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data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Discovery" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Discovery"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Discovery</span> </div> </a> <ul id="toc-Discovery-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Etymology" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Etymology"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Etymology</span> </div> </a> <ul id="toc-Etymology-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Classifications" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Classifications"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Classifications</span> </div> </a> <button aria-controls="toc-Classifications-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 Classifications subsection</span> </button> <ul id="toc-Classifications-sublist" class="vector-toc-list"> <li id="toc-Methods_of_observation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Methods_of_observation"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Methods of observation</span> </div> </a> <ul id="toc-Methods_of_observation-sublist" class="vector-toc-list"> <li id="toc-Visual_binaries" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Visual_binaries"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.1</span> <span>Visual binaries</span> </div> </a> <ul id="toc-Visual_binaries-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Spectroscopic_binaries" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Spectroscopic_binaries"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.2</span> <span>Spectroscopic binaries</span> </div> </a> <ul id="toc-Spectroscopic_binaries-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Eclipsing_binaries" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Eclipsing_binaries"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.3</span> <span>Eclipsing binaries</span> </div> </a> <ul id="toc-Eclipsing_binaries-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Non-eclipsing_binaries_that_can_be_detected_through_photometry" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Non-eclipsing_binaries_that_can_be_detected_through_photometry"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.4</span> <span>Non-eclipsing binaries that can be detected through photometry</span> </div> </a> <ul id="toc-Non-eclipsing_binaries_that_can_be_detected_through_photometry-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Astrometric_binaries" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Astrometric_binaries"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1.5</span> <span>Astrometric binaries</span> </div> </a> <ul id="toc-Astrometric_binaries-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Configuration_of_the_system" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Configuration_of_the_system"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Configuration of the system</span> </div> </a> <ul id="toc-Configuration_of_the_system-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Cataclysmic_variables_and_X-ray_binaries" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Cataclysmic_variables_and_X-ray_binaries"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Cataclysmic variables and X-ray binaries</span> </div> </a> <ul id="toc-Cataclysmic_variables_and_X-ray_binaries-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Orbital_period" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Orbital_period"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Orbital period</span> </div> </a> <button aria-controls="toc-Orbital_period-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 Orbital period subsection</span> </button> <ul id="toc-Orbital_period-sublist" class="vector-toc-list"> <li id="toc-Variations_in_period" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Variations_in_period"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Variations in period</span> </div> </a> <ul id="toc-Variations_in_period-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Designations" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Designations"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Designations</span> </div> </a> <button aria-controls="toc-Designations-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 Designations subsection</span> </button> <ul id="toc-Designations-sublist" class="vector-toc-list"> <li id="toc-A_and_B" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#A_and_B"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>A and B</span> </div> </a> <ul id="toc-A_and_B-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Discoverer_designations" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Discoverer_designations"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Discoverer designations</span> </div> </a> <ul id="toc-Discoverer_designations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Hot_and_cold" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Hot_and_cold"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3</span> <span>Hot and cold</span> </div> </a> <ul id="toc-Hot_and_cold-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Evolution" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Evolution"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Evolution</span> </div> </a> <button aria-controls="toc-Evolution-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 Evolution subsection</span> </button> <ul id="toc-Evolution-sublist" class="vector-toc-list"> <li id="toc-Formation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Formation"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.1</span> <span>Formation</span> </div> </a> <ul id="toc-Formation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Mass_transfer_and_accretion" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Mass_transfer_and_accretion"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.2</span> <span>Mass transfer and accretion</span> </div> </a> <ul id="toc-Mass_transfer_and_accretion-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Runaways_and_novae" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Runaways_and_novae"> <div class="vector-toc-text"> <span class="vector-toc-numb">6.3</span> <span>Runaways and novae</span> </div> </a> <ul id="toc-Runaways_and_novae-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Astrophysics" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Astrophysics"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Astrophysics</span> </div> </a> <button aria-controls="toc-Astrophysics-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 Astrophysics subsection</span> </button> <ul id="toc-Astrophysics-sublist" class="vector-toc-list"> <li id="toc-Calculating_the_center_of_mass_in_binary_stars" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Calculating_the_center_of_mass_in_binary_stars"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.1</span> <span>Calculating the center of mass in binary stars</span> </div> </a> <ul id="toc-Calculating_the_center_of_mass_in_binary_stars-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Center-of-mass_animations" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Center-of-mass_animations"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.2</span> <span>Center-of-mass animations</span> </div> </a> <ul id="toc-Center-of-mass_animations-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Research_findings" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Research_findings"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.3</span> <span>Research findings</span> </div> </a> <ul id="toc-Research_findings-sublist" class="vector-toc-list"> <li id="toc-Planets" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Planets"> <div class="vector-toc-text"> <span class="vector-toc-numb">7.3.1</span> <span>Planets</span> </div> </a> <ul id="toc-Planets-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> </ul> </li> <li id="toc-Examples" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Examples"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Examples</span> </div> </a> <ul id="toc-Examples-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Multiple-star_examples" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Multiple-star_examples"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>Multiple-star examples</span> </div> </a> <ul id="toc-Multiple-star_examples-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes_and_references" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#Notes_and_references"> <div class="vector-toc-text"> <span class="vector-toc-numb">11</span> <span>Notes and references</span> </div> </a> <ul id="toc-Notes_and_references-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">12</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">Binary star</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 79 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-79" 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">79 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/Dubbelster" title="Dubbelster – Afrikaans" lang="af" hreflang="af" data-title="Dubbelster" 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%86%D8%AC%D9%85_%D8%AB%D9%86%D8%A7%D8%A6%D9%8A" title="نجم ثنائي – Arabic" lang="ar" hreflang="ar" data-title="نجم ثنائي" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Estrella_binaria" title="Estrella binaria – Asturian" lang="ast" hreflang="ast" data-title="Estrella binaria" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AF%E0%A7%81%E0%A6%97%E0%A7%8D%E0%A6%AE_%E0%A6%A4%E0%A6%BE%E0%A6%B0%E0%A6%BE" title="যুগ্ম তারা – Bangla" lang="bn" hreflang="bn" data-title="যুগ্ম তারা" 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%D0%B4%D0%B2%D0%BE%D0%B9%D0%BD%D1%8B%D1%8F_%D0%B7%D0%BE%D1%80%D0%BA%D1%96" title="Падвойныя зоркі – Belarusian" lang="be" hreflang="be" data-title="Падвойныя зоркі" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%94%D0%B2%D0%BE%D0%B9%D0%BD%D0%B0_%D0%B7%D0%B2%D0%B5%D0%B7%D0%B4%D0%B0" title="Двойна звезда – Bulgarian" lang="bg" hreflang="bg" data-title="Двойна звезда" 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/Dvostruka_zvijezda" title="Dvostruka zvijezda – Bosnian" lang="bs" hreflang="bs" data-title="Dvostruka zvijezda" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-ca badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://ca.wikipedia.org/wiki/Estrella_bin%C3%A0ria" title="Estrella binària – Catalan" lang="ca" hreflang="ca" data-title="Estrella binària" 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%98%D0%BA%D0%BA%C4%95%D0%BB%D0%BB%D0%B5_%C3%A7%C4%83%D0%BB%D1%82%C4%83%D1%80" title="Иккĕлле çăлтăр – Chuvash" lang="cv" hreflang="cv" data-title="Иккĕлле çăлтăр" 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/Dvojhv%C4%9Bzda" title="Dvojhvězda – Czech" lang="cs" hreflang="cs" data-title="Dvojhvězda" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-cy mw-list-item"><a href="https://cy.wikipedia.org/wiki/Seren_ddwbl" title="Seren ddwbl – Welsh" lang="cy" hreflang="cy" data-title="Seren ddwbl" data-language-autonym="Cymraeg" data-language-local-name="Welsh" class="interlanguage-link-target"><span>Cymraeg</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Dobbeltstjerne" title="Dobbeltstjerne – Danish" lang="da" hreflang="da" data-title="Dobbeltstjerne" 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/Doppelstern" title="Doppelstern – German" lang="de" hreflang="de" data-title="Doppelstern" 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/Kaksikt%C3%A4ht" title="Kaksiktäht – Estonian" lang="et" hreflang="et" data-title="Kaksiktäht" 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%94%CE%B9%CF%80%CE%BB%CF%8C%CF%82_%CE%B1%CF%83%CF%84%CE%AD%CF%81%CE%B1%CF%82" title="Διπλός αστέρας – Greek" lang="el" hreflang="el" data-title="Διπλός αστέρας" 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/Estrella_binaria" title="Estrella binaria – Spanish" lang="es" hreflang="es" data-title="Estrella binaria" 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/Duopa_stelo" title="Duopa stelo – Esperanto" lang="eo" hreflang="eo" data-title="Duopa stelo" 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/Izar_bitar" title="Izar bitar – Basque" lang="eu" hreflang="eu" data-title="Izar bitar" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%B3%D8%AA%D8%A7%D8%B1%D9%87_%D8%AF%D9%88%D8%AA%D8%A7%DB%8C%DB%8C" title="ستاره دوتایی – Persian" lang="fa" hreflang="fa" data-title="ستاره دوتایی" 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/%C3%89toile_binaire" title="Étoile binaire – French" lang="fr" hreflang="fr" data-title="Étoile binaire" 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/D%C3%A9r%C3%A9alta" title="Déréalta – Irish" lang="ga" hreflang="ga" data-title="Déréalta" 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/Estrela_binaria" title="Estrela binaria – Galician" lang="gl" hreflang="gl" data-title="Estrela binaria" 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%A6%E0%AB%8D%E0%AA%B5%E0%AA%BF%E0%AA%B8%E0%AA%82%E0%AA%97%E0%AB%80_%E0%AA%A4%E0%AA%BE%E0%AA%B0%E0%AB%8B" title="દ્વિસંગી તારો – Gujarati" lang="gu" hreflang="gu" data-title="દ્વિસંગી તારો" 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/%EC%8C%8D%EC%84%B1" title="쌍성 – Korean" lang="ko" hreflang="ko" data-title="쌍성" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D4%BF%D6%80%D5%AF%D5%B6%D5%A1%D5%AF%D5%AB_%D5%A1%D5%BD%D5%BF%D5%B2" title="Կրկնակի աստղ – Armenian" lang="hy" hreflang="hy" data-title="Կրկնակի աստղ" 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%A6%E0%A5%8D%E0%A4%B5%E0%A4%BF%E0%A4%A4%E0%A4%BE%E0%A4%B0%E0%A4%BE" title="द्वितारा – Hindi" lang="hi" hreflang="hi" data-title="द्वितारा" 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/Dvojna_zvijezda" title="Dvojna zvijezda – Croatian" lang="hr" hreflang="hr" data-title="Dvojna zvijezda" 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/Duopla_stelo" title="Duopla stelo – Ido" lang="io" hreflang="io" data-title="Duopla stelo" data-language-autonym="Ido" data-language-local-name="Ido" class="interlanguage-link-target"><span>Ido</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Bintang_biner" title="Bintang biner – Indonesian" lang="id" hreflang="id" data-title="Bintang biner" 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/Tv%C3%ADstirni" title="Tvístirni – Icelandic" lang="is" hreflang="is" data-title="Tvístirni" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target"><span>Íslenska</span></a></li><li class="interlanguage-link interwiki-it badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://it.wikipedia.org/wiki/Stella_binaria" title="Stella binaria – Italian" lang="it" hreflang="it" data-title="Stella binaria" 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%9B%D7%95%D7%9B%D7%91_%D7%9B%D7%A4%D7%95%D7%9C" title="כוכב כפול – Hebrew" lang="he" hreflang="he" data-title="כוכב כפול" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-jv mw-list-item"><a href="https://jv.wikipedia.org/wiki/Lintang_gandha" title="Lintang gandha – Javanese" lang="jv" hreflang="jv" data-title="Lintang gandha" data-language-autonym="Jawa" data-language-local-name="Javanese" class="interlanguage-link-target"><span>Jawa</span></a></li><li class="interlanguage-link interwiki-kn mw-list-item"><a href="https://kn.wikipedia.org/wiki/%E0%B2%85%E0%B2%B5%E0%B2%B3%E0%B2%BF_%E0%B2%A8%E0%B2%95%E0%B3%8D%E0%B2%B7%E0%B2%A4%E0%B3%8D%E0%B2%B0%E0%B2%97%E0%B2%B3%E0%B3%81" title="ಅವಳಿ ನಕ್ಷತ್ರಗಳು – Kannada" lang="kn" hreflang="kn" data-title="ಅವಳಿ ನಕ್ಷತ್ರಗಳು" data-language-autonym="ಕನ್ನಡ" data-language-local-name="Kannada" class="interlanguage-link-target"><span>ಕನ್ನಡ</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D2%9A%D0%BE%D1%81%D0%B0%D1%80%D0%B6%D2%B1%D0%BB%D0%B4%D1%8B%D0%B7" title="Қосаржұлдыз – Kazakh" lang="kk" hreflang="kk" data-title="Қосаржұлдыз" 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/Nyota_maradufu" title="Nyota maradufu – Swahili" lang="sw" hreflang="sw" data-title="Nyota maradufu" data-language-autonym="Kiswahili" data-language-local-name="Swahili" class="interlanguage-link-target"><span>Kiswahili</span></a></li><li class="interlanguage-link interwiki-ht mw-list-item"><a href="https://ht.wikipedia.org/wiki/%C3%89twal_bin%C3%A8" title="Étwal binè – Haitian Creole" lang="ht" hreflang="ht" data-title="Étwal binè" data-language-autonym="Kreyòl ayisyen" data-language-local-name="Haitian Creole" class="interlanguage-link-target"><span>Kreyòl