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id="toc-Physical_characteristics-sublist" class="vector-toc-list"> <li id="toc-Rotation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Rotation"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Rotation</span> </div> </a> <ul id="toc-Rotation-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Orbit" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Orbit"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Orbit</span> </div> </a> <ul id="toc-Orbit-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Exploration" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Exploration"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Exploration</span> </div> </a> <ul id="toc-Exploration-sublist" class="vector-toc-list"> </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">7</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Notes</span> </div> </a> <ul id="toc-Notes-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">9</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">10</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" > <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">Hydra (moon)</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 67 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-67" 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">67 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/Hidra_(maan)" title="Hidra (maan) – Afrikaans" lang="af" hreflang="af" data-title="Hidra (maan)" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%87%D9%8A%D8%AF%D8%B1%D8%A7_(%D9%82%D9%85%D8%B1)" title="هيدرا (قمر) – Arabic" lang="ar" hreflang="ar" data-title="هيدرا (قمر)" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-an mw-list-item"><a href="https://an.wikipedia.org/wiki/Hidra_(satelite)" title="Hidra (satelite) – Aragonese" lang="an" hreflang="an" data-title="Hidra (satelite)" data-language-autonym="Aragonés" data-language-local-name="Aragonese" class="interlanguage-link-target"><span>Aragonés</span></a></li><li class="interlanguage-link interwiki-azb mw-list-item"><a href="https://azb.wikipedia.org/wiki/%D9%87%DB%8C%D8%AF%D8%B1%D8%A7_(%D8%A7%D9%88%DB%8C%D8%AF%D9%88)" title="هیدرا (اویدو) – South Azerbaijani" lang="azb" hreflang="azb" data-title="هیدرا (اویدو)" data-language-autonym="تۆرکجه" data-language-local-name="South Azerbaijani" class="interlanguage-link-target"><span>تۆرکجه</span></a></li><li class="interlanguage-link interwiki-zh-min-nan mw-list-item"><a href="https://zh-min-nan.wikipedia.org/wiki/Hydra_(o%C4%93-chhe%E2%81%BF)" title="Hydra (oē-chheⁿ) – Minnan" lang="nan" hreflang="nan" data-title="Hydra (oē-chheⁿ)" data-language-autonym="閩南語 / Bân-lâm-gú" data-language-local-name="Minnan" class="interlanguage-link-target"><span>閩南語 / Bân-lâm-gú</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%93%D1%96%D0%B4%D1%80%D0%B0_(%D1%81%D0%BF%D0%B0%D0%B4%D0%B0%D1%80%D0%BE%D0%B6%D0%BD%D1%96%D0%BA_%D0%9F%D0%BB%D1%83%D1%82%D0%BE%D0%BD%D0%B0)" title="Гідра (спадарожнік Плутона) – Belarusian" lang="be" hreflang="be" data-title="Гідра (спадарожнік Плутона)" 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%93%D1%96%D0%B4%D1%80%D0%B0_(%D1%81%D0%BF%D0%B0%D0%B4%D0%B0%D1%80%D0%BE%D0%B6%D0%BD%D1%96%D0%BA)" title="Гідра (спадарожнік) – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="Гідра (спадарожнік)" 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-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%A5%D0%B8%D0%B4%D1%80%D0%B0_(%D1%81%D0%BF%D1%8A%D1%82%D0%BD%D0%B8%D0%BA)" title="Хидра (спътник) – Bulgarian" lang="bg" hreflang="bg" data-title="Хидра (спътник)" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Hydra_(satelit)" title="Hydra (satelit) – Bosnian" lang="bs" hreflang="bs" data-title="Hydra (satelit)" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-br mw-list-item"><a href="https://br.wikipedia.org/wiki/Hydra_(loarenn)" title="Hydra (loarenn) – Breton" lang="br" hreflang="br" data-title="Hydra (loarenn)" data-language-autonym="Brezhoneg" data-language-local-name="Breton" class="interlanguage-link-target"><span>Brezhoneg</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Hidra_(sat%C3%A8l%C2%B7lit)" title="Hidra (satèl·lit) – Catalan" lang="ca" hreflang="ca" data-title="Hidra (satèl·lit)" 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/Hydra_(m%C4%9Bs%C3%ADc)" title="Hydra (měsíc) – Czech" lang="cs" hreflang="cs" data-title="Hydra (měsíc)" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-cy mw-list-item"><a href="https://cy.wikipedia.org/wiki/Hydra_(lloeren)" title="Hydra (lloeren) – Welsh" lang="cy" hreflang="cy" data-title="Hydra (lloeren)" data-language-autonym="Cymraeg" data-language-local-name="Welsh" class="interlanguage-link-target"><span>Cymraeg</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Hydra_(m%C3%A5ne)" title="Hydra (måne) – Danish" lang="da" hreflang="da" data-title="Hydra (måne)" 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/Hydra_(Mond)" title="Hydra (Mond) – German" lang="de" hreflang="de" data-title="Hydra (Mond)" 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/Hydra_(kaaslane)" title="Hydra (kaaslane) – Estonian" lang="et" hreflang="et" data-title="Hydra (kaaslane)" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%8E%CE%B4%CF%81%CE%B1_(%CE%B4%CE%BF%CF%81%CF%85%CF%86%CF%8C%CF%81%CE%BF%CF%82)" title="Ύδρα (δορυφόρος) – Greek" lang="el" hreflang="el" data-title="Ύδρα (δορυφόρος)" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Hidra_(sat%C3%A9lite)" title="Hidra (satélite) – Spanish" lang="es" hreflang="es" data-title="Hidra (satélite)" 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/Hidro_(luno)" title="Hidro (luno) – Esperanto" lang="eo" hreflang="eo" data-title="Hidro (luno)" 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/Hidra_(satelitea)" title="Hidra (satelitea) – Basque" lang="eu" hreflang="eu" data-title="Hidra (satelitea)" 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/%D9%87%DB%8C%D8%AF%D8%B1%D8%A7_(%D9%82%D9%85%D8%B1)" title="هیدرا (قمر) – Persian" lang="fa" hreflang="fa" data-title="هیدرا (قمر)" 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/Hydre_(lune)" title="Hydre (lune) – French" lang="fr" hreflang="fr" data-title="Hydre (lune)" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Hydra" title="Hydra – Irish" lang="ga" hreflang="ga" data-title="Hydra" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-gv mw-list-item"><a href="https://gv.wikipedia.org/wiki/Hydra_(eayst)" title="Hydra (eayst) – Manx" lang="gv" hreflang="gv" data-title="Hydra (eayst)" 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/Hydra_(l%C3%BAa)" title="Hydra (lúa) – Galician" lang="gl" hreflang="gl" data-title="Hydra (lúa)" 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/%ED%9E%88%EB%93%9C%EB%9D%BC_(%EC%9C%84%EC%84%B1)" title="히드라 (위성) – Korean" lang="ko" hreflang="ko" data-title="히드라 (위성)" 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/%D5%80%D5%AB%D5%A4%D6%80%D5%A1_(%D5%A1%D6%80%D5%A2%D5%A1%D5%B6%D5%B5%D5%A1%D5%AF)" title="Հիդրա (արբանյակ) – Armenian" lang="hy" hreflang="hy" data-title="Հիդրա (արբանյակ)" 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%B9%E0%A4%BE%E0%A4%8F%E0%A4%A1%E0%A5%8D%E0%A4%B0%E0%A4%BE_(%E0%A4%89%E0%A4%AA%E0%A4%97%E0%A5%8D%E0%A4%B0%E0%A4%B9)" title="हाएड्रा (उपग्रह) – Hindi" lang="hi" hreflang="hi" data-title="हाएड्रा (उपग्रह)" 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/Hidra_(mjesec)" title="Hidra (mjesec) – Croatian" lang="hr" hreflang="hr" data-title="Hidra (mjesec)" 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/S/2005_P_1" title="S/2005 P 1 – Ido" lang="io" hreflang="io" data-title="S/2005 P 1" 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/Hydra_(satelit)" title="Hydra (satelit) – Indonesian" lang="id" hreflang="id" data-title="Hydra (satelit)" 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-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Idra_(satellite)" title="Idra (satellite) – Italian" lang="it" hreflang="it" data-title="Idra (satellite)" 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%94%D7%99%D7%93%D7%A8%D7%94_(%D7%99%D7%A8%D7%97)" title="הידרה (ירח) – Hebrew" lang="he" hreflang="he" data-title="הידרה (ירח)" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-kv mw-list-item"><a href="https://kv.wikipedia.org/wiki/%D0%93%D0%B8%D0%B4%D1%80%D0%B0_(%D1%82%D3%A7%D0%BB%D1%8B%D1%81%D1%8C)" title="Гидра (тӧлысь) – Komi" lang="kv" hreflang="kv" data-title="Гидра (тӧлысь)" data-language-autonym="Коми" data-language-local-name="Komi" class="interlanguage-link-target"><span>Коми</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Hydra_(satelles)" title="Hydra (satelles) – Latin" lang="la" hreflang="la" data-title="Hydra (satelles)" 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/Hidra_(pavadonis)" title="Hidra (pavadonis) – Latvian" lang="lv" hreflang="lv" data-title="Hidra (pavadonis)" 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/Hidra_(palydovas)" title="Hidra (palydovas) – Lithuanian" lang="lt" hreflang="lt" data-title="Hidra (palydovas)" 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/Hydra_(hold)" title="Hydra (hold) – Hungarian" lang="hu" hreflang="hu" data-title="Hydra (hold)" 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%A5%D0%B8%D0%B4%D1%80%D0%B0_(%D0%BC%D0%B5%D1%81%D0%B5%D1%87%D0%B8%D0%BD%D0%B0)" title="Хидра (месечина) – Macedonian" lang="mk" hreflang="mk" data-title="Хидра (месечина)" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-mr mw-list-item"><a href="https://mr.wikipedia.org/wiki/%E0%A4%B9%E0%A4%BE%E0%A4%AF%E0%A4%A1%E0%A5%8D%E0%A4%B0%E0%A4%BE_(%E0%A4%89%E0%A4%AA%E0%A4%97%E0%A5%8D%E0%A4%B0%E0%A4%B9)" title="हायड्रा (उपग्रह) – Marathi" lang="mr" hreflang="mr" data-title="हायड्रा (उपग्रह)" data-language-autonym="मराठी" data-language-local-name="Marathi" class="interlanguage-link-target"><span>मराठी</span></a></li><li class="interlanguage-link interwiki-my mw-list-item"><a href="https://my.wikipedia.org/wiki/%E1%80%9F%E1%80%AD%E1%80%AF%E1%80%80%E1%80%BA%E1%80%92%E1%80%9B%E1%80%AC_(%E1%80%82%E1%80%BC%E1%80%AD%E1%80%AF%E1%80%9F%E1%80%BA%E1%80%9B%E1%80%B6%E1%80%9C)" title="ဟိုက်ဒရာ (ဂြိုဟ်ရံလ) – Burmese" lang="my" hreflang="my" data-title="ဟိုက်ဒရာ (ဂြိုဟ်ရံလ)" data-language-autonym="မြန်မာဘာသာ" data-language-local-name="Burmese" class="interlanguage-link-target"><span>မြန်မာဘာသာ</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Hydra_(maan)" title="Hydra (maan) – Dutch" lang="nl" hreflang="nl" data-title="Hydra (maan)" 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/%E3%83%92%E3%83%89%E3%83%A9_(%E8%A1%9B%E6%98%9F)" title="ヒドラ (衛星) – Japanese" lang="ja" hreflang="ja" data-title="ヒドラ (衛星)" 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/Hydra_(m%C3%A5ne)" title="Hydra (måne) – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Hydra (måne)" 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/Plutom%C3%A5nen_Hydra" title="Plutomånen Hydra – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Plutomånen Hydra" 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/Hydra_(Maand)" title="Hydra (Maand) – Low German" lang="nds" hreflang="nds" data-title="Hydra (Maand)" 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/Hydra_(ksi%C4%99%C5%BCyc)" title="Hydra (księżyc) – Polish" lang="pl" hreflang="pl" data-title="Hydra (księżyc)" 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/Hidra_(sat%C3%A9lite)" title="Hidra (satélite) – Portuguese" lang="pt" hreflang="pt" data-title="Hidra (satélite)" 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/Hydra_(satelit)" title="Hydra (satelit) – Romanian" lang="ro" hreflang="ro" data-title="Hydra (satelit)" 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%93%D0%B8%D0%B4%D1%80%D0%B0_(%D1%81%D0%BF%D1%83%D1%82%D0%BD%D0%B8%D0%BA)" title="Гидра (спутник) – Russian" lang="ru" hreflang="ru" data-title="Гидра (спутник)" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-scn mw-list-item"><a href="https://scn.wikipedia.org/wiki/Hydra" title="Hydra – Sicilian" lang="scn" hreflang="scn" data-title="Hydra" data-language-autonym="Sicilianu" data-language-local-name="Sicilian" class="interlanguage-link-target"><span>Sicilianu</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Hydra_(moon)" title="Hydra (moon) – Simple English" lang="en-simple" hreflang="en-simple" data-title="Hydra (moon)" 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/Hydra_(mesiac)" title="Hydra (mesiac) – Slovak" lang="sk" hreflang="sk" data-title="Hydra (mesiac)" 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/Hidra_(luna)" title="Hidra (luna) – Slovenian" lang="sl" hreflang="sl" data-title="Hidra (luna)" 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%85%D8%A7%D9%86%DA%AF%DB%8C_%DA%BE%DB%8C%D8%AF%D8%B1%D8%A7" title="مانگی ھیدرا – Central Kurdish" lang="ckb" hreflang="ckb" data-title="مانگی ھیدرا" 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/%D0%A5%D0%B8%D0%B4%D1%80%D0%B0_(%D0%BC%D0%B5%D1%81%D0%B5%D1%86)" title="Хидра (месец) – Serbian" lang="sr" hreflang="sr" data-title="Хидра (месец)" 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/Hidra_(mjesec)" title="Hidra (mjesec) – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Hidra (mjesec)" 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-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Hydra_(kuu)" title="Hydra (kuu) – Finnish" lang="fi" hreflang="fi" data-title="Hydra (kuu)" 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/Hydra_(m%C3%A5ne)" title="Hydra (måne) – Swedish" lang="sv" hreflang="sv" data-title="Hydra (måne)" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B9%84%E0%B8%AE%E0%B8%94%E0%B8%A3%E0%B8%B2_(%E0%B8%94%E0%B8%B2%E0%B8%A7%E0%B8%9A%E0%B8%A3%E0%B8%B4%E0%B8%A7%E0%B8%B2%E0%B8%A3)" title="ไฮดรา (ดาวบริวาร) – Thai" lang="th" hreflang="th" data-title="ไฮดรา (ดาวบริวาร)" 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/Hydra_(uydu)" title="Hydra (uydu) – Turkish" lang="tr" hreflang="tr" data-title="Hydra (uydu)" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%93%D1%96%D0%B4%D1%80%D0%B0_(%D1%81%D1%83%D0%BF%D1%83%D1%82%D0%BD%D0%B8%D0%BA)" title="Гідра (супутник) – Ukrainian" lang="uk" hreflang="uk" data-title="Гідра (супутник)" 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/Hydra_(v%E1%BB%87_tinh)" title="Hydra (vệ tinh) – Vietnamese" lang="vi" hreflang="vi" data-title="Hydra (vệ tinh)" 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-war mw-list-item"><a href="https://war.wikipedia.org/wiki/Hydra_(bulan)" title="Hydra (bulan) – Waray" lang="war" hreflang="war" data-title="Hydra (bulan)" data-language-autonym="Winaray" data-language-local-name="Waray" class="interlanguage-link-target"><span>Winaray</span></a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%E5%86%A5%E5%8D%AB%E4%B8%89" title="冥卫三 – Wu" lang="wuu" hreflang="wuu" data-title="冥卫三" 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Click here for more information." src="//upload.wikimedia.org/wikipedia/en/thumb/9/94/Symbol_support_vote.svg/19px-Symbol_support_vote.svg.png" decoding="async" width="19" height="20" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/94/Symbol_support_vote.svg/29px-Symbol_support_vote.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/94/Symbol_support_vote.svg/39px-Symbol_support_vote.svg.png 2x" data-file-width="180" data-file-height="185" /></a></span></div></div> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></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">Moon of Pluto</div> <p class="mw-empty-elt"> </p> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox"><caption class="infobox-title fn org">Hydra</caption><tbody><tr><td colspan="2" class="infobox-image"><span class="mw-default-size" typeof="mw:File/Frameless"><a href="/wiki/File:Hydra_reprocessed.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/94/Hydra_reprocessed.png/290px-Hydra_reprocessed.png" decoding="async" width="290" height="290" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/94/Hydra_reprocessed.png/435px-Hydra_reprocessed.png 1.5x, //upload.wikimedia.org/wikipedia/commons/9/94/Hydra_reprocessed.png 2x" data-file-width="500" data-file-height="500" /></a></span><div class="infobox-caption">Near true-color image of Hydra, taken by <i><a href="/wiki/New_Horizons" title="New Horizons">New Horizons</a></i> on 14 July 2015</div></td></tr><tr><th colspan="2" class="infobox-header" style="background-color:#E0CCFF">Discovery<sup id="cite_ref-Nomenclature_1-0" class="reference"><a href="#cite_note-Nomenclature-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></th></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><a href="/wiki/List_of_minor_planet_discoverers" title="List of minor planet discoverers">Discovered by</a></th><td class="infobox-data"><a href="/wiki/Hubble_Space_Telescope" title="Hubble Space Telescope">Hubble Space Telescope</a></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;">Discovery date</th><td class="infobox-data">15 May 2005</td></tr><tr><th colspan="2" class="infobox-header" style="background-color:#E0CCFF">Designations</th></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">Designation</div></th><td class="infobox-data">Pluto III<sup id="cite_ref-Nomenclature_1-1" class="reference"><a href="#cite_note-Nomenclature-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;">Pronunciation</th><td class="infobox-data"><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="'h' in 'hi'">h</span><span title="/aɪ/: 'i' in 'tide'">aɪ</span><span title="'d' in 'dye'">d</span><span title="'r' in 'rye'">r</span><span title="/ə/: 'a' in 'about'">ə</span></span>/</a></span></span><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></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">Named after</div></th><td class="infobox-data"><a href="/wiki/Lernaean_Hydra" title="Lernaean Hydra">Lernaean Hydra</a></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Provisional_designation_in_astronomy" title="Provisional designation in astronomy">Alternative names</a></div></th><td class="infobox-data">S/2005 P 1</td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><a href="/wiki/List_of_adjectivals_and_demonyms_of_astronomical_bodies" title="List of adjectivals and demonyms of astronomical bodies">Adjectives</a></th><td class="infobox-data">Hydrian<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> <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="'h' in 'hi'">h</span><span title="/aɪ/: 'i' in 'tide'">aɪ</span><span title="'d' in 'dye'">d</span><span title="'r' in 'rye'">r</span><span title="/i/: 'y' in 'happy'">i</span><span title="/ən/: 'on' in 'button'">ən</span></span>/</a></span></span><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></td></tr><tr><th colspan="2" class="infobox-header" style="background-color:#E0CCFF"><a href="/wiki/Osculating_orbit" title="Osculating orbit">Orbital characteristics</a><sup id="cite_ref-ShowalterHamilton2015_5-0" class="reference"><a href="#cite_note-ShowalterHamilton2015-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></th></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Semi-major_and_semi-minor_axes" title="Semi-major and semi-minor axes">Semi-major axis</a></div></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7007647380000000000♠"></span>64<span style="margin-left:.25em;">738</span><span style="margin-left:0.3em;margin-right:0.15em;">±</span>3 km</span></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><a href="/wiki/Orbital_eccentricity" title="Orbital eccentricity">Eccentricity</a></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="6997586200000000000♠"></span>0.005<span style="margin-left:.25em;">862</span><span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.000<span style="margin-left:.25em;">025</span></span></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Orbital_period" title="Orbital period">Orbital period (sidereal)</a></div></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7006330063292800000♠"></span>38.201<span style="margin-left:.25em;">77</span><span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.000<span style="margin-left:.25em;">03</span> d</span></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">Average <a href="/wiki/Orbital_speed" title="Orbital speed">orbital speed</a></div></th><td class="infobox-data">0.123 km/s</td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><a href="/wiki/Orbital_inclination" title="Orbital inclination">Inclination</a></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="6997422369678982628♠"></span>0.242°<span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.005°</span></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><a href="/wiki/Natural_satellite" title="Natural satellite">Satellite of</a></th><td class="infobox-data"><a href="/wiki/Pluto" title="Pluto">Pluto</a></td></tr><tr><th colspan="2" class="infobox-header" style="background-color:#E0CCFF"><span class="anchor" id="Infobox_Physical_characteristics"></span>Physical characteristics</th></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><a href="/wiki/Mean_radius_(astronomy)" title="Mean radius (astronomy)">Dimensions</a></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7004509000000000000♠"></span>50.9 km × 36.1 km × 30.9 km</span><sup id="cite_ref-phasecurves_6-0" class="reference"><a href="#cite_note-phasecurves-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><br />(<a href="/wiki/Geometric_mean" title="Geometric mean">Geometric mean</a> of 38 km)</td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><a