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subsection</span> </button> <ul id="toc-History_and_derivation-sublist" class="vector-toc-list"> <li id="toc-Calculating_the_value_of_a_parsec" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Calculating_the_value_of_a_parsec"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>Calculating the value of a parsec</span> </div> </a> <ul id="toc-Calculating_the_value_of_a_parsec-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Usage_and_measurement" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Usage_and_measurement"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Usage and measurement</span> </div> </a> <ul id="toc-Usage_and_measurement-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Distances_in_parsecs" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Distances_in_parsecs"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Distances in parsecs</span> </div> </a> <button aria-controls="toc-Distances_in_parsecs-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Distances in parsecs subsection</span> </button> <ul id="toc-Distances_in_parsecs-sublist" class="vector-toc-list"> <li id="toc-Distances_less_than_a_parsec" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Distances_less_than_a_parsec"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Distances less than a parsec</span> </div> </a> <ul id="toc-Distances_less_than_a_parsec-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Parsecs_and_kiloparsecs" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Parsecs_and_kiloparsecs"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Parsecs and kiloparsecs</span> </div> </a> <ul id="toc-Parsecs_and_kiloparsecs-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Megaparsecs_and_gigaparsecs" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Megaparsecs_and_gigaparsecs"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Megaparsecs and gigaparsecs</span> </div> </a> <ul id="toc-Megaparsecs_and_gigaparsecs-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Volume_units" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Volume_units"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Volume units</span> </div> </a> <ul id="toc-Volume_units-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">5</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">6</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">7</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <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">Parsec</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 87 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-87" 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">87 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/Parsek" title="Parsek – Afrikaans" lang="af" hreflang="af" data-title="Parsek" 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%81%D8%B1%D8%B3%D8%AE_%D9%81%D9%84%D9%83%D9%8A" title="فرسخ فلكي – Arabic" lang="ar" hreflang="ar" data-title="فرسخ فلكي" 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/P%C3%A1rsec" title="Pársec – Aragonese" lang="an" hreflang="an" data-title="Pársec" data-language-autonym="Aragonés" data-language-local-name="Aragonese" class="interlanguage-link-target"><span>Aragonés</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/P%C3%A1rsec" title="Pársec – Asturian" lang="ast" hreflang="ast" data-title="Pársec" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Parsek" title="Parsek – Azerbaijani" lang="az" hreflang="az" data-title="Parsek" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AA%E0%A6%BE%E0%A6%B0%E0%A6%B8%E0%A7%87%E0%A6%95" title="পারসেক – Bangla" lang="bn" hreflang="bn" data-title="পারসেক" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Belarusian" lang="be" hreflang="be" data-title="Парсек" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/%D0%9F%D0%B0%D1%80%D1%81%D1%8D%D0%BA" title="Парсэк – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="Парсэк" 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%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Bulgarian" lang="bg" hreflang="bg" data-title="Парсек" 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/Parsek" title="Parsek – Bosnian" lang="bs" hreflang="bs" data-title="Parsek" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Parsec" title="Parsec – Catalan" lang="ca" hreflang="ca" data-title="Parsec" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cv mw-list-item"><a href="https://cv.wikipedia.org/wiki/%D0%9F%D0%B0%D1%80%C3%A7%D0%B5%D0%BA" title="Парçек – Chuvash" lang="cv" hreflang="cv" data-title="Парçек" data-language-autonym="Чӑвашла" data-language-local-name="Chuvash" class="interlanguage-link-target"><span>Чӑвашла</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Parsek" title="Parsek – Czech" lang="cs" hreflang="cs" data-title="Parsek" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Parsec" title="Parsec – Danish" lang="da" hreflang="da" data-title="Parsec" 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/Parsec" title="Parsec – German" lang="de" hreflang="de" data-title="Parsec" 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/Parsek" title="Parsek – Estonian" lang="et" hreflang="et" data-title="Parsek" 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%A0%CE%B1%CF%81%CF%83%CE%AD%CE%BA" title="Παρσέκ – Greek" lang="el" hreflang="el" data-title="Παρσέκ" 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/P%C3%A1rsec" title="Pársec – Spanish" lang="es" hreflang="es" data-title="Pársec" 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/Parseko" title="Parseko – Esperanto" lang="eo" hreflang="eo" data-title="Parseko" 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/Parsec" title="Parsec – Basque" lang="eu" hreflang="eu" data-title="Parsec" 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%BE%D8%A7%D8%B1%D8%B3%DA%A9" title="پارسک – Persian" lang="fa" hreflang="fa" data-title="پارسک" 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/Parsec" title="Parsec – French" lang="fr" hreflang="fr" data-title="Parsec" 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/Parsoic" title="Parsoic – Irish" lang="ga" hreflang="ga" data-title="Parsoic" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Parsec" title="Parsec – Galician" lang="gl" hreflang="gl" data-title="Parsec" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-gu mw-list-item"><a href="https://gu.wikipedia.org/wiki/%E0%AA%AA%E0%AA%BE%E0%AA%B0%E0%AA%B8%E0%AB%87%E0%AA%95" title="પારસેક – Gujarati" lang="gu" hreflang="gu" data-title="પારસેક" data-language-autonym="ગુજરાતી" data-language-local-name="Gujarati" class="interlanguage-link-target"><span>ગુજરાતી</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%ED%8C%8C%EC%84%B9" title="파섹 – Korean" lang="ko" hreflang="ko" data-title="파섹" 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%8A%D5%A1%D6%80%D5%BD%D5%A5%D5%AF" title="Պարսեկ – Armenian" lang="hy" hreflang="hy" data-title="Պարսեկ" 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%AA%E0%A4%BE%E0%A4%B0%E0%A4%B8%E0%A5%88%E0%A4%95" title="पारसैक – Hindi" lang="hi" hreflang="hi" data-title="पारसैक" 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/Parsek" title="Parsek – Croatian" lang="hr" hreflang="hr" data-title="Parsek" 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/Parseko" title="Parseko – Ido" lang="io" hreflang="io" data-title="Parseko" data-language-autonym="Ido" data-language-local-name="Ido" class="interlanguage-link-target"><span>Ido</span></a></li><li class="interlanguage-link interwiki-ig mw-list-item"><a href="https://ig.wikipedia.org/wiki/Parsec" title="Parsec – Igbo" lang="ig" hreflang="ig" data-title="Parsec" data-language-autonym="Igbo" data-language-local-name="Igbo" class="interlanguage-link-target"><span>Igbo</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Parsek" title="Parsek – Indonesian" lang="id" hreflang="id" data-title="Parsek" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-is mw-list-item"><a href="https://is.wikipedia.org/wiki/Parsek" title="Parsek – Icelandic" lang="is" hreflang="is" data-title="Parsek" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target"><span>Íslenska</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Parsec" title="Parsec – Italian" lang="it" hreflang="it" data-title="Parsec" 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%A4%D7%90%D7%A8%D7%A1%D7%A7" title="פארסק – Hebrew" lang="he" hreflang="he" data-title="פארסק" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-kn mw-list-item"><a href="https://kn.wikipedia.org/wiki/%E0%B2%AA%E0%B2%BE%E0%B2%B0%E0%B3%8D%E0%B2%B8%E0%B3%86%E0%B2%95%E0%B3%8D" title="ಪಾರ್ಸೆಕ್ – Kannada" lang="kn" hreflang="kn" data-title="ಪಾರ್ಸೆಕ್" data-language-autonym="ಕನ್ನಡ" data-language-local-name="Kannada" class="interlanguage-link-target"><span>ಕನ್ನಡ</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%9E%E1%83%90%E1%83%A0%E1%83%A1%E1%83%94%E1%83%99%E1%83%98" title="პარსეკი – Georgian" lang="ka" hreflang="ka" data-title="პარსეკი" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Kazakh" lang="kk" hreflang="kk" data-title="Парсек" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-sw mw-list-item"><a href="https://sw.wikipedia.org/wiki/Parsek" title="Parsek – Swahili" lang="sw" hreflang="sw" data-title="Parsek" data-language-autonym="Kiswahili" data-language-local-name="Swahili" class="interlanguage-link-target"><span>Kiswahili</span></a></li><li class="interlanguage-link interwiki-ku mw-list-item"><a href="https://ku.wikipedia.org/wiki/Parsek" title="Parsek – Kurdish" lang="ku" hreflang="ku" data-title="Parsek" data-language-autonym="Kurdî" data-language-local-name="Kurdish" class="interlanguage-link-target"><span>Kurdî</span></a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Kyrgyz" lang="ky" hreflang="ky" data-title="Парсек" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Parseks" title="Parseks – Latvian" lang="lv" hreflang="lv" data-title="Parseks" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Parsec" title="Parsec – Luxembourgish" lang="lb" hreflang="lb" data-title="Parsec" data-language-autonym="Lëtzebuergesch" data-language-local-name="Luxembourgish" class="interlanguage-link-target"><span>Lëtzebuergesch</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Parsekas" title="Parsekas – Lithuanian" lang="lt" hreflang="lt" data-title="Parsekas" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-li mw-list-item"><a href="https://li.wikipedia.org/wiki/Parsec" title="Parsec – Limburgish" lang="li" hreflang="li" data-title="Parsec" data-language-autonym="Limburgs" data-language-local-name="Limburgish" class="interlanguage-link-target"><span>Limburgs</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Parszek" title="Parszek – Hungarian" lang="hu" hreflang="hu" data-title="Parszek" 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%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Macedonian" lang="mk" hreflang="mk" data-title="Парсек" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%AA%E0%B4%BE%E0%B5%BC%E0%B4%B8%E0%B5%86%E0%B4%95%E0%B5%8D%E2%80%8C" title="പാർസെക്‌ – Malayalam" lang="ml" hreflang="ml" data-title="പാർസെക്‌" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-mr mw-list-item"><a href="https://mr.wikipedia.org/wiki/%E0%A4%AA%E0%A4%BE%E0%A4%B0%E0%A5%8D%E0%A4%B8%E0%A5%87%E0%A4%95" title="पार्सेक – Marathi" lang="mr" hreflang="mr" data-title="पार्सेक" data-language-autonym="मराठी" data-language-local-name="Marathi" class="interlanguage-link-target"><span>मराठी</span></a></li><li class="interlanguage-link interwiki-xmf mw-list-item"><a href="https://xmf.wikipedia.org/wiki/%E1%83%9E%E1%83%90%E1%83%A0%E1%83%A1%E1%83%94%E1%83%99%E1%83%98" title="პარსეკი – Mingrelian" lang="xmf" hreflang="xmf" data-title="პარსეკი" data-language-autonym="მარგალური" data-language-local-name="Mingrelian" class="interlanguage-link-target"><span>მარგალური</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Parsek" title="Parsek – Malay" lang="ms" hreflang="ms" data-title="Parsek" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-my mw-list-item"><a href="https://my.wikipedia.org/wiki/%E1%80%95%E1%80%AB%E1%80%86%E1%80%80%E1%80%BA" title="ပါဆက် – Burmese" lang="my" hreflang="my" data-title="ပါဆက်" 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/Parsec" title="Parsec – Dutch" lang="nl" hreflang="nl" data-title="Parsec" 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%91%E3%83%BC%E3%82%BB%E3%82%AF" title="パーセク – Japanese" lang="ja" hreflang="ja" data-title="パーセク" 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/Parsec" title="Parsec – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Parsec" 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/Parsec" title="Parsec – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Parsec" 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-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Parsec" title="Parsec – Occitan" lang="oc" hreflang="oc" data-title="Parsec" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Parsek" title="Parsek – Uzbek" lang="uz" hreflang="uz" data-title="Parsek" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="Uzbek" class="interlanguage-link-target"><span>Oʻzbekcha / ўзбекча</span></a></li><li class="interlanguage-link interwiki-pnb mw-list-item"><a href="https://pnb.wikipedia.org/wiki/%D9%BE%D8%A7%D8%B1%D8%B3%DA%A9" title="پارسک – Western Punjabi" lang="pnb" hreflang="pnb" data-title="پارسک" data-language-autonym="پنجابی" data-language-local-name="Western Punjabi" class="interlanguage-link-target"><span>پنجابی</span></a></li><li class="interlanguage-link interwiki-pms mw-list-item"><a href="https://pms.wikipedia.org/wiki/Parsec" title="Parsec – Piedmontese" lang="pms" hreflang="pms" data-title="Parsec" data-language-autonym="Piemontèis" data-language-local-name="Piedmontese" class="interlanguage-link-target"><span>Piemontèis</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Parsek" title="Parsek – Polish" lang="pl" hreflang="pl" data-title="Parsek" 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/Parsec" title="Parsec – Portuguese" lang="pt" hreflang="pt" data-title="Parsec" 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/Parsec" title="Parsec – Romanian" lang="ro" hreflang="ro" data-title="Parsec" 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%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Russian" lang="ru" hreflang="ru" data-title="Парсек" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sah mw-list-item"><a href="https://sah.wikipedia.org/wiki/%D0%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Yakut" lang="sah" hreflang="sah" data-title="Парсек" data-language-autonym="Саха тыла" data-language-local-name="Yakut" class="interlanguage-link-target"><span>Саха тыла</span></a></li><li class="interlanguage-link interwiki-scn mw-list-item"><a href="https://scn.wikipedia.org/wiki/Parsec" title="Parsec – Sicilian" lang="scn" hreflang="scn" data-title="Parsec" 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/Parsec" title="Parsec – Simple English" lang="en-simple" hreflang="en-simple" data-title="Parsec" 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/Parsek" title="Parsek – Slovak" lang="sk" hreflang="sk" data-title="Parsek" 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/Parsek" title="Parsek – Slovenian" lang="sl" hreflang="sl" data-title="Parsek" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Serbian" lang="sr" hreflang="sr" data-title="Парсек" 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/Parsek" title="Parsek – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Parsek" 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/Parsek" title="Parsek – Finnish" lang="fi" hreflang="fi" data-title="Parsek" 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/Parsec" title="Parsec – Swedish" lang="sv" hreflang="sv" data-title="Parsec" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-tl mw-list-item"><a href="https://tl.wikipedia.org/wiki/Parsec" title="Parsec – Tagalog" lang="tl" hreflang="tl" data-title="Parsec" data-language-autonym="Tagalog" data-language-local-name="Tagalog" class="interlanguage-link-target"><span>Tagalog</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%AA%E0%AF%81%E0%AE%9F%E0%AF%88%E0%AE%A8%E0%AF%8A%E0%AE%9F%E0%AE%BF" title="புடைநொடி – Tamil" lang="ta" hreflang="ta" data-title="புடைநொடி" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-tt mw-list-item"><a href="https://tt.wikipedia.org/wiki/%D0%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Tatar" lang="tt" hreflang="tt" data-title="Парсек" data-language-autonym="Татарча / tatarça" data-language-local-name="Tatar" class="interlanguage-link-target"><span>Татарча / tatarça</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%9E%E0%B8%B2%E0%B8%A3%E0%B9%8C%E0%B9%80%E0%B8%8B%E0%B8%81" title="พาร์เซก – Thai" lang="th" hreflang="th" data-title="พาร์เซก" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tg mw-list-item"><a href="https://tg.wikipedia.org/wiki/%D0%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Tajik" lang="tg" hreflang="tg" data-title="Парсек" data-language-autonym="Тоҷикӣ" data-language-local-name="Tajik" class="interlanguage-link-target"><span>Тоҷикӣ</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Parsek" title="Parsek – Turkish" lang="tr" hreflang="tr" data-title="Parsek" 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%9F%D0%B0%D1%80%D1%81%D0%B5%D0%BA" title="Парсек – Ukrainian" lang="uk" hreflang="uk" data-title="Парсек" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-ur mw-list-item"><a href="https://ur.wikipedia.org/wiki/%D9%BE%D8%A7%D8%B1%D8%B3%DA%A9" title="پارسک – Urdu" lang="ur" hreflang="ur" data-title="پارسک" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Parsec" title="Parsec – Vietnamese" lang="vi" hreflang="vi" data-title="Parsec" 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-vls mw-list-item"><a href="https://vls.wikipedia.org/wiki/Parsec" title="Parsec – West Flemish" lang="vls" hreflang="vls" data-title="Parsec" data-language-autonym="West-Vlams" data-language-local-name="West Flemish" class="interlanguage-link-target"><span>West-Vlams</span></a></li><li class="interlanguage-link interwiki-war mw-list-item"><a href="https://war.wikipedia.org/wiki/Parsec" title="Parsec – Waray" lang="war" hreflang="war" data-title="Parsec" 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/%E7%A7%92%E5%B7%AE%E8%B7%9D" title="秒差距 – Wu" lang="wuu" hreflang="wuu" data-title="秒差距" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target"><span>吴语</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E7%A7%92%E5%B7%AE%E8%B7%9D" title="秒差距 – Cantonese" lang="yue" hreflang="yue" data-title="秒差距" data-language-autonym="粵語" data-language-local-name="Cantonese" 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class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></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">Unit of length used in astronomy</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">For other uses, see <a href="/wiki/Parsec_(disambiguation)" class="mw-disambig" title="Parsec (disambiguation)">Parsec (disambiguation)</a>.