ayisyen</span></a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%9A%D0%BE%D1%88_%D0%B6%D1%8B%D0%BB%D0%B4%D1%8B%D0%B7" title="Кош жылдыз – Kyrgyz" lang="ky" hreflang="ky" data-title="Кош жылдыз" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Stella_binaria" title="Stella binaria – Latin" lang="la" hreflang="la" data-title="Stella binaria" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Fizik%C4%81l%C4%81_dubultzvaigzne" title="Fizikālā dubultzvaigzne – Latvian" lang="lv" hreflang="lv" data-title="Fizikālā dubultzvaigzne" 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/Duebelst%C3%A4r" title="Duebelstär – Luxembourgish" lang="lb" hreflang="lb" data-title="Duebelstär" 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/Dvinar%C4%97_%C5%BEvaig%C5%BEd%C4%97" title="Dvinarė žvaigždė – Lithuanian" lang="lt" hreflang="lt" data-title="Dvinarė žvaigždė" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Kett%C5%91scsillag" title="Kettőscsillag – Hungarian" lang="hu" hreflang="hu" data-title="Kettőscsillag" 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%94%D0%B2%D0%BE%D1%98%D0%BD%D0%B0_%D1%95%D0%B2%D0%B5%D0%B7%D0%B4%D0%B0" title="Двојна ѕвезда – Macedonian" lang="mk" hreflang="mk" data-title="Двојна ѕвезда" 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%A6%E0%B5%8D%E0%B4%B5%E0%B4%A8%E0%B5%8D%E0%B4%A6%E0%B5%8D%E0%B4%B5%E0%B4%A8%E0%B4%95%E0%B5%8D%E0%B4%B7%E0%B4%A4%E0%B5%8D%E0%B4%B0%E0%B4%82" title="ദ്വന്ദ്വനക്ഷത്രം – Malayalam" lang="ml" hreflang="ml" data-title="ദ്വന്ദ്വനക്ഷത്രം" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-xmf mw-list-item"><a href="https://xmf.wikipedia.org/wiki/%E1%83%9F%E1%83%98%E1%83%A0%E1%83%9B%E1%83%A3%E1%83%A0%E1%83%98%E1%83%AA%E1%83%AE%E1%83%98" title="ჟირმურიცხი – Mingrelian" lang="xmf" hreflang="xmf" data-title="ჟირმურიცხი" 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/Bintang_dedua" title="Bintang dedua – Malay" lang="ms" hreflang="ms" data-title="Bintang dedua" 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%80%E1%80%BC%E1%80%9A%E1%80%BA%E1%80%85%E1%80%AF%E1%80%B6%E1%80%90%E1%80%BD%E1%80%B2" title="ကြယ်စုံတွဲ – Burmese" lang="my" hreflang="my" data-title="ကြယ်စုံတွဲ" 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/Dubbelster" title="Dubbelster – Dutch" lang="nl" hreflang="nl" data-title="Dubbelster" 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/%E9%80%A3%E6%98%9F" title="連星 – Japanese" lang="ja" hreflang="ja" data-title="連星" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-pih mw-list-item"><a href="https://pih.wikipedia.org/wiki/Binarii_sdar" title="Binarii sdar – Norfuk / Pitkern" lang="pih" hreflang="pih" data-title="Binarii sdar" data-language-autonym="Norfuk / Pitkern" data-language-local-name="Norfuk / Pitkern" class="interlanguage-link-target"><span>Norfuk / Pitkern</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Dobbeltstjerne" title="Dobbeltstjerne – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Dobbeltstjerne" 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/Dobbeltstjerne" title="Dobbeltstjerne – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Dobbeltstjerne" 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-nov mw-list-item"><a href="https://nov.wikipedia.org/wiki/Duopli_stele" title="Duopli stele – Novial" lang="nov" hreflang="nov" data-title="Duopli stele" data-language-autonym="Novial" data-language-local-name="Novial" class="interlanguage-link-target"><span>Novial</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Estela_bin%C3%A0ria" title="Estela binària – Occitan" lang="oc" hreflang="oc" data-title="Estela binària" 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/Qo%CA%BBshaloq_yulduzlar" title="Qoʻshaloq yulduzlar – Uzbek" lang="uz" hreflang="uz" data-title="Qoʻshaloq yulduzlar" 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-pa mw-list-item"><a href="https://pa.wikipedia.org/wiki/%E0%A8%A6%E0%A9%8B%E0%A8%B9%E0%A8%B0%E0%A8%BE_%E0%A8%A4%E0%A8%BE%E0%A8%B0%E0%A8%BE" title="ਦੋਹਰਾ ਤਾਰਾ – Punjabi" lang="pa" hreflang="pa" data-title="ਦੋਹਰਾ ਤਾਰਾ" data-language-autonym="ਪੰਜਾਬੀ" data-language-local-name="Punjabi" class="interlanguage-link-target"><span>ਪੰਜਾਬੀ</span></a></li><li class="interlanguage-link interwiki-pnb mw-list-item"><a href="https://pnb.wikipedia.org/wiki/%D8%AF%D9%88%DB%81%D8%B1%D8%A7_%D8%AA%D8%A7%D8%B1%DB%81" title="دوہرا تارہ – Western Punjabi" lang="pnb" hreflang="pnb" data-title="دوہرا تارہ" data-language-autonym="پنجابی" data-language-local-name="Western Punjabi" class="interlanguage-link-target"><span>پنجابی</span></a></li><li class="interlanguage-link interwiki-nds mw-list-item"><a href="https://nds.wikipedia.org/wiki/Dubbelsteern" title="Dubbelsteern – Low German" lang="nds" hreflang="nds" data-title="Dubbelsteern" data-language-autonym="Plattdüütsch" data-language-local-name="Low German" class="interlanguage-link-target"><span>Plattdüütsch</span></a></li><li class="interlanguage-link interwiki-pl badge-Q70894304 mw-list-item" title=""><a href="https://pl.wikipedia.org/wiki/Gwiazda_binarna" title="Gwiazda binarna – Polish" lang="pl" hreflang="pl" data-title="Gwiazda binarna" 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/Estrela_bin%C3%A1ria" title="Estrela binária – Portuguese" lang="pt" hreflang="pt" data-title="Estrela binária" 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/Stea_binar%C4%83" title="Stea binară – Romanian" lang="ro" hreflang="ro" data-title="Stea binară" 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%94%D0%B2%D0%BE%D0%B9%D0%BD%D0%B0%D1%8F_%D0%B7%D0%B2%D0%B5%D0%B7%D0%B4%D0%B0" title="Двойная звезда – Russian" lang="ru" hreflang="ru" data-title="Двойная звезда" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Binary_star" title="Binary star – Simple English" lang="en-simple" hreflang="en-simple" data-title="Binary star" 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/Dvojhviezda" title="Dvojhviezda – Slovak" lang="sk" hreflang="sk" data-title="Dvojhviezda" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/Dvojne_i_vi%C5%A1estruke_zvezde" title="Dvojne i višestruke zvezde – Serbian" lang="sr" hreflang="sr" data-title="Dvojne i višestruke zvezde" 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/Dvojne_i_vi%C5%A1estruke_zvijezde" title="Dvojne i višestruke zvijezde – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Dvojne i višestruke zvijezde" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-su mw-list-item"><a href="https://su.wikipedia.org/wiki/B%C3%A9ntang_ganda" title="Béntang ganda – Sundanese" lang="su" hreflang="su" data-title="Béntang ganda" data-language-autonym="Sunda" data-language-local-name="Sundanese" class="interlanguage-link-target"><span>Sunda</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Kaksoist%C3%A4hti" title="Kaksoistähti – Finnish" lang="fi" hreflang="fi" data-title="Kaksoistähti" 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/Dubbelstj%C3%A4rna" title="Dubbelstjärna – Swedish" lang="sv" hreflang="sv" data-title="Dubbelstjärna" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%87%E0%AE%B0%E0%AF%81%E0%AE%AE_%E0%AE%B5%E0%AE%BF%E0%AE%A3%E0%AF%8D%E0%AE%AE%E0%AF%80%E0%AE%A9%E0%AF%8D" title="இரும விண்மீன் – Tamil" lang="ta" hreflang="ta" data-title="இரும விண்மீன்" 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%9A%D1%83%D1%88_%D0%B9%D0%BE%D0%BB%D0%B4%D1%8B%D0%B7" title="Куш йолдыз – Tatar" lang="tt" hreflang="tt" data-title="Куш йолдыз" 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 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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 the hip hop group, see <a href="/wiki/Binary_Star_(hip_hop_group)" title="Binary Star (hip hop group)">Binary Star (hip hop group)</a>.</div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Sirius_A_and_B_Hubble_photo.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f3/Sirius_A_and_B_Hubble_photo.jpg/260px-Sirius_A_and_B_Hubble_photo.jpg" decoding="async" width="260" height="284" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/f/f3/Sirius_A_and_B_Hubble_photo.jpg 1.5x" data-file-width="369" data-file-height="403" /></a><figcaption>The well-known binary star <a href="/wiki/Sirius" title="Sirius">Sirius</a>, seen here in a <a href="/wiki/Hubble_Space_Telescope" title="Hubble Space Telescope">Hubble</a> photograph from 2005, with Sirius A in the center, and <a href="/wiki/White_dwarf" title="White dwarf">white dwarf</a>, Sirius B, to the left bottom from it</figcaption></figure> <p>A <b>binary star</b> or <b>binary star system</b> is a <a href="/wiki/Star_system" title="Star system">system</a> of two <a href="/wiki/Star" title="Star">stars</a> that are <a href="/wiki/Gravity" title="Gravity">gravitationally</a> bound to and in <a href="/wiki/Orbit" title="Orbit">orbit</a> around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars using a <a href="/wiki/Telescope" title="Telescope">telescope</a>, in which case they are called <i>visual binaries</i>. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as <a href="/wiki/Spectroscopy" title="Spectroscopy">spectroscopy</a> (<i>spectroscopic binaries</i>) or <a href="/wiki/Astrometry" title="Astrometry">astrometry</a> (<i>astrometric binaries</i>). If a binary star happens to orbit in a plane along our line of sight, its components will <a href="/wiki/Eclipse" title="Eclipse">eclipse</a> and <a href="/wiki/Transit_(astronomy)" class="mw-redirect" title="Transit (astronomy)">transit</a> each other; these pairs are called <i>eclipsing binaries</i>, or, together with other binaries that change brightness as they orbit, <i>photometric binaries</i>. </p><p>If components in binary star systems are close enough, they can gravitationally distort each other's outer stellar atmospheres. In some cases, these <i>close <a href="/wiki/Binary_system" title="Binary system">binary systems</a></i> can exchange mass, which may bring their <a href="/wiki/Stellar_evolution" title="Stellar evolution">evolution</a> to stages that single stars cannot attain. Examples of binaries are <a href="/wiki/Sirius" title="Sirius">Sirius</a>, and <a href="/wiki/Cygnus_X-1" title="Cygnus X-1">Cygnus X-1</a> (Cygnus X-1 being a well-known <a href="/wiki/Black_hole" title="Black hole">black hole</a>). Binary stars are also common as the nuclei of many <a href="/wiki/Planetary_nebula" title="Planetary nebula">planetary nebulae</a>, and are the progenitors of both <a href="/wiki/Nova" title="Nova">novae</a> and <a href="/wiki/Type_Ia_supernova" title="Type Ia supernova">type Ia supernovae</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Discovery">Discovery</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=1" title="Edit section: Discovery"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Double_star" title="Double star">Double stars</a>, a pair of stars that appear close to each other, have been observed since the invention of the <a href="/wiki/Telescope" title="Telescope">telescope</a>. Early examples include <a href="/wiki/Mizar" title="Mizar">Mizar</a> and <a href="/wiki/Acrux" title="Acrux">Acrux</a>. Mizar, in the <a href="/wiki/Big_Dipper" title="Big Dipper">Big Dipper</a> (<a href="/wiki/Ursa_Major" title="Ursa Major">Ursa Major</a>), was observed to be double by <a href="/wiki/Giovanni_Battista_Riccioli" title="Giovanni Battista Riccioli">Giovanni Battista Riccioli</a> in 1650<sup id="cite_ref-aitken1_1-0" class="reference"><a href="#cite_note-aitken1-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> (and probably earlier by <a href="/wiki/Benedetto_Castelli" title="Benedetto Castelli">Benedetto Castelli</a> and <a href="/wiki/Galileo_Galilei" title="Galileo Galilei">Galileo</a>).<sup id="cite_ref-newviewofmizar_3-0" class="reference"><a href="#cite_note-newviewofmizar-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> The bright southern star <a href="/wiki/Acrux" title="Acrux">Acrux</a>, in the <a href="/wiki/Crux" title="Crux">Southern Cross</a>, was discovered to be double by Father Fontenay in 1685.<sup id="cite_ref-aitken1_1-1" class="reference"><a href="#cite_note-aitken1-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>Evidence that stars in pairs were more than just optical alignments came in 1767 when English natural philosopher and clergyman <a href="/wiki/John_Michell" title="John Michell">John Michell</a> became the first person to apply the mathematics of statistics to the study of the stars, demonstrating in a paper that many more stars occur in pairs or groups than a perfectly random distribution and chance alignment could account for. He focused his investigation on the <a href="/wiki/Pleiades" title="Pleiades">Pleiades</a> cluster, and calculated that the likelihood of finding such a close grouping of stars was about one in half a million. He concluded that the stars in these double or multiple star systems might be drawn to one another by gravitational pull, thus providing the first evidence for the existence of binary stars and star clusters.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/William_Herschel" title="William Herschel">William Herschel</a> began observing double stars in 1779, hoping to find a near star paired with a distant star so he could measure the near star's changing position as the Earth orbited the Sun (measure its <a href="/wiki/Parallax" title="Parallax">parallax</a>), allowing him to calculate the distance to the near star. He would soon publish catalogs of about 700 double stars.<sup id="cite_ref-Aitken_5-0" class="reference"><a href="#cite_note-Aitken-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Heintz4_6-0" class="reference"><a href="#cite_note-Heintz4-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> By 1803, he had observed changes in the relative positions in a number of double stars over the course of 25 years, and concluded that, instead of showing parallax changes, they seemed to be <a href="/wiki/Orbit" title="Orbit">orbiting</a> each other in binary systems.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> The first orbit of a binary star was computed in 1827, when <a href="/wiki/F%C3%A9lix_Savary" title="Félix Savary">Félix Savary</a> computed the orbit of <a href="/wiki/Xi_Ursae_Majoris" title="Xi Ursae Majoris">Xi Ursae Majoris</a>.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>Over the years, many more double stars have been catalogued and measured. As of June 2017, the <a href="/wiki/Washington_Double_Star_Catalog" title="Washington Double Star Catalog">Washington Double Star Catalog</a>, a database of visual double stars compiled by the <a href="/wiki/United_States_Naval_Observatory" title="United States Naval Observatory">United States Naval Observatory</a>, contains over 100,000 pairs of double stars,<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> including optical doubles as well as binary stars. Orbits are known for only a few thousand of these double stars.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Etymology">Etymology</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=2" title="Edit section: Etymology"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The term <i>binary</i> was first used in this context by Sir <a href="/wiki/William_Herschel" title="William Herschel">William Herschel</a> in 1802,<sup id="cite_ref-aitkenix_11-0" class="reference"><a href="#cite_note-aitkenix-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> when he wrote:<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <style data-mw-deduplicate="TemplateStyles:r1244412712">.mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}}</style><blockquote class="templatequote"><p>If, on the contrary, two stars should really be situated very near each other, and at the same time so far insulated as not to be materially affected by the attractions of neighbouring stars, they will then compose a separate system, and remain united by the bond of their own mutual gravitation towards each other. This should be called a real double star; and any two stars that are thus mutually connected, form the binary sidereal system which we are now to consider.</p></blockquote> <p>By the modern definition, the term <i>binary star</i> is generally restricted to pairs of stars which revolve around a common center of mass. Binary stars which can be <a href="/wiki/Optical_resolution" title="Optical resolution">resolved</a> with a telescope or <a href="/wiki/Interferometry" title="Interferometry">interferometric</a> methods are known as <i>visual binaries</i>.<sup id="cite_ref-Heintz12_13-0" class="reference"><a href="#cite_note-Heintz12-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-csep10_14-0" class="reference"><a href="#cite_note-csep10-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> For most of the known visual binary stars one whole revolution has not been observed yet; rather, they are observed to have travelled along a curved path or a partial arc.