <i>Space.com</i><span class="reference-accessdate">. Retrieved <span class="nowrap">April 22,</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Space.com&rft.atitle=Happy+Aphelion+Day%21+Earth+is+at+its+farthest+from+the+sun+for+2023+today&rft.date=2023-07-06&rft.au=Joe+Rao&rft_id=https%3A%2F%2Fwww.space.com%2Fearth-farthest-from-sun-aphelion-july-2023&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.skymarvels.com/gallery/Vid%20-%20Earth-Moon%20Barycenter.htm">"Earth-Moon Barycenter - SkyMarvels.com"</a>. <i>www.skymarvels.com</i><span class="reference-accessdate">. Retrieved <span class="nowrap">April 23,</span> 2024</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.skymarvels.com&rft.atitle=Earth-Moon+Barycenter+-+SkyMarvels.com&rft_id=https%3A%2F%2Fwww.skymarvels.com%2Fgallery%2FVid%2520-%2520Earth-Moon%2520Barycenter.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-Sun-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-Sun_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Sun_5-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Since the Sun, Ἥλιος in Greek, begins with a vowel (H is the long ē vowel in Greek), the final o in "apo" is omitted from the prefix. =The pronunciation "Ap-helion" is given in many dictionaries <a rel="nofollow" class="external autonumber" href="https://www.oxforddictionaries.com/definition/english/aphelion">[1]</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20151222075218/https://www.oxforddictionaries.com/definition/english/aphelion">Archived</a> December 22, 2015, at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, pronouncing the "p" and "h" in separate syllables. However, the pronunciation <span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="/ə/: 'a' in 'about'">ə</span><span title="/ˈ/: primary stress follows">ˈ</span><span title="'f' in 'find'">f</span><span title="/iː/: 'ee' in 'fleece'">iː</span><span title="'l' in 'lie'">l</span><span title="/i/: 'y' in 'happy'">i</span><span title="/ə/: 'a' in 'about'">ə</span><span title="'n' in 'nigh'">n</span></span>/</a></span></span> <a rel="nofollow" class="external autonumber" href="http://www.dictionary.com/browse/aphelion">[2]</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20170729001850/http://www.dictionary.com/browse/aphelion">Archived</a> July 29, 2017, at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> is also common (<i>e.g.,</i> <i>McGraw Hill Dictionary of Scientific and Technical Terms,</i> 5th edition, 1994, p. 114), since in late Greek, 'p' from ἀπό followed by the 'h' from ἥλιος becomes phi; thus, the Greek word is αφήλιον. (see, for example, Walker, John, <i>A Key to the Classical Pronunciation of Greek, Latin, and Scripture Proper Names</i>, Townsend Young 1859 <a rel="nofollow" class="external autonumber" href="https://play.google.com/store/books/details?id=LuF-9HKGbl4C&rdid=book-LuF-9HKGbl4C&rdot=1">[3]</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190921013331/https://play.google.com/store/books/details?id=LuF-9HKGbl4C&rdid=book-LuF-9HKGbl4C&rdot=1">Archived</a> September 21, 2019, at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, page 26.) Many <a rel="nofollow" class="external autonumber" href="https://www.merriam-webster.com/dictionary/aphelion">[4]</a> dictionaries give both pronunciations</span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFChisholm1911" class="citation encyclopaedia cs1"><a href="/wiki/Hugh_Chisholm" title="Hugh Chisholm">Chisholm, Hugh</a>, ed. (1911). <span class="cs1-ws-icon" title="s:1911 Encyclopædia Britannica/Perigee"><a class="external text" href="https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Perigee">"Perigee" </a></span>. <i><a href="/wiki/Encyclop%C3%A6dia_Britannica_Eleventh_Edition" title="Encyclopædia Britannica Eleventh Edition">Encyclopædia Britannica</a></i>. Vol. 21 (11th ed.). Cambridge University Press. p. 149.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Perigee&rft.btitle=Encyclop%C3%A6dia+Britannica&rft.pages=149&rft.edition=11th&rft.pub=Cambridge+University+Press&rft.date=1911&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-nasaglossary-7"><span class="mw-cite-backlink">^ <a href="#cite_ref-nasaglossary_7-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-nasaglossary_7-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-nasaglossary_7-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-nasaglossary_7-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://solarsystem.nasa.gov/basics/glossary">"Basics of Space Flight"</a>. NASA. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190930063643/https://solarsystem.nasa.gov/basics/glossary/">Archived</a> from the original on September 30, 2019<span class="reference-accessdate">. Retrieved <span class="nowrap">May 30,</span> 2017</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Basics+of+Space+Flight&rft.pub=NASA&rft_id=https%3A%2F%2Fsolarsystem.nasa.gov%2Fbasics%2Fglossary&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text">Klein, Ernest, <i>A Comprehensive Etymological Dictionary of the English Language</i>, Elsevier, Amsterdam, 1965. (<a rel="nofollow" class="external text" href="https://archive.org/stream/AComprehensiveEtymologicalDictionaryOfTheEnglishLanguageByErnestKlein/A%20Comprehensive%20Etymological%20Dictionary%20of%20the%20English%20Language%20by%20Ernest%20Klein_djvu.txt">Archived version</a>)</span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://history.nasa.gov/alsj/a15/a15mr-f.htm">"Apollo 15 Mission Report"</a>. <i>Glossary</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100319081116/http://history.nasa.gov/alsj/a15/a15mr-f.htm">Archived</a> from the original on March 19, 2010<span class="reference-accessdate">. Retrieved <span class="nowrap">October 16,</span> 2009</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Glossary&rft.atitle=Apollo+15+Mission+Report&rft_id=https%3A%2F%2Fhistory.nasa.gov%2Falsj%2Fa15%2Fa15mr-f.