href="/wiki/Mass" title="Mass">Mass</a></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7016300999999999999♠"></span>(3.01<span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.30)<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>16</sup> kg</span><sup id="cite_ref-Porter2023_7-0" class="reference"><a href="#cite_note-Porter2023-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 10">: 10 </span></sup></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;">Mean <a href="/wiki/Density" title="Density">density</a></div></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7003122000000000000♠"></span>1.220<span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.150 g/cm<sup>3</sup></span><sup id="cite_ref-Porter2023_7-1" class="reference"><a href="#cite_note-Porter2023-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup class="reference nowrap"><span title="Page: 10">: 10 </span></sup></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Surface_gravity" title="Surface gravity">Surface gravity</a></div></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="6994520055269000000♠"></span>0.005<span style="margin-left:.25em;">200</span><span style="margin-left:.25em;">552</span><span style="margin-left:.25em;">69</span> g</span><sup id="cite_ref-by-the-numbers_8-0" class="reference"><a href="#cite_note-by-the-numbers-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Synodic_rotation_period" class="mw-redirect" title="Synodic rotation period">Synodic rotation period</a></div></th><td class="infobox-data">0.4295 d (10.31 h)<sup id="cite_ref-Lakdawalla2015_9-0" class="reference"><a href="#cite_note-Lakdawalla2015-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> (July 2015)</td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Axial_tilt" title="Axial tilt">Axial tilt</a></div></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="7000191986217719376♠"></span>110°</span><sup id="cite_ref-arxiv1604_10-0" class="reference"><a href="#cite_note-arxiv1604-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><a href="/wiki/Albedo" title="Albedo">Albedo</a></th><td class="infobox-data">0.83 ± 0.08 (geometric)<sup id="cite_ref-scimag000_11-0" class="reference"><a href="#cite_note-scimag000-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><a href="/wiki/Temperature" title="Temperature">Temperature</a></th><td class="infobox-data">23 <a href="/wiki/Kelvin" title="Kelvin">K</a><sup id="cite_ref-Cook2018_12-0" class="reference"><a href="#cite_note-Cook2018-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label" style="max-width:11em;"><div style="display: inline-block; line-height: 1.2em; padding: .1em 0;"><a href="/wiki/Apparent_magnitude" title="Apparent magnitude">Apparent magnitude</a></div></th><td class="infobox-data">22.9–23.3 (measured)<sup id="cite_ref-Stern06b_13-0" class="reference"><a href="#cite_note-Stern06b-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup></td></tr></tbody></table> <p><b>Hydra</b> is a <a href="/wiki/Moons_of_Pluto" title="Moons of Pluto">natural satellite of Pluto</a>, with a diameter of approximately 51 km (32 mi) across its longest dimension.<sup id="cite_ref-phasecurves_6-1" class="reference"><a href="#cite_note-phasecurves-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> It is the second-largest moon of <a href="/wiki/Pluto" title="Pluto">Pluto</a>, being slightly larger than <a href="/wiki/Nix_(moon)" title="Nix (moon)">Nix</a>. Hydra was discovered along with Nix by astronomers using the <a href="/wiki/Hubble_Space_Telescope" title="Hubble Space Telescope">Hubble Space Telescope</a> on 15 May 2005,<sup id="cite_ref-Nomenclature_1-2" class="reference"><a href="#cite_note-Nomenclature-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> and was named after the <a href="/wiki/Lernaean_Hydra" title="Lernaean Hydra">Hydra</a>, the nine-headed underworld serpent in <a href="/wiki/Greek_mythology" title="Greek mythology">Greek mythology</a>.<sup id="cite_ref-ChasingNH_14-0" class="reference"><a href="#cite_note-ChasingNH-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> By distance, Hydra is the fifth and outermost moon of Pluto, orbiting beyond Pluto's fourth moon <a href="/wiki/Kerberos_(moon)" title="Kerberos (moon)">Kerberos</a>.<sup id="cite_ref-scimag000_11-1" class="reference"><a href="#cite_note-scimag000-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p><p>Hydra has a highly <a href="/wiki/Albedo" title="Albedo">reflective</a> surface caused by the presence of <a href="/wiki/Ice" title="Ice">water ice</a>, similar to other Plutonian moons.<sup id="cite_ref-IcyMoon_15-0" class="reference"><a href="#cite_note-IcyMoon-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> Hydra's reflectivity is intermediate, in between those of Pluto and <a href="/wiki/Charon_(moon)" title="Charon (moon)">Charon</a>.<sup id="cite_ref-HydraEmerges_16-0" class="reference"><a href="#cite_note-HydraEmerges-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> The <i><a href="/wiki/New_Horizons" title="New Horizons">New Horizons</a></i> spacecraft imaged Pluto and its moons in July 2015 and returned multiple images of Hydra.<sup id="cite_ref-CapturesTwo_17-0" class="reference"><a href="#cite_note-CapturesTwo-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Discovery">Discovery</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydra_(moon)&action=edit&section=1" title="Edit section: Discovery"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Pluto_system_2005_discovery_images.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/31/Pluto_system_2005_discovery_images.jpg/220px-Pluto_system_2005_discovery_images.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/31/Pluto_system_2005_discovery_images.jpg/330px-Pluto_system_2005_discovery_images.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/31/Pluto_system_2005_discovery_images.jpg/440px-Pluto_system_2005_discovery_images.jpg 2x" data-file-width="800" data-file-height="600" /></a><figcaption>Discovery images of Nix and Hydra</figcaption></figure> <p>Members of the <i>New Horizons</i> team suspected that Pluto and Charon might be accompanied by other small, distant moons, weakly bound to the Pluto system. They used the <a href="/wiki/Hubble_Space_Telescope" title="Hubble Space Telescope">Hubble Space Telescope</a> to test this hypothesis. This led to the discovery of Nix and Hydra – both surprisingly close to Pluto/Charon – and that no significant moons existed in Pluto's extended sphere of influence. </p><p>The discovery images were taken on 15 May 2005 and 18 May 2005. Hydra and Nix were independently discovered by Max J. Mutchler on 15 June 2005 and by Andrew J. Steffl on 15 August 2005.<sup id="cite_ref-UniverseToday_18-0" class="reference"><a href="#cite_note-UniverseToday-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> The discoveries were announced on 31 October 2005, after confirmation by <a href="/wiki/Precovery" title="Precovery">precovering</a> archival Hubble images of Pluto from 2002.<sup id="cite_ref-hubblesite_19-0" class="reference"><a href="#cite_note-hubblesite-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> The two newly discovered moons were subsequently <a href="/wiki/Provisional_designation_in_astronomy" title="Provisional designation in astronomy">provisionally designated</a> <b>S/2005 P 1</b> for Hydra and S/2005 P 2 for Nix.<sup id="cite_ref-IAUC8625_20-0" class="reference"><a href="#cite_note-IAUC8625-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-IAUC8723_21-0" class="reference"><a href="#cite_note-IAUC8723-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> The moons were informally referred to as "P1" and "P2" respectively, by the discovery team.<sup id="cite_ref-IAUC8625_20-1" class="reference"><a href="#cite_note-IAUC8625-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Naming">Naming</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydra_(moon)&action=edit&section=2" title="Edit section: Naming"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Pluto_and_its_satellites_(2005).jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Pluto_and_its_satellites_%282005%29.jpg/170px-Pluto_and_its_satellites_%282005%29.jpg" decoding="async" width="170" height="155" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Pluto_and_its_satellites_%282005%29.jpg/255px-Pluto_and_its_satellites_%282005%29.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Pluto_and_its_satellites_%282005%29.jpg/340px-Pluto_and_its_satellites_%282005%29.jpg 2x" data-file-width="868" data-file-height="792" /></a><figcaption>Hubble image of Pluto's moons (annotated)</figcaption></figure> <p>The name Hydra was approved on 21 June 2006 by the <a href="/wiki/International_Astronomical_Union" title="International Astronomical Union">International Astronomical Union (IAU)</a> and was announced along with the naming of Nix in the IAU Circular 8723.<sup id="cite_ref-IAUC8723_21-1" class="reference"><a href="#cite_note-IAUC8723-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> Hydra was named after the <a href="/wiki/Lernaean_Hydra" title="Lernaean Hydra">Lernaean Hydra</a>, a multi-headed serpent that battled <a href="/wiki/Heracles" title="Heracles">Heracles</a> in <a href="/wiki/Greek_mythology" title="Greek mythology">Greek mythology</a>.<sup id="cite_ref-ChasingNH_14-1" class="reference"><a href="#cite_note-ChasingNH-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> Particularly, the nine heads of Hydra subtly references Pluto's former ninth planetary status.<sup id="cite_ref-ChasingNH_14-2" class="reference"><a href="#cite_note-ChasingNH-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> The two newly named moons were intentionally named that the order of their initials <i>N</i> and <i>H</i> honors the <i>New Horizons</i> mission to Pluto, similarly to how the first two letters of Pluto's name honors <a href="/wiki/Percival_Lowell" title="Percival Lowell">Percival Lowell</a>.<sup id="cite_ref-UniverseToday2006_22-0" class="reference"><a href="#cite_note-UniverseToday2006-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-ChasingNH_14-3" class="reference"><a href="#cite_note-ChasingNH-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> Hydra's name was also intentionally chosen that its initial <i>H</i> honors the Hubble Space Telescope used by the Pluto Companion Search Team to discover Hydra and Nix.<sup id="cite_ref-UniverseToday2006_22-1" class="reference"><a href="#cite_note-UniverseToday2006-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-PlutosMoons_23-0" class="reference"><a href="#cite_note-PlutosMoons-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p><p>The names of features on the bodies in the Pluto system are related to mythology and the literature and history of exploration. In particular, the names of features on Hydra must be related to legendary serpents and dragons from literature, mythology, and history.