<sup id="cite_ref-Heintz5_15-0" class="reference"><a href="#cite_note-Heintz5-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Gwiazda_podw%C3%B3jna_za%C4%87mieniowa_schemat.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/3d/Gwiazda_podw%C3%B3jna_za%C4%87mieniowa_schemat.svg/220px-Gwiazda_podw%C3%B3jna_za%C4%87mieniowa_schemat.svg.png" decoding="async" width="220" height="79" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/3d/Gwiazda_podw%C3%B3jna_za%C4%87mieniowa_schemat.svg/330px-Gwiazda_podw%C3%B3jna_za%C4%87mieniowa_schemat.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/3d/Gwiazda_podw%C3%B3jna_za%C4%87mieniowa_schemat.svg/440px-Gwiazda_podw%C3%B3jna_za%C4%87mieniowa_schemat.svg.png 2x" data-file-width="1201" data-file-height="431" /></a><figcaption>Eclipsing binary showing different phases of the smaller secondary relative to the primary star (center)</figcaption></figure> <p>The more general term <i><a href="/wiki/Double_star" title="Double star">double star</a></i> is used for pairs of stars which are seen to be close together in the sky.<sup id="cite_ref-aitkenix_11-1" class="reference"><a href="#cite_note-aitkenix-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> This distinction is rarely made in languages other than English.<sup id="cite_ref-Heintz12_13-1" class="reference"><a href="#cite_note-Heintz12-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> Double stars may be <a href="/wiki/Binary_system_(astronomy)" class="mw-redirect" title="Binary system (astronomy)">binary systems</a> or may be merely two stars that appear to be close together in the sky but have vastly different true distances from the Sun. The latter are termed <i>optical doubles</i> or <i>optical pairs</i>.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Classifications">Classifications</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=3" title="Edit section: Classifications"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:HD_106906_b_imaged_by_SPHERE.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/fd/HD_106906_b_imaged_by_SPHERE.jpg/220px-HD_106906_b_imaged_by_SPHERE.jpg" decoding="async" width="220" height="193" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/fd/HD_106906_b_imaged_by_SPHERE.jpg/330px-HD_106906_b_imaged_by_SPHERE.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/fd/HD_106906_b_imaged_by_SPHERE.jpg/440px-HD_106906_b_imaged_by_SPHERE.jpg 2x" data-file-width="1348" data-file-height="1182" /></a><figcaption>Edge-on disc of gas and dust present around the binary star system <a href="/wiki/HD_106906" title="HD 106906">HD 106906</a></figcaption></figure> <div class="mw-heading mw-heading3"><h3 id="Methods_of_observation">Methods of observation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=4" title="Edit section: Methods of observation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Binary stars are classified into four types according to the way in which they are observed: visually, by observation; <a href="/wiki/Spectroscopy" title="Spectroscopy">spectroscopically</a>, by periodic changes in <a href="/wiki/Spectral_line" title="Spectral line">spectral lines</a>; <a href="/wiki/Photometry_(astronomy)" title="Photometry (astronomy)">photometrically</a>, by changes in brightness caused by an eclipse; or <a href="/wiki/Astrometry" title="Astrometry">astrometrically</a>, by measuring a deviation in a star's position caused by an unseen companion.<sup id="cite_ref-Heintz12_13-2" class="reference"><a href="#cite_note-Heintz12-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> Any binary star can belong to several of these classes; for example, several spectroscopic binaries are also eclipsing binaries. </p> <div class="mw-heading mw-heading4"><h4 id="Visual_binaries">Visual binaries</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=5" title="Edit section: Visual binaries"><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">Main article: <a href="/wiki/Visual_binary" title="Visual binary">Visual binary</a></div> <p>A <i><a href="/wiki/Visual_binary" title="Visual binary">visual binary</a></i> star is a binary star for which the angular separation between the two components is great enough to permit them to be observed as a double star in a <a href="/wiki/Telescope" title="Telescope">telescope</a>, or even high-powered <a href="/wiki/Binoculars" title="Binoculars">binoculars</a>. The <a href="/wiki/Angular_resolution" title="Angular resolution">angular resolution</a> of the telescope is an important factor in the detection of visual binaries, and as better angular resolutions are applied to binary star observations, an increasing number of visual binaries will be detected. The relative brightness of the two stars is also an important factor, as glare from a bright star may make it difficult to detect the presence of a fainter component. </p><p>The brighter star of a visual binary is the <i>primary</i> star, and the dimmer is considered the <i>secondary.</i> In some publications (especially older ones), a faint secondary is called the <i><a href="/wiki/Comes" title="Comes">comes</a></i> (plural <i>comites</i>; companion). If the stars are the same brightness, the discoverer designation for the primary is customarily accepted.<sup id="cite_ref-aitken41_18-0" class="reference"><a href="#cite_note-aitken41-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p><p>The <a href="/wiki/Position_angle" title="Position angle">position angle</a> of the secondary with respect to the primary is measured, together with the angular distance between the two stars. The time of observation is also recorded. After a sufficient number of observations are recorded over a period of time, they are plotted in <a href="/wiki/Polar_coordinate_system" title="Polar coordinate system">polar coordinates</a> with the primary star at the origin, and the most probable <a href="/wiki/Ellipse" title="Ellipse">ellipse</a> is drawn through these points such that the <a href="/wiki/Kepler%27s_laws_of_planetary_motion" title="Kepler's laws of planetary motion">Keplerian law of areas</a> is satisfied. This ellipse is known as the <i>apparent ellipse</i>, and is the projection of the actual elliptical orbit of the secondary with respect to the primary on the plane of the sky. From this projected ellipse the complete elements of the orbit may be computed, where the <a href="/wiki/Semi-major_axis" class="mw-redirect" title="Semi-major axis">semi-major axis</a> can only be expressed in angular units unless the <a href="/wiki/Parallax" title="Parallax">stellar parallax</a>, and hence the distance, of the system is known.<sup id="cite_ref-csep10_14-1" class="reference"><a href="#cite_note-csep10-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Spectroscopic_binaries">Spectroscopic binaries</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=6" title="Edit section: Spectroscopic binaries"><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-More_citations_needed_section plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Binary_star" title="Special:EditPage/Binary star">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a> in this section. Unsourced material may be challenged and removed.</span> <span class="date-container"><i>(<span class="date">July 2012</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> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Algol_AB_movie_imaged_with_the_CHARA_interferometer_-_labeled.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/11/Algol_AB_movie_imaged_with_the_CHARA_interferometer_-_labeled.gif/220px-Algol_AB_movie_imaged_with_the_CHARA_interferometer_-_labeled.gif" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/11/Algol_AB_movie_imaged_with_the_CHARA_interferometer_-_labeled.gif/330px-Algol_AB_movie_imaged_with_the_CHARA_interferometer_-_labeled.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/1/11/Algol_AB_movie_imaged_with_the_CHARA_interferometer_-_labeled.gif 2x" data-file-width="340" data-file-height="340" /></a><figcaption><a href="/wiki/Algol" title="Algol">Algol B</a> orbits <a href="/wiki/Algol" title="Algol">Algol A</a>. This animation was assembled from 55 images of the <a href="/wiki/CHARA_array" title="CHARA array">CHARA interferometer</a> in the <a href="/wiki/H_band_(infrared)" title="H band (infrared)">near-infrared H-band</a>, sorted according to orbital phase.</figcaption></figure> <p>Sometimes, the only evidence of a binary star comes from the <a href="/wiki/Doppler_effect" title="Doppler effect">Doppler effect</a> on its emitted light. In these cases, the binary consists of a pair of stars where the <a href="/wiki/Spectral_line" title="Spectral line">spectral lines</a> in the light emitted from each star shifts first towards the blue, then towards the red, as each moves first towards us, and then away from us, during its motion about their common <a href="/wiki/Center_of_mass" title="Center of mass">center of mass</a>, with the period of their common orbit. </p><p>In these systems, the separation between the stars is usually very small, and the orbital velocity very high. Unless the plane of the orbit happens to be <a href="/wiki/Perpendicular" title="Perpendicular">perpendicular</a> to the line of sight, the orbital velocities have components in the line of sight, and the observed <a href="/wiki/Radial_velocity" title="Radial velocity">radial velocity</a> of the system varies periodically. Since radial velocity can be measured with a <a href="/wiki/Spectrometer" title="Spectrometer">spectrometer</a> by observing the <a href="/wiki/Doppler_effect" title="Doppler effect">Doppler shift</a> of the stars' <a href="/wiki/Spectral_line" title="Spectral line">spectral lines</a>, the binaries detected in this manner are known as <i>spectroscopic binaries</i>. Most of these cannot be resolved as a visual binary, even with <a href="/wiki/Telescope" title="Telescope">telescopes</a> of the highest existing <a href="/wiki/Angular_resolution" title="Angular resolution">resolving power</a>. </p><p>In some spectroscopic binaries, spectral lines from both stars are visible, and the lines are alternately double and single. Such a system is known as a double-lined spectroscopic binary (often denoted "SB2"). In other systems, the spectrum of only one of the stars is seen, and the lines in the spectrum shift periodically towards the blue, then towards red and back again. Such stars are known as single-lined spectroscopic binaries ("SB1"). </p><p>The orbit of a spectroscopic binary is determined by making a long series of observations of the radial velocity of one or both components of the system. The observations are plotted against time, and from the resulting curve a period is determined. If the orbit is <a href="/wiki/Circle" title="Circle">circular</a>, then the curve is a <a href="/wiki/Trigonometric_function" class="mw-redirect" title="Trigonometric function">sine</a> curve. If the orbit is <a href="/wiki/Ellipse" title="Ellipse">elliptical</a>, the shape of the curve depends on the <a href="/wiki/Orbital_eccentricity" title="Orbital eccentricity">eccentricity</a> of the ellipse and the orientation of the major axis with reference to the line of sight. </p><p>It is impossible to determine individually the <a href="/wiki/Semi-major_axis" class="mw-redirect" title="Semi-major axis">semi-major axis</a> <i>a</i> and the inclination of the orbit plane <i>i</i>. However, the product of the semi-major axis and the sine of the inclination (i.e. <span class="nowrap"><i>a</i> sin <i>i</i></span>) may be determined directly in linear units (e.g. kilometres). If either <i>a</i> or <i>i</i> can be determined by other means, as in the case of eclipsing binaries, a complete solution for the orbit can be found.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p><p>Binary stars that are both visual and spectroscopic binaries are rare and are a valuable source of information when found. About 40 are known. Visual binary stars often have large true separations, with periods measured in decades to centuries; consequently, they usually have orbital speeds too small to be measured spectroscopically. Conversely, spectroscopic binary stars move fast in their orbits because they are close together, usually too close to be detected as visual binaries. Binaries that are found to be both visual and spectroscopic thus must be relatively close to Earth. </p> <div class="mw-heading mw-heading4"><h4 id="Eclipsing_binaries"><span class="anchor" id="Eclipsing_binary"></span>Eclipsing binaries</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=7" title="Edit section: Eclipsing binaries"><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">"Eclipsing binaries" redirects here. For the novel, see <a href="/wiki/E._E._Smith_bibliography#Family_D'Alembert" title="E. E. Smith bibliography">E. E. Smith bibliography § Family D'Alembert</a>.</div> <p>An <i>eclipsing binary star</i> is a binary star system in which the orbital plane of the two stars lies so nearly in the line of sight of the observer that the components undergo mutual <a href="/wiki/Eclipse" title="Eclipse">eclipses</a>.<sup id="cite_ref-B-EBS_20-0" class="reference"><a href="#cite_note-B-EBS-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> In the case where the binary is also a spectroscopic binary and the <a href="/wiki/Parallax" title="Parallax">parallax</a> of the system is known, the binary is quite valuable for stellar analysis. <a href="/wiki/Algol" title="Algol">Algol</a>, a triple star system in the <a href="/wiki/Perseus_(constellation)" title="Perseus (constellation)">constellation Perseus</a>, contains the best-known example of an eclipsing binary. </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><span><video id="mwe_player_0" poster="//upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv/260px--Artist%E2%80%99s_impression_of_eclipsing_binary.ogv.jpg" controls="" preload="none" data-mw-tmh="" class="mw-file-element" width="260" height="146" data-durationhint="37" data-mwtitle="Artist’s_impression_of_eclipsing_binary.ogv" data-mwprovider="wikimediacommons" resource="/wiki/File:Artist%E2%80%99s_impression_of_eclipsing_binary.ogv"><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/7/7e/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv.480p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="480p.vp9.webm" data-width="854" data-height="480" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/7/7e/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv.720p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="720p.vp9.webm" data-width="1280" data-height="720" /><source src="//upload.wikimedia.org/wikipedia/commons/7/7e/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv" type="video/ogg; codecs="theora, vorbis"" data-width="1280" data-height="720" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/7/7e/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv.144p.mjpeg.mov" type="video/quicktime" data-transcodekey="144p.mjpeg.mov" data-width="256" data-height="144" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/7/7e/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv.240p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="240p.vp9.webm" data-width="426" data-height="240" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/7/7e/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv.360p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="360p.vp9.webm" data-width="640" data-height="360" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/7/7e/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv/Artist%E2%80%99s_impression_of_eclipsing_binary.ogv.360p.webm" type="video/webm; codecs="vp8, vorbis"" data-transcodekey="360p.webm" data-width="640" data-height="360" /></video></span><figcaption>This video shows an artist's impression of an eclipsing binary star system. As the two stars orbit each other they pass in front of one another and their combined brightness, seen from a distance, decreases.