</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 ib-unit"><tbody><tr><th colspan="2" class="infobox-above">Parsec</th></tr><tr><td colspan="2" class="infobox-image notheme" style="background-color: #f8f9fa;"><span class="mw-default-size" typeof="mw:File/Frameless"><a href="/wiki/File:Stellarparallax_parsec1.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Stellarparallax_parsec1.svg/220px-Stellarparallax_parsec1.svg.png" decoding="async" width="220" height="345" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Stellarparallax_parsec1.svg/330px-Stellarparallax_parsec1.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Stellarparallax_parsec1.svg/440px-Stellarparallax_parsec1.svg.png 2x" data-file-width="555" data-file-height="870" /></a></span><div class="infobox-caption">A parsec is the distance from the Sun to an <a href="/wiki/Astronomical_object" title="Astronomical object">astronomical object</a> that has a <a href="/wiki/Parallax" title="Parallax">parallax</a> angle of one <a href="/wiki/Minute_and_second_of_arc#Symbols_and_abbreviations" title="Minute and second of arc">arcsecond</a> (not to scale)</div></td></tr><tr><th colspan="2" class="infobox-header">General information</th></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/System_of_units_of_measurement" title="System of units of measurement">Unit system</a></th><td class="infobox-data">astronomical units</td></tr><tr><th scope="row" class="infobox-label">Unit of</th><td class="infobox-data"><a href="/wiki/Length" title="Length">length</a>/<a href="/wiki/Distance" title="Distance">distance</a></td></tr><tr><th scope="row" class="infobox-label">Symbol</th><td class="infobox-data">pc</td></tr><tr><th colspan="2" class="infobox-header">Conversions </th></tr><tr class="nowrap"><td>1 pc <i>in ...</i></td><td><i>... is equal to ...</i></td></tr><tr style="display:none"><th colspan="2"> </th></tr><tr><th scope="row" class="infobox-label"><span class="nowrap">   </span><a href="/wiki/Metric_system" title="Metric system">metric</a> (<a href="/wiki/International_System_of_Units" title="International System of Units">SI</a>) units</th><td class="infobox-data"><span class="nowrap">   </span>3.0857<span style="margin:0 .15em 0 .25em">×</span>10<sup>16</sup> <a href="/wiki/Metre" title="Metre">m</a> <br /><span class="nowrap">   </span>≈31 <a href="/wiki/Petametre" class="mw-redirect" title="Petametre">petametres</a></td></tr><tr><th scope="row" class="infobox-label"><span class="nowrap">   </span><a href="/wiki/Imperial_units" title="Imperial units">imperial</a>  <a href="/wiki/United_States_customary_units" title="United States customary units">US</a> units</th><td class="infobox-data"><span class="nowrap">   </span>1.9174<span style="margin:0 .15em 0 .25em">×</span>10<sup>13</sup> <a href="/wiki/Mile" title="Mile">mi</a></td></tr><tr><th scope="row" class="infobox-label"><span class="nowrap">   </span><a href="/wiki/Astronomical_system_of_units" title="Astronomical system of units">astronomical units</a></th><td class="infobox-data"><span class="nowrap">   </span>206,265 <a href="/wiki/Astronomical_unit" title="Astronomical unit">au</a><br /><span class="nowrap">   </span>3.26156 <a href="/wiki/Light-year" title="Light-year">ly</a></td></tr></tbody></table><style data-mw-deduplicate="TemplateStyles:r1236303919">@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-has-images-with-white-backgrounds img{background:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-has-images-with-white-backgrounds img{background:white}}</style> <p>The <b>parsec</b> (symbol: <b>pc</b>) is a <a href="/wiki/Unit_of_length" title="Unit of length">unit of length</a> used to measure the large distances to <a href="/wiki/Astronomical_object" title="Astronomical object">astronomical objects</a> outside the <a href="/wiki/Solar_System" title="Solar System">Solar System</a>, approximately equal to 3.26 <a href="/wiki/Light-year" title="Light-year">light-years</a> or 206,265 <a href="/wiki/Astronomical_unit" title="Astronomical unit">astronomical units</a> (AU), i.e. 30.9 <a href="/wiki/1000000000000_(number)" class="mw-redirect" title="1000000000000 (number)">trillion</a> <a href="/wiki/Kilometre" title="Kilometre">kilometres</a> (19.2 trillion <a href="/wiki/Mile" title="Mile">miles</a>).<sup id="cite_ref-trillion_1-0" class="reference"><a href="#cite_note-trillion-1"><span class="cite-bracket">[</span>a<span class="cite-bracket">]</span></a></sup> The parsec unit is obtained by the use of <a href="/wiki/Parallax" title="Parallax">parallax</a> and <a href="/wiki/Trigonometry" title="Trigonometry">trigonometry</a>, and is defined as the distance at which 1 AU <a href="/wiki/Subtended_angle" title="Subtended angle">subtends</a> an angle of one <a href="/wiki/Arcsecond" class="mw-redirect" title="Arcsecond">arcsecond</a><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> (<style data-mw-deduplicate="TemplateStyles:r1214402035">.mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num{display:block;line-height:1em;margin:0.0em 0.1em;border-bottom:1px solid}.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0.1em 0.1em}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">3600</span></span>⁠</span> of a <a href="/wiki/Degree_(angle)" title="Degree (angle)">degree</a>). The nearest star, <a href="/wiki/Proxima_Centauri" title="Proxima Centauri">Proxima Centauri</a>, is about 1.3 parsecs (4.2 light-years) from the <a href="/wiki/Sun" title="Sun">Sun</a>: from that distance, the gap between the Earth and the Sun spans slightly less than <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">3600</span></span>⁠</span> of one degree of view.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Most <a href="/wiki/Naked-eye_stars" class="mw-redirect" title="Naked-eye stars">stars visible to the naked eye</a> are within a few hundred parsecs of the Sun, with the most distant at a few thousand parsecs, and the <a href="/wiki/Andromeda_Galaxy" title="Andromeda Galaxy">Andromeda Galaxy</a> at over 700,000 parsecs.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p><p>The word <i>parsec</i> is a <a href="/wiki/Portmanteau" class="mw-redirect" title="Portmanteau">portmanteau</a> of "parallax of one second" and was coined by the British astronomer <a href="/wiki/Herbert_Hall_Turner" title="Herbert Hall Turner">Herbert Hall Turner</a> in 1913<sup id="cite_ref-dyson_5-0" class="reference"><a href="#cite_note-dyson-5"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> to simplify astronomers' calculations of astronomical distances from only raw observational data. Partly for this reason, it is the unit preferred in <a href="/wiki/Astronomy" title="Astronomy">astronomy</a> and <a href="/wiki/Astrophysics" title="Astrophysics">astrophysics</a>, though the <a href="/wiki/Light-year" title="Light-year">light-year</a> remains prominent in <a href="/wiki/Popular_science" title="Popular science">popular science</a> texts and common usage. Although parsecs are used for the shorter distances within the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a>, multiples of parsecs are required for the larger scales in the universe, including <a href="/wiki/Kilo-" title="Kilo-">kilo</a>parsecs (kpc) for the more distant objects within and around the Milky Way, <a href="/wiki/Mega-" title="Mega-">mega</a>parsecs (Mpc) for mid-distance galaxies, and <a href="/wiki/Giga-" title="Giga-">giga</a>parsecs (Gpc) for many <a href="/wiki/Quasar" title="Quasar">quasars</a> and the most distant galaxies. </p><p>In August 2015, the <a href="/wiki/International_Astronomical_Union" title="International Astronomical Union">International Astronomical Union</a> (IAU) passed Resolution B2 which, as part of the definition of a standardized absolute and apparent <a href="/wiki/Bolometric_magnitude" class="mw-redirect" title="Bolometric magnitude">bolometric magnitude</a> scale, mentioned an existing explicit definition of the parsec as exactly <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num"><span class="nowrap"><span data-sort-value="7005648000000000000♠"></span>648<span style="margin-left:.25em;">000</span></span></span><span class="sr-only">/</span><span class="den"><span class="texhtml mvar" style="font-style:italic;">π</span></span></span>⁠</span> au, or approximately <span class="nowrap"><span data-sort-value="7016308567758149136♠"></span>3.085<span style="margin-left:.25em;">677</span><span style="margin-left:.25em;">581</span><span style="margin-left:.25em;">491</span><span style="margin-left:.25em;">3673</span><span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>16</sup></span> metres (based on the IAU 2012 definition of the astronomical unit). This corresponds to the small-angle definition of the parsec found in many astronomical references.