<sup id="cite_ref-nomenclature_24-0" class="reference"><a href="#cite_note-nomenclature-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Origin">Origin</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydra_(moon)&action=edit&section=3" title="Edit section: Origin"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Pluto's smaller moons, including Hydra, were thought to have formed from <a href="/wiki/Collisional_family" title="Collisional family">debris ejected from a massive collision</a> between Pluto and another Kuiper belt object, similarly to how the <a href="/wiki/Moon" title="Moon">Moon</a> is believed to have formed from debris ejected by a <a href="/wiki/Giant-impact_hypothesis" title="Giant-impact hypothesis">large collision of Earth</a>.<sup id="cite_ref-SternFormation_25-0" class="reference"><a href="#cite_note-SternFormation-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> The ejecta from the collision would then coalesce into the moons of Pluto.<sup id="cite_ref-chaos_26-0" class="reference"><a href="#cite_note-chaos-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> It was thought that Hydra had initially formed at a closer proximity to Pluto, and its orbit had undergone changes through <a href="/wiki/Tidal_interactions" class="mw-redirect" title="Tidal interactions">tidal interactions</a>.<sup id="cite_ref-arxiv1803_27-0" class="reference"><a href="#cite_note-arxiv1803-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-obliquity_28-0" class="reference"><a href="#cite_note-obliquity-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> In this case, Hydra along with the smaller moons of Pluto would have migrated outwards with Charon into their current orbits around the Pluto-Charon barycenter.<sup id="cite_ref-tidaldamping_29-0" class="reference"><a href="#cite_note-tidaldamping-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-arxiv1803_27-1" class="reference"><a href="#cite_note-arxiv1803-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> Through 'tidal damping' by mutual tidal interactions with Charon, Hydra's orbit around the Pluto-Charon barycenter gradually became more circular over time.<sup id="cite_ref-arxiv1803_27-2" class="reference"><a href="#cite_note-arxiv1803-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> Hydra is believed to have formed from two smaller objects merging into one single object.<sup id="cite_ref-Lakdawalla2015_9-1" class="reference"><a href="#cite_note-Lakdawalla2015-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-TimSharp_30-0" class="reference"><a href="#cite_note-TimSharp-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Physical_characteristics">Physical characteristics</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydra_(moon)&action=edit&section=4" title="Edit section: Physical characteristics"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="noresize thumb tright" style=";"> <div class="thumbinner" style="overflow:hidden;width:337px;"> <div class="thumbimage" style="height:244px; overflow:hidden; position:relative; background-color:white;"> <div style=";left:0px; top:0px; width:600px; position:absolute;"> <span typeof="mw:File"><a href="/wiki/File:Pure-Ice_Hydra_Charon_Spectra-composite.jpg" class="mw-file-description" title="Spectra comparison of Hydra and Charon. Hydra's spectrum closely matches that of pure water ice, which is shown for comparison."><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Pure-Ice_Hydra_Charon_Spectra-composite.jpg/600px-Pure-Ice_Hydra_Charon_Spectra-composite.jpg" decoding="async" width="600" height="246" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Pure-Ice_Hydra_Charon_Spectra-composite.jpg/900px-Pure-Ice_Hydra_Charon_Spectra-composite.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Pure-Ice_Hydra_Charon_Spectra-composite.jpg/1200px-Pure-Ice_Hydra_Charon_Spectra-composite.jpg 2x" data-file-width="2400" data-file-height="985" /></a></span></div> <div style="text-align:left; background-color:transparent; line-height:110%;"> </div> <div style="visibility:hidden"><span class="noviewer" typeof="mw:File/Frameless"><a href="/wiki/File:Pure-Ice_Hydra_Charon_Spectra-composite.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Pure-Ice_Hydra_Charon_Spectra-composite.jpg/600px-Pure-Ice_Hydra_Charon_Spectra-composite.jpg" decoding="async" width="600" height="246" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Pure-Ice_Hydra_Charon_Spectra-composite.jpg/900px-Pure-Ice_Hydra_Charon_Spectra-composite.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Pure-Ice_Hydra_Charon_Spectra-composite.jpg/1200px-Pure-Ice_Hydra_Charon_Spectra-composite.jpg 2x" data-file-width="2400" data-file-height="985" /></a></span></div> </div> <div class="thumbcaption"><div class="magnify"><a href="/wiki/File:Pure-Ice_Hydra_Charon_Spectra-composite.jpg" title="File:Pure-Ice Hydra Charon Spectra-composite.jpg"> </a></div>Spectra comparison of Hydra and Charon. Hydra's spectrum closely matches that of pure water ice, which is shown for comparison.</div> </div></div> <p>Hydra is irregular in shape, measuring 50.9 km (31.6 mi) along its longest axis and its shortest axis measuring 30.9 km (19.2 mi) across.<sup id="cite_ref-phasecurves_6-2" class="reference"><a href="#cite_note-phasecurves-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> This gives Hydra the measured dimensions of 50.9 km × 36.1 km × 30.9 km (31.6 mi × 22.4 mi × 19.2 mi).<sup id="cite_ref-phasecurves_6-3" class="reference"><a href="#cite_note-phasecurves-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>The surface of Hydra is highly reflective due to the presence of water ice on its surface.<sup id="cite_ref-IcyMoon_15-1" class="reference"><a href="#cite_note-IcyMoon-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> The surface of Hydra displays a <a href="/wiki/Color_of_water" title="Color of water">neutral spectrum</a> similarly to Pluto's small moons, although the spectrum of Hydra appears slightly bluer.<sup id="cite_ref-SimonPort2015_31-0" class="reference"><a href="#cite_note-SimonPort2015-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Codex_Regius_32-0" class="reference"><a href="#cite_note-Codex_Regius-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> The water ice on Hydra's surface is relatively pure and shows no significant darkening compared to Charon.<sup id="cite_ref-IcyMoon_15-2" class="reference"><a href="#cite_note-IcyMoon-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> One explanation suggests that Hydra's surface is continually refreshed by micrometeorite impacts ejecting darker material from the surface of Hydra.<sup id="cite_ref-IcyMoon_15-3" class="reference"><a href="#cite_note-IcyMoon-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> The surface spectrum of Hydra is slightly bluish compared to that of Nix.<sup id="cite_ref-Codex_Regius_32-1" class="reference"><a href="#cite_note-Codex_Regius-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> Explanations for Hydra's bluish color suggest that the surface of Hydra has a higher amount of water ice compared to Nix, which could also explain Hydra's very high <a href="/wiki/Geometric_albedo" title="Geometric albedo">geometric albedo</a>, or its reflectivity, of 83 percent.<sup id="cite_ref-Codex_Regius_32-2" class="reference"><a href="#cite_note-Codex_Regius-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-arxiv1604_10-1" class="reference"><a href="#cite_note-arxiv1604-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>Derived from crater counting data from <i>New Horizons</i>, the surface of Hydra is estimated to be about four billion years old.<sup id="cite_ref-arxiv1803_27-3" class="reference"><a href="#cite_note-arxiv1803-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-arxiv1604_10-2" class="reference"><a href="#cite_note-arxiv1604-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> Large craters and indentations on Hydra suggest that it may have lost some of its original mass from <a href="/wiki/Impact_event" title="Impact event">impact events</a> since its formation.<sup id="cite_ref-arxiv1604_10-3" class="reference"><a href="#cite_note-arxiv1604-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Rotation">Rotation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydra_(moon)&action=edit&section=5" title="Edit section: Rotation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Hydra is not <a href="/wiki/Tidal_locking" title="Tidal locking">tidally locked</a> and rotates <a href="/wiki/Chaos_theory" title="Chaos theory">chaotically</a>; its rotational period and axial tilt vary quickly over astronomical timescales, to the point that its rotational axis regularly flips over.<sup id="cite_ref-chaos_26-1" class="reference"><a href="#cite_note-chaos-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> Hydra's chaotic <a href="/wiki/Tumbling_(rigid_body)" class="mw-redirect" title="Tumbling (rigid body)">tumbling</a> is largely caused by the varying gravitational influences of Pluto and Charon as they orbit around their <a href="/wiki/Barycenter" class="mw-redirect" title="Barycenter">barycenter</a>.<sup id="cite_ref-chaos_26-2" class="reference"><a href="#cite_note-chaos-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> Hydra's chaotic tumbling is also strengthened by its irregular shape, which creates <a href="/wiki/Torque" title="Torque">torques</a> that act on the object.<sup id="cite_ref-ShowalterHamilton2015_5-1" class="reference"><a href="#cite_note-ShowalterHamilton2015-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> At the time of the <i>New Horizons</i> flyby of Pluto and its moons, Hydra's rotation period was approximately 10 hours and its rotational axis was tilted about 110 degrees to its orbit — it was rotating sideways at the time of the <i>New Horizons</i> flyby.<sup id="cite_ref-Lakdawalla2015_9-2" class="reference"><a href="#cite_note-Lakdawalla2015-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-arxiv1604_10-4" class="reference"><a href="#cite_note-arxiv1604-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>Hydra rotates relatively quickly compared to the rest of Pluto's moons, which all have rotation periods greater than one day.<sup id="cite_ref-Lakdawalla2015_9-3" class="reference"><a href="#cite_note-Lakdawalla2015-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> This rapid rotation of Hydra is common among the rotation periods of most <a href="/wiki/Kuiper_belt_object" class="mw-redirect" title="Kuiper belt object">Kuiper belt objects</a>.