</figcaption></figure> <p>Eclipsing binaries are variable stars, not because the light of the individual components vary but because of the eclipses. The <a href="/wiki/Light_curve" title="Light curve">light curve</a> of an eclipsing binary is characterized by periods of practically constant light, with periodic drops in intensity when one star passes in front of the other. The brightness may drop twice during the orbit, once when the secondary passes in front of the primary and once when the primary passes in front of the secondary. The deeper of the two eclipses is called the primary regardless of which star is being occulted, and if a shallow second eclipse also occurs it is called the secondary eclipse. The size of the brightness drops depends on the relative brightness of the two stars, the proportion of the occulted star that is hidden, and the <a href="/wiki/Surface_brightness" title="Surface brightness">surface brightness</a> (i.e. <a href="/wiki/Effective_temperature" title="Effective temperature">effective temperature</a>) of the stars. Typically the occultation of the hotter star causes the primary eclipse.<sup id="cite_ref-B-EBS_20-1" class="reference"><a href="#cite_note-B-EBS-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p><p>An eclipsing binary's period of orbit may be determined from a study of its <a href="/wiki/Light_curve" title="Light curve">light curve</a>, and the relative sizes of the individual stars can be determined in terms of the radius of the orbit, by observing how quickly the brightness changes as the disc of the nearest star slides over the disc of the other star.<sup id="cite_ref-B-EBS_20-2" class="reference"><a href="#cite_note-B-EBS-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> If it is also a spectroscopic binary, the <a href="/wiki/Orbital_elements" title="Orbital elements">orbital elements</a> can also be determined, and the mass of the stars can be determined relatively easily, which means that the relative densities of the stars can be determined in this case.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p><p>Since about 1995, measurement of extragalactic eclipsing binaries' fundamental parameters has become possible with 8-meter class telescopes. This makes it feasible to use them to directly measure the distances to external galaxies, a process that is more accurate than using <a href="/wiki/Standard_candle" class="mw-redirect" title="Standard candle">standard candles</a>.<sup id="cite_ref-wilson2008_22-0" class="reference"><a href="#cite_note-wilson2008-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> By 2006, they had been used to give direct distance estimates to the <a href="/wiki/Large_Magellanic_Cloud" title="Large Magellanic Cloud">LMC</a>, <a href="/wiki/Small_Magellanic_Cloud" title="Small Magellanic Cloud">SMC</a>, <a href="/wiki/Andromeda_Galaxy" title="Andromeda Galaxy">Andromeda Galaxy</a>, and <a href="/wiki/Triangulum_Galaxy" title="Triangulum Galaxy">Triangulum Galaxy</a>. Eclipsing binaries offer a direct method to gauge the distance to galaxies to an improved 5% level of accuracy.<sup id="cite_ref-Bonanos2006_23-0" class="reference"><a href="#cite_note-Bonanos2006-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Non-eclipsing_binaries_that_can_be_detected_through_photometry">Non-eclipsing binaries that can be detected through photometry</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=8" title="Edit section: Non-eclipsing binaries that can be detected through photometry"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Nearby non-eclipsing binaries can also be <a href="/wiki/Photometry_(astronomy)" title="Photometry (astronomy)">photometrically</a> detected by observing how the stars affect each other in three ways. The first is by observing extra light which the stars reflect from their companion. Second is by observing ellipsoidal light variations which are caused by deformation of the star's shape by their companions. The third method is by looking at how <a href="/wiki/Relativistic_beaming" title="Relativistic beaming">relativistic beaming</a> affects the apparent magnitude of the stars. Detecting binaries with these methods requires accurate <a href="/wiki/Photometry_(astronomy)" title="Photometry (astronomy)">photometry</a>.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Astrometric_binaries">Astrometric binaries</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=9" title="Edit section: Astrometric binaries"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Astronomers have discovered some stars that seemingly orbit around an empty space. <i>Astrometric binaries</i> are relatively nearby stars which can be seen to wobble around a point in space, with no visible companion. The same mathematics used for ordinary binaries can be applied to infer the <a href="/wiki/Mass" title="Mass">mass</a> of the missing companion. The companion could be very dim, so that it is currently undetectable or masked by the glare of its primary, or it could be an object that emits little or no <a href="/wiki/Electromagnetic_radiation" title="Electromagnetic radiation">electromagnetic radiation</a>, for example a <a href="/wiki/Neutron_star" title="Neutron star">neutron star</a>.<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> </p><p>The visible star's position is carefully measured and detected to vary, due to the gravitational influence from its counterpart. The position of the star is repeatedly measured relative to more distant stars, and then checked for periodic shifts in position. Typically this type of measurement can only be performed on nearby stars, such as those within 10 <a href="/wiki/Parsec" title="Parsec">parsecs</a>. Nearby stars often have a relatively high <a href="/wiki/Proper_motion" title="Proper motion">proper motion</a>, so astrometric binaries will appear to follow a <i>wobbly</i> path across the sky. </p><p>If the companion is sufficiently massive to cause an observable shift in position of the star, then its presence can be deduced. From precise <a href="/wiki/Astrometry" title="Astrometry">astrometric</a> measurements of the movement of the visible star over a sufficiently long period of time, information about the mass of the companion and its orbital period can be determined.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> Even though the companion is not visible, the characteristics of the system can be determined from the observations using <a href="/wiki/Johannes_Kepler" title="Johannes Kepler">Kepler</a>'s <a href="/wiki/Kepler%27s_laws_of_planetary_motion" title="Kepler's laws of planetary motion">laws</a>.<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> </p><p>This method of detecting binaries is also <a href="/wiki/Methods_of_detecting_extrasolar_planets#Astrometry" class="mw-redirect" title="Methods of detecting extrasolar planets">used to locate</a> <a href="/wiki/Extrasolar_planet" class="mw-redirect" title="Extrasolar planet">extrasolar planets</a> orbiting a star. However, the requirements to perform this measurement are very exacting, due to the great difference in the mass ratio, and the typically long period of the planet's orbit. Detection of position shifts of a star is a very exacting science, and it is difficult to achieve the necessary precision. Space telescopes can avoid the blurring effect of <a href="/wiki/Atmosphere_of_Earth" title="Atmosphere of Earth">Earth's atmosphere</a>, resulting in more precise resolution. </p> <div class="mw-heading mw-heading3"><h3 id="Configuration_of_the_system"><span class="anchor" id="Configuration"></span>Configuration of the system</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=10" title="Edit section: Configuration of the system"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1237032888/mw-parser-output/.tmulti">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner img{background-color:white}}</style><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:224px;max-width:224px"><div class="trow"><div class="tsingle" style="width:222px;max-width:222px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Binary_star_system_-_detached_configuration_q%3D3.svg" class="mw-file-description"><img alt="Detached binary star system" src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Binary_star_system_-_detached_configuration_q%3D3.svg/220px-Binary_star_system_-_detached_configuration_q%3D3.svg.png" decoding="async" width="220" height="153" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Binary_star_system_-_detached_configuration_q%3D3.svg/330px-Binary_star_system_-_detached_configuration_q%3D3.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Binary_star_system_-_detached_configuration_q%3D3.svg/440px-Binary_star_system_-_detached_configuration_q%3D3.svg.png 2x" data-file-width="198" data-file-height="138" /></a></span></div><div class="thumbcaption">Detached</div></div></div><div class="trow"><div class="tsingle" style="width:222px;max-width:222px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Binary_star_system_-_semidetached_configuration_q%3D3.svg" class="mw-file-description"><img alt="Semidetached binary star system" src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Binary_star_system_-_semidetached_configuration_q%3D3.svg/220px-Binary_star_system_-_semidetached_configuration_q%3D3.svg.png" decoding="async" width="220" height="153" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Binary_star_system_-_semidetached_configuration_q%3D3.svg/330px-Binary_star_system_-_semidetached_configuration_q%3D3.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Binary_star_system_-_semidetached_configuration_q%3D3.svg/440px-Binary_star_system_-_semidetached_configuration_q%3D3.svg.png 2x" data-file-width="198" data-file-height="138" /></a></span></div><div class="thumbcaption">Semidetached</div></div></div><div class="trow"><div class="tsingle" style="width:222px;max-width:222px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Binary_star_system_-_contact_configuration_q%3D3.svg" class="mw-file-description"><img alt="Contact binary star system" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Binary_star_system_-_contact_configuration_q%3D3.svg/220px-Binary_star_system_-_contact_configuration_q%3D3.svg.png" decoding="async" width="220" height="153" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Binary_star_system_-_contact_configuration_q%3D3.svg/330px-Binary_star_system_-_contact_configuration_q%3D3.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Binary_star_system_-_contact_configuration_q%3D3.svg/440px-Binary_star_system_-_contact_configuration_q%3D3.svg.png 2x" data-file-width="198" data-file-height="138" /></a></span></div><div class="thumbcaption">Contact</div></div></div><div class="trow" style="display:flex"><div class="thumbcaption">Configurations of a binary star system with a mass ratio of 3. The black lines represent the inner critical Roche equipotentials, the Roche lobes.</div></div></div></div> <p>Another classification is based on the distance between the stars, relative to their sizes:<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </p><p><i>Detached binaries</i> are binary stars where each component is within its <a href="/wiki/Roche_lobe" title="Roche lobe">Roche lobe</a>, i.e. the area where the <a href="/wiki/Gravitation" class="mw-redirect" title="Gravitation">gravitational pull</a> of the star itself is larger than that of the other component. While on the <a href="/wiki/Main_sequence" title="Main sequence">main sequence</a> the stars have no major effect on each other, and essentially evolve separately. Most binaries belong to this class. </p><p><i>Semidetached binary stars</i> are binary stars where one of the components fills the binary star's Roche lobe and the other does not. In this <a href="/wiki/Interacting_binary_star" title="Interacting binary star">interacting binary star</a>, gas from the surface of the Roche-lobe-filling component (donor) is transferred to the other, accreting star. The <a href="/wiki/Mass_transfer" title="Mass transfer">mass transfer</a> dominates the evolution of the system. In many cases, the inflowing gas forms an <a href="/wiki/Accretion_disc" class="mw-redirect" title="Accretion disc">accretion disc</a> around the accretor. </p><p>A <i><a href="/wiki/Contact_binary" title="Contact binary">contact binary</a></i> is a type of binary star in which both components of the binary fill their <a href="/wiki/Roche_lobe" title="Roche lobe">Roche lobes</a>. The uppermost part of the <a href="/wiki/Stellar_atmosphere" title="Stellar atmosphere">stellar atmospheres</a> forms a <i>common envelope</i> that surrounds both stars. As the friction of the envelope brakes the <a href="/wiki/Orbital_motion" class="mw-redirect" title="Orbital motion">orbital motion</a>, the stars may eventually <a href="/wiki/Stellar_collision" title="Stellar collision">merge</a>.<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> <a href="/wiki/W_Ursae_Majoris" title="W Ursae Majoris">W Ursae Majoris</a> is an example. </p> <div class="mw-heading mw-heading3"><h3 id="Cataclysmic_variables_and_X-ray_binaries">Cataclysmic variables and X-ray binaries</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=11" title="Edit section: Cataclysmic variables and X-ray binaries"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Accretion_Disk_Binary_System.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Accretion_Disk_Binary_System.jpg/220px-Accretion_Disk_Binary_System.jpg" decoding="async" width="220" height="144" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Accretion_Disk_Binary_System.jpg/330px-Accretion_Disk_Binary_System.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Accretion_Disk_Binary_System.jpg/440px-Accretion_Disk_Binary_System.jpg 2x" data-file-width="800" data-file-height="525" /></a><figcaption>Artist's conception of a <a href="/wiki/Cataclysmic_variable_star" title="Cataclysmic variable star">cataclysmic variable system</a></figcaption></figure> <p>When a binary system contains a <a href="/wiki/Compact_star" class="mw-redirect" title="Compact star">compact object</a> such as a <a href="/wiki/White_dwarf" title="White dwarf">white dwarf</a>, <a href="/wiki/Neutron_star" title="Neutron star">neutron star</a> or <a href="/wiki/Stellar-mass_black_hole" class="mw-redirect" title="Stellar-mass black hole">black hole</a>, gas from the other (donor) star can <a href="/wiki/Accretion_(astronomy)" class="mw-redirect" title="Accretion (astronomy)">accrete</a> onto the compact object. This releases <a href="/wiki/Gravitational_potential_energy" class="mw-redirect" title="Gravitational potential energy">gravitational potential energy</a>, causing the gas to become hotter and emit radiation. <a href="/wiki/Cataclysmic_variable_star" title="Cataclysmic variable star">Cataclysmic variable stars</a>, where the compact object is a white dwarf, are examples of such systems.<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> In <a href="/wiki/X-ray_binaries" class="mw-redirect" title="X-ray binaries">X-ray binaries</a>, the compact object can be either a <a href="/wiki/Neutron_star" title="Neutron star">neutron star</a> or a <a href="/wiki/Stellar-mass_black_hole" class="mw-redirect" title="Stellar-mass black hole">black hole</a>. These binaries are classified as <a href="/wiki/Low-mass_X-ray_binary" class="mw-redirect" title="Low-mass X-ray binary">low-mass</a> or <a href="/wiki/High-mass_X-ray_binary" class="mw-redirect" title="High-mass X-ray binary">high-mass</a> according to the mass of the donor star. High-mass X-ray binaries contain a young, <a href="/wiki/Stellar_classification" title="Stellar classification">early-type</a>, high-mass donor star which transfers mass by its <a href="/wiki/Stellar_wind" title="Stellar wind">stellar wind</a>, while low-mass X-ray binaries are semidetached binaries in which gas from a <a href="/wiki/Stellar_classification" title="Stellar classification">late-type</a> donor star or a white dwarf overflows the Roche lobe and falls towards the neutron star or black hole.<sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> Probably the best known example of an X-ray binary is the <a href="/wiki/High-mass_X-ray_binary" class="mw-redirect" title="High-mass X-ray binary">high-mass X-ray binary</a> <a href="/wiki/Cygnus_X-1" title="Cygnus X-1">Cygnus X-1</a>. In Cygnus X-1, the mass of the unseen companion is estimated to be about nine times that of the Sun,<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> far exceeding the <a href="/wiki/Tolman%E2%80%93Oppenheimer%E2%80%93Volkoff_limit" title="Tolman–Oppenheimer–Volkoff limit">Tolman–Oppenheimer–Volkoff limit</a> for the maximum theoretical mass of a neutron star. It is therefore believed to be a black hole; it was the first object for which this was widely believed.