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFR._DendyD._ZeleznikarM._Zemba2021" class="citation conference cs1">R. Dendy; D. Zeleznikar; M. Zemba (September 27, 2021). <a rel="nofollow" class="external text" href="https://ntrs.nasa.gov/citations/20210019019"><i>NASA Lunar Exploration – Gateway's Power and Propulsion Element Communications Links</i></a>. 38th International Communications Satellite Systems Conference (ICSSC). Arlington, VA. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20220329140256/https://ntrs.nasa.gov/citations/20210019019">Archived</a> from the original on March 29, 2022<span class="reference-accessdate">. Retrieved <span class="nowrap">July 18,</span> 2022</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=conference&rft.btitle=NASA+Lunar+Exploration+%E2%80%93+Gateway%27s+Power+and+Propulsion+Element+Communications+Links&rft.place=Arlington%2C+VA&rft.date=2021-09-27&rft.au=R.+Dendy&rft.au=D.+Zeleznikar&rft.au=M.+Zemba&rft_id=https%3A%2F%2Fntrs.nasa.gov%2Fcitations%2F20210019019&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFFrank,_J.Rees,_M.J.1976" class="citation journal cs1">Frank, J.; Rees, M.J. (September 1, 1976). <a rel="nofollow" class="external text" href="https://doi.org/10.1093%2Fmnras%2F176.3.633">"Effects of massive black holes on dense stellar systems"</a>. <i>MNRAS</i>. <b>176</b> (6908): <span class="nowrap">633–</span>646. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1976MNRAS.176..633F">1976MNRAS.176..633F</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1093%2Fmnras%2F176.3.633">10.1093/mnras/176.3.633</a></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=MNRAS&rft.atitle=Effects+of+massive+black+holes+on+dense+stellar+systems.&rft.volume=176&rft.issue=6908&rft.pages=%3Cspan+class%3D%22nowrap%22%3E633-%3C%2Fspan%3E646&rft.date=1976-09-01&rft_id=info%3Adoi%2F10.1093%2Fmnras%2F176.3.633&rft_id=info%3Abibcode%2F1976MNRAS.176..633F&rft.au=Frank%2C+J.&rft.au=Rees%2C+M.J.&rft_id=https%3A%2F%2Fdoi.org%2F10.1093%252Fmnras%252F176.3.633&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-Asimov's-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-Asimov's_12-0">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.infinityplus.co.uk/stories/perimelasma.htm"><i>Perimelasma</i></a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190225210759/http://www.infinityplus.co.uk/stories/perimelasma.htm">Archived</a> February 25, 2019, at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, by Geoffrey Landis, first published in <i><a href="/wiki/Asimov%27s_Science_Fiction" title="Asimov's Science Fiction">Asimov's Science Fiction</a></i>, January 1998, republished at <i><a href="/wiki/Infinity_Plus" title="Infinity Plus">Infinity Plus</a></i></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFR._SchödelT._OttR._GenzelR._Hofmann2002" class="citation journal cs1">R. Schödel; T. Ott; R. Genzel; R. Hofmann; M. Lehnert; A. Eckart; N. Mouawad; T. Alexander; M. J. Reid; R. Lenzen; M. Hartung; F. Lacombe; D. Rouan; E. Gendron; G. Rousset; A.-M. Lagrange; W. Brandner; N. Ageorges; C. Lidman; A. F. M. Moorwood; J. Spyromilio; N. Hubin; K. M. Menten (October 17, 2002). "A star in a 15.2-year orbit around the supermassive black hole at the centre of the Milky Way". <i>Nature</i>. <b>419</b> (6908): <span class="nowrap">694–</span>696. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0210426">astro-ph/0210426</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2002Natur.419..694S">2002Natur.419..694S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fnature01121">10.1038/nature01121</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/12384690">12384690</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:4302128">4302128</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=A+star+in+a+15.2-year+orbit+around+the+supermassive+black+hole+at+the+centre+of+the+Milky+Way&rft.volume=419&rft.issue=6908&rft.pages=%3Cspan+class%3D%22nowrap%22%3E694-%3C%2Fspan%3E696&rft.date=2002-10-17&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A4302128%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2002Natur.419..694S&rft_id=info%3Aarxiv%2Fastro-ph%2F0210426&rft_id=info%3Apmid%2F12384690&rft_id=info%3Adoi%2F10.1038%2Fnature01121&rft.au=R.+Sch%C3%B6del&rft.au=T.+Ott&rft.au=R.+Genzel&rft.au=R.+Hofmann&rft.au=M.+Lehnert&rft.au=A.+Eckart&rft.au=N.+Mouawad&rft.au=T.+Alexander&rft.au=M.+J.+Reid&rft.au=R.+Lenzen&rft.au=M.+Hartung&rft.au=F.+Lacombe&rft.au=D.+Rouan&rft.au=E.+Gendron&rft.au=G.+Rousset&rft.au=A.-M.+Lagrange&rft.au=W.+Brandner&rft.au=N.+Ageorges&rft.au=C.+Lidman&rft.au=A.+F.+M.+Moorwood&rft.au=J.+Spyromilio&rft.au=N.+Hubin&rft.au=K.+M.+Menten&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://lasp.colorado.edu/home/maven/science/science-orbit/">"MAVEN » Science Orbit"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20181108025706/http://lasp.colorado.edu/home/maven/science/science-orbit/">Archived</a> from the original on November 8, 2018<span class="reference-accessdate">. Retrieved <span class="nowrap">November 7,</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=MAVEN+%C2%BB+Science+Orbit&rft_id=http%3A%2F%2Flasp.colorado.edu%2Fhome%2Fmaven%2Fscience%2Fscience-orbit%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.planetary.org/blogs/guest-blogs/marc-rayman/20181019-dawn-journal-11-years-in-space.html">"Dawn Journal: 11 Years in Space"</a>. <i>www.planetary.org</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20181024152511/http://www.planetary.org/blogs/guest-blogs/marc-rayman/20181019-dawn-journal-11-years-in-space.html">Archived</a> from the original on October 24, 2018<span class="reference-accessdate">. Retrieved <span class="nowrap">October 24,</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.planetary.org&rft.atitle=Dawn+Journal%3A+11+Years+in+Space&rft_id=http%3A%2F%2Fwww.planetary.org%2Fblogs%2Fguest-blogs%2Fmarc-rayman%2F20181019-dawn-journal-11-years-in-space.