<sup id="cite_ref-Lakdawalla2015_9-4" class="reference"><a href="#cite_note-Lakdawalla2015-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Hydra's surface material could get ejected due to <a href="/wiki/Centrifugal_force" title="Centrifugal force">centrifugal forces</a> if it were rotating at a faster rate.<sup id="cite_ref-TimSharp_30-1" class="reference"><a href="#cite_note-TimSharp-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Codex_Regius_32-3" class="reference"><a href="#cite_note-Codex_Regius-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Orbit">Orbit</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydra_(moon)&action=edit&section=6" title="Edit section: Orbit"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1237032888/mw-parser-output/.tmulti">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner img{background-color:white}}</style><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:408px;max-width:408px"><div class="trow"><div class="theader">Animation of moons of Pluto around the <a href="/wiki/Barycenter" class="mw-redirect" title="Barycenter">barycenter</a> of Pluto – <a href="/wiki/Ecliptic" title="Ecliptic">Ecliptic</a> plane</div></div><div class="trow"><div class="tsingle" style="width:202px;max-width:202px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Animation_of_moons_of_Pluto_-_Front_view.gif" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/60/Animation_of_moons_of_Pluto_-_Front_view.gif/200px-Animation_of_moons_of_Pluto_-_Front_view.gif" decoding="async" width="200" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/60/Animation_of_moons_of_Pluto_-_Front_view.gif/300px-Animation_of_moons_of_Pluto_-_Front_view.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/60/Animation_of_moons_of_Pluto_-_Front_view.gif/400px-Animation_of_moons_of_Pluto_-_Front_view.gif 2x" data-file-width="560" data-file-height="420" /></a></span></div><div class="thumbcaption">Front view</div></div><div class="tsingle" style="width:202px;max-width:202px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Animation_of_moons_of_Pluto_-_Side_view.gif" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/56/Animation_of_moons_of_Pluto_-_Side_view.gif/200px-Animation_of_moons_of_Pluto_-_Side_view.gif" decoding="async" width="200" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/56/Animation_of_moons_of_Pluto_-_Side_view.gif/300px-Animation_of_moons_of_Pluto_-_Side_view.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/56/Animation_of_moons_of_Pluto_-_Side_view.gif/400px-Animation_of_moons_of_Pluto_-_Side_view.gif 2x" data-file-width="560" data-file-height="420" /></a></span></div><div class="thumbcaption">Side view</div></div></div><div class="trow" style="display:flex"><div class="thumbcaption"><style data-mw-deduplicate="TemplateStyles:r981673959">.mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{}</style><span class="legend nowrap"><span class="legend-color mw-no-invert" style="background-color:khaki; color:black;"> </span>  <a href="/wiki/Pluto" title="Pluto">Pluto</a></span> <b>·</b> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r981673959"><span class="legend nowrap"><span class="legend-color mw-no-invert" style="background-color:RoyalBlue; color:white;"> </span>  <a href="/wiki/Charon_(moon)" title="Charon (moon)">Charon</a></span> <b>·</b> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r981673959"><span class="legend nowrap"><span class="legend-color mw-no-invert" style="background-color:Lime; color:black;"> </span>  <a href="/wiki/Styx_(moon)" title="Styx (moon)">Styx</a></span> <b>·</b> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r981673959"><span class="legend nowrap"><span class="legend-color mw-no-invert" style="background-color:Magenta; color:black;"> </span>  <a href="/wiki/Nix_(moon)" title="Nix (moon)">Nix</a></span> <b>·</b> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r981673959"><span class="legend nowrap"><span class="legend-color mw-no-invert" style="background-color:Cyan; color:black;"> </span>  <a href="/wiki/Kerberos_(moon)" title="Kerberos (moon)">Kerberos</a></span> <b>·</b> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r981673959"><span class="legend nowrap"><span class="legend-color mw-no-invert" style="background-color:Orangered; color:black;"> </span>  Hydra</span></div></div></div></div> <p>Hydra orbits the Pluto-Charon barycenter at a distance of 64,738 km (40,226 mi).<sup id="cite_ref-arxiv1604_10-5" class="reference"><a href="#cite_note-arxiv1604-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> Hydra is the outermost moon of Pluto, orbiting beyond <a href="/wiki/Kerberos_(moon)" title="Kerberos (moon)">Kerberos</a>.<sup id="cite_ref-scimag000_11-2" class="reference"><a href="#cite_note-scimag000-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> Similarly to all of Pluto's moons, Hydra's orbit is nearly circular and is coplanar to Charon's orbit; all of Pluto's moons have very low <a href="/wiki/Orbital_inclination" title="Orbital inclination">orbital inclinations</a> to Pluto's equator.<sup id="cite_ref-scimag000_11-3" class="reference"><a href="#cite_note-scimag000-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p><p>The nearly circular and coplanar orbits of Pluto's moons suggest that they may have gone through tidal evolutions since their formation.<sup id="cite_ref-Steffl-etal_33-0" class="reference"><a href="#cite_note-Steffl-etal-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-obliquity_28-1" class="reference"><a href="#cite_note-obliquity-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> At the time of the formation of Pluto's smaller moons, Hydra may have had a more <a href="/wiki/Orbital_eccentricity" title="Orbital eccentricity">eccentric</a> orbit around the Pluto-Charon barycenter.<sup id="cite_ref-tidaldamping_29-1" class="reference"><a href="#cite_note-tidaldamping-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> The present circular orbit of Hydra may have been caused by Charon's tidal damping of the eccentricity of Hydra's orbit, through tidal interactions. The mutual tidal interactions of Charon on Hydra's orbit would cause Hydra to transfer its orbital eccentricity to Charon, thus causing the orbit of Hydra to gradually become more circular over time.<sup id="cite_ref-tidaldamping_29-2" class="reference"><a href="#cite_note-tidaldamping-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </p><p>Hydra has an orbital period of approximately 38.2 days and is resonant with other moons of Pluto. Hydra is in a 2:3 <a href="/wiki/Orbital_resonance" title="Orbital resonance">orbital resonance</a> with Nix, and a 6:11 resonance with <a href="/wiki/Styx_(moon)" title="Styx (moon)">Styx</a> (the ratios represent numbers of orbits completed per unit time; the period ratios are the inverses).<sup id="cite_ref-ShowalterHamilton2015_5-2" class="reference"><a href="#cite_note-ShowalterHamilton2015-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Witze2015_34-0" class="reference"><a href="#cite_note-Witze2015-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> As a result of this "Laplace-like" 3-body resonance, it has conjunctions with Styx and Nix in a 5:3 ratio.<sup id="cite_ref-Witze2015_34-1" class="reference"><a href="#cite_note-Witze2015-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p><p>Hydra's orbit is close to a 1:6 orbital resonance with Charon,<sup id="cite_ref-NYT2015_35-0" class="reference"><a href="#cite_note-NYT2015-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> with a timing discrepancy of 0.3%. A hypothesis explaining the near-resonance suggests that the resonance originated before the outward migration of Charon after the formation of all five known moons, and is maintained by the periodic local fluctuation of 5% in the Pluto–Charon gravitational field strength.<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>a<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-WardCanup2006_37-0" class="reference"><a href="#cite_note-WardCanup2006-37"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p> <div class="center"><div class="noresize thumb tnone" style=";"> <div class="thumbinner" style="overflow:hidden;width:627px;"> <div class="thumbimage" style="height:126px; overflow:hidden; position:relative; background-color:white;"> <div style=";left:0px; top:0px; width:625px; position:absolute;"> <span typeof="mw:File"><a href="/wiki/File:Hydra,_Nix,_Styx_conjunctions_cycle.png" class="mw-file-description" title="Sequence of conjunctions of Hydra (blue), Nix (red) and Styx (black) over one third of their resonance cycle. Movements are counterclockwise and orbits completed are tallied at upper right of diagrams (click on image to see the whole cycle)"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4f/Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png/625px-Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png" decoding="async" width="625" height="250" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4f/Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png/938px-Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4f/Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png/1250px-Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png 2x" data-file-width="1870" data-file-height="748" /></a></span></div> <div style="text-align:left; background-color:transparent; line-height:110%;"> </div> <div style="visibility:hidden"><span class="noviewer" typeof="mw:File/Frameless"><a href="/wiki/File:Hydra,_Nix,_Styx_conjunctions_cycle.png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4f/Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png/625px-Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png" decoding="async" width="625" height="250" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4f/Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png/938px-Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4f/Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png/1250px-Hydra%2C_Nix%2C_Styx_conjunctions_cycle.png 2x" data-file-width="1870" data-file-height="748" /></a></span></div> </div> <div class="thumbcaption"><div class="magnify"><a href="/wiki/File:Hydra,_Nix,_Styx_conjunctions_cycle.png" title="File:Hydra, Nix, Styx conjunctions cycle.png"> </a></div>Sequence of conjunctions of Hydra (blue), Nix (red) and Styx (black) over one third of their resonance cycle. Movements are counterclockwise and orbits completed are tallied at upper right of diagrams (click on image to see the whole cycle)</div> </div></div></div> <div class="mw-heading mw-heading2"><h2 id="Exploration">Exploration</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydra_(moon)&action=edit&section=7" title="Edit section: Exploration"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1237032888/mw-parser-output/.tmulti"><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:462px;max-width:462px"><div class="trow"><div class="tsingle" style="width:152px;max-width:152px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Hydra_(moon)_2015-07-13_23-16.png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/63/Hydra_%28moon%29_2015-07-13_23-16.png/150px-Hydra_%28moon%29_2015-07-13_23-16.png" decoding="async" width="150" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/63/Hydra_%28moon%29_2015-07-13_23-16.png/225px-Hydra_%28moon%29_2015-07-13_23-16.