<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Orbital_period">Orbital period</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=12" title="Edit section: Orbital period"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Orbital_period" title="Orbital period">Orbital periods</a> can be less than an hour (for <a href="/wiki/AM_CVn_star" class="mw-redirect" title="AM CVn star">AM CVn stars</a>), or a few days (components of <a href="/wiki/Beta_Lyrae" title="Beta Lyrae">Beta Lyrae</a>), but also hundreds of thousands of years (<a href="/wiki/Proxima_Centauri" title="Proxima Centauri">Proxima Centauri</a> around <a href="/wiki/Alpha_Centauri" title="Alpha Centauri">Alpha Centauri</a> AB). </p> <div class="mw-heading mw-heading3"><h3 id="Variations_in_period">Variations in period</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=13" title="Edit section: Variations in period"><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">Main article: <a href="/wiki/Applegate_mechanism" title="Applegate mechanism">Applegate mechanism</a></div> <p>The Applegate mechanism explains long term orbital period variations seen in certain eclipsing binaries. As a <a href="/wiki/Main-sequence_star" class="mw-redirect" title="Main-sequence star">main-sequence star</a> goes through an activity cycle, the outer layers of the star are subject to a magnetic torque changing the distribution of angular momentum, resulting in a change in the star's oblateness. The orbit of the stars in the binary pair is gravitationally coupled to their shape changes, so that the period shows modulations (typically on the order of ∆P/P ~ 10<sup>−5</sup>) on the same time scale as the activity cycles (typically on the order of decades).<sup id="cite_ref-Applegate_1992_34-0" class="reference"><a href="#cite_note-Applegate_1992-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p><p>Another phenomenon observed in some Algol binaries has been monotonic period increases. This is quite distinct from the far more common observations of alternating period increases and decreases explained by the Applegate mechanism. Monotonic period increases have been attributed to mass transfer, usually (but not always) from the less massive to the more massive star<sup id="cite_ref-Hall_1989_35-0" class="reference"><a href="#cite_note-Hall_1989-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Designations">Designations</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=14" title="Edit section: Designations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="A_and_B">A and B</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=15" title="Edit section: A and B"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:This_artist%E2%80%99s_impression_shows_the_strange_object_AR_Scorpii.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8b/This_artist%E2%80%99s_impression_shows_the_strange_object_AR_Scorpii.jpg/220px-This_artist%E2%80%99s_impression_shows_the_strange_object_AR_Scorpii.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8b/This_artist%E2%80%99s_impression_shows_the_strange_object_AR_Scorpii.jpg/330px-This_artist%E2%80%99s_impression_shows_the_strange_object_AR_Scorpii.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8b/This_artist%E2%80%99s_impression_shows_the_strange_object_AR_Scorpii.jpg/440px-This_artist%E2%80%99s_impression_shows_the_strange_object_AR_Scorpii.jpg 2x" data-file-width="5500" data-file-height="4123" /></a><figcaption>Artist's impression of the binary star system <a href="/wiki/AR_Scorpii" title="AR Scorpii">AR Scorpii</a></figcaption></figure> <p>The components of binary stars are denoted by the suffixes <i>A</i> and <i>B</i> appended to the system's designation, <i>A</i> denoting the primary and <i>B</i> the secondary. The suffix <i>AB</i> may be used to denote the pair (for example, the binary star α Centauri AB consists of the stars α Centauri A and α Centauri B.) Additional letters, such as <i>C</i>, <i>D</i>, etc., may be used for systems with more than two stars.<sup id="cite_ref-Heintz19_36-0" class="reference"><a href="#cite_note-Heintz19-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> In cases where the binary star has a <a href="/wiki/Bayer_designation" title="Bayer designation">Bayer designation</a> and is widely separated, it is possible that the members of the pair will be designated with superscripts; an example is <a href="/wiki/Zeta_Reticuli" title="Zeta Reticuli">Zeta Reticuli</a>, whose components are ζ<sup>1</sup> Reticuli and ζ<sup>2</sup> Reticuli.<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Discoverer_designations">Discoverer designations</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=16" title="Edit section: Discoverer designations"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Double stars are also designated by an abbreviation giving the discoverer together with an index number.<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> α Centauri, for example, was found to be double by Father Richaud in 1689, and so is designated <i>RHD 1</i>.<sup id="cite_ref-aitken1_1-2" class="reference"><a href="#cite_note-aitken1-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> These discoverer codes can be found in the <a href="/wiki/Washington_Double_Star_Catalog" title="Washington Double Star Catalog">Washington Double Star Catalog</a>.<sup id="cite_ref-40" class="reference"><a href="#cite_note-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Hot_and_cold">Hot and cold</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=17" title="Edit section: Hot and cold"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The secondary star in a binary star system may be designated as the <i>hot companion</i> or <i>cool companion</i>, depending on its temperature relative to the primary star. </p><p>Examples: </p> <ul><li><a href="/wiki/Antares" title="Antares">Antares</a> (Alpha Scorpii) is a red supergiant star in a binary system with a hotter blue main-sequence star Antares B. Antares B can therefore be termed a hot companion of the cool supergiant.<sup id="cite_ref-41" class="reference"><a href="#cite_note-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Symbiotic_star" class="mw-redirect" title="Symbiotic star">Symbiotic stars</a>, such as <a href="/wiki/R_Aquarii" title="R Aquarii">R Aquarii</a>, are binary star systems composed of a late-type giant star and a hotter companion object. Since the nature of the companion is not well-established in all cases, it may be termed a "hot companion".<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup></li> <li>The <a href="/wiki/Luminous_blue_variable" title="Luminous blue variable">luminous blue variable</a> <a href="/wiki/Eta_Carinae" title="Eta Carinae">Eta Carinae</a> has been determined to be a binary star system. The secondary appears to have a higher temperature than the primary and has therefore been described as being the "hot companion" star. It may be a <a href="/wiki/Wolf%E2%80%93Rayet_star" title="Wolf–Rayet star">Wolf–Rayet star</a>.<sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/NASA" title="NASA">NASA</a>'s <a href="/wiki/Kepler_mission" class="mw-redirect" title="Kepler mission">Kepler mission</a> has discovered examples of eclipsing binary stars where the secondary is the hotter component. <a href="/wiki/KOI-74b" class="mw-redirect" title="KOI-74b">KOI-74b</a> is a 12,000 K <a href="/wiki/White_dwarf" title="White dwarf">white dwarf</a> companion of KOI-74 (<a href="/wiki/Kepler_space_telescope#Kepler_Input_Catalog" title="Kepler space telescope">KIC</a> <a rel="nofollow" class="external text" href="https://archive.stsci.edu/kepler/kic10/search.php?kic_kepler_id=6889235&action=Search">6889235</a>), a 9,400 K early <a href="/wiki/A-type_main-sequence_star" title="A-type main-sequence star">A-type main-sequence star</a>.<sup id="cite_ref-rowe_44-0" class="reference"><a href="#cite_note-rowe-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-van_kerkwijk_45-0" class="reference"><a href="#cite_note-van_kerkwijk-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Borenstein_46-0" class="reference"><a href="#cite_note-Borenstein-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> <a href="/wiki/KOI-81b" class="mw-redirect" title="KOI-81b">KOI-81b</a> is a 13,000 K white dwarf companion of KOI-81 (<a href="/wiki/Kepler_space_telescope#Kepler_Input_Catalog" title="Kepler space telescope">KIC</a> <a rel="nofollow" class="external text" href="https://archive.stsci.edu/kepler/kic10/search.php?kic_kepler_id=8823868&action=Search">8823868</a>), a 10,000 K late <a href="/wiki/B-type_main-sequence_star" title="B-type main-sequence star">B-type main-sequence star</a>.<sup id="cite_ref-rowe_44-1" class="reference"><a href="#cite_note-rowe-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-van_kerkwijk_45-1" class="reference"><a href="#cite_note-van_kerkwijk-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Borenstein_46-1" class="reference"><a href="#cite_note-Borenstein-46"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup></li></ul> <div class="mw-heading mw-heading2"><h2 id="Evolution">Evolution</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=18" title="Edit section: Evolution"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><span><video id="mwe_player_1" poster="//upload.wikimedia.org/wikipedia/commons/thumb/f/f7/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv/260px--Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv.jpg" controls="" preload="none" data-mw-tmh="" class="mw-file-element" width="260" height="146" data-durationhint="103" data-mwtitle="Artist's_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv" data-mwprovider="wikimediacommons" resource="/wiki/File:Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv"><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/f/f7/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv.480p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="480p.vp9.webm" data-width="854" data-height="480" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/f/f7/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv.720p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="720p.vp9.webm" data-width="1280" data-height="720" /><source src="//upload.wikimedia.org/wikipedia/commons/f/f7/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv" type="video/ogg; codecs="theora, vorbis"" data-width="1280" data-height="720" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/f/f7/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv.144p.mjpeg.mov" type="video/quicktime" data-transcodekey="144p.mjpeg.mov" data-width="256" data-height="144" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/f/f7/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv.240p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="240p.vp9.webm" data-width="426" data-height="240" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/f/f7/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv.360p.vp9.webm" type="video/webm; codecs="vp9, opus"" data-transcodekey="360p.vp9.webm" data-width="640" data-height="360" /><source src="//upload.wikimedia.org/wikipedia/commons/transcoded/f/f7/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv/Artist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv.360p.webm" type="video/webm; codecs="vp8, vorbis"" data-transcodekey="360p.webm" data-width="640" data-height="360" /><track src="https://commons.wikimedia.org/w/api.php?action=timedtext&title=File%3AArtist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv&lang=be-tarask&trackformat=vtt&origin=%2A" kind="subtitles" type="text/vtt" srclang="be-tarask" label="беларуская (тарашкевіца) ‪(be-tarask)‬" data-dir="ltr" /><track src="https://commons.wikimedia.org/w/api.php?action=timedtext&title=File%3AArtist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv&lang=es&trackformat=vtt&origin=%2A" kind="subtitles" type="text/vtt" srclang="es" label="español ‪(es)‬" data-dir="ltr" /><track src="https://commons.wikimedia.org/w/api.php?action=timedtext&title=File%3AArtist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv&lang=id&trackformat=vtt&origin=%2A" kind="subtitles" type="text/vtt" srclang="id" label="Bahasa Indonesia ‪(id)‬" data-dir="ltr" /><track src="https://commons.wikimedia.org/w/api.php?action=timedtext&title=File%3AArtist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv&lang=mk&trackformat=vtt&origin=%2A" kind="subtitles" type="text/vtt" srclang="mk" label="македонски ‪(mk)‬" data-dir="ltr" /><track src="https://commons.wikimedia.org/w/api.php?action=timedtext&title=File%3AArtist%27s_impression_of_the_evolution_of_a_hot_high-mass_binary_star.ogv&lang=ru&trackformat=vtt&origin=%2A" kind="subtitles" type="text/vtt" srclang="ru" label="русский ‪(ru)‬" data-dir="ltr" /></video></span><figcaption>Artist's impression of the evolution of a hot high-mass binary star</figcaption></figure> <div class="mw-heading mw-heading3"><h3 id="Formation">Formation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=19" title="Edit section: Formation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>While it is not impossible that some binaries might be created through <a href="/wiki/Gravitational_capture" title="Gravitational capture">gravitational capture</a> between two single stars, given the very low likelihood of such an event (three objects being actually required, as <a href="/wiki/Conservation_of_energy" title="Conservation of energy">conservation of energy</a> rules out a single gravitating body capturing another) and the high number of binaries currently in existence, this cannot be the primary formation process. The observation of binaries consisting of stars not yet on the <a href="/wiki/Main_sequence" title="Main sequence">main sequence</a> supports the theory that binaries develop during <a href="/wiki/Star_formation" title="Star formation">star formation</a>. Fragmentation of the <a href="/wiki/Molecular_cloud" title="Molecular cloud">molecular cloud</a> during the formation of <a href="/wiki/Protostar" title="Protostar">protostars</a> is an acceptable explanation for the formation of a binary or multiple star system.<sup id="cite_ref-47" class="reference"><a href="#cite_note-47"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-48" class="reference"><a href="#cite_note-48"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> </p><p>The outcome of the <a href="/wiki/Three-body_problem" title="Three-body problem">three-body problem</a>, in which the three stars are of comparable mass, is that eventually one of the three stars will be ejected from the system and, assuming no significant further perturbations, the remaining two will form a stable binary system. </p> <div class="mw-heading mw-heading3"><h3 id="Mass_transfer_and_accretion">Mass transfer and accretion</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=20" title="Edit section: Mass transfer and accretion"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>As a <a href="/wiki/Main_sequence" title="Main sequence">main-sequence star</a> increases in size during its <a href="/wiki/Stellar_evolution" title="Stellar evolution">evolution</a>, it may at some point exceed its <a href="/wiki/Roche_lobe" title="Roche lobe">Roche lobe</a>, meaning that some of its matter ventures into a region where the <a href="/wiki/Gravitation" class="mw-redirect" title="Gravitation">gravitational pull</a> of its companion star is larger than its own.<sup id="cite_ref-49" class="reference"><a href="#cite_note-49"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup> The result is that matter will transfer from one star to another through a process known as Roche lobe overflow (RLOF), either being absorbed by direct impact or through an <a href="/wiki/Accretion_disc" class="mw-redirect" title="Accretion disc">accretion disc</a>. The mathematical point through which this transfer happens is called the first <a href="/wiki/Lagrangian_point" class="mw-redirect" title="Lagrangian point">Lagrangian point</a>.<sup id="cite_ref-50" class="reference"><a href="#cite_note-50"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup> It is not uncommon that the accretion disc is the brightest (and thus sometimes the only visible) element of a binary star. </p><p>If a star grows outside of its Roche lobe too fast for all abundant matter to be transferred to the other component, it is also possible that matter will leave the system through other Lagrange points or as <a href="/wiki/Stellar_wind" title="Stellar wind">stellar wind</a>, thus being effectively lost to both components.<sup id="cite_ref-51" class="reference"><a href="#cite_note-51"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup> Since the evolution of a star is determined by its mass, the process influences the evolution of both companions, and creates stages that cannot be attained by single stars.