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCecconiLamyZarkaPrangé2009" class="citation journal cs1">Cecconi, B.; Lamy, L.; Zarka, P.; Prangé, R.; Kurth, W. S.; Louarn, P. (March 4, 2009). <a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009JGRA..114.3215C/abstract">"Goniopolarimetric study of the revolution 29 perikrone using the Cassini Radio and Plasma Wave Science instrument high-frequency radio receiver"</a>. <i>Journal of Geophysical Research: Space Physics</i>. <b>114</b> (A3): A03215. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009JGRA..114.3215C">2009JGRA..114.3215C</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1029%2F2008JA013830">10.1029/2008JA013830</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20191209095159/https://ui.adsabs.harvard.edu/abs/2009JGRA..114.3215C/abstract">Archived</a> from the original on December 9, 2019<span class="reference-accessdate">. Retrieved <span class="nowrap">December 9,</span> 2019</span> – via ui.adsabs.harvard.edu.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Geophysical+Research%3A+Space+Physics&rft.atitle=Goniopolarimetric+study+of+the+revolution+29+perikrone+using+the+Cassini+Radio+and+Plasma+Wave+Science+instrument+high-frequency+radio+receiver&rft.volume=114&rft.issue=A3&rft.pages=A03215&rft.date=2009-03-04&rft_id=info%3Adoi%2F10.1029%2F2008JA013830&rft_id=info%3Abibcode%2F2009JGRA..114.3215C&rft.aulast=Cecconi&rft.aufirst=B.&rft.au=Lamy%2C+L.&rft.au=Zarka%2C+P.&rft.au=Prang%C3%A9%2C+R.&rft.au=Kurth%2C+W.+S.&rft.au=Louarn%2C+P.&rft_id=https%3A%2F%2Fui.adsabs.harvard.edu%2Fabs%2F2009JGRA..114.3215C%2Fabstract&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-McKevitt_Bulla_Dixon_Criscola_2021-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-McKevitt_Bulla_Dixon_Criscola_2021_17-0">^</a></b></span> <span class="reference-text">Example of use: <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMcKevittBullaDixonCriscola2021" class="citation journal cs1">McKevitt, James; Bulla, Sophie; Dixon, Tom; Criscola, Franco; Parkinson-Swift, Jonathan; Bornberg, Christina; Singh, Jaspreet; Patel, Kuren; Laad, Aryan; Forder, Ethan; Ayin-Walsh, Louis; Beegadhur, Shayne; Wedde, Paul; Pappula, Bharath Simha Reddy; McDougall, Thomas; Foghis, Madalin; Kent, Jack; Morgan, James; Raj, Utkarsh; Heinreichsberger, Carina (June 18, 2021). "An L-class Multirole Observatory and Science Platform for Neptune". <i>2021 Global Space Exploration Conference Proceedings</i>. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/2106.09409">2106.09409</a></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=2021+Global+Space+Exploration+Conference+Proceedings&rft.atitle=An+L-class+Multirole+Observatory+and+Science+Platform+for+Neptune&rft.date=2021-06-18&rft_id=info%3Aarxiv%2F2106.09409&rft.aulast=McKevitt&rft.aufirst=James&rft.au=Bulla%2C+Sophie&rft.au=Dixon%2C+Tom&rft.au=Criscola%2C+Franco&rft.au=Parkinson-Swift%2C+Jonathan&rft.au=Bornberg%2C+Christina&rft.au=Singh%2C+Jaspreet&rft.au=Patel%2C+Kuren&rft.au=Laad%2C+Aryan&rft.au=Forder%2C+Ethan&rft.au=Ayin-Walsh%2C+Louis&rft.au=Beegadhur%2C+Shayne&rft.au=Wedde%2C+Paul&rft.au=Pappula%2C+Bharath+Simha+Reddy&rft.au=McDougall%2C+Thomas&rft.au=Foghis%2C+Madalin&rft.au=Kent%2C+Jack&rft.au=Morgan%2C+James&rft.au=Raj%2C+Utkarsh&rft.au=Heinreichsberger%2C+Carina&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-:0-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-:0_18-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://dictionary.reference.com/browse/apsis">"the definition of apsis"</a>. <i>Dictionary.com</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20151208101127/http://dictionary.reference.com/browse/apsis">Archived</a> from the original on December 8, 2015<span class="reference-accessdate">. Retrieved <span class="nowrap">November 28,</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Dictionary.com&rft.atitle=the+definition+of+apsis&rft_id=http%3A%2F%2Fdictionary.reference.com%2Fbrowse%2Fapsis&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-darlinglon-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-darlinglon_19-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDarling" class="citation encyclopaedia cs1">Darling, David. <a rel="nofollow" class="external text" href="http://www.daviddarling.info/encyclopedia/L/line_of_nodes.html">"line of nodes"</a>. <i>The Encyclopedia of Astrobiology, Astronomy, and Spaceflight</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190823203510/http://www.daviddarling.info/encyclopedia/L/line_of_nodes.html">Archived</a> from the original on August 23, 2019<span class="reference-accessdate">. Retrieved <span class="nowrap">May 17,</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=line+of+nodes&rft.btitle=The+Encyclopedia+of+Astrobiology%2C+Astronomy%2C+and+Spaceflight&rft.aulast=Darling&rft.aufirst=David&rft_id=http%3A%2F%2Fwww.daviddarling.info%2Fencyclopedia%2FL%2Fline_of_nodes.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.timeanddate.com/astronomy/perihelion-aphelion-solstice.html">"Perihelion, Aphelion and the Solstices"</a>. timeanddate.com. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180103052358/https://www.timeanddate.com/astronomy/perihelion-aphelion-solstice.html">Archived</a> from the original on January 3, 2018<span class="reference-accessdate">. Retrieved <span class="nowrap">January 10,</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Perihelion%2C+Aphelion+and+the+Solstices&rft.pub=timeanddate.com&rft_id=https%3A%2F%2Fwww.timeanddate.com%2Fastronomy%2Fperihelion-aphelion-solstice.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://aa.usno.navy.mil/faq/docs/apsides.php">"Variation in Times of Perihelion and Aphelion"</a>. Astronomical Applications Department of the U.S. Naval Observatory. August 11, 2011. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180111165154/http://aa.usno.navy.mil/faq/docs/apsides.php">Archived</a> from the original on January 11, 2018<span class="reference-accessdate">. Retrieved <span class="nowrap">January 10,</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Variation+in+Times+of+Perihelion+and+Aphelion&rft.pub=Astronomical+Applications+Department+of+the+U.S.+Naval+Observatory&rft.date=2011-08-11&rft_id=http%3A%2F%2Faa.usno.navy.mil%2Ffaq%2Fdocs%2Fapsides.php&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.nasa.gov/audience/foreducators/postsecondary/features/F_Planet_Seasons.html">"Solar System Exploration: Science & Technology: Science Features: Weather, Weather, Everywhere?"</a>. <a href="/wiki/NASA" title="NASA">NASA</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150929033150/http://www.nasa.gov/audience/foreducators/postsecondary/features/F_Planet_Seasons.html">Archived</a> from the original on September 29, 2015<span class="reference-accessdate">. Retrieved <span class="nowrap">September 19,</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Solar+System+Exploration%3A+Science+%26+Technology%3A+Science+Features%3A+Weather%2C+Weather%2C+Everywhere%3F&rft.pub=NASA&rft_id=http%3A%2F%2Fwww.nasa.gov%2Faudience%2Fforeducators%2Fpostsecondary%2Ffeatures%2FF_Planet_Seasons.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-Earth_at_Aphelion-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-Earth_at_Aphelion_23-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://spaceweather.com/glossary/aphelion.html">"Earth at Aphelion"</a>. Space Weather. July 2008. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150717184242/http://spaceweather.com/glossary/aphelion.html">Archived</a> from the original on July 17, 2015<span class="reference-accessdate">. Retrieved <span class="nowrap">July 7,</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Earth+at+Aphelion&rft.pub=Space+Weather&rft.date=2008-07&rft_id=http%3A%2F%2Fspaceweather.com%2Fglossary%2Faphelion.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFRockport" class="citation web cs1">Rockport, Steve C. <a rel="nofollow" class="external text" href="https://usm.maine.edu/planet/how-much-does-aphelion-affect-our-weather-were-aphelion-summer-would-our-summers-be-warmer-if">"How much does aphelion affect our weather? We're at aphelion in the summer. Would our summers be warmer if we were at perihelion, instead?"</a>. <i>Planetarium</i>. <a href="/wiki/University_of_Southern_Maine" title="University of Southern Maine">University of Southern Maine</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20200706154815/https://usm.maine.edu/planet/how-much-does-aphelion-affect-our-weather-were-aphelion-summer-would-our-summers-be-warmer-if">Archived</a> from the original on July 6, 2020<span class="reference-accessdate">. Retrieved <span class="nowrap">July 4,</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Planetarium&rft.atitle=How+much+does+aphelion+affect+our+weather%3F+We%27re+at+aphelion+in+the+summer.+Would+our+summers+be+warmer+if+we+were+at+perihelion%2C+instead%3F&rft.aulast=Rockport&rft.aufirst=Steve+C.&rft_id=https%3A%2F%2Fusm.maine.edu%2Fplanet%2Fhow-much-does-aphelion-affect-our-weather-were-aphelion-summer-would-our-summers-be-warmer-if&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-25">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20151002065753/http://data.giss.nasa.gov/ar5/srorbpar.html">"Data.GISS: Earth's Orbital Parameters"</a>. <i>data.giss.nasa.gov</i>. Archived from <a rel="nofollow" class="external text" href="https://data.giss.nasa.gov/ar5/srorbpar.html">the original</a> on October 2, 2015.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=data.giss.nasa.gov&rft.atitle=Data.GISS%3A+Earth%27s+Orbital+Parameters&rft_id=http%3A%2F%2Fdata.giss.nasa.gov%2Far5%2Fsrorbpar.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFEspenak" class="citation web cs1">Espenak, Fred. <a rel="nofollow" class="external text" href="http://astropixels.com/ephemeris/perap2001.html">"Earth at Perihelion and Aphelion: 2001 to 2100"</a>. <i>astropixels</i>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20210713131143/http://astropixels.com/ephemeris/perap2001.html">Archived</a> from the original on July 13, 2021<span class="reference-accessdate">. Retrieved <span class="nowrap">June 24,</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=astropixels&rft.atitle=Earth+at+Perihelion+and+Aphelion%3A+2001+to+2100&rft.aulast=Espenak&rft.aufirst=Fred&rft_id=http%3A%2F%2Fastropixels.com%2Fephemeris%2Fperap2001.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-27">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20160804162808/http://solarsystem.nasa.gov/planets/compare">"NASA planetary comparison chart"</a>. Archived from <a rel="nofollow" class="external text" href="https://solarsystem.nasa.gov/planets/compare">the original</a> on August 4, 2016<span class="reference-accessdate">. Retrieved <span class="nowrap">August 4,</span> 2016</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=NASA+planetary+comparison+chart&rft_id=http%3A%2F%2Fsolarsystem.nasa.gov%2Fplanets%2Fcompare&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ssd.jpl.nasa.gov/sbdb.cgi?soln=J971A%2F1&sstr=Hale-Bopp&cad=1">"JPL SBDB: Hale-Bopp (Epoch 1996)"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20200716170854/https://ssd.jpl.nasa.gov/sbdb.cgi?soln=J971A%2F1&sstr=Hale-Bopp&cad=1">Archived</a> from the original on July 16, 2020<span class="reference-accessdate">. Retrieved <span class="nowrap">July 16,</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=JPL+SBDB%3A+Hale-Bopp+%28Epoch+1996%29&rft_id=https%3A%2F%2Fssd.jpl.nasa.gov%2Fsbdb.cgi%3Fsoln%3DJ971A%252F1%26sstr%3DHale-Bopp%26cad%3D1&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-29">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=1995O1">"JPL