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/63/Hydra_%28moon%29_2015-07-13_23-16.png/300px-Hydra_%28moon%29_2015-07-13_23-16.png 2x" data-file-width="512" data-file-height="512" /></a></span></div><div class="thumbcaption">Hydra imaged from a distance of 640,000 km (400,000 mi)</div></div><div class="tsingle" style="width:152px;max-width:152px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Hydra_(moon)_2015-07-14_04-57.png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Hydra_%28moon%29_2015-07-14_04-57.png/150px-Hydra_%28moon%29_2015-07-14_04-57.png" decoding="async" width="150" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Hydra_%28moon%29_2015-07-14_04-57.png/225px-Hydra_%28moon%29_2015-07-14_04-57.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Hydra_%28moon%29_2015-07-14_04-57.png/300px-Hydra_%28moon%29_2015-07-14_04-57.png 2x" data-file-width="512" data-file-height="512" /></a></span></div><div class="thumbcaption">Hydra imaged from a distance of 360,000 km (220,000 mi)</div></div><div class="tsingle" style="width:152px;max-width:152px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Hydra_(moon)_2015-07-14_07-41.png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Hydra_%28moon%29_2015-07-14_07-41.png/150px-Hydra_%28moon%29_2015-07-14_07-41.png" decoding="async" width="150" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Hydra_%28moon%29_2015-07-14_07-41.png/225px-Hydra_%28moon%29_2015-07-14_07-41.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/70/Hydra_%28moon%29_2015-07-14_07-41.png/300px-Hydra_%28moon%29_2015-07-14_07-41.png 2x" data-file-width="512" data-file-height="512" /></a></span></div><div class="thumbcaption">Hydra imaged from a distance of 230,000 km (140,000 mi)</div></div></div></div></div> <p>The <i><a href="/wiki/New_Horizons" title="New Horizons">New Horizons</a></i> spacecraft visited the Pluto system and imaged Pluto and its moons during its flyby on 14 July 2015. At the time of the <i>New Horizons</i> flyby, Hydra was behind Pluto and was further away from <i>New Horizons</i> at closest approach.<sup id="cite_ref-SimonPort2015_31-1" class="reference"><a href="#cite_note-SimonPort2015-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> The larger distance of Hydra from <i>New Horizons</i> resulted in lower resolution images of Hydra.<sup id="cite_ref-SimonPort2015_31-2" class="reference"><a href="#cite_note-SimonPort2015-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> Before the flyby, the <a href="/wiki/Long_Range_Reconnaissance_Imager" title="Long Range Reconnaissance Imager">Long Range Reconnaissance Imager</a> on board <i>New Horizons</i> performed measurements of Hydra's size, estimating Hydra to be about 45 km (28 mi) in diameter.<sup id="cite_ref-Measurement_38-0" class="reference"><a href="#cite_note-Measurement-38"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> Hydra's surface composition, reflectivity, and other basic physical properties were later measured by <i>New Horizons</i> during the flyby.<sup id="cite_ref-Measurement_38-1" class="reference"><a href="#cite_note-Measurement-38"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> </p><p>The first detailed image of Hydra was <a href="/wiki/Downlink" class="mw-redirect" title="Downlink">downlinked</a>, or received from the <i>New Horizons</i> spacecraft on 15 July 2015 after the flyby.<sup id="cite_ref-HydraEmerges_16-1" class="reference"><a href="#cite_note-HydraEmerges-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> The first detailed image of Hydra, taken from a distance of 640,000 km (400,000 mi), appeared to show brightness variations and a dark circular feature 10 km (6.2 mi) across.<sup id="cite_ref-HydraEmerges_16-2" class="reference"><a href="#cite_note-HydraEmerges-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> The highest resolution images of Hydra were taken from a distance of 231,000 km (144,000 mi), with an image resolution of 1.2 km (0.75 mi) per pixel.<sup id="cite_ref-CapturesTwo_17-1" class="reference"><a href="#cite_note-CapturesTwo-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> Derived from those images, Hydra was given the approximate size estimate of 55 km × 40 km (34 mi × 25 mi).<sup id="cite_ref-CapturesTwo_17-2" class="reference"><a href="#cite_note-CapturesTwo-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;" class=""></div> <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=Hydra_(moon)&action=edit&section=8" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/List_of_natural_satellites" title="List of natural satellites">List of natural satellites</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hydra_(moon)&action=edit&section=9" title="Edit section: Notes"><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 reflist-lower-alpha"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-36"><span class="mw-cite-backlink"><b><a href="#cite_ref-36">^</a></b></span> <span class="reference-text">The instantaneous force at Hydra's distance in the Pluto–Charon–Hydra alignment case is 4.62% larger than in the quadrature case (where Hydra is 90° from the Pluto–Charon axis); the Charon–Pluto–Hydra case is almost exactly halfway between those values. In Buie <i>et al.</i>, the quote is "The gravitational force exerted by Pluto on either P1 or P2 varies by roughly 15% (peak-to-peak)." Pluto's gravitational pull, <i>by itself</i>, varies by 18% for Nix and 13% for Hydra.</span> </li> </ol></div></div> <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=Hydra_(moon)&action=edit&section=10" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist reflist-columns references-column-width" style="column-width: 30em;"> <ol class="references"> <li id="cite_note-Nomenclature-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-Nomenclature_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Nomenclature_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Nomenclature_1-2"><sup><i><b>c</b></i></sup></a></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 web cs1"><a rel="nofollow" class="external text" href="https://planetarynames.wr.usgs.gov/Page/Planets">"Planet and Satellite Names and Discoverers"</a>. <i>Gazetteer of Planetary Nomenclature</i>. 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"Resonant interactions and chaotic rotation of Pluto's small moons". <i>Nature</i>. <b>522</b> (7554): 45–49. <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/2015Natur.522...45S">2015Natur.522...45S</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%2Fnature14469">10.1038/nature14469</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/26040889">26040889</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:205243819">205243819</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=Resonant+interactions+and+chaotic+rotation+of+Pluto%27s+small+moons&rft.volume=522&rft.issue=7554&rft.pages=45-49&rft.date=2015-06-03&rft_id=info%3Adoi%2F10.1038%2Fnature14469&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A205243819%23id-name%3DS2CID&rft_id=info%3Apmid%2F26040889&rft_id=info%3Abibcode%2F2015Natur.522...45S&rft.aulast=Showalter&rft.aufirst=M.+R.&rft.au=Hamilton%2C+D.+P.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHydra+%28moon%29" class="Z3988"></span></span> </li> <li id="cite_note-phasecurves-6"><span class="mw-cite-backlink">^ <a href="#cite_ref-phasecurves_6-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-phasecurves_6-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-phasecurves_6-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-phasecurves_6-3"><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 id="CITEREFVerbiscerPorterBurattiWeaver2018" class="citation journal cs1">Verbiscer, A. 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NASA<span class="reference-accessdate">. Retrieved <span class="nowrap">7 March</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=solarsystem.nasa.gov&rft.atitle=Hydra+By+the+Numbers&rft_id=https%3A%2F%2Fsolarsystem.nasa.gov%2Fmoons%2Fpluto-moons%2Fhydra%2Fby-the-numbers%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHydra+%28moon%29" class="Z3988"></span><br />(Original value of <span class="nowrap"><span data-sort-value="6998509999999999999♠"></span>0.051 m/s<sup>2</sup></span> converted to g)</span> </li> <li id="cite_note-Lakdawalla2015-9"><span class="mw-cite-backlink">^ <a href="#cite_ref-Lakdawalla2015_9-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Lakdawalla2015_9-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Lakdawalla2015_9-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Lakdawalla2015_9-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Lakdawalla2015_9-4"><sup><i><b>e</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="http://www.planetary.org/blogs/emily-lakdawalla/2015/dps15-1110-small-moons.html">"DPS 2015: Pluto's small moons Styx, Nix, Kerberos, and Hydra [UPDATED]"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=DPS+2015%3A+Pluto%27s+small+moons+Styx%2C+Nix%2C+Kerberos%2C+and+Hydra+%5BUPDATED%5D&rft_id=http%3A%2F%2Fwww.planetary.org%2Fblogs%2Femily-lakdawalla%2F2015%2Fdps15-1110-small-moons.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHydra+%28moon%29" class="Z3988"></span></span> </li> <li id="cite_note-arxiv1604-10"><span class="mw-cite-backlink">^ <a href="#cite_ref-arxiv1604_10-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-arxiv1604_10-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-arxiv1604_10-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-arxiv1604_10-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-arxiv1604_10-4"><sup><i><b>e</b></i></sup></a> <a href="#cite_ref-arxiv1604_10-5"><sup><i><b>f</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWeaverBuieShowalterStern2016" class="citation journal cs1">Weaver, H. 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A.; Bagenal, F.; Ennico, K.; Gladstone, G. R.; et al. (15 October 2015). "The Pluto system: Initial results from its exploration by New Horizons". <i>Science</i>. <b>350</b> (6258): aad1815. <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/1510.07704">1510.07704</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/2015Sci...350.1815S">2015Sci...350.1815S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.aad1815">10.1126/science.aad1815</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/26472913">26472913</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:1220226">1220226</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=The+Pluto+system%3A+Initial+results+from+its+exploration+by+New+Horizons&rft.volume=350&rft.issue=6258&rft.pages=aad1815&rft.date=2015-10-15&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A1220226%23id-name%3DS2CID&rft_id=info%3Abibcode%2F2015Sci...350.1815S&rft_id=info%3Aarxiv%2F1510.07704&rft_id=info%3Apmid%2F26472913&rft_id=info%3Adoi%2F10.1126%2Fscience.aad1815&rft.aulast=Stern&rft.aufirst=S.