<sup id="cite_ref-52" class="reference"><a href="#cite_note-52"><span class="cite-bracket">[</span>52<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-53" class="reference"><a href="#cite_note-53"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-54" class="reference"><a href="#cite_note-54"><span class="cite-bracket">[</span>54<span class="cite-bracket">]</span></a></sup> </p><p>Studies of the eclipsing ternary <a href="/wiki/Algol" title="Algol">Algol</a> led to the <i><a href="/wiki/Algol_paradox" title="Algol paradox">Algol paradox</a></i> in the theory of <a href="/wiki/Stellar_evolution" title="Stellar evolution">stellar evolution</a>: although components of a binary star form at the same time, and massive stars evolve much faster than the less massive ones, it was observed that the more massive component Algol A is still in the <a href="/wiki/Main_sequence" title="Main sequence">main sequence</a>, while the less massive Algol B is a <a href="/wiki/Subgiant" title="Subgiant">subgiant</a> at a later evolutionary stage. The paradox can be solved by <a href="/wiki/Mass_transfer" title="Mass transfer">mass transfer</a>: when the more massive star became a subgiant, it filled its <a href="/wiki/Roche_lobe" title="Roche lobe">Roche lobe</a>, and most of the mass was transferred to the other star, which is still in the main sequence. In some binaries similar to Algol, a gas flow can actually be seen.<sup id="cite_ref-55" class="reference"><a href="#cite_note-55"><span class="cite-bracket">[</span>55<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Runaways_and_novae">Runaways and novae</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=21" title="Edit section: Runaways and novae"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Artist%27s_illustration_of_scenario_for_plasma_ejections_from_V_Hydrae.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Artist%27s_illustration_of_scenario_for_plasma_ejections_from_V_Hydrae.jpg/220px-Artist%27s_illustration_of_scenario_for_plasma_ejections_from_V_Hydrae.jpg" decoding="async" width="220" height="198" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Artist%27s_illustration_of_scenario_for_plasma_ejections_from_V_Hydrae.jpg/330px-Artist%27s_illustration_of_scenario_for_plasma_ejections_from_V_Hydrae.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Artist%27s_illustration_of_scenario_for_plasma_ejections_from_V_Hydrae.jpg/440px-Artist%27s_illustration_of_scenario_for_plasma_ejections_from_V_Hydrae.jpg 2x" data-file-width="3000" data-file-height="2701" /></a><figcaption>Artist rendering of <a href="/wiki/Coronal_mass_ejection" title="Coronal mass ejection">plasma ejections</a> from <a href="/wiki/V_Hydrae" title="V Hydrae">V Hydrae</a></figcaption></figure> <p>It is also possible for widely separated binaries to lose gravitational contact with each other during their lifetime, as a result of external perturbations. The components will then move on to evolve as single stars. A close encounter between two binary systems can also result in the gravitational disruption of both systems, with some of the stars being ejected at high velocities, leading to <a href="/wiki/Runaway_star" class="mw-redirect" title="Runaway star">runaway stars</a>.<sup id="cite_ref-56" class="reference"><a href="#cite_note-56"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup> </p><p>If a <a href="/wiki/White_dwarf" title="White dwarf">white dwarf</a> has a close companion star that overflows its <a href="/wiki/Roche_lobe" title="Roche lobe">Roche lobe</a>, the white dwarf will steadily <a href="/wiki/Accretion_(astrophysics)" title="Accretion (astrophysics)">accrete</a> gases from the star's outer atmosphere. These are compacted on the white dwarf's surface by its intense gravity, compressed and heated to very high temperatures as additional material is drawn in. The white dwarf consists of <a href="/wiki/Degenerate_matter" title="Degenerate matter">degenerate matter</a> and so is largely unresponsive to heat, while the accreted hydrogen is not. <a href="/wiki/Nuclear_fusion" title="Nuclear fusion">Hydrogen fusion</a> can occur in a stable manner on the surface through the <a href="/wiki/CNO_cycle" title="CNO cycle">CNO cycle</a>, causing the enormous amount of energy liberated by this process to blow the remaining gases away from the white dwarf's surface. The result is an extremely bright outburst of light, known as a <a href="/wiki/Nova" title="Nova">nova</a>.<sup id="cite_ref-57" class="reference"><a href="#cite_note-57"><span class="cite-bracket">[</span>57<span class="cite-bracket">]</span></a></sup> </p><p>In extreme cases this event can cause the white dwarf to exceed the <a href="/wiki/Chandrasekhar_limit" title="Chandrasekhar limit">Chandrasekhar limit</a> and trigger a <a href="/wiki/Supernova" title="Supernova">supernova</a> that destroys the entire star, another possible cause for runaways.<sup id="cite_ref-58" class="reference"><a href="#cite_note-58"><span class="cite-bracket">[</span>58<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-59" class="reference"><a href="#cite_note-59"><span class="cite-bracket">[</span>59<span class="cite-bracket">]</span></a></sup> An example of such an event is the supernova <a href="/wiki/SN_1572" title="SN 1572">SN 1572</a>, which was observed by <a href="/wiki/Tycho_Brahe" title="Tycho Brahe">Tycho Brahe</a>. The <a href="/wiki/Hubble_Space_Telescope" title="Hubble Space Telescope">Hubble Space Telescope</a> recently<sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Manual_of_Style/Dates_and_numbers#Chronological_items" title="Wikipedia:Manual of Style/Dates and numbers"><span title="The time period mentioned near this tag is ambiguous. (September 2023)">when?</span></a></i>]</sup> took a picture of the remnants of this event. </p> <div class="mw-heading mw-heading2"><h2 id="Astrophysics">Astrophysics</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=22" title="Edit section: Astrophysics"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Binaries provide the best method for astronomers to determine the mass of a distant star. The gravitational pull between them causes them to orbit around their common center of mass. From the orbital pattern of a visual binary, or the time variation of the spectrum of a spectroscopic binary, the mass of its stars can be determined, for example with the <a href="/wiki/Binary_mass_function" title="Binary mass function">binary mass function</a>. In this way, the relation between a star's appearance (temperature and radius) and its mass can be found, which allows for the determination of the mass of non-binaries. </p><p>Because a large proportion of stars exist in binary systems, binaries are particularly important to our understanding of the processes by which stars form. In particular, the period and masses of the binary tell us about the amount of <a href="/wiki/Angular_momentum" title="Angular momentum">angular momentum</a> in the system. Because this is a <a href="/wiki/Conservation_law_(physics)" class="mw-redirect" title="Conservation law (physics)">conserved quantity</a> in physics, binaries give us important clues about the conditions under which the stars were formed. </p> <div class="mw-heading mw-heading3"><h3 id="Calculating_the_center_of_mass_in_binary_stars">Calculating the center of mass in binary stars</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=23" title="Edit section: Calculating the center of mass in binary stars"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In a simple binary case, the distance <i>r</i><sub>1</sub> from the center of the first star to the center of mass or <a href="/wiki/Barycenter" class="mw-redirect" title="Barycenter">barycenter</a> is given by </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 r_{1}=a\cdot {\frac {m_{2}}{m_{1}+m_{2}}}={\frac {a}{1+{\frac {m_{1}}{m_{2}}}}},}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> <mo>=</mo> <mi>a</mi> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> <mrow> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> <mo>+</mo> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mrow> </mfrac> </mrow> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>a</mi> <mrow> <mn>1</mn> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mfrac> </mrow> </mrow> </mfrac> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle r_{1}=a\cdot {\frac {m_{2}}{m_{1}+m_{2}}}={\frac {a}{1+{\frac {m_{1}}{m_{2}}}}},}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/bb73ee50ea002cc6629e57df5b68e32b1bc470c6" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -3.505ex; width:29.671ex; height:6.343ex;" alt="{\displaystyle r_{1}=a\cdot {\frac {m_{2}}{m_{1}+m_{2}}}={\frac {a}{1+{\frac {m_{1}}{m_{2}}}}},}"></span> </p><p>where </p> <ul><li><i>a</i> is the distance between the two stellar centers, and</li> <li><i>m</i><sub>1</sub> and <i>m</i><sub>2</sub> are the <a href="/wiki/Mass" title="Mass">masses</a> of the two stars.</li></ul> <p>If <i>a</i> is taken to be the <a href="/wiki/Semimajor_axis" class="mw-redirect" title="Semimajor axis">semimajor axis</a> of the orbit of one body around the other, then <i>r</i><sub>1</sub> is the semimajor axis of the first body's orbit around the center of mass or <i>barycenter</i>, and <span class="nowrap"><i>r</i><sub>2</sub> = <i>a</i> − <i>r</i><sub>1</sub></span> is the semimajor axis of the second body's orbit. When the center of mass is located within the more massive body, that body appears to wobble rather than following a discernible orbit. </p> <div class="mw-heading mw-heading3"><h3 id="Center-of-mass_animations">Center-of-mass animations</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=24" title="Edit section: Center-of-mass animations"><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">Main article: <a href="/wiki/Barycenter" class="mw-redirect" title="Barycenter">Barycenter</a></div> <p>The red cross marks the center of mass of the system. These images do not represent any specific real system. </p> <table class="wikitable" width="480"> <tbody><tr> <td valign="top"><span typeof="mw:File"><a href="/wiki/File:Orbit1.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/73/Orbit1.gif/160px-Orbit1.gif" decoding="async" width="160" height="160" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/7/73/Orbit1.gif 1.5x" data-file-width="200" data-file-height="200" /></a></span><br />(a) Two bodies of similar mass orbiting around a common center of mass, or <i>barycenter</i> </td> <td valign="top"><span typeof="mw:File"><a href="/wiki/File:Orbit2.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Orbit2.gif/160px-Orbit2.gif" decoding="async" width="160" height="160" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/f/f2/Orbit2.gif 1.5x" data-file-width="200" data-file-height="200" /></a></span><br />(b) Two bodies with a difference in mass orbiting around a common barycenter, like the Charon–Pluto system </td></tr> <tr> <td valign="top"><span typeof="mw:File"><a href="/wiki/File:Orbit3.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/59/Orbit3.gif/160px-Orbit3.gif" decoding="async" width="160" height="160" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/5/59/Orbit3.gif 1.5x" data-file-width="200" data-file-height="200" /></a></span><br />(c) Two bodies with a major difference in mass orbiting around a common barycenter (similar to the <a href="/wiki/Earth%E2%80%93Moon_system" class="mw-redirect" title="Earth–Moon system">Earth–Moon system</a>) </td> <td valign="top"><span typeof="mw:File"><a href="/wiki/File:Orbit4.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Orbit4.gif/160px-Orbit4.gif" decoding="async" width="160" height="160" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/5/5a/Orbit4.gif 1.5x" data-file-width="200" data-file-height="200" /></a></span><br />(d) Two bodies with an extreme difference in mass orbiting around a common barycenter (similar to the <a href="/wiki/Sun%E2%80%93Earth_system" class="mw-redirect" title="Sun–Earth system">Sun–Earth system</a>) </td></tr> <tr> <td valign="top" colspan="2"><span typeof="mw:File"><a href="/wiki/File:Orbit5.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Orbit5.gif/320px-Orbit5.gif" decoding="async" width="320" height="160" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/0/0e/Orbit5.gif 1.5x" data-file-width="400" data-file-height="200" /></a></span><br />(e) Two bodies with similar mass orbiting in an <a href="/wiki/Ellipse" title="Ellipse">ellipse</a> around a common barycenter </td></tr></tbody></table> <div class="mw-heading mw-heading3"><h3 id="Research_findings">Research findings</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=25" title="Edit section: Research findings"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <table class="wikitable" style="text-align: center; float: right; margin-left: 0.5em;"> <caption>Multiplicity likelihood for <a href="/wiki/Population_I" class="mw-redirect" title="Population I">population I</a> <a href="/wiki/Main-sequence" class="mw-redirect" title="Main-sequence">main-sequence</a> stars<sup id="cite_ref-Duchene2013_60-0" class="reference"><a href="#cite_note-Duchene2013-60"><span class="cite-bracket">[</span>60<span class="cite-bracket">]</span></a></sup> </caption> <tbody><tr> <th>Mass range </th> <th>Multiplicity<br /> frequency </th> <th>Average<br /> companions </th></tr> <tr> <td>≤ 0.1 <a href="/wiki/Solar_mass" title="Solar mass"><var>M</var><sub>☉</sub></a> </td> <td><span class="nowrap"><span data-sort-value="6999220000000000000♠"></span>22%<span style="margin-left:0.3em;"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1.2em;font-size:85%;text-align:right;">+6%<br />−4%</span></span></span> </td> <td><span class="nowrap"><span data-sort-value="6999220000000000000♠"></span>0.22<span style="margin-left:0.3em;"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1.2em;font-size:85%;text-align:right;">+0.06<br />−0.04</span></span></span> </td></tr> <tr> <td><span class="nowrap"><span data-sort-value="6999100000000000000♠"></span>0.1–0.5 <var>M</var><sub>☉</sub></span> </td> <td><span class="nowrap"><span data-sort-value="6999260000000000000♠"></span>26%<span style="margin-left:0.3em;margin-right:0.15em;">±</span>3%</span> </td> <td><span class="nowrap"><span data-sort-value="6999330000000000000♠"></span>0.33<span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.05</span> </td></tr> <tr> <td><span class="nowrap"><span data-sort-value="6999700000000000000♠"></span>0.7–1.3 <var>M</var><sub>☉</sub></span> </td> <td><span class="nowrap"><span data-sort-value="6999440000000000000♠"></span>44%<span style="margin-left:0.3em;margin-right:0.15em;">±</span>2%</span> </td> <td><span class="nowrap"><span data-sort-value="6999620000000000000♠"></span>0.62<span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.03</span> </td></tr> <tr> <td><span class="nowrap"><span data-sort-value="7000150000000000000♠"></span>1.5–5 <var>M</var><sub>☉</sub></span> </td> <td>≥ 50% </td> <td><span class="nowrap"><span data-sort-value="7000100000000000000♠"></span>1.00<span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.10</span> </td></tr> <tr> <td><span class="nowrap"><span data-sort-value="7000800000000000000♠"></span>8–16 <var>M</var><sub>☉</sub></span> </td> <td>≥ 60% </td> <td><span class="nowrap"><span data-sort-value="7000100000000000000♠"></span>1.00<span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.20</span> </td></tr> <tr> <td>≥ 16 <var>M</var><sub>☉</sub> </td> <td>≥ 80% </td> <td><span class="nowrap"><span data-sort-value="7000130000000000000♠"></span>1.30<span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.20</span> </td></tr></tbody></table> <p>It is estimated that approximately one third of the <a href="/wiki/Star_system" title="Star system">star systems</a> in the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a> are binary or multiple, with the remaining two thirds being single stars.<sup id="cite_ref-61" class="reference"><a href="#cite_note-61"><span class="cite-bracket">[</span>61<span class="cite-bracket">]</span></a></sup> The overall multiplicity frequency of <a href="/wiki/Main_sequence_star" class="mw-redirect" title="Main sequence star">ordinary stars</a> is a <a href="/wiki/Monotonically_increasing" class="mw-redirect" title="Monotonically increasing">monotonically increasing</a> function of <a href="/wiki/Stellar_mass" title="Stellar mass">stellar mass</a>. That is, the likelihood of being in a binary or a multi-star system steadily increases as the masses of the components increase.