SBDB: Hale-Bopp"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20200717063814/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=1995O1">Archived</a> from the original on July 17, 2020<span class="reference-accessdate">. Retrieved <span class="nowrap">July 16,</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=JPL+SBDB%3A+Hale-Bopp&rft_id=https%3A%2F%2Fssd.jpl.nasa.gov%2Fsbdb.cgi%3Fsstr%3D1995O1&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-30">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.oaa.gr.jp/~oaacs/nk/nk1293.htm">"101P/Chernykh – A (NK 1293) by Syuichi Nakano"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20201003194829/http://www.oaa.gr.jp/~oaacs/nk/nk1293.htm">Archived</a> from the original on October 3, 2020<span class="reference-accessdate">. Retrieved <span class="nowrap">July 17,</span> 2020</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=101P%2FChernykh+%E2%80%93+A+%28NK+1293%29+by+Syuichi+Nakano&rft_id=http%3A%2F%2Fwww.oaa.gr.jp%2F~oaacs%2Fnk%2Fnk1293.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-31"><span class="mw-cite-backlink"><b><a href="#cite_ref-31">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20201128092431/https://ssd.jpl.nasa.gov/sbdb.cgi?ID=c00101_0">JPL SBDB: 101P/Chernykh (Epoch 2012)</a></span> </li> <li id="cite_note-Horizons2024-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-Horizons2024_32-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%2790000223%27&START_TIME=%272024-Apr-21%2003:00%27&STOP_TIME=%272024-Apr-21%2003:40%27&STEP_SIZE=%27120%27&QUANTITIES=%2719%27">"Horizons Batch for 12P/Pons-Brooks (90000223) at 2024-Apr-21 03:20"</a> (Perihelion occurs when rdot flips from negative to positive). <a href="/wiki/JPL_Horizons_On-Line_Ephemeris_System" title="JPL Horizons On-Line Ephemeris System">JPL Horizons</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230212102447/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%2790000223%27&START_TIME=%272024-Apr-21%2003:00%27&STOP_TIME=%272024-Apr-21%2003:40%27&STEP_SIZE=%27120%27&QUANTITIES=%2719%27">Archived</a> from the original on February 12, 2023<span class="reference-accessdate">. Retrieved <span class="nowrap">February 11,</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Horizons+Batch+for+12P%2FPons-Brooks+%2890000223%29+at+2024-Apr-21+03%3A20&rft.pub=JPL+Horizons&rft_id=https%3A%2F%2Fssd.jpl.nasa.gov%2Fhorizons_batch.cgi%3Fbatch%3D1%26COMMAND%3D%252790000223%2527%26START_TIME%3D%25272024-Apr-21%252003%3A00%2527%26STOP_TIME%3D%25272024-Apr-21%252003%3A40%2527%26STEP_SIZE%3D%2527120%2527%26QUANTITIES%3D%252719%2527&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span> (JPL#K242/3 Soln.date: 2022-Oct-24)</span> </li> <li id="cite_note-Eris-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-Eris_33-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Eris%27&START_TIME=%272257-11-28%27&STOP_TIME=%272257-12-17%27&STEP_SIZE=%273%20hours%27&QUANTITIES=%2719%27">"Horizons Batch for Eris at perihelion around 7 December 2257 ±2 weeks"</a>. <i><a href="/wiki/JPL_Horizons_On-Line_Ephemeris_System" title="JPL Horizons On-Line Ephemeris System">JPL Horizons</a></i> (Perihelion occurs when rdot flips from negative to positive. The JPL SBDB generically (incorrectly) lists an unperturbed two-body perihelion date in 2260). Jet Propulsion Laboratory. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20210913110143/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Eris%27&START_TIME=%272257-11-28%27&STOP_TIME=%272257-12-17%27&STEP_SIZE=%273%20hours%27&QUANTITIES=%2719%27">Archived</a> from the original on September 13, 2021<span class="reference-accessdate">. Retrieved <span class="nowrap">September 13,</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=JPL+Horizons&rft.atitle=Horizons+Batch+for+Eris+at+perihelion+around+7+December+2257+%C2%B12+weeks&rft_id=https%3A%2F%2Fssd.jpl.nasa.gov%2Fhorizons_batch.cgi%3Fbatch%3D1%26COMMAND%3D%2527Eris%2527%26START_TIME%3D%25272257-11-28%2527%26STOP_TIME%3D%25272257-12-17%2527%26STEP_SIZE%3D%25273%2520hours%2527%26QUANTITIES%3D%252719%2527&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Eris">"JPL SBDB: Eris (Epoch 2021)"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180131234951/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Eris">Archived</a> from the original on January 31, 2018<span class="reference-accessdate">. Retrieved <span class="nowrap">January 5,</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=JPL+SBDB%3A+Eris+%28Epoch+2021%29&rft_id=https%3A%2F%2Fssd.jpl.nasa.gov%2Fsbdb.cgi%3Fsstr%3DEris&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span></span> </li> <li id="cite_note-Horizons2021-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-Horizons2021_35-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Vesta%27&START_TIME=%272021-Dec-25%2023:00%27&STOP_TIME=%272021-Dec-26%2004:00%27&STEP_SIZE=%2715%20minutes%27&QUANTITIES=%2719%27">"Horizons Batch for 4 Vesta on 2021-Dec-26"</a> (Perihelion occurs when rdot flips from negative to positive). <a href="/wiki/JPL_Horizons_On-Line_Ephemeris_System" title="JPL Horizons On-Line Ephemeris System">JPL Horizons</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20210926095954/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Vesta%27&START_TIME=%272021-Dec-25%2023%3A00%27&STOP_TIME=%272021-Dec-26%2004%3A00%27&STEP_SIZE=%2715%20minutes%27&QUANTITIES=%2719%27">Archived</a> from the original on September 26, 2021<span class="reference-accessdate">. Retrieved <span class="nowrap">September 26,</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Horizons+Batch+for+4+Vesta+on+2021-Dec-26&rft.pub=JPL+Horizons&rft_id=https%3A%2F%2Fssd.jpl.nasa.gov%2Fhorizons_batch.cgi%3Fbatch%3D1%26COMMAND%3D%2527Vesta%2527%26START_TIME%3D%25272021-Dec-25%252023%3A00%2527%26STOP_TIME%3D%25272021-Dec-26%252004%3A00%2527%26STEP_SIZE%3D%252715%2520minutes%2527%26QUANTITIES%3D%252719%2527&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span> (Epoch 