+A.&rft.au=Bagenal%2C+F.&rft.au=Ennico%2C+K.&rft.au=Gladstone%2C+G.+R.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHydra+%28moon%29" class="Z3988"></span></span> </li> <li id="cite_note-Cook2018-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-Cook2018_12-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCookDalle_OreProtopapaBinzel2018" class="citation journal cs1">Cook, Jason C.; <a href="/wiki/Cristina_Dalle_Ore" title="Cristina Dalle Ore">Dalle Ore, Cristina M.</a>; Protopapa, Silvia; Binzel, Richard P.; Cartwright, Richard; Cruikshank, Dale P.; et al. 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"Composition of Pluto's small satellites: Analysis of <i>New Horizons</i> spectral images". <i>Icarus</i>. <b>315</b> (1964): 30–45. <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/2017LPI....48.2478C">2017LPI....48.2478C</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.icarus.2018.05.024">10.1016/j.icarus.2018.05.024</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:125374498">125374498</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Icarus&rft.atitle=Composition+of+Pluto%27s+small+satellites%3A+Analysis+of+New+Horizons+spectral+images&rft.volume=315&rft.issue=1964&rft.pages=30-45&rft.date=2018-11-15&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A125374498%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1016%2Fj.icarus.2018.05.024&rft_id=info%3Abibcode%2F2017LPI....48.2478C&rft.aulast=Cook&rft.aufirst=Jason+C.&rft.au=Dalle+Ore%2C+Cristina+M.&rft.au=Protopapa%2C+Silvia&rft.au=Binzel%2C+Richard+P.&rft.au=Cartwright%2C+Richard&rft.au=Cruikshank%2C+Dale+P.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHydra+%28moon%29" class="Z3988"></span></span> </li> <li id="cite_note-Stern06b-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-Stern06b_13-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFStern,_S._A.Mutchler,_M._J.Weaver,_H._A.Steffl,_A._J.2006" class="citation journal cs1">Stern, S. A.; Mutchler, M. J.; Weaver, H. A.; Steffl, A. J. (2006). 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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:Pluto" title="Template:Pluto"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Pluto" title="Template talk:Pluto"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Pluto" title="Special:EditPage/Template:Pluto"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Pluto" style="font-size:114%;margin:0 4em"><a href="/wiki/Pluto" title="Pluto">Pluto</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="3"><div> <ul><li><a href="/wiki/Atmosphere_of_Pluto" title="Atmosphere of Pluto">Atmosphere</a></li> <li><a href="/wiki/Climate_of_Pluto" title="Climate of Pluto">Climate</a></li> <li><a href="/wiki/Geology_of_Pluto" title="Geology of Pluto">Geology</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Geography_of_Pluto" title="Geography of Pluto">Geography</a><br />(<a href="/wiki/List_of_geological_features_on_Pluto" title="List of geological features on Pluto">features</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:1%;text-align: right;">Regions</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/Geography_of_Pluto#The_Brass_Knuckles" title="Geography of Pluto">Brass Knuckles</a>" <ul><li><a href="/wiki/Safronov_Regio" title="Safronov Regio">Safronov</a></li> <li><a href="/wiki/Sharaf_Regio" title="Sharaf Regio">Sharaf</a></li> <li><a href="/wiki/Harrington_Regio" title="Harrington Regio">Harrington</a></li> <li><a href="/wiki/Vucub-Came_Macula" title="Vucub-Came Macula">Vucub-Came</a></li> <li><a href="/wiki/Hun-Came_Macula" title="Hun-Came Macula">Hun-Came</a></li> <li><a href="/wiki/Meng-p%CA%BBo_Macula" class="mw-redirect" title="Meng-pʻo Macula">Meng-pʻo</a></li></ul></li> <li><a href="/wiki/Belton_Regio" title="Belton Regio">Belton</a></li> <li><a href="/wiki/Cadejo_Macula" title="Cadejo Macula">Cadejo</a></li> <li><a href="/wiki/Hayabusa_Terra" title="Hayabusa Terra">Hayabusa</a></li> <li><a href="/wiki/Lowell_Regio" title="Lowell Regio">Lowell</a></li> <li><a href="/wiki/Morgoth_Macula" title="Morgoth Macula">Morgoth</a></li> <li><a href="/wiki/Pioneer_Terra" class="mw-redirect" title="Pioneer Terra">Pioneer</a></li> <li><a href="/wiki/Tombaugh_Regio" title="Tombaugh Regio">Tombaugh "The Heart"</a></li> <li><a href="/wiki/Venera_Terra" class="mw-redirect" title="Venera Terra">Venera</a></li> <li><a href="/wiki/Viking_Terra" class="mw-redirect" title="Viking Terra">Viking</a></li> <li><a href="/wiki/Voyager_Terra" title="Voyager Terra">Voyager</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: right;">Hills and<br /> mountains</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/Baret_Montes" title="Baret Montes">Baret Montes</a></li> <li><a href="/wiki/Challenger_Colles" title="Challenger Colles">Challenger Colles</a></li> <li><a href="/wiki/Coleta_de_Dados_Colles" title="Coleta de Dados Colles">Coleta de Dados Colles</a></li> <li><a href="/wiki/Hillary_Montes" title="Hillary Montes">Hillary Montes</a></li> <li><a href="/wiki/Piccard_Mons" title="Piccard Mons">Piccard Mons</a></li> <li><a href="/wiki/Tenzing_Montes" title="Tenzing Montes">Tenzing Montes</a></li> <li><a href="/wiki/Wright_Mons" title="Wright Mons">Wright Mons</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: right;">Plains</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/Sputnik_Planitia" title="Sputnik Planitia">Sputnik Planitia</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: right;">Valleys and<br />depressions</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/Adlivun_Cavus" title="Adlivun Cavus">Adlivun Cavus</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: right;">Lineae</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/Luna_Linea" title="Luna Linea">Luna Linea</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: right;">Craters</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/Burney_(crater)" title="Burney (crater)">Burney</a></li></ul> </div></td></tr></tbody></table><div></div></td><td class="noviewer navbox-image" rowspan="5" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"><a href="/wiki/File:Pluto_in_True_Color_-_High-Res.jpg" class="mw-file-description" title="Pluto"><img alt="Pluto" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Pluto_in_True_Color_-_High-Res.jpg/90px-Pluto_in_True_Color_-_High-Res.jpg" decoding="async" width="90" height="90" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Pluto_in_True_Color_-_High-Res.jpg/135px-Pluto_in_True_Color_-_High-Res.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Pluto_in_True_Color_-_High-Res.jpg/180px-Pluto_in_True_Color_-_High-Res.jpg 2x" data-file-width="8000" data-file-height="8000" /></a></span><br /><span typeof="mw:File"><a href="/wiki/File:NH-PlutoCharon-Color-NewHorizons-20150711.jpg" class="mw-file-description" title="Both to scale"><img alt="Both to scale" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/58/NH-PlutoCharon-Color-NewHorizons-20150711.jpg/90px-NH-PlutoCharon-Color-NewHorizons-20150711.jpg" decoding="async" width="90" height="47" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/58/NH-PlutoCharon-Color-NewHorizons-20150711.jpg/135px-NH-PlutoCharon-Color-NewHorizons-20150711.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/58/NH-PlutoCharon-Color-NewHorizons-20150711.jpg/180px-NH-PlutoCharon-Color-NewHorizons-20150711.jpg 2x" data-file-width="1422" data-file-height="744" /></a></span><br /><span typeof="mw:File"><a href="/wiki/File:Charon_in_True_Color_-_High-Res.jpg" class="mw-file-description" title="Charon"><img alt="Charon" src="//upload.wikimedia.org/wikipedia/commons/thumb/2/2e/Charon_in_True_Color_-_High-Res.jpg/90px-Charon_in_True_Color_-_High-Res.jpg" decoding="async" width="90" height="90" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/2e/Charon_in_True_Color_-_High-Res.jpg/135px-Charon_in_True_Color_-_High-Res.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/2e/Charon_in_True_Color_-_High-Res.jpg/180px-Charon_in_True_Color_-_High-Res.jpg 2x" data-file-width="2000" data-file-height="2000" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Moons_of_Pluto" title="Moons of Pluto">Moons</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><b><a href="/wiki/Charon_(moon)" title="Charon (moon)">Charon</a></b></li> <li><a class="mw-selflink selflink">Hydra</a></li> <li><a href="/wiki/Kerberos_(moon)" title="Kerberos (moon)">Kerberos</a></li> <li><a href="/wiki/Nix_(moon)" title="Nix (moon)">Nix</a></li> <li><a href="/wiki/Styx_(moon)" title="Styx (moon)">Styx</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Exploration_of_Pluto" title="Exploration of Pluto">Exploration</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><i><a href="/wiki/New_Horizons" title="New Horizons">New Horizons</a></i></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Astronomy</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:1%;text-align: right;">Official definitions</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/Definition_of_planet" title="Definition of planet">Definition of planet</a></li> <li><a href="/wiki/IAU_definition_of_planet" title="IAU definition of planet">IAU definition of planet</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: right;">Scientist opinions</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/Alan_Stern#Planetary_classification" title="Alan Stern">Alan Stern</a></li> <li><a href="/wiki/Michael_E._Brown#Other_work" title="Michael E. Brown">Michael E. Brown</a></li> <li><a href="/wiki/Neil_deGrasse_Tyson#Pluto" title="Neil deGrasse Tyson">Neil deGrasse Tyson</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: right;">Discovery</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/Planets_beyond_Neptune#Discovery_of_Pluto" title="Planets beyond Neptune">Planet X</a></li> <li><a href="/wiki/Lowell_Observatory" title="Lowell Observatory">Lowell Observatory</a> <ul><li><a href="/wiki/Percival_Lowell#Pluto" title="Percival Lowell">Percival Lowell</a></li> <li><a href="/wiki/Clyde_Tombaugh#Pluto" title="Clyde Tombaugh">Clyde Tombaugh</a></li> <li><a href="/wiki/Roger_Putnam#Role_in_discovering_Pluto" title="Roger Putnam">Roger Putnam</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: right;">General</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/Double_planet" title="Double planet">Double planet</a></li> <li><a href="/wiki/Dwarf_planet" title="Dwarf planet">Dwarf planet</a></li> <li><a href="/wiki/Planet" title="Planet">Planet</a></li> <li><a href="/wiki/Plutino" title="Plutino">Plutino</a></li> <li><a href="/wiki/Trans-Neptunian_object" title="Trans-Neptunian object">Trans-Neptunian object</a></li> <li><a href="/wiki/Kuiper_belt" title="Kuiper belt">Kuiper belt</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</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/Pluto_in_fiction" title="Pluto in fiction">Fiction</a></li> <li><a href="/wiki/Pluto_(mythology)" title="Pluto (mythology)">Mythology</a></li> <li><a href="/wiki/Venetia_Burney" title="Venetia Burney">Venetia Burney</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Moons_of_likely_dwarf_planets" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2" style="text-align: center;"><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:Moons_of_dwarf_planets" title="Template:Moons of dwarf planets"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Moons_of_dwarf_planets" title="Template talk:Moons of dwarf planets"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Moons_of_dwarf_planets" title="Special:EditPage/Template:Moons of dwarf planets"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Moons_of_likely_dwarf_planets" style="font-size:114%;margin:0 4em"><a href="/wiki/Natural_satellite" title="Natural satellite">Moons</a> of <a href="/wiki/List_of_possible_dwarf_planets" title="List of possible dwarf planets">likely dwarf planets</a></div></th></tr><tr><td colspan="2" class="navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><td colspan="2" class="navbox-list navbox-odd" style="width:100%;padding:0;background:transparent;color:inherit;"><div style="padding:0px"><table class="navbox-columns-table" style="border-spacing: 0px; text-align:left;width:100%;"><tbody><tr><td class="navbox-abovebelow" style="font-weight:bold;"><a href="/wiki/Moons_of_Pluto" title="Moons of Pluto">Pluto</a></td><td class="navbox-abovebelow" style="border-left:2px solid #fdfdfd;font-weight:bold;"><a href="/wiki/Moons_of_Haumea" title="Moons of Haumea">Haumea</a></td><td class="navbox-abovebelow" style="border-left:2px solid #fdfdfd;font-weight:bold;"><a href="/wiki/Eris_(dwarf_planet)" title="Eris (dwarf planet)">Eris</a></td><td class="navbox-abovebelow" style="border-left:2px solid #fdfdfd;font-weight:bold;"><a href="/wiki/Makemake" title="Makemake">Makemake</a></td><td class="navbox-abovebelow" style="border-left:2px solid #fdfdfd;font-weight:bold;"><a href="/wiki/225088_Gonggong" class="mw-redirect" title="225088 Gonggong">Gonggong</a></td></tr><tr style="vertical-align:top"><td class="navbox-list" style="padding:0px;text-align: center;width:20%;"><div> <ul><li><a href="/wiki/Charon_(moon)" title="Charon (moon)">Charon</a></li> <li><a href="/wiki/Styx_(moon)" title="Styx (moon)">Styx</a></li> <li><a href="/wiki/Nix_(moon)" title="Nix (moon)">Nix</a></li> <li><a href="/wiki/Kerberos_(moon)" title="Kerberos (moon)">Kerberos</a></li> <li><a class="mw-selflink selflink">Hydra</a></li></ul> </div></td><td class="navbox-list" style="border-left:2px solid #fdfdfd;padding:0px;text-align: center;width:20%;"><div> <ul><li><a href="/wiki/Rings_of_Haumea" class="mw-redirect" title="Rings of Haumea">ring</a></li> <li><a href="/wiki/Namaka_(moon)" title="Namaka (moon)">Namaka</a></li> <li><a href="/wiki/Hi%CA%BBiaka_(moon)" title="Hiʻiaka (moon)">Hiʻiaka</a></li></ul> </div></td><td class="navbox-list" style="border-left:2px solid #fdfdfd;padding:0px;text-align: center;width:20%;"><div> <ul><li><a href="/wiki/Dysnomia_(moon)" title="Dysnomia (moon)">Dysnomia</a></li></ul> </div></td><td class="navbox-list" style="border-left:2px solid #fdfdfd;padding:0px;text-align: center;width:20%;"><div> <ul><li><a href="/wiki/S/2015_(136472)_1" title="S/2015 (136472) 1">S/2015 (136472) 1</a></li></ul> </div></td><td class="navbox-list" style="border-left:2px solid #fdfdfd;padding:0px;text-align: center;width:20%;"><div> <ul><li><a href="/wiki/Xiangliu_(moon)" title="Xiangliu (moon)">Xiangliu</a></li></ul> </div></td></tr></tbody></table></div></td></tr></tbody></table><div></div></td></tr><tr><td colspan="2" class="navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><td colspan="2" class="navbox-list navbox-even" style="width:100%;padding:0;background:transparent;color:inherit;"><div style="padding:0px"><table class="navbox-columns-table" style="border-spacing: 0px; text-align:left;width:100%;"><tbody><tr><td class="navbox-abovebelow" style="font-weight:bold;"><a href="/wiki/50000_Quaoar" class="mw-redirect" title="50000 Quaoar">Quaoar</a></td><td class="navbox-abovebelow" style="border-left:2px solid #fdfdfd;font-weight:bold;"><a href="/wiki/90482_Orcus" class="mw-redirect" title="90482 Orcus">Orcus</a></td><td class="navbox-abovebelow" style="border-left:2px solid #fdfdfd;font-weight:bold;"><a href="/wiki/120347_Salacia" title="120347 Salacia">Salacia</a></td><td class="navbox-abovebelow" style="border-left:2px solid #fdfdfd;font-weight:bold;"><a href="/wiki/174567_Varda" title="174567 Varda">Varda</a></td><td class="navbox-abovebelow" style="border-left:2px solid #fdfdfd;font-weight:bold;"><span class="nowrap"><a href="/wiki/2013_FY27" class="mw-redirect" title="2013 FY27">2013 FY<span style="position: relative; top: 0.3em;"><span style="font-size:80%;">27</span></span></a></span></td></tr><tr style="vertical-align:top"><td class="navbox-list" style="padding:0px;text-align: center;width:20%;"><div> <ul><li><a href="/wiki/50000_Quaoar#Rings" class="mw-redirect" title="50000 Quaoar">rings</a></li> <li><a href="/wiki/Weywot" title="Weywot">Weywot</a></li></ul> </div></td><td class="navbox-list" style="border-left:2px solid #fdfdfd;padding:0px;text-align: center;width:20%;"><div> <ul><li><a href="/wiki/Vanth_(moon)" title="Vanth (moon)">Vanth</a></li></ul> </div></td><td class="navbox-list" style="border-left:2px solid #fdfdfd;padding:0px;text-align: center;width:20%;"><div> <ul><li><a href="/wiki/Actaea_(moon)" title="Actaea (moon)">Actaea</a></li></ul> </div></td><td class="navbox-list" style="border-left:2px solid #fdfdfd;padding:0px;text-align: center;width:20%;"><div> <ul><li><a href="/wiki/Ilmar%C3%AB" title="Ilmarë">Ilmarë</a></li></ul> </div></td><td class="navbox-list" style="border-left:2px solid #fdfdfd;padding:0px;text-align: center;width:20%;"><div> <ul><li><a href="/wiki/S/2018_(532037)_1" class="mw-redirect" title="S/2018 (532037) 1"><span class="nowrap">2013 FY<sub>27</sub></span> I</a></li></ul> </div></td></tr></tbody></table></div></td></tr></tbody></table><div></div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Trans-Neptunian_objects" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse 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:Trans-Neptunian_objects_navbox" title="Template:Trans-Neptunian objects navbox"><abbr title="View this template">v</abbr></a></li><li 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disc">Scattered-disc objects</a></li> <li><a href="/wiki/Detached_object" title="Detached object">Detached objects</a></li> <li><a href="/wiki/Resonant_trans-Neptunian_object" title="Resonant trans-Neptunian object">Resonant objects</a> <ul><li><a href="/wiki/Neptune_trojan" title="Neptune trojan">Neptune trojans</a></li> <li><a href="/wiki/Plutino" title="Plutino">Plutinos</a></li> <li><a href="/wiki/Resonant_trans-Neptunian_object#1:2_resonance_("twotinos",_period_~330_years)" title="Resonant trans-Neptunian object">Twotinos</a></li></ul></li> <li><a href="/wiki/Minor-planet_moon#Trans-Neptunian_objects" title="Minor-planet moon">TNO moons</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;white-space: normal; text-align:center;"><a href="/wiki/Dwarf_planet" title="Dwarf planet">Dwarf planets</a> <span class="nowrap">(moons)</span></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Orcus_(dwarf_planet)" title="Orcus (dwarf planet)">Orcus</a> <ul><li><a href="/wiki/Vanth_(moon)" title="Vanth (moon)">Vanth</a></li></ul></li> <li><a href="/wiki/Pluto" title="Pluto">Pluto</a> <ul><li><a href="/wiki/Charon_(moon)" title="Charon (moon)">Charon</a></li> <li><a href="/wiki/Styx_(moon)" title="Styx (moon)">Styx</a></li> <li><a href="/wiki/Nix_(moon)" title="Nix (moon)">Nix</a></li> <li><a href="/wiki/Kerberos_(moon)" title="Kerberos (moon)">Kerberos</a></li> <li><a class="mw-selflink selflink">Hydra</a></li></ul></li> <li><a href="/wiki/Haumea" title="Haumea">Haumea</a> <ul><li><a href="/wiki/Namaka_(moon)" title="Namaka (moon)">Namaka</a></li> <li><a href="/wiki/Hi%CA%BBiaka_(moon)" title="Hiʻiaka (moon)">Hiʻiaka</a></li> <li><a href="/wiki/Haumea#Ring" title="Haumea">Ring</a></li></ul></li> <li><a href="/wiki/Quaoar" title="Quaoar">Quaoar</a> <ul><li><a href="/wiki/Weywot_(moon)" class="mw-redirect" title="Weywot (moon)">Weywot</a></li> <li><a href="/wiki/50000_Quaoar#Rings" class="mw-redirect" title="50000 Quaoar">Rings</a></li></ul></li> <li><a href="/wiki/Makemake" title="Makemake">Makemake</a> <ul><li><a href="/wiki/S/2015_(136472)_1" title="S/2015 (136472) 1">MK2</a></li></ul></li> <li><a href="/wiki/Gonggong_(dwarf_planet)" title="Gonggong (dwarf planet)">Gonggong</a> <ul><li><a href="/wiki/Xiangliu_(moon)" title="Xiangliu (moon)">Xiangliu</a></li></ul></li> <li><a href="/wiki/Eris_(dwarf_planet)" title="Eris (dwarf planet)">Eris</a> <ul><li><a href="/wiki/Dysnomia_(moon)" title="Dysnomia (moon)">Dysnomia</a></li></ul></li> <li><a href="/wiki/Sedna_(dwarf_planet)" title="Sedna (dwarf planet)">Sedna</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;white-space: normal; text-align:center;"><a href="/wiki/Sednoid" title="Sednoid">Sednoids</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/90377_Sedna" class="mw-redirect" title="90377 Sedna">90377 Sedna</a></li> <li><span class="nowrap"><a href="/wiki/2012_VP113" title="2012 VP113">2012 VP<span style="position: relative; top: 0.3em;"><span style="font-size:80%;">113</span></span></a></span></li> <li><a href="/wiki/541132_Lele%C4%81k%C5%ABhonua" title="541132 Leleākūhonua">541132 Leleākūhonua</a></li></ul> </div></td></tr></tbody></table></div> <style data-mw-deduplicate="TemplateStyles:r1130092004">.mw-parser-output .portal-bar{font-size:88%;font-weight:bold;display:flex;justify-content:center;align-items:baseline}.mw-parser-output .portal-bar-bordered{padding:0 2em;background-color:#fdfdfd;border:1px solid #a2a9b1;clear:both;margin:1em auto 0}.mw-parser-output .portal-bar-related{font-size:100%;justify-content:flex-start}.mw-parser-output .portal-bar-unbordered{padding:0 1.7em;margin-left:0}.mw-parser-output .portal-bar-header{margin:0 1em 0 0.5em;flex:0 0 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