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="History_and_derivation">History and derivation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Parsec&action=edit&section=1" title="Edit section: History and derivation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Stellar_parallax" title="Stellar parallax">Stellar parallax</a></div> <p>Imagining an elongated <a href="/wiki/Right_triangle" title="Right triangle">right triangle</a> in space, where the shorter leg measures one au (<a href="/wiki/Astronomical_unit" title="Astronomical unit">astronomical unit</a>, the average <a href="/wiki/Earth" title="Earth">Earth</a>–<a href="/wiki/Sun" title="Sun">Sun</a> distance) and the <a href="/wiki/Subtended" class="mw-redirect" title="Subtended">subtended angle</a> of the vertex opposite that leg measures one <a href="/wiki/Arcsecond" class="mw-redirect" title="Arcsecond">arcsecond</a> (<style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="frac"><span class="num">1</span>⁄<span class="den">3600</span></span> of a degree), the parsec is defined as the length of the <i>adjacent</i> leg. The value of a parsec can be derived through the rules of <a href="/wiki/Trigonometry" title="Trigonometry">trigonometry</a>. The distance from Earth whereupon the radius of its solar orbit subtends one arcsecond. </p><p>One of the oldest methods used by astronomers to calculate the distance to a <a href="/wiki/Star" title="Star">star</a> is to record the difference in angle between two measurements of the position of the star in the sky. The first measurement is taken from the Earth on one side of the Sun, and the second is taken approximately half a year later, when the Earth is on the opposite side of the Sun.<sup id="cite_ref-orbit_8-0" class="reference"><a href="#cite_note-orbit-8"><span class="cite-bracket">[</span>b<span class="cite-bracket">]</span></a></sup> The distance between the two positions of the Earth when the two measurements were taken is twice the distance between the Earth and the Sun. The difference in angle between the two measurements is twice the parallax angle, which is formed by lines from the Sun and Earth to the star at the distant <a href="/wiki/Vertex_(geometry)#Of_an_angle" title="Vertex (geometry)">vertex</a>. Then the distance to the star could be calculated using trigonometry.<sup id="cite_ref-NASAparallax_9-0" class="reference"><a href="#cite_note-NASAparallax-9"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> The first successful published direct measurements of an object at interstellar distances were undertaken by German astronomer <a href="/wiki/Friedrich_Wilhelm_Bessel" title="Friedrich Wilhelm Bessel">Friedrich Wilhelm Bessel</a> in 1838, who used this approach to calculate the 3.5-parsec distance of <a href="/wiki/61_Cygni" title="61 Cygni">61 Cygni</a>.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:ParallaxV2.svg" class="mw-file-description"><img alt="Diagrams illustrating the apparent change in position of a celestial object when viewed from different positions in Earth's orbit." src="//upload.wikimedia.org/wikipedia/commons/thumb/5/51/ParallaxV2.svg/300px-ParallaxV2.svg.png" decoding="async" width="300" height="218" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/51/ParallaxV2.svg/450px-ParallaxV2.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/51/ParallaxV2.svg/600px-ParallaxV2.svg.png 2x" data-file-width="550" data-file-height="400" /></a><figcaption>Stellar parallax motion from annual parallax</figcaption></figure> <p>The parallax of a star is defined as half of the <a href="/wiki/Angular_distance" title="Angular distance">angular distance</a> that a star appears to move relative to the <a href="/wiki/Celestial_sphere" title="Celestial sphere">celestial sphere</a> as Earth orbits the Sun. Equivalently, it is the subtended angle, from that star's perspective, of the <a href="/wiki/Semimajor_axis" class="mw-redirect" title="Semimajor axis">semimajor axis</a> of the Earth's orbit. Substituting the star's parallax for the one arcsecond angle in the imaginary right triangle, the long leg of the triangle will measure the distance from the Sun to the star. A parsec can be defined as the length of the right triangle side adjacent to the vertex occupied by a star whose parallax angle is one arcsecond. </p><p>The use of the parsec as a unit of distance follows naturally from Bessel's method, because the distance in parsecs can be computed simply as the <a href="/wiki/Multiplicative_inverse" title="Multiplicative inverse">reciprocal</a> of the parallax angle in arcseconds (i.e.: if the parallax angle is 1 arcsecond, the object is 1 pc from the Sun; if the parallax angle is 0.5 arcseconds, the object is 2 pc away; etc.). No <a href="/wiki/Trigonometric_function" class="mw-redirect" title="Trigonometric function">trigonometric functions</a> are required in this relationship because the very small angles involved mean that the approximate solution of the <a href="/wiki/Skinny_triangle" title="Skinny triangle">skinny triangle</a> can be applied. </p><p>Though it may have been used before, the term <i>parsec</i> was first mentioned in an astronomical publication in 1913. <a href="/wiki/Astronomer_Royal" title="Astronomer Royal">Astronomer Royal</a> <a href="/wiki/Frank_Watson_Dyson" title="Frank Watson Dyson">Frank Watson Dyson</a> expressed his concern for the need of a name for that unit of distance. He proposed the name <i>astron</i>, but mentioned that <a href="/wiki/Carl_Charlier" title="Carl Charlier">Carl Charlier</a> had suggested <i><a href="/wiki/Siriometer" title="Siriometer">siriometer</a></i> and <a href="/wiki/Herbert_Hall_Turner" title="Herbert Hall Turner">Herbert Hall Turner</a> had proposed <i>parsec</i>.<sup id="cite_ref-dyson_5-1" class="reference"><a href="#cite_note-dyson-5"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> It was Turner's proposal that stuck. </p> <div class="mw-heading mw-heading3"><h3 id="Calculating_the_value_of_a_parsec">Calculating the value of a parsec</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Parsec&action=edit&section=2" title="Edit section: Calculating the value of a parsec"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>By the 2015 definition, <span class="nowrap"><span data-sort-value="7011149597870700000♠"></span>1 au</span> of arc length subtends an angle of <span class="nowrap"><span data-sort-value="6994484813681109537♠"></span>1″</span> at the center of the circle of radius <span class="nowrap"><span data-sort-value="7016308567758146719♠"></span>1 pc</span>. That is, 1 pc = 1 au/tan(<span class="nowrap"><span data-sort-value="6994484813681109537♠"></span>1″</span>) ≈ 206,264.8 au by definition.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Converting from degree/minute/second units to <a href="/wiki/Radians" class="mw-redirect" title="Radians">radians</a>, </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\frac {1{\text{ pc}}}{1{\text{ au}}}}={\frac {180\times 60\times 60}{\pi }}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>1</mn> <mrow class="MJX-TeXAtom-ORD"> <mtext> pc</mtext> </mrow> </mrow> <mrow> <mn>1</mn> <mrow class="MJX-TeXAtom-ORD"> <mtext> au</mtext> </mrow> </mrow> </mfrac> </mrow> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>180</mn> <mo>×</mo> <mn>60</mn> <mo>×</mo> <mn>60</mn> </mrow> <mi>π</mi> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {1{\text{ pc}}}{1{\text{ au}}}}={\frac {180\times 60\times 60}{\pi }}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f1524f756b10f4b7a6034d41f58b393f425d7ef9" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:22.787ex; height:5.343ex;" alt="{\displaystyle {\frac {1{\text{ pc}}}{1{\text{ au}}}}={\frac {180\times 60\times 60}{\pi }}}"></span>, and</dd> <dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 1{\text{ au}}=149\,597\,870\,700{\text{ m}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mn>1</mn> <mrow class="MJX-TeXAtom-ORD"> <mtext> au</mtext> </mrow> <mo>=</mo> <mn>149</mn> <mspace width="thinmathspace" /> <mn>597</mn> <mspace width="thinmathspace" /> <mn>870</mn> <mspace width="thinmathspace" /> <mn>700</mn> <mrow class="MJX-TeXAtom-ORD"> <mtext> m</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle 1{\text{ au}}=149\,597\,870\,700{\text{ m}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1d55c89aa92e8c7b6a93399fcbc4347a1990df68" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:24.924ex; height:2.176ex;" alt="{\displaystyle 1{\text{ au}}=149\,597\,870\,700{\text{ m}}}"></span> (exact by the 2012 definition of the au)</dd></dl> <p>Therefore, <span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \pi ~\mathrm {pc} =180\times 60\times 60~\mathrm {au} =180\times 60\times 60\times 149\,597\,870\,700~\mathrm {m} =96\,939\,420\,213\,600\,000~\mathrm {m} }"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>π</mi> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">p</mi> <mi mathvariant="normal">c</mi> </mrow> <mo>=</mo> <mn>180</mn> <mo>×</mo> <mn>60</mn> <mo>×</mo> <mn>60</mn> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">a</mi> <mi mathvariant="normal">u</mi> </mrow> <mo>=</mo> <mn>180</mn> <mo>×</mo> <mn>60</mn> <mo>×</mo> <mn>60</mn> <mo>×</mo> <mn>149</mn> <mspace width="thinmathspace" /> <mn>597</mn> <mspace width="thinmathspace" /> <mn>870</mn> <mspace width="thinmathspace" /> <mn>700</mn> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> </mrow> <mo>=</mo> <mn>96</mn> <mspace width="thinmathspace" /> <mn>939</mn> <mspace width="thinmathspace" /> <mn>420</mn> <mspace width="thinmathspace" /> <mn>213</mn> <mspace width="thinmathspace" /> <mn>600</mn> <mspace width="thinmathspace" /> <mn>000</mn> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \pi ~\mathrm {pc} =180\times 60\times 60~\mathrm {au} =180\times 60\times 60\times 149\,597\,870\,700~\mathrm {m} =96\,939\,420\,213\,600\,000~\mathrm {m} }</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/29eba1f0282776906f1bfa7cd08ec14d6e760719" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:88.886ex; height:2.509ex;" alt="{\displaystyle \pi ~\mathrm {pc} =180\times 60\times 60~\mathrm {au} =180\times 60\times 60\times 