2021-Jul-01/Soln.date: 2021-Apr-13)</span> </li> <li id="cite_note-36"><span class="mw-cite-backlink"><b><a href="#cite_ref-36">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20210926095422/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=4">JPL SBDB: 4 Vesta (Epoch 2021)</a></span> </li> <li id="cite_note-37"><span class="mw-cite-backlink"><b><a href="#cite_ref-37">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20180314133928/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2015TH367">"JPL SBDB: 2015 TH367"</a>. Archived from the original on March 14, 2018<span class="reference-accessdate">. Retrieved <span class="nowrap">September 23,</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=JPL+SBDB%3A+2015+TH367&rft_id=https%3A%2F%2Fssd.jpl.nasa.gov%2Fsbdb.cgi%3Fsstr%3D2015TH367&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApsis" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: CS1 maint: bot: original URL status unknown (<a href="/wiki/Category:CS1_maint:_bot:_original_URL_status_unknown" title="Category:CS1 maint: bot: original URL status unknown">link</a>)</span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apsis&action=edit&section=15" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409" /> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Wiktionary-logo-en-v2.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/40px-Wiktionary-logo-en-v2.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/60px-Wiktionary-logo-en-v2.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/99/Wiktionary-logo-en-v2.svg/80px-Wiktionary-logo-en-v2.svg.png 2x" data-file-width="512" data-file-height="512" /></a></span></div> <div class="side-box-text plainlist">Look up <i><b><a href="https://en.wiktionary.org/wiki/apsis" class="extiw" title="wiktionary:apsis">apsis</a></b></i> in Wiktionary, the free dictionary.</div></div> </div> <ul><li><a rel="nofollow" class="external text" href="http://www.perseus.gr/Astro-Lunar-Scenes-Apo-Perigee.htm">Apogee – Perigee</a> Photographic Size Comparison, perseus.gr</li> <li><a rel="nofollow" class="external text" href="http://www.perseus.gr/Astro-Solar-Scenes-Aph-Perihelion.htm">Aphelion – Perihelion</a> Photographic Size Comparison, perseus.gr</li> <li><a rel="nofollow" class="external text" href="http://aa.usno.navy.mil/data/docs/EarthSeasons.php">Earth's Seasons: Equinoxes, Solstices, Perihelion, and Aphelion, 2000–2020</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071013000301/http://aa.usno.navy.mil/data/docs/EarthSeasons.php">Archived</a> October 13, 2007, at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, usno.navy.mil</li> <li><a rel="nofollow" class="external text" href="http://aa.usno.navy.mil/data/docs/EarthSeasons.php">Dates and times of Earth's perihelion and aphelion, 2000–2025</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071013000301/http://aa.usno.navy.mil/data/docs/EarthSeasons.php">Archived</a> October 13, 2007, at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> from the <a href="/wiki/United_States_Naval_Observatory" title="United States Naval Observatory">United States Naval Observatory</a></li> <li><a rel="nofollow" class="external text" href="https://newton.spacedys.com/astdys/index.php?pc=3.2.1&pc0=3.2&udfs=0.3">List of asteroids currently closer to the Sun than Mercury</a> (These objects will be close to perihelion)</li> <li>JPL SBDB <a rel="nofollow" class="external text" href="https://ssd.jpl.nasa.gov/sbdb_query.cgi?obj_group=all;obj_kind=all;obj_numbered=all;ast_orbit_class=MBA;OBJ_field=0;ORB_field=0;c1_group=OBJ;c1_item=Ai;c1_op=%3C;c1_value=8;table_format=HTML;max_rows=200;format_option=comp;c_fields=AcBhBgBjBiBnBsAiBq;.cgifields=format_option;.cgifields=obj_kind;.cgifields=obj_group;.cgifields=obj_numbered;.cgifields=ast_orbit_class;.cgifields=table_format;.cgifields=com_orbit_class&query=1&c_sort=BqA">list of Main-Belt Asteroids (H<8) sorted by perihelion date</a></li></ul> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output .navbox-group{white-space:nowrap;text-align:right}.mw-parser-output .navbox,.mw-parser-output .navbox-subgroup{background-color:#fdfdfd}.mw-parser-output .navbox-list{line-height:1.5em;border-color:#fdfdfd}.mw-parser-output .navbox-list-with-group{text-align:left;border-left-width:2px;border-left-style:solid}.mw-parser-output tr+tr>.navbox-abovebelow,.mw-parser-output tr+tr>.navbox-group,.mw-parser-output tr+tr>.navbox-image,.mw-parser-output tr+tr>.navbox-list{border-top:2px solid #fdfdfd}.mw-parser-output .navbox-title{background-color:#ccf}.mw-parser-output .navbox-abovebelow,.mw-parser-output .navbox-group,.mw-parser-output .navbox-subgroup .navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Gravitational_orbits256" style="padding:3px"><table class="nowraplinks hlist mw-collapsible mw-collapsed navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231" /><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Orbits" title="Template:Orbits"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Orbits" title="Template talk:Orbits"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Orbits" title="Special:EditPage/Template:Orbits"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Gravitational_orbits256" style="font-size:114%;margin:0 4em">Gravitational <a href="/wiki/Orbit" title="Orbit">orbits</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_orbits" title="List of orbits">Types</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:6em">General</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Box_orbit" title="Box orbit">Box</a></li> <li><a href="/wiki/Parabolic_trajectory" title="Parabolic trajectory">Capture</a></li> <li><a