<sup id="cite_ref-Duchene2013_60-1" class="reference"><a href="#cite_note-Duchene2013-60"><span class="cite-bracket">[</span>60<span class="cite-bracket">]</span></a></sup> </p><p>There is a direct correlation between the <a href="/wiki/Orbital_period#Two_bodies_orbiting_each_other" title="Orbital period">period of revolution</a> of a binary star and the <a href="/wiki/Orbital_eccentricity" title="Orbital eccentricity">eccentricity</a> of its orbit, with systems of short period having smaller eccentricity. Binary stars may be found with any conceivable separation, from pairs orbiting so closely that they are <a href="/wiki/Contact_binary" title="Contact binary">practically in contact</a> with each other, to pairs so distantly separated that their connection is indicated only by their common <a href="/wiki/Proper_motion" title="Proper motion">proper motion</a> through space. Among gravitationally bound binary star systems, there exists a so-called <a href="/wiki/Log-normal_distribution" title="Log-normal distribution">log normal distribution</a> of periods, with the majority of these systems orbiting with a period of about 100 years. This is supporting evidence for the theory that binary systems are formed during <a href="/wiki/Star_formation" title="Star formation">star formation</a>.<sup id="cite_ref-62" class="reference"><a href="#cite_note-62"><span class="cite-bracket">[</span>62<span class="cite-bracket">]</span></a></sup> </p><p>In pairs where the two stars are of equal <a href="/wiki/Absolute_magnitude" title="Absolute magnitude">brightness</a>, they are also of the same <a href="/wiki/Stellar_classification" title="Stellar classification">spectral type</a>. In systems where the brightnesses are different, the fainter star is bluer if the brighter star is a <a href="/wiki/Giant_star" title="Giant star">giant star</a>, and redder if the brighter star belongs to the <a href="/wiki/Main_sequence" title="Main sequence">main sequence</a>.<sup id="cite_ref-63" class="reference"><a href="#cite_note-63"><span class="cite-bracket">[</span>63<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Artist%27s_concept_of_exoplanet_LTT_1445Ac.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/57/Artist%27s_concept_of_exoplanet_LTT_1445Ac.jpg/220px-Artist%27s_concept_of_exoplanet_LTT_1445Ac.jpg" decoding="async" width="220" height="124" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/57/Artist%27s_concept_of_exoplanet_LTT_1445Ac.jpg/330px-Artist%27s_concept_of_exoplanet_LTT_1445Ac.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/57/Artist%27s_concept_of_exoplanet_LTT_1445Ac.jpg/440px-Artist%27s_concept_of_exoplanet_LTT_1445Ac.jpg 2x" data-file-width="16000" data-file-height="9000" /></a><figcaption>Artist's impression of the planets orbiting the primary star of <a href="/wiki/LTT_1445" title="LTT 1445">LTT 1445</a>, a <a href="/wiki/Triple_star_system" class="mw-redirect" title="Triple star system">triple star system</a>.</figcaption></figure> <p>The mass of a star can be directly determined only from its gravitational attraction. Apart from the Sun and stars which act as <a href="/wiki/Gravitational_lens" title="Gravitational lens">gravitational lenses</a>, this can be done only in binary and multiple star systems, making the binary stars an important class of stars. In the case of a visual binary star, after the orbit and the <a href="/wiki/Parallax" title="Parallax">stellar parallax</a> of the system has been determined, the combined mass of the two stars may be obtained by a direct application of the <a href="/wiki/Kepler%27s_laws_of_planetary_motion" title="Kepler's laws of planetary motion">Keplerian harmonic law</a>.<sup id="cite_ref-64" class="reference"><a href="#cite_note-64"><span class="cite-bracket">[</span>64<span class="cite-bracket">]</span></a></sup> </p><p>Unfortunately, it is impossible to obtain the complete orbit of a spectroscopic binary unless it is also a visual or an eclipsing binary, so from these objects only a determination of the joint product of mass and the <a href="/wiki/Trigonometric_function" class="mw-redirect" title="Trigonometric function">sine</a> of the angle of inclination relative to the line of sight is possible. In the case of eclipsing binaries which are also spectroscopic binaries, it is possible to find a complete solution for the specifications (mass, <a href="/wiki/Density" title="Density">density</a>, size, <a href="/wiki/Luminosity" title="Luminosity">luminosity</a>, and approximate shape) of both members of the system. </p> <div class="mw-heading mw-heading4"><h4 id="Planets">Planets</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=26" title="Edit section: Planets"><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">Main article: <a href="/wiki/Habitability_of_binary_star_systems" title="Habitability of binary star systems">Habitability of binary star systems</a></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Planets_in_binary_star_systems_-_P-_and_S-type.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/05/Planets_in_binary_star_systems_-_P-_and_S-type.svg/220px-Planets_in_binary_star_systems_-_P-_and_S-type.svg.png" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/05/Planets_in_binary_star_systems_-_P-_and_S-type.svg/330px-Planets_in_binary_star_systems_-_P-_and_S-type.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/05/Planets_in_binary_star_systems_-_P-_and_S-type.svg/440px-Planets_in_binary_star_systems_-_P-_and_S-type.svg.png 2x" data-file-width="220" data-file-height="220" /></a><figcaption>Schematic of a binary star system with one planet on an S-type orbit and one on a P-type orbit</figcaption></figure> <p>While a number of binary star systems have been found to harbor <a href="/wiki/Extrasolar_planets" class="mw-redirect" title="Extrasolar planets">extrasolar planets</a>, such systems are comparatively rare compared to single star systems. Observations by the <a href="/wiki/Kepler_space_telescope" title="Kepler space telescope">Kepler space telescope</a> have shown that most single stars of the same type as the <a href="/wiki/Sun" title="Sun">Sun</a> have plenty of planets, but only one-third of binary stars do. According to theoretical simulations,<sup id="cite_ref-65" class="reference"><a href="#cite_note-65"><span class="cite-bracket">[</span>65<span class="cite-bracket">]</span></a></sup> even widely separated binary stars often disrupt the discs of rocky grains from which <a href="/wiki/Protoplanets" class="mw-redirect" title="Protoplanets">protoplanets</a> form. On the other hand, other simulations suggest that the presence of a binary companion can actually improve the rate of planet formation within stable orbital zones by "stirring up" the protoplanetary disk, increasing the accretion rate of the protoplanets within.<sup id="cite_ref-formation_66-0" class="reference"><a href="#cite_note-formation-66"><span class="cite-bracket">[</span>66<span class="cite-bracket">]</span></a></sup> </p><p>Detecting planets in multiple star systems introduces additional technical difficulties, which may be why they are only rarely found.<sup id="cite_ref-67" class="reference"><a href="#cite_note-67"><span class="cite-bracket">[</span>67<span class="cite-bracket">]</span></a></sup> Examples include the <a href="/wiki/White_dwarf" title="White dwarf">white dwarf</a>-<a href="/wiki/Pulsar" title="Pulsar">pulsar</a> binary <a href="/wiki/PSR_B1620-26" class="mw-redirect" title="PSR B1620-26">PSR B1620-26</a>, the <a href="/wiki/Subgiant" title="Subgiant">subgiant</a>-<a href="/wiki/Red_dwarf" title="Red dwarf">red dwarf</a> binary <a href="/wiki/Gamma_Cephei" title="Gamma Cephei">Gamma Cephei</a>, and the <a href="/wiki/White_dwarf" title="White dwarf">white dwarf</a>-<a href="/wiki/Red_dwarf" title="Red dwarf">red dwarf</a> binary <a href="/wiki/NN_Serpentis" title="NN Serpentis">NN Serpentis</a>, among others.<sup id="cite_ref-68" class="reference"><a href="#cite_note-68"><span class="cite-bracket">[</span>68<span class="cite-bracket">]</span></a></sup> </p><p>A study of fourteen previously known planetary systems found three of these systems to be binary systems. All planets were found to be in S-type orbits around the primary star. In these three cases the secondary star was much dimmer than the primary and so was not previously detected. This discovery resulted in a recalculation of parameters for both the planet and the primary star.<sup id="cite_ref-exobinary_69-0" class="reference"><a href="#cite_note-exobinary-69"><span class="cite-bracket">[</span>69<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Science_fiction" title="Science fiction">Science fiction</a> has often featured <a href="/wiki/Planet" title="Planet">planets</a> of binary or ternary stars as a setting, for example, George Lucas' <a href="/wiki/Tatooine" title="Tatooine">Tatooine</a> from <i><a href="/wiki/Star_Wars" title="Star Wars">Star Wars</a></i>, and one notable story, "<a href="/wiki/Nightfall_(Asimov_short_story)" class="mw-redirect" title="Nightfall (Asimov short story)">Nightfall</a>", even takes this to a six-star system. In reality, some orbital ranges are impossible for dynamical reasons (the planet would be expelled from its orbit relatively quickly, being either ejected from the system altogether or transferred to a more inner or outer orbital range), whilst other orbits present serious challenges for eventual <a href="/wiki/Biosphere" title="Biosphere">biospheres</a> because of likely extreme variations in surface temperature during different parts of the orbit. Planets that orbit just one star in a binary system are said to have "S-type" orbits, whereas those that orbit around both stars have "P-type" or "<a href="/wiki/Circumbinary_planet" title="Circumbinary planet">circumbinary</a>" orbits. It is estimated that 50–60% of binary systems are capable of supporting habitable terrestrial planets within stable orbital ranges.<sup id="cite_ref-formation_66-1" class="reference"><a href="#cite_note-formation-66"><span class="cite-bracket">[</span>66<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Examples">Examples</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=27" title="Edit section: Examples"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Albireo.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/5/57/Albireo.jpg" decoding="async" width="198" height="205" class="mw-file-element" data-file-width="198" data-file-height="205" /></a><figcaption>The two visibly distinguishable components of <a href="/wiki/Albireo" title="Albireo">Albireo</a></figcaption></figure> <p>The large distance between the components, as well as their difference in color, make <a href="/wiki/Albireo" title="Albireo">Albireo</a> one of the easiest observable visual binaries. The brightest member, which is the third-brightest star in the <a href="/wiki/Constellation" title="Constellation">constellation</a> <a href="/wiki/Cygnus_(constellation)" title="Cygnus (constellation)">Cygnus</a>, is actually a close binary itself. Also in the Cygnus constellation is <a href="/wiki/Cygnus_X-1" title="Cygnus X-1">Cygnus X-1</a>, an <a href="/wiki/X-ray" title="X-ray">X-ray</a> source considered to be a <a href="/wiki/Black_hole" title="Black hole">black hole</a>. It is a <a href="/wiki/High-mass_X-ray_binary" class="mw-redirect" title="High-mass X-ray binary">high-mass X-ray binary</a>, with the optical counterpart being a <a href="/wiki/Variable_star" title="Variable star">variable star</a>.<sup id="cite_ref-70" class="reference"><a href="#cite_note-70"><span class="cite-bracket">[</span>70<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Sirius" title="Sirius">Sirius</a> is another binary and the brightest star in the night time sky, with a visual <a href="/wiki/Apparent_magnitude" title="Apparent magnitude">apparent magnitude</a> of −1.46. It is located in the constellation <a href="/wiki/Canis_Major" title="Canis Major">Canis Major</a>. In 1844 <a href="/wiki/Friedrich_Bessel" class="mw-redirect" title="Friedrich Bessel">Friedrich Bessel</a> deduced that Sirius was a binary. In 1862 <a href="/wiki/Alvan_Graham_Clark" title="Alvan Graham Clark">Alvan Graham Clark</a> discovered the companion (Sirius B; the visible star is Sirius A). In 1915 astronomers at the <a href="/wiki/Mount_Wilson_Observatory" title="Mount Wilson Observatory">Mount Wilson Observatory</a> determined that Sirius B was a <a href="/wiki/White_dwarf" title="White dwarf">white dwarf</a>, the first to be discovered. In 2005, using the <a href="/wiki/Hubble_Space_Telescope" title="Hubble Space Telescope">Hubble Space Telescope</a>, astronomers determined Sirius B to be 12,000 km (7,456 mi) in diameter, with a mass that is 98% of the Sun.<sup id="cite_ref-71" class="reference"><a href="#cite_note-71"><span class="cite-bracket">[</span>71<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Two_Brown_Dwarfs_in_Our_Backyard.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Two_Brown_Dwarfs_in_Our_Backyard.jpg/220px-Two_Brown_Dwarfs_in_Our_Backyard.jpg" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Two_Brown_Dwarfs_in_Our_Backyard.jpg/330px-Two_Brown_Dwarfs_in_Our_Backyard.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7f/Two_Brown_Dwarfs_in_Our_Backyard.jpg/440px-Two_Brown_Dwarfs_in_Our_Backyard.jpg 2x" data-file-width="2702" data-file-height="2706" /></a><figcaption><a href="/wiki/Luhman_16" title="Luhman 16">Luhman 16</a>, the third closest star system, contains two <a href="/wiki/Brown_dwarf" title="Brown dwarf">brown dwarfs</a>.</figcaption></figure> <p>An example of an eclipsing binary is <a href="/wiki/Epsilon_Aurigae" title="Epsilon Aurigae">Epsilon Aurigae</a> in the constellation <a href="/wiki/Auriga_(constellation)" class="mw-redirect" title="Auriga (constellation)">Auriga</a>. The visible component belongs to the <a href="/wiki/Stellar_classification" title="Stellar classification">spectral class</a> F0, the other (eclipsing) component is not visible. The last such eclipse occurred from 2009 to 2011, and it is hoped that the extensive observations that will likely be carried out may yield further insights into the nature of this system. Another eclipsing binary is <a href="/wiki/Beta_Lyrae" title="Beta Lyrae">Beta Lyrae</a>, which is a semidetached binary star system in the constellation of <a href="/wiki/Lyra" title="Lyra">Lyra</a>. </p><p>Other interesting binaries include <a href="/wiki/61_Cygni" title="61 Cygni">61 Cygni</a> (a binary in the constellation <a href="/wiki/Cygnus_(constellation)" title="Cygnus (constellation)">Cygnus</a>, composed of two <a href="/wiki/Stellar_classification" title="Stellar classification">K class (orange)</a> <a href="/wiki/Main_sequence" title="Main sequence">main-sequence</a> stars, 61 Cygni A and 61 Cygni B, which is known for its large <a href="/wiki/Proper_motion" title="Proper motion">proper motion</a>), <a href="/wiki/Procyon" title="Procyon">Procyon</a> (the brightest star in the constellation <a href="/wiki/Canis_Minor" title="Canis Minor">Canis Minor</a> and the eighth-brightest star in the night time sky, which is a binary consisting of the main star with a faint <a href="/wiki/White_dwarf" title="White dwarf">white dwarf</a> companion), SS Lacertae (an eclipsing binary which stopped eclipsing), V907 Sco (an eclipsing binary which stopped, restarted, then stopped again), <a href="/wiki/BG_Geminorum" title="BG Geminorum">BG Geminorum</a> (an eclipsing binary which is thought to contain a black hole with a K0 star in orbit around it), and <a href="/wiki/2MASS_J18082002%E2%88%925104378" title="2MASS J18082002−5104378">2MASS J18082002−5104378</a> (a binary in the "<a href="/wiki/Milky_Way#Age_and_cosmological_history" title="Milky Way">thin disk</a>" of the <a href="/wiki/Milky_Way" title="Milky Way">Milky Way</a>, and containing one of the oldest known stars).<sup id="cite_ref-ApJ-20181105_72-0" class="reference"><a href="#cite_note-ApJ-20181105-72"><span class="cite-bracket">[</span>72<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Multiple-star_examples">Multiple-star examples</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=28" title="Edit section: Multiple-star examples"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Planet_Lost_in_the_Glare_of_Binary_Stars.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f9/Planet_Lost_in_the_Glare_of_Binary_Stars.jpg/220px-Planet_Lost_in_the_Glare_of_Binary_Stars.jpg" decoding="async" width="220" height="124" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f9/Planet_Lost_in_the_Glare_of_Binary_Stars.jpg/330px-Planet_Lost_in_the_Glare_of_Binary_Stars.