149\,597\,870\,700~\mathrm {m} =96\,939\,420\,213\,600\,000~\mathrm {m} }"></span> (exact by the 2015 definition) </p><p>Therefore, </p><p><span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 1~\mathrm {pc} ={\frac {96\,939\,420\,213\,600\,000}{\pi }}~\mathrm {m} =30\,856\,775\,814\,913\,673~\mathrm {m} }"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mn>1</mn> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">p</mi> <mi mathvariant="normal">c</mi> </mrow> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>96</mn> <mspace width="thinmathspace" /> <mn>939</mn> <mspace width="thinmathspace" /> <mn>420</mn> <mspace width="thinmathspace" /> <mn>213</mn> <mspace width="thinmathspace" /> <mn>600</mn> <mspace width="thinmathspace" /> <mn>000</mn> </mrow> <mi>π</mi> </mfrac> </mrow> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> </mrow> <mo>=</mo> <mn>30</mn> <mspace width="thinmathspace" /> <mn>856</mn> <mspace width="thinmathspace" /> <mn>775</mn> <mspace width="thinmathspace" /> <mn>814</mn> <mspace width="thinmathspace" /> <mn>913</mn> <mspace width="thinmathspace" /> <mn>673</mn> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle 1~\mathrm {pc} ={\frac {96\,939\,420\,213\,600\,000}{\pi }}~\mathrm {m} =30\,856\,775\,814\,913\,673~\mathrm {m} }</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8123d3336bbebbf352f2db7b6ecd0c90b743488e" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:59.529ex; height:5.176ex;" alt="{\displaystyle 1~\mathrm {pc} ={\frac {96\,939\,420\,213\,600\,000}{\pi }}~\mathrm {m} =30\,856\,775\,814\,913\,673~\mathrm {m} }"></span> (to the nearest <a href="/wiki/Metre" title="Metre">metre</a>). </p><p>Approximately, </p> <dl><dd><span typeof="mw:File"><a href="/wiki/File:Parsec_(1).svg" class="mw-file-description" title="Diagram of parsec."><img alt="Diagram of parsec." src="//upload.wikimedia.org/wikipedia/commons/thumb/7/79/Parsec_%281%29.svg/400px-Parsec_%281%29.svg.png" decoding="async" width="400" height="134" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/79/Parsec_%281%29.svg/600px-Parsec_%281%29.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/79/Parsec_%281%29.svg/800px-Parsec_%281%29.svg.png 2x" data-file-width="512" data-file-height="171" /></a></span></dd></dl> <p>In the diagram above (not to scale), <b>S</b> represents the Sun, and <b>E</b> the Earth at one point in its orbit (such as to form a right angle at <b>S</b><sup id="cite_ref-orbit_8-1" class="reference"><a href="#cite_note-orbit-8"><span class="cite-bracket">[</span>b<span class="cite-bracket">]</span></a></sup>). Thus the distance <b>ES</b> is one astronomical unit (au). The angle <b>SDE</b> is one arcsecond (<link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">3600</span></span>⁠</span> of a <a href="/wiki/Degree_(angle)" title="Degree (angle)">degree</a>) so by definition <b>D</b> is a point in space at a distance of one parsec from the Sun. Through trigonometry, the distance <b>SD</b> is calculated as follows: </p><p><span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\begin{aligned}\mathrm {SD} &={\frac {\mathrm {ES} }{\tan 1''}}\\&={\frac {\mathrm {ES} }{\tan \left({\frac {1}{60\times 60}}\times {\frac {\pi }{180}}\right)}}\\&\approx {\frac {1\,\mathrm {au} }{{\frac {1}{60\times 60}}\times {\frac {\pi }{180}}}}={\frac {648\,000}{\pi }}\,\mathrm {au} \approx 206\,264.81~\mathrm {au} .\end{aligned}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtable columnalign="right left right left right left right left right left right left" rowspacing="3pt" columnspacing="0em 2em 0em 2em 0em 2em 0em 2em 0em 2em 0em" displaystyle="true"> <mtr> <mtd> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">S</mi> <mi mathvariant="normal">D</mi> </mrow> </mtd> <mtd> <mi></mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">E</mi> <mi mathvariant="normal">S</mi> </mrow> <mrow> <mi>tan</mi> <mo>⁡</mo> <msup> <mn>1</mn> <mo>″</mo> </msup> </mrow> </mfrac> </mrow> </mtd> </mtr> <mtr> <mtd /> <mtd> <mi></mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">E</mi> <mi mathvariant="normal">S</mi> </mrow> <mrow> <mi>tan</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mrow> <mn>60</mn> <mo>×</mo> <mn>60</mn> </mrow> </mfrac> </mrow> <mo>×</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>π</mi> <mn>180</mn> </mfrac> </mrow> </mrow> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow> </mtd> </mtr> <mtr> <mtd /> <mtd> <mi></mi> <mo>≈</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>1</mn> <mspace width="thinmathspace" /> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">a</mi> <mi mathvariant="normal">u</mi> </mrow> </mrow> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mrow> <mn>60</mn> <mo>×</mo> <mn>60</mn> </mrow> </mfrac> </mrow> <mo>×</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>π</mi> <mn>180</mn> </mfrac> </mrow> </mrow> </mfrac> </mrow> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>648</mn> <mspace width="thinmathspace" /> <mn>000</mn> </mrow> <mi>π</mi> </mfrac> </mrow> <mspace width="thinmathspace" /> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">a</mi> <mi mathvariant="normal">u</mi> </mrow> <mo>≈</mo> <mn>206</mn> <mspace width="thinmathspace" /> <mn>264.81</mn> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">a</mi> <mi mathvariant="normal">u</mi> </mrow> <mo>.</mo> </mtd> </mtr> </mtable> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\begin{aligned}\mathrm {SD} &={\frac {\mathrm {ES} }{\tan 1''}}\\&={\frac {\mathrm {ES} }{\tan \left({\frac {1}{60\times 60}}\times {\frac {\pi }{180}}\right)}}\\&\approx {\frac {1\,\mathrm {au} }{{\frac {1}{60\times 60}}\times {\frac {\pi }{180}}}}={\frac {648\,000}{\pi }}\,\mathrm {au} \approx 206\,264.81~\mathrm {au} .\end{aligned}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1a40985ca7e1f418cc3dab15844d8e3b802ea9a0" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -9.838ex; width:50.552ex; height:20.843ex;" alt="{\displaystyle {\begin{aligned}\mathrm {SD} &={\frac {\mathrm {ES} }{\tan 1''}}\\&={\frac {\mathrm {ES} }{\tan \left({\frac {1}{60\times 60}}\times {\frac {\pi }{180}}\right)}}\\&\approx {\frac {1\,\mathrm {au} }{{\frac {1}{60\times 60}}\times {\frac {\pi }{180}}}}={\frac {648\,000}{\pi }}\,\mathrm {au} \approx 206\,264.81~\mathrm {au} .\end{aligned}}}"></span> </p><p>Because the astronomical unit is defined to be <span class="nowrap"><span data-sort-value="7011149597870700000♠"></span>149<span style="margin-left:.25em;">597</span><span style="margin-left:.25em;">870</span><span style="margin-left:.25em;">700</span> <a href="/wiki/Metre" title="Metre">m</a></span>,<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> the following can be calculated: </p> <table style="margin-left:1em"> <tbody><tr> <td rowspan="5" valign="top">Therefore, 1 parsec </td> <td>≈ <span class="nowrap"><span data-sort-value="7005206264806247096♠"></span>206<span style="margin-left:.25em;">264</span>.806<span style="margin-left:.25em;">247</span><span style="margin-left:.25em;">096</span></span> astronomical units </td></tr> <tr> <td>≈ <span class="nowrap"><span data-sort-value="7016308567758100000♠"></span>3.085<span style="margin-left:.25em;">677</span><span style="margin-left:.25em;">581</span><span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>16</sup></span> metres </td></tr> <tr> <td>≈ <span class="nowrap"><span data-sort-value="7001308567758150000♠"></span>30.856<span style="margin-left:.25em;">775</span><span style="margin-left:.25em;">815</span></span> trillion <a href="/wiki/Kilometre" title="Kilometre">kilometres</a> </td></tr> <tr> <td>≈ <span class="nowrap"><span data-sort-value="7001191735115770000♠"></span>19.173<span style="margin-left:.25em;">511</span><span style="margin-left:.25em;">577</span></span> trillion <a href="/wiki/Mile" title="Mile">miles</a> </td></tr></tbody></table> <p>Therefore, if <span class="nowrap"><span data-sort-value="7015946073047258080♠"></span>1 <a href="/wiki/Light-year" title="Light-year">ly</a></span> ≈ 9.46<span style="margin:0 .15em 0 .25em">×</span>10<sup>15</sup> m, </p> <dl><dd>Then <span class="nowrap"><span data-sort-value="7016308567758146719♠"></span>1 pc</span> ≈ <span class="nowrap"><span data-sort-value="7016308567758133296♠"></span>3.261<span style="margin-left:.25em;">563</span><span style="margin-left:.25em;">777</span> ly</span></dd></dl> <p>A corollary states that a parsec is also the distance from which a disc that is one au in diameter must be viewed for it to have an <a href="/wiki/Angular_diameter" title="Angular diameter">angular diameter</a> of one arcsecond (by placing the observer at <b>D</b> and a disc spanning <b>ES</b>). </p><p>Mathematically, to calculate distance, given obtained angular measurements from instruments in arcseconds, the formula would be: </p><p><span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\text{Distance}}_{\text{star}}={\frac {{\text{Distance}}_{\text{earth-sun}}}{\tan {\frac {\theta }{3600}}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mrow class="MJX-TeXAtom-ORD"> <mtext>Distance</mtext> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mtext>star</mtext> </mrow> </msub> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msub> <mrow class="MJX-TeXAtom-ORD"> <mtext>Distance</mtext> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mtext>earth-sun</mtext> </mrow> </msub> <mrow> <mi>tan</mi> <mo>⁡</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>θ</mi> <mn>3600</mn> </mfrac> </mrow> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\text{Distance}}_{\text{star}}={\frac {{\text{Distance}}_{\text{earth-sun}}}{\tan {\frac {\theta }{3600}}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7dd31e2f9cdce9fb9f4c95251f2ebdb4f714ac87" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -3.505ex; width:31.453ex; height:6.843ex;" alt="{\displaystyle {\text{Distance}}_{\text{star}}={\frac {{\text{Distance}}_{\text{earth-sun}}}{\tan {\frac {\theta }{3600}}}}}"></span> </p><p>where <i>θ</i> is the measured angle in arcseconds, Distance<sub>earth-sun</sub> is a constant (<span class="nowrap"><span data-sort-value="7011149597870700000♠"></span>1 au</span> or 1.5813<span style="margin:0 .15em 0 .25em">×</span>10<sup>−5</sup> ly). The calculated stellar distance will be in the same measurement unit as used in Distance<sub>earth-sun</sub> (e.g. if Distance<sub>earth-sun</sub> = <span class="nowrap"><span data-sort-value="7011149597870700000♠"></span>1 au</span>, unit for Distance<sub>star</sub> is in astronomical units; if Distance<sub>earth-sun</sub> = 1.5813<span style="margin:0 .15em 0 .25em">×</span>10<sup>−5</sup> ly, unit for Distance<sub>star</sub> is in light-years). </p><p>The length of the parsec used in <a href="/wiki/IAU" class="mw-redirect" title="IAU">IAU</a> 2015 Resolution B2<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> (exactly <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num"><span class="nowrap"><span data-sort-value="7005648000000000000♠"></span>648<span style="margin-left:.25em;">000</span></span></span><span class="sr-only">/</span><span class="den"><span class="texhtml mvar" style="font-style:italic;">π</span></span></span>⁠</span> astronomical units) corresponds exactly to that derived using the small-angle calculation. This differs from the classic inverse-<a href="/wiki/Tangent" title="Tangent">tangent</a> definition by about <span class="nowrap"><span data-sort-value="7005200000000000000♠"></span>200 km</span>, i.e.: only after the 11th <a href="/wiki/Significant_figure" class="mw-redirect" title="Significant figure">significant figure</a>. As the astronomical unit was defined by the IAU (2012) as an exact length in metres, so now the parsec corresponds to an exact length in metres. To the nearest meter, the small-angle parsec corresponds to <span class="nowrap"><span data-sort-value="7016308567758149136♠"></span>30<span style="margin-left:.25em;">856</span><span style="margin-left:.25em;">775</span><span style="margin-left:.25em;">814</span><span style="margin-left:.25em;">913</span><span style="margin-left:.25em;">673</span> m</span>. </p> <div class="mw-heading mw-heading2"><h2 id="Usage_and_measurement">Usage and measurement</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Parsec&action=edit&section=3" title="Edit section: Usage and measurement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The parallax method is the fundamental calibration step for <a href="/wiki/Cosmic_distance_ladder" title="Cosmic distance ladder">distance determination in astrophysics</a>; however, the accuracy of ground-based <a href="/wiki/Telescope" title="Telescope">telescope</a> measurements of parallax angle is limited to about <span class="nowrap"><span data-sort-value="6992484813681109537♠"></span>0.01″</span>, and thus to stars no more than <span class="nowrap"><span data-sort-value="7018308567758146719♠"></span>100 pc</span> distant.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> This is because the Earth's atmosphere limits the sharpness of a star's image.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (August 2022)">citation needed</span></a></i>]</sup> Space-based telescopes are not limited by this effect and can accurately measure distances to objects beyond the limit of ground-based observations. Between 1989 and 1993, the <i><a href="/wiki/Hipparcos" title="Hipparcos">Hipparcos</a></i> satellite, launched by the <a href="/wiki/European_Space_Agency" title="European Space Agency">European Space Agency</a> (ESA), measured parallaxes for about <span class="nowrap"><span data-sort-value="7005100000000000000♠"></span>100<span style="margin-left:.25em;">000</span></span> stars with an <a href="/wiki/Astrometry" title="Astrometry">astrometric</a> precision of about <span class="nowrap"><span data-sort-value="6991470269270676250♠"></span>0.97 <a href="/wiki/Milliarcsecond" class="mw-redirect" title="Milliarcsecond">mas</a></span>, and obtained accurate measurements for stellar distances of stars up to <span class="nowrap"><span data-sort-value="7019308567758146719♠"></span>1000 pc</span> away.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p><p>ESA's <a href="/wiki/Gaia_mission" class="mw-redirect" title="Gaia mission"><i>Gaia</i> satellite</a>, which launched on 19 December 2013, is intended to measure one billion stellar distances to within <span class="nowrap"><span data-sort-value="7001200000000000000♠"></span>20 microarcsecond</span>s, producing errors of 10% in measurements as far as the <a href="/wiki/Galactic_Center" title="Galactic Center">Galactic Centre</a>, about <span class="nowrap"><span data-sort-value="7020246854206517375♠"></span>8000 pc</span> away in the <a href="/wiki/Constellation" title="Constellation">constellation</a> of <a href="/wiki/Sagittarius_(constellation)" title="Sagittarius (constellation)">Sagittarius</a>.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Distances_in_parsecs">Distances in parsecs</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Parsec&action=edit&section=4" title="Edit section: Distances in parsecs"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Distances_less_than_a_parsec">Distances less than a parsec</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Parsec&action=edit&section=5" title="Edit section: Distances less than a parsec"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Distances expressed in fractions of a parsec usually involve objects within a single star system. So, for example: </p> <ul><li>One astronomical unit (au), the distance from the Sun to the Earth, is just under <span class="nowrap"><span data-sort-value="7011154283879073359♠"></span>5<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>−6</sup> pc</span>.</li> <li>The most distant <a href="/wiki/Space_probe" class="mw-redirect" title="Space probe">space probe</a>, <i><a href="/wiki/Voyager_1" title="Voyager 1">Voyager 1</a></i>, was <span class="nowrap"><span data-sort-value="7013243675958608464♠"></span>0.000<span style="margin-left:.25em;">7897</span> pc</span> from Earth as of February 2024<sup class="plainlinks noexcerpt noprint asof-tag update" style="display:none;"><a class="external text" href="https://en.wikipedia.org/w/index.php?title=Parsec&action=edit">[update]</a></sup>. <i>Voyager 1</i> took <span class="nowrap"><span data-sort-value="7009145164960000000♠"></span>46 years</span> to cover that distance.</li> <li>The <a href="/wiki/Oort_cloud" title="Oort cloud">Oort cloud</a> is estimated to be approximately <span class="nowrap"><span data-sort-value="7016185140654888031♠"></span>0.6 pc</span> in <a href="/wiki/Diameter" title="Diameter">diameter</a></li></ul> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:M87_jet.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/39/M87_jet.jpg/170px-M87_jet.jpg" decoding="async" width="170" height="178" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/39/M87_jet.jpg/255px-M87_jet.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/39/M87_jet.jpg/340px-M87_jet.jpg 2x" data-file-width="1222" data-file-height="1276" /></a><figcaption>As observed by the <a href="/wiki/Hubble_Space_Telescope" title="Hubble Space Telescope">Hubble Space Telescope</a>, the <a href="/wiki/Astrophysical_jet" title="Astrophysical jet">astrophysical jet</a> erupting from the <a href="/wiki/Active_galactic_nucleus" title="Active galactic nucleus">active galactic nucleus</a> of <a href="/wiki/Messier_87" title="Messier 87">M87</a> <a href="/wiki/Subtends" class="mw-redirect" title="Subtends">subtends</a> <span class="nowrap"><span data-sort-value="6995969627362219074♠"></span>20″</span> and is thought to be 1.5 kiloparsecs (4,892 <a href="/wiki/Light-year" title="Light-year">ly</a>) long (the jet is somewhat foreshortened from Earth's perspective).</figcaption></figure> <div class="mw-heading mw-heading3"><h3 id="Parsecs_and_kiloparsecs">Parsecs and kiloparsecs</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Parsec&action=edit&section=6" title="Edit section: Parsecs and kiloparsecs"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-Unreferenced_section plainlinks metadata ambox ambox-content ambox-Unreferenced" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>does not <a href="/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources">cite</a> any <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">sources</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Parsec" title="Special:EditPage/Parsec">improve this section</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and <a href="/wiki/Wikipedia:Verifiability#Burden_of_evidence" title="Wikipedia:Verifiability">removed</a>.</span> <span class="date-container"><i>(<span class="date">June 2024</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <p>Distances expressed in parsecs (pc) include distances between nearby stars, such as those in the same <a href="/wiki/Spiral_arm" title="Spiral arm">spiral arm</a> or <a href="/wiki/Globular_cluster" title="Globular cluster">globular cluster</a>. A distance of 1,000 parsecs (3,262 ly) is denoted by the kiloparsec (kpc). Astronomers typically use kiloparsecs to express distances between parts of a <a href="/wiki/Galaxy" title="Galaxy">galaxy</a> or within <a href="/wiki/Galaxy_group" title="Galaxy group">groups of galaxies</a>. So, for example : </p> <ul><li><a href="/wiki/Proxima_Centauri" title="Proxima Centauri">Proxima Centauri</a>, the nearest known star to Earth other than the Sun, is about 1.3 parsecs (4.24 ly) away by direct parallax measurement.