href="/wiki/Circular_orbit" title="Circular orbit">Circular</a></li> <li><a href="/wiki/Elliptic_orbit" title="Elliptic orbit">Elliptical</a> / <a href="/wiki/Highly_elliptical_orbit" title="Highly elliptical orbit">Highly elliptical</a></li> <li><a href="/wiki/Parabolic_trajectory" title="Parabolic trajectory">Escape</a></li> <li><a href="/wiki/Horseshoe_orbit" title="Horseshoe orbit">Horseshoe</a></li> <li><a href="/wiki/Hyperbolic_trajectory" title="Hyperbolic trajectory">Hyperbolic trajectory</a></li> <li><a href="/wiki/Inclined_orbit" title="Inclined orbit">Inclined</a> / <a href="/wiki/Non-inclined_orbit" class="mw-redirect" title="Non-inclined orbit">Non-inclined</a></li> <li><a href="/wiki/Kepler_orbit" title="Kepler orbit">Kepler</a></li> <li><a href="/wiki/Lagrange_point" title="Lagrange point">Lagrange point</a></li> <li><a href="/wiki/Osculating_orbit" title="Osculating orbit">Osculating</a></li> <li><a href="/wiki/Parabolic_trajectory" title="Parabolic trajectory">Parabolic trajectory</a></li> <li><a href="/wiki/Parking_orbit" title="Parking orbit">Parking</a></li> <li><a href="/wiki/Retrograde_and_prograde_motion" title="Retrograde and prograde motion">Prograde / Retrograde</a></li> <li><a href="/wiki/Synchronous_orbit" title="Synchronous orbit">Synchronous</a> <ul><li><a href="/wiki/Semi-synchronous_orbit" title="Semi-synchronous orbit">semi</a></li> <li><a href="/wiki/Subsynchronous_orbit" title="Subsynchronous orbit">sub</a></li></ul></li> <li><a href="/wiki/Hohmann_transfer_orbit" title="Hohmann transfer orbit">Transfer orbit</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6em"><a href="/wiki/Geocentric_orbit" title="Geocentric orbit">Geocentric</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Geosynchronous_orbit" title="Geosynchronous orbit">Geosynchronous</a> <ul><li><a href="/wiki/Geostationary_orbit" title="Geostationary orbit">Geostationary</a></li> <li><a href="/wiki/Geostationary_transfer_orbit" title="Geostationary transfer orbit">Geostationary transfer</a></li></ul></li> <li><a href="/wiki/Graveyard_orbit" title="Graveyard orbit">Graveyard</a></li> <li><a href="/wiki/High_Earth_orbit" title="High Earth orbit">High Earth</a></li> <li><a href="/wiki/Low_Earth_orbit" title="Low Earth orbit">Low Earth</a></li> <li><a href="/wiki/Medium_Earth_orbit" title="Medium Earth orbit">Medium Earth</a></li> <li><a href="/wiki/Molniya_orbit" title="Molniya orbit">Molniya</a></li> <li><a href="/wiki/Near-equatorial_orbit" title="Near-equatorial orbit">Near-equatorial</a></li> <li><a href="/wiki/Orbit_of_the_Moon" title="Orbit of the Moon">Orbit of the Moon</a></li> <li><a href="/wiki/Polar_orbit" title="Polar orbit">Polar</a></li> <li><a href="/wiki/Sun-synchronous_orbit" title="Sun-synchronous orbit">Sun-synchronous</a></li> <li><a href="/wiki/Transatmospheric_orbit" title="Transatmospheric orbit">Transatmospheric</a></li> <li><a href="/wiki/Tundra_orbit" title="Tundra orbit">Tundra</a></li> <li><a href="/wiki/Very_low_Earth_orbit" title="Very low Earth orbit">Very low Earth</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6em">About<br />other points</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li>Mars <ul><li><a href="/wiki/Areocentric_orbit" title="Areocentric orbit">Areocentric</a></li> <li><a href="/wiki/Areosynchronous_orbit" title="Areosynchronous orbit">Areosynchronous</a></li> <li><a href="/wiki/Areostationary_orbit" title="Areostationary orbit">Areostationary</a></li></ul></li> <li>Lagrange points <ul><li><a href="/wiki/Distant_retrograde_orbit" title="Distant retrograde orbit">Distant retrograde</a></li> <li><a href="/wiki/Halo_orbit" title="Halo orbit">Halo</a></li> <li><a href="/wiki/Lissajous_orbit" title="Lissajous orbit">Lissajous</a></li> <li><a href="/wiki/Libration_point_orbit" title="Libration point orbit">Libration</a></li></ul></li> <li><a href="/wiki/Lunar_orbit" title="Lunar orbit">Lunar</a></li> <li>Sun <ul><li><a href="/wiki/Heliocentric_orbit" title="Heliocentric orbit">Heliocentric</a> <ul><li><a href="/wiki/Earth%27s_orbit" title="Earth's orbit">Earth's orbit</a></li></ul></li> <li><a href="/wiki/Mars_cycler" title="Mars cycler">Mars cycler</a></li> <li><a href="/wiki/Sun-synchronous_orbit" title="Sun-synchronous orbit">Heliosynchronous</a></li></ul></li> <li>Other <ul><li><a href="/wiki/Lunar_cycler" title="Lunar cycler">Lunar cycler</a></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Orbital_elements" title="Orbital elements">Parameters</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:6em"><div class="hlist"><ul><li>Shape</li><li>Size</li></ul></div></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><span class="texhtml mvar" style="font-style:italic;">e</span>  <a href="/wiki/Orbital_eccentricity" title="Orbital eccentricity">Eccentricity</a></li> <li><span class="texhtml mvar" style="font-style:italic;">a</span>  <a href="/wiki/Semi-major_and_semi-minor_axes" title="Semi-major and semi-minor axes">Semi-major axis</a></li> <li><span class="texhtml mvar" style="font-style:italic;">b</span>  <a href="/wiki/Semi-major_and_semi-minor_axes" title="Semi-major and semi-minor axes">Semi-minor axis</a></li> <li><span class="texhtml mvar" style="font-style:italic;">Q</span>, <span class="texhtml mvar" style="font-style:italic;">q</span>  <a class="mw-selflink selflink">Apsides</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6em">Orientation</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><span class="texhtml mvar" style="font-style:italic;">i</span>  <a href="/wiki/Orbital_inclination" title="Orbital inclination">Inclination</a></li> <li><span class="texhtml mvar" style="font-style:italic;">Ω</span>  <a href="/wiki/Longitude_of_the_ascending_node" title="Longitude of the ascending node">Longitude of the ascending node</a></li> <li><span class="texhtml mvar" style="font-style:italic;">ω</span>  <a href="/wiki/Argument_of_periapsis" title="Argument