</li> <li>The distance to the <a href="/wiki/Open_cluster" title="Open cluster">open cluster</a> <a href="/wiki/Pleiades" title="Pleiades">Pleiades</a> is <span class="nowrap"><span data-sort-value="7018401138085590734♠"></span>130<span style="margin-left:0.3em;margin-right:0.15em;">±</span>10 pc</span> (<span class="nowrap"><span data-sort-value="7018397350679848393♠"></span>420<span style="margin-left:0.3em;margin-right:0.15em;">±</span>30 ly</span>) from us per <i><a href="/wiki/Hipparcos" title="Hipparcos">Hipparcos</a></i> parallax measurement.</li> <li>The <a href="/wiki/Galactic_Center" title="Galactic Center">centre</a> of the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a> is more than 8 kiloparsecs (26,000 ly) from the Earth and the Milky Way is roughly 34 kiloparsecs (110,000 ly) across.</li> <li><a href="/wiki/ESO_383-76" title="ESO 383-76">ESO 383-76</a>, one of the <a href="/wiki/List_of_largest_galaxies" title="List of largest galaxies">largest known galaxies</a>, has a diameter of 540.9 kpc (1.8 million ly).</li> <li>The <a href="/wiki/Andromeda_Galaxy" title="Andromeda Galaxy">Andromeda Galaxy</a> (<a href="/wiki/Messier_object" title="Messier object">M31</a>) is about 780 kpc (2.5 million ly) away from the Earth.</li></ul> <div class="mw-heading mw-heading3"><h3 id="Megaparsecs_and_gigaparsecs">Megaparsecs and gigaparsecs</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Parsec&action=edit&section=7" title="Edit section: Megaparsecs and gigaparsecs"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Astronomers typically express the distances between neighbouring galaxies and <a href="/wiki/Galaxy_cluster" title="Galaxy cluster">galaxy clusters</a> in megaparsecs (Mpc). A megaparsec is one million parsecs, or about 3,260,000 light years.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> Sometimes, galactic distances are given in units of Mpc/<i>h</i> (as in "50/<i>h</i> Mpc", also written "<span class="nowrap">50 Mpc <i>h</i><sup>−1</sup></span>"). <i>h</i> is a constant (the "<a href="/wiki/Dimensionless_Hubble_constant" class="mw-redirect" title="Dimensionless Hubble constant">dimensionless Hubble constant</a>") in the range <span class="nowrap">0.5 < <i>h</i> < 0.75</span> reflecting the uncertainty in the value of the <a href="/wiki/Hubble_constant" class="mw-redirect" title="Hubble constant">Hubble constant</a> <i>H</i> for the rate of expansion of the universe: <span class="nowrap"><i>h</i> = <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num"><i>H</i></span><span class="sr-only">/</span><span class="den">100 (km/s)/Mpc</span></span>⁠</span></span>. The Hubble constant becomes relevant when converting an observed <a href="/wiki/Redshift" title="Redshift">redshift</a> <i>z</i> into a distance <i>d</i> using the formula <span class="nowrap"><i>d</i> ≈ <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num"><i><a href="/wiki/Speed_of_light" title="Speed of light">c</a></i></span><span class="sr-only">/</span><span class="den"><i>H</i></span></span>⁠</span> × <i>z</i></span>.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p><p>One gigaparsec (Gpc) is <a href="/wiki/1000000000_(number)" class="mw-redirect" title="1000000000 (number)">one billion</a> parsecs — one of the largest <a href="/wiki/Orders_of_magnitude_(length)" title="Orders of magnitude (length)">units of length</a> commonly used. One gigaparsec is about 3.26 billion ly, or roughly <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035"><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">14</span></span>⁠</span> of the distance to the <a href="/wiki/Cosmological_horizon#Practical_horizons" title="Cosmological horizon">horizon</a> of the <a href="/wiki/Observable_universe" title="Observable universe">observable universe</a> (dictated by the <a href="/wiki/Cosmic_microwave_background_radiation" class="mw-redirect" title="Cosmic microwave background radiation">cosmic microwave background radiation</a>). Astronomers typically use gigaparsecs to express the sizes of <a href="/wiki/Large-scale_structure_of_the_cosmos" class="mw-redirect" title="Large-scale structure of the cosmos">large-scale structures</a> such as the size of, and distance to, the <a href="/wiki/CfA2_Great_Wall" title="CfA2 Great Wall">CfA2 Great Wall</a>; the distances between galaxy clusters; and the distance to <a href="/wiki/Quasar" title="Quasar">quasars</a>. </p><p>For example: </p> <ul><li>The <a href="/wiki/Andromeda_Galaxy" title="Andromeda Galaxy">Andromeda Galaxy</a> is about 0.78 Mpc (2.5 million ly) from the Earth.</li> <li>The nearest large <a href="/wiki/Galaxy_cluster" title="Galaxy cluster">galaxy cluster</a>, the <a href="/wiki/Virgo_Cluster" title="Virgo Cluster">Virgo Cluster</a>, is about 16.5 Mpc (54 million ly) from the Earth.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup></li> <li>The galaxy <a href="/wiki/RXJ1242-11" class="mw-redirect" title="RXJ1242-11">RXJ1242-11</a>, observed to have a <a href="/wiki/Supermassive_black_hole" title="Supermassive black hole">supermassive black hole</a> core similar to the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a>'s, is about 200 Mpc (650 million ly) from the Earth.</li> <li>The <a href="/wiki/Galaxy_filament" title="Galaxy filament">galaxy filament</a> <a href="/wiki/Hercules%E2%80%93Corona_Borealis_Great_Wall" title="Hercules–Corona Borealis Great Wall">Hercules–Corona Borealis Great Wall</a>, currently the <a href="/wiki/List_of_largest_known_cosmic_structures" class="mw-redirect" title="List of largest known cosmic structures">largest known structure</a> in the universe, is about 3 Gpc (9.8 billion ly) across.</li> <li>The <a href="/wiki/Particle_horizon" title="Particle horizon">particle horizon</a> (the boundary of the <a href="/wiki/Observable_universe" title="Observable universe">observable universe</a>) has a radius of about 14 Gpc (46 billion ly).<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup></li></ul> <div class="mw-heading mw-heading2"><h2 id="Volume_units">Volume units</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Parsec&action=edit&section=8" title="Edit section: Volume units"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>To determine the number of stars in the Milky Way, volumes in cubic kiloparsecs<sup id="cite_ref-vol_22-0" class="reference"><a href="#cite_note-vol-22"><span class="cite-bracket">[</span>c<span class="cite-bracket">]</span></a></sup> (kpc<sup>3</sup>) are selected in various directions. All the stars in these volumes are counted and the total number of stars statistically determined. The number of globular clusters, dust clouds, and interstellar gas is determined in a similar fashion. To determine the number of galaxies in <a href="/wiki/Supercluster" title="Supercluster">superclusters</a>, volumes in cubic megaparsecs<sup id="cite_ref-vol_22-1" class="reference"><a href="#cite_note-vol-22"><span class="cite-bracket">[</span>c<span class="cite-bracket">]</span></a></sup> (Mpc<sup>3</sup>) are selected. All the galaxies in these volumes are classified and tallied. The total number of galaxies can then be determined statistically. The huge <a href="/wiki/Bo%C3%B6tes_void" class="mw-redirect" title="Boötes void">Boötes void</a> is measured in cubic megaparsecs.<sup id="cite_ref-KirshnerOemler1981_23-0" class="reference"><a href="#cite_note-KirshnerOemler1981-23"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p><p>In <a href="/wiki/Physical_cosmology" title="Physical cosmology">physical cosmology</a>, volumes of cubic gigaparsecs<sup id="cite_ref-vol_22-2" class="reference"><a href="#cite_note-vol-22"><span class="cite-bracket">[</span>c<span class="cite-bracket">]</span></a></sup> (Gpc<sup>3</sup>) are selected to determine the distribution of matter in the visible universe and to determine the number of galaxies and quasars. The Sun is currently the only star in its cubic parsec,<sup id="cite_ref-vol_22-3" class="reference"><a href="#cite_note-vol-22"><span class="cite-bracket">[</span>c<span class="cite-bracket">]</span></a></sup> (pc<sup>3</sup>) but in globular clusters the stellar density could be from <span class="nowrap"><span data-sort-value="7002100000000000000♠"></span>100–1000 pc<sup>−3</sup></span>. </p><p>The observational volume of gravitational wave interferometers (e.g., <a href="/wiki/LIGO" title="LIGO">LIGO</a>, <a href="/wiki/Virgo_interferometer" title="Virgo interferometer">Virgo</a>) is stated in terms of cubic megaparsecs<sup id="cite_ref-vol_22-4" class="reference"><a href="#cite_note-vol-22"><span class="cite-bracket">[</span>c<span class="cite-bracket">]</span></a></sup> (Mpc<sup>3</sup>) and is essentially the value of the effective distance cubed. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Parsec&action=edit&section=9" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/List_of_humorous_units_of_measurement#Attoparsec" title="List of humorous units of measurement">Attoparsec</a></li> <li><a href="/wiki/Distance_measure" title="Distance measure">Distance measure</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=Parsec&action=edit&section=10" 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-trillion-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-trillion_1-0">^</a></b></span> <span class="reference-text">One trillion here is <a href="/wiki/Long_and_short_scales" title="Long and short scales">short scale</a>, ie. 10<sup>12</sup> (one million million, or billion in long scale).</span> </li> <li id="cite_note-orbit-8"><span class="mw-cite-backlink">^ <a href="#cite_ref-orbit_8-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-orbit_8-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Terrestrial observations of a star's position should be taken when the Earth is at the furthest points in its orbit from a line between the Sun and the star, in order to form a right angle at the Sun and a full au of separation as viewed from the star.</span> </li> <li id="cite_note-vol-22"><span class="mw-cite-backlink">^ <a href="#cite_ref-vol_22-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-vol_22-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-vol_22-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-vol_22-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-vol_22-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text"><table><tbody><tr style="vertical-align:top"><td><span class="nowrap"><span data-sort-value="7000100000000000000♠"></span>1 pc<sup>3</sup></span></td><td><a href="/wiki/Approximation" title="Approximation">≈</a> <span class="nowrap"><span data-sort-value="7049293800000000000♠"></span>2.938<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>49</sup> m<sup>3</sup></span></td></tr><tr style="vertical-align:top"><td><span class="nowrap"><span data-sort-value="7000100000000000000♠"></span>1 kpc<sup>3</sup></span></td><td>≈ <span class="nowrap"><span data-sort-value="7058293800000000000♠"></span>2.938<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>58</sup> m<sup>3</sup></span></td></tr><tr style="vertical-align:top"><td><span class="nowrap"><span data-sort-value="7000100000000000000♠"></span>1 Mpc<sup>3</sup></span></td><td>≈ <span class="nowrap"><span data-sort-value="7067293800000000000♠"></span>2.938<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>67</sup> m<sup>3</sup></span></td></tr><tr style="vertical-align:top"><td><span class="nowrap"><span data-sort-value="7000100000000000000♠"></span>1 Gpc<sup>3</sup></span></td><td>≈ <span class="nowrap"><span data-sort-value="7076293800000000000♠"></span>2.938<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>76</sup> m<sup>3</sup></span></td></tr><tr style="vertical-align:top"><td><span class="nowrap"><span data-sort-value="7000100000000000000♠"></span>1 Tpc<sup>3</sup></span></td><td>≈ <span class="nowrap"><span data-sort-value="7085293800000000000♠"></span>2.938<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>85</sup> m<sup>3</sup></span></td></tr></tbody></table></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=Parsec&action=edit&section=11" 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"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output 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.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://heasarc.gsfc.nasa.gov/docs/cosmic/milkyway_info.html">"Cosmic Distance Scales – The Milky Way"</a><span class="reference-accessdate">. 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Mr. <a href="/wiki/Carl_Charlier" title="Carl Charlier">Charlier</a> has suggested <a href="/wiki/Sirius" title="Sirius">Siriometer</a>, but if the violence to the Greek language can be overlooked, the word <i>Astron</i> might be adopted. 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(31 August 2012), <a rel="nofollow" class="external text" href="http://www.iau.org/static/resolutions/IAU2012_English.pdf">"RESOLUTION B2 on the re-definition of the astronomical unit of length"</a> <span class="cs1-format">(PDF)</span>, <i>RESOLUTION B2</i>, Beijing: <a href="/wiki/International_Astronomical_Union" title="International Astronomical Union">International Astronomical Union</a>, <q>The XXVIII General Assembly of the International Astronomical Union recommends [adopted] that the astronomical unit be redefined to be a conventional unit of length equal to exactly <span class="nowrap"><span data-sort-value="7011149597870700000♠"></span>149<span style="margin-left:.25em;">597</span><span style="margin-left:.25em;">870</span><span style="margin-left:.25em;">700</span> m</span>, in agreement with the value adopted in IAU 2009 Resolution B2</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=RESOLUTION+B2+on+the+re-definition+of+the+astronomical+unit+of+length&rft.btitle=RESOLUTION+B2&rft.place=Beijing&rft.pub=International+Astronomical+Union&rft.date=2012-08-31&rft_id=http%3A%2F%2Fwww.iau.org%2Fstatic%2Fresolutions%2FIAU2012_English.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AParsec" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFInternational_Astronomical_Union2015" class="citation cs2">International Astronomical Union, ed. 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(1 March 2005). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110810231727/http://www.scientificamerican.com/article.cfm?id=misconceptions-about-the-2005-03&page=5">"Misconceptions about the Big Bang"</a>. <i>Scientific American</i>. <b>292</b> (3): 36–45. <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/2005SciAm.292c..36L">2005SciAm.292c..36L</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%2Fscientificamerican0305-36">10.1038/scientificamerican0305-36</a>. Archived from <a rel="nofollow" class="external text" href="http://www.scientificamerican.com/article.cfm?id=misconceptions-about-the-2005-03&page=5">the original</a> on 10 August 2011<span class="reference-accessdate">. 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University of Tennessee, Knoxville. Archived from <a rel="nofollow" class="external text" href="http://csep10.phys.utk.edu/guidry/violence/distances.html">the original</a> on 12 December 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">26 March</span> 2010</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Astronomy+162%3A+Stars%2C+Galaxies%2C+and+Cosmology&rft.atitle=Astronomical+Distance+Scales&rft.aulast=Guidry&rft.aufirst=Michael&rft_id=http%3A%2F%2Fcsep10.phys.utk.edu%2Fguidry%2Fviolence%2Fdistances.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AParsec" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMerrifield" class="citation web cs1">Merrifield, Michael. <a rel="nofollow" class="external text" href="http://www.sixtysymbols.com/videos/parsec.htm">"pc Parsec"</a>. <i>Sixty Symbols</i>. <a href="/wiki/Brady_Haran" title="Brady Haran">Brady Haran</a> for the <a href="/wiki/University_of_Nottingham" title="University of Nottingham">University of Nottingham</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Sixty+Symbols&rft.atitle=pc+Parsec&rft.aulast=Merrifield&rft.aufirst=Michael&rft_id=http%3A%2F%2Fwww.sixtysymbols.com%2Fvideos%2Fparsec.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AParsec" class="Z3988"></span></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist 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href="/wiki/Special:EditPage/Template:Units_of_length_used_in_Astronomy" title="Special:EditPage/Template:Units of length used in Astronomy"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Units_of_length_used_in_Astronomy" style="font-size:114%;margin:0 4em"><a href="/wiki/Unit_of_length" title="Unit of length">Units of length</a> used in <a href="/wiki/Astronomy" title="Astronomy">Astronomy</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><a href="/wiki/Astronomical_system_of_units" title="Astronomical system of units">Astronomical system of units</a></li></ul> </div></td></tr><tr><td colspan="2" class="navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Earth_radius_(unit)" class="mw-redirect" title="Earth radius (unit)">Earth radius</a> (<var>R</var><sub>🜨</sub> or <i>R<sub>E</sub></i>)</li> <li><a href="/wiki/Light-second" title="Light-second">Light-second</a> (ls)</li> <li><a href="/wiki/Solar_radius" title="Solar radius">Solar radius</a> (<var>R</var><sub>☉</sub>)</li> <li><a href="/wiki/Gigametre" class="mw-redirect" title="Gigametre">gigametre</a> (Gm)</li> <li><a href="/wiki/Astronomical_unit" title="Astronomical unit">Astronomical unit</a> (au)</li> <li><a href="/wiki/Terametre" class="mw-redirect" title="Terametre">terametre</a> (Tm)</li> <li><a href="/wiki/Light-year" title="Light-year">light-year</a> (ly)</li> <li><a class="mw-selflink selflink">parsec</a> (pc)</li> <li><a href="/wiki/Kiloparsec" class="mw-redirect" title="Kiloparsec">kiloparsec</a> (kpc)</li> <li><a href="/wiki/Megaparsec" class="mw-redirect" title="Megaparsec">megaparsec</a> (Mpc)</li> <li><a href="/wiki/Gigaparsec" class="mw-redirect" title="Gigaparsec">gigaparsec</a> (Gpc)</li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <dl><dt>See also</dt> <dd><a href="/wiki/Cosmic_distance_ladder" title="Cosmic distance ladder">Cosmic distance ladder</a></dd> <dd><a href="/wiki/Orders_of_magnitude_(length)" title="Orders of magnitude (length)">Orders of magnitude (length)</a></dd> <dd><a href="/wiki/Conversion_of_units" title="Conversion of units">Conversion of units</a></dd></dl> </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 auto;min-height:24px}.mw-parser-output .portal-bar-content{display:flex;flex-flow:row wrap;flex:0 1 auto;padding:0.15em 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