of periapsis">Argument of periapsis</a></li> <li><span class="texhtml mvar" style="font-style:italic;">ϖ</span>  <a href="/wiki/Longitude_of_the_periapsis" class="mw-redirect" title="Longitude of the periapsis">Longitude of the periapsis</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6em">Position</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><span class="texhtml mvar" style="font-style:italic;">M</span>  <a href="/wiki/Mean_anomaly" title="Mean anomaly">Mean anomaly</a></li> <li><span class="texhtml mvar" style="font-style:italic;">ν</span>, <span class="texhtml mvar" style="font-style:italic;">θ</span>, <span class="texhtml mvar" style="font-style:italic;">f</span>  <a href="/wiki/True_anomaly" title="True anomaly">True anomaly</a></li> <li><span class="texhtml mvar" style="font-style:italic;">E</span>  <a href="/wiki/Eccentric_anomaly" title="Eccentric anomaly">Eccentric anomaly</a></li> <li><span class="texhtml mvar" style="font-style:italic;">L</span>  <a href="/wiki/Mean_longitude" title="Mean longitude">Mean longitude</a></li> <li><span class="texhtml mvar" style="font-style:italic;">l</span>  <a href="/wiki/True_longitude" title="True longitude">True longitude</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6em">Variation</th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><span class="texhtml mvar" style="font-style:italic;">T</span>  <a href="/wiki/Orbital_period" title="Orbital period">Orbital period</a></li> <li><span class="texhtml mvar" style="font-style:italic;">n</span>  <a href="/wiki/Mean_motion" title="Mean motion">Mean motion</a></li> <li><span class="texhtml mvar" style="font-style:italic;">v</span>  <a href="/wiki/Orbital_speed" title="Orbital speed">Orbital speed</a></li> <li><span class="texhtml"><i>t</i><sub>0</sub></span>  <a href="/wiki/Epoch_(astronomy)" title="Epoch (astronomy)">Epoch</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Orbital_maneuver" title="Orbital maneuver">Maneuvers</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Bi-elliptic_transfer" title="Bi-elliptic transfer">Bi-elliptic transfer</a></li> <li><a href="/wiki/Collision_avoidance_(spacecraft)" title="Collision avoidance (spacecraft)">Collision avoidance (spacecraft)</a></li> <li><a href="/wiki/Delta-v" title="Delta-v">Delta-v</a></li> <li><a href="/wiki/Delta-v_budget" title="Delta-v budget">Delta-v budget</a></li> <li><a href="/wiki/Gravity_assist" title="Gravity assist">Gravity assist</a></li> <li><a href="/wiki/Gravity_turn" title="Gravity turn">Gravity turn</a></li> <li><a href="/wiki/Hohmann_transfer_orbit" title="Hohmann transfer orbit">Hohmann transfer</a></li> <li><a href="/wiki/Orbital_inclination_change" title="Orbital inclination change">Inclination change</a></li> <li><a href="/wiki/Low-energy_transfer" title="Low-energy transfer">Low-energy transfer</a></li> <li><a href="/wiki/Oberth_effect" title="Oberth effect">Oberth effect</a></li> <li><a href="/wiki/Orbit_phasing" title="Orbit phasing">Phasing</a></li> <li><a href="/wiki/Tsiolkovsky_rocket_equation" title="Tsiolkovsky rocket equation">Rocket equation</a></li> <li><a href="/wiki/Space_rendezvous" title="Space rendezvous">Rendezvous</a></li> <li><a href="/wiki/Trans-lunar_injection" title="Trans-lunar injection">Trans-lunar injection</a></li> <li><a href="/wiki/Transposition,_docking,_and_extraction" title="Transposition, docking, and extraction">Transposition, docking, and extraction</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Orbital_mechanics" title="Orbital mechanics">Orbital<br />mechanics</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astronomical_coordinate_systems" title="Astronomical coordinate systems">Astronomical coordinate systems</a></li> <li><a href="/wiki/Characteristic_energy" title="Characteristic energy">Characteristic energy</a></li> <li><a href="/wiki/Escape_velocity" title="Escape velocity">Escape velocity</a></li> <li><a href="/wiki/Ephemeris" title="Ephemeris">Ephemeris</a></li> <li><a href="/wiki/Equatorial_coordinate_system" title="Equatorial coordinate system">Equatorial coordinate system</a></li> <li><a href="/wiki/Ground_track" class="mw-redirect" title="Ground track">Ground track</a></li> <li><a href="/wiki/Hill_sphere" title="Hill sphere">Hill sphere</a></li> <li><a href="/wiki/Interplanetary_Transport_Network" title="Interplanetary Transport Network">Interplanetary Transport Network</a></li> <li><a href="/wiki/Kepler%27s_laws_of_planetary_motion" title="Kepler's laws of planetary motion">Kepler's laws of planetary motion</a></li> <li><a href="/wiki/Kozai_mechanism" title="Kozai mechanism">Kozai mechanism</a></li> <li><a href="/wiki/Lagrange_point" title="Lagrange point">Lagrangian point</a></li> <li><a href="/wiki/N-body_problem" title="N-body problem"><i>n</i>-body problem</a></li> <li><a href="/wiki/Orbit_equation" title="Orbit equation">Orbit equation</a></li> <li><a href="/wiki/Orbital_state_vectors" title="Orbital state vectors">Orbital state vectors</a></li> <li><a href="/wiki/Perturbation_(astronomy)" title="Perturbation (astronomy)">Perturbation</a></li> <li><a href="/wiki/Retrograde_and_prograde_motion" title="Retrograde and prograde motion">Retrograde and prograde motion</a></li> <li><a href="/wiki/Specific_orbital_energy" title="Specific orbital energy">Specific orbital energy</a></li> <li><a href="/wiki/Specific_angular_momentum" title="Specific angular momentum">Specific angular momentum</a></li> <li><a href="/wiki/Two-line_element_set" title="Two-line element set">Two-line elements</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="List-Class article"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/d/db/Symbol_list_class.svg/16px-Symbol_list_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/d/db/Symbol_list_class.svg/23px-Symbol_list_class.svg.png 1.5x, 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