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f9/Planet_Lost_in_the_Glare_of_Binary_Stars.jpg/440px-Planet_Lost_in_the_Glare_of_Binary_Stars.jpg 2x" data-file-width="5120" data-file-height="2880" /></a><figcaption>Planet lost in the glare of binary stars (illustration)</figcaption></figure> <p>Systems with more than two stars are termed <a href="/wiki/Multiple_star" class="mw-redirect" title="Multiple star">multiple stars</a>. <a href="/wiki/Algol" title="Algol">Algol</a> is the most noted ternary (long thought to be a binary), located in the constellation <a href="/wiki/Perseus_(constellation)" title="Perseus (constellation)">Perseus</a>. Two components of the system eclipse each other, the variation in the intensity of Algol first being recorded in 1670 by <a href="/wiki/Geminiano_Montanari" title="Geminiano Montanari">Geminiano Montanari</a>. The name Algol means "demon star" (from <a href="/wiki/Arabic_language" class="mw-redirect" title="Arabic language">Arabic</a>: <span lang="ar" dir="rtl">الغول</span> <i><a href="/wiki/Ghoul" title="Ghoul">al-ghūl</a></i>), which was probably given due to its peculiar behavior. Another visible ternary is <a href="/wiki/Alpha_Centauri" title="Alpha Centauri">Alpha Centauri</a>, in the southern constellation of <a href="/wiki/Centaurus" title="Centaurus">Centaurus</a>, which contains the <a href="/wiki/List_of_brightest_stars" title="List of brightest stars">third-brightest star</a> in the night sky, with an <a href="/wiki/Apparent_magnitude" title="Apparent magnitude">apparent visual magnitude</a> of −0.01. This system also underscores the fact that no search for habitable planets is complete if binaries are discounted. Alpha Centauri A and B have an 11 AU distance at closest approach, and both should have stable habitable zones.<sup id="cite_ref-73" class="reference"><a href="#cite_note-73"><span class="cite-bracket">[</span>73<span class="cite-bracket">]</span></a></sup> </p><p>There are also examples of systems beyond ternaries: <a href="/wiki/Castor_(star)" title="Castor (star)">Castor</a> is a sextuple star system, which is the second-brightest star in the constellation <a href="/wiki/Gemini_(constellation)" title="Gemini (constellation)">Gemini</a> and one of the brightest stars in the nighttime sky. Astronomically, Castor was discovered to be a visual binary in 1719. Each of the components of Castor is itself a spectroscopic binary. Castor also has a faint and widely separated companion, which is also a spectroscopic binary. The <a href="/wiki/Alcor%E2%80%93Mizar" class="mw-redirect" title="Alcor–Mizar">Alcor–Mizar</a> visual binary in Ursa Majoris also consists of six stars: four comprising Mizar and two comprising Alcor. <a href="/wiki/QZ_Carinae" title="QZ Carinae">QZ Carinae</a> is a complex <a href="/wiki/Star_system" title="Star system">multiple star system</a> made up of at least nine individual stars.<sup id="cite_ref-74" class="reference"><a href="#cite_note-74"><span class="cite-bracket">[</span>74<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=29" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col"> <ul><li><a href="/wiki/104_Aquarii" title="104 Aquarii">104 Aquarii</a>, possible binary</li> <li><a href="/wiki/107_Aquarii" title="107 Aquarii">107 Aquarii</a>, "double star", about 240 light-years from Earth</li> <li><a href="/wiki/Beta_Centauri" title="Beta Centauri">Beta Centauri</a></li> <li><a href="/wiki/Binary_black_hole" title="Binary black hole">Binary black hole</a></li> <li><a href="/wiki/Brown_dwarf#Binary_brown_dwarfs" title="Brown dwarf">Binary brown dwarfs</a></li> <li><a href="/wiki/Circumbinary_planet" title="Circumbinary planet">Circumbinary planet</a></li> <li><a href="/wiki/Habitability_of_binary_star_systems" title="Habitability of binary star systems">Habitability of binary star systems</a></li> <li><a href="/wiki/HD_30453" title="HD 30453">HD 30453</a>, a spectroscopic binary with a 3rd component</li> <li><a href="/wiki/Hills_mechanism" title="Hills mechanism">Hills mechanism</a></li> <li><a href="/wiki/Heartbeat_star" title="Heartbeat star">Heartbeat star</a>, a type of binary star system</li> <li><a href="/wiki/Rotational_Brownian_motion_(astronomy)" title="Rotational Brownian motion (astronomy)">Rotational Brownian motion (astronomy)</a></li> <li><a href="/wiki/Two-body_problem_in_general_relativity" title="Two-body problem in general relativity">Two-body problem in general relativity</a></li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="Notes_and_references">Notes and references</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=30" title="Edit section: Notes and references"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-columns references-column-width" style="column-width: 30em;"> <ol class="references"> <li id="cite_note-aitken1-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-aitken1_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-aitken1_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-aitken1_1-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><i>The Binary Stars</i>, <a href="/wiki/Robert_Grant_Aitken" title="Robert Grant Aitken">Robert Grant Aitken</a>, New York: Dover, 1964, p. 1.</span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://leo.astronomy.cz/mizar/riccioli.htm">Vol. 1, part 1, p. 422, <i>Almagestum Novum</i></a><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110810035504/http://leo.astronomy.cz/mizar/riccioli.htm">Archived</a> 2011-08-10 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, Giovanni Battista Riccioli, Bononiae: Ex typographia haeredis Victorij Benatij, 1651.</span> </li> <li id="cite_note-newviewofmizar-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-newviewofmizar_3-0">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://leo.astronomy.cz/mizar/article.htm">A New View of Mizar</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20080307111656/http://leo.astronomy.cz/mizar/article.htm">Archived</a> 2008-03-07 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, Leos Ondra, accessed on line May 26, 2007.</span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text">This Month in Physics History, November 27, 1783: John Michell anticipates black holes, APS News, November 2009 (Volume 18, Number 10), www.aps.org</span> </li> <li id="cite_note-Aitken-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-Aitken_5-0">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFAitken1935" class="citation book cs1">Aitken, Robert Grant (1935). <a rel="nofollow" class="external text" href="https://archive.org/stream/binarystars00aitk#page/4/mode/2up"><i>The Binary Stars</i></a>. New York and London: McGraw-Hill Book Company, Inc. pp. 4–9. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1117504094" title="Special:BookSources/978-1117504094"><bdi>978-1117504094</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Binary+Stars&rft.place=New+York+and+London&rft.pages=4-9&rft.pub=McGraw-Hill+Book+Company%2C+Inc.&rft.date=1935&rft.isbn=978-1117504094&rft.aulast=Aitken&rft.aufirst=Robert+Grant&rft_id=https%3A%2F%2Farchive.org%2Fstream%2Fbinarystars00aitk%23page%2F4%2Fmode%2F2up&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABinary+star" class="Z3988"></span></span> </li> <li id="cite_note-Heintz4-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-Heintz4_6-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHeintz1978" class="citation book cs1">Heintz, W. 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Reidel Publishing Company. p. <a rel="nofollow" class="external text" href="https://archive.org/details/DoubleStars/page/4">4</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-90-277-0885-4" title="Special:BookSources/978-90-277-0885-4"><bdi>978-90-277-0885-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Double+Stars&rft.place=Dordrecht&rft.pages=4&rft.pub=D.+Reidel+Publishing+Company&rft.date=1978&rft.isbn=978-90-277-0885-4&rft.aulast=Heintz&rft.aufirst=W.+D.&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2FDoubleStars%2Fpage%2F4&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABinary+star" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHerschel1803" class="citation journal cs1">Herschel, William (1803). "Account of the Changes That Have Happened, during the Last Twenty-Five Years, in the Relative Situation of Double-Stars; with an Investigation of the Cause to Which They Are Owing". <i>Philosophical Transactions of the Royal Society of London</i>. <b>93</b>: 339–382. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1098%2Frstl.1803.0015">10.1098/rstl.1803.0015</a>. <a href="/wiki/JSTOR_(identifier)" class="mw-redirect" title="JSTOR (identifier)">JSTOR</a> <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/107080">107080</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:109971828">109971828</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Philosophical+Transactions+of+the+Royal+Society+of+London&rft.atitle=Account+of+the+Changes+That+Have+Happened%2C+during+the+Last+Twenty-Five+Years%2C+in+the+Relative+Situation+of+Double-Stars%3B+with+an+Investigation+of+the+Cause+to+Which+They+Are+Owing&rft.volume=93&rft.pages=339-382&rft.date=1803&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A109971828%23id-name%3DS2CID&rft_id=https%3A%2F%2Fwww.jstor.org%2Fstable%2F107080%23id-name%3DJSTOR&rft_id=info%3Adoi%2F10.1098%2Frstl.1803.0015&rft.aulast=Herschel&rft.aufirst=William&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABinary+star" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text">p. 291, French astronomers, visual double stars and the double stars working group of the Société Astronomique de France, E. Soulié, <i>The Third Pacific Rim Conference on Recent Development of Binary Star Research</i>, proceedings of a conference sponsored by Chiang Mai University, Thai Astronomical Society and the University of Nebraska-Lincoln held in Chiang Mai, Thailand, 26 October-1 November 1995, <i>ASP Conference Series</i> <b>130</b> (1997), ed. Kam-Ching Leung, pp. 291–294, <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/1997ASPC..130..291S/abstract">1997ASPC..130..291S</a>.</span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text">"Introduction and Growth of the WDS", <a rel="nofollow" class="external text" href="http://ad.usno.navy.mil/wds/wdstext.html#intro">The Washington Double Star Catalog</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20080917194922/http://ad.usno.navy.mil/wds/wdstext.html#intro">Archived</a> 2008-09-17 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, Brian D. Mason, Gary L. Wycoff, and William I. Hartkopf, Astrometry Department, <a href="/wiki/United_States_Naval_Observatory" title="United States Naval Observatory">United States Naval Observatory</a>, accessed on line August 20, 2008.</span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://ad.usno.navy.mil/wds/orb6.html">Sixth Catalog of Orbits of Visual Binary Stars</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20090412084731/http://ad.usno.navy.mil/wds/orb6.html">Archived</a> 2009-04-12 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, William I. Hartkopf and Brian D. Mason, <a href="/wiki/United_States_Naval_Observatory" title="United States Naval Observatory">United States Naval Observatory</a>, accessed on line August 20, 2008.</span> </li> <li id="cite_note-aitkenix-11"><span class="mw-cite-backlink">^ <a href="#cite_ref-aitkenix_11-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-aitkenix_11-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><i>The Binary Stars</i>, <a href="/wiki/Robert_Grant_Aitken" title="Robert Grant Aitken">Robert Grant Aitken</a>, New York: Dover, 1964, p. ix.</span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHerschel1802" class="citation journal cs1">Herschel, William (1802). <a rel="nofollow" class="external text" href="https://zenodo.org/record/1432308">"Catalogue of 500 New Nebulae, Nebulous Stars, Planetary Nebulae, and Clusters of Stars; With Remarks on the Construction of the Heavens"</a>. <i>Philosophical Transactions of the Royal Society of London</i>. <b>92</b>: 477–528 [481]. <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/1802RSPT...92..477H">1802RSPT...92..477H</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1098%2Frstl.1802.0021">10.1098/rstl.1802.0021</a></span>. <a href="/wiki/JSTOR_(identifier)" class="mw-redirect" title="JSTOR (identifier)">JSTOR</a> <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/107131">107131</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Philosophical+Transactions+of+the+Royal+Society+of+London&rft.atitle=Catalogue+of+500+New+Nebulae%2C+Nebulous+Stars%2C+Planetary+Nebulae%2C+and+Clusters+of+Stars%3B+With+Remarks+on+the+Construction+of+the+Heavens&rft.volume=92&rft.pages=477-528+481&rft.date=1802&rft_id=https%3A%2F%2Fwww.jstor.org%2Fstable%2F107131%23id-name%3DJSTOR&rft_id=info%3Adoi%2F10.1098%2Frstl.1802.0021&rft_id=info%3Abibcode%2F1802RSPT...92..477H&rft.aulast=Herschel&rft.aufirst=William&rft_id=https%3A%2F%2Fzenodo.org%2Frecord%2F1432308&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABinary+star" class="Z3988"></span></span> </li> <li id="cite_note-Heintz12-13"><span class="mw-cite-backlink">^ <a href="#cite_ref-Heintz12_13-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Heintz12_13-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Heintz12_13-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHeintz1978" class="citation book cs1">Heintz, W. 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Candidate Substellar Companions to Binary Systems". <i>The Astronomical Journal</i>. <b>140</b> (6): 1657. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1010.4048">1010.4048</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2010AJ....140.1657M">2010AJ....140.1657M</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1088%2F0004-6256%2F140%2F6%2F1657">10.1088/0004-6256/140/6/1657</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:59585356">59585356</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astronomical+Journal&rft.atitle=The+PHASES+Differential+Astrometry+Data+Archive.+V.+Candidate+Substellar+Companions+to+Binary+Systems&rft.volume=140&rft.issue=6&rft.pages=1657&rft.date=2010&rft_id=info%3Aarxiv%2F1010.4048&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A59585356%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1088%2F0004-6256%2F140%2F6%2F1657&rft_id=info%3Abibcode%2F2010AJ....140.1657M&rft.au=Muterspaugh&rft.au=Lane&rft.au=Kulkarni&rft.au=Maciej+Konacki&rft.au=Burke&rft.au=Colavita&rft.au=Shao&rft.au=Hartkopf&rft.au=Boss&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABinary+star" class="Z3988"></span></span> </li> <li id="cite_note-exobinary-69"><span class="mw-cite-backlink"><b><a href="#cite_ref-exobinary_69-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDaemgenHormuthBrandnerBergfors2009" class="citation journal cs1">Daemgen, S.; Hormuth, F.; Brandner, W.; Bergfors, C.; Janson, M.; Hippler, S.; Henning, T. (2009). <a rel="nofollow" class="external text" href="http://www.mpia.de/homes/henning/Publications/daemgen.pdf">"Binarity of transit host stars – Implications for planetary parameters"</a> <span class="cs1-format">(PDF)</span>. <i><a href="/wiki/Astronomy_and_Astrophysics" class="mw-redirect" title="Astronomy and Astrophysics">Astronomy and Astrophysics</a></i>. <b>498</b> (2): 567–574. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/0902.2179">0902.2179</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009A&A...498..567D">2009A&A...498..567D</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1051%2F0004-6361%2F200810988">10.1051/0004-6361/200810988</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:9893376">9893376</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astronomy+and+Astrophysics&rft.atitle=Binarity+of+transit+host+stars+%E2%80%93+Implications+for+planetary+parameters&rft.volume=498&rft.issue=2&rft.pages=567-574&rft.date=2009&rft_id=info%3Aarxiv%2F0902.2179&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A9893376%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1051%2F0004-6361%2F200810988&rft_id=info%3Abibcode%2F2009A%26A...498..567D&rft.aulast=Daemgen&rft.aufirst=S.&rft.au=Hormuth%2C+F.&rft.au=Brandner%2C+W.&rft.au=Bergfors%2C+C.&rft.au=Janson%2C+M.&rft.au=Hippler%2C+S.&rft.au=Henning%2C+T.&rft_id=http%3A%2F%2Fwww.mpia.de%2Fhomes%2Fhenning%2FPublications%2Fdaemgen.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABinary+star" class="Z3988"></span></span> </li> <li id="cite_note-70"><span class="mw-cite-backlink"><b><a href="#cite_ref-70">^</a></b></span> <span class="reference-text">See sources at <a href="/wiki/Cygnus_X-1" title="Cygnus X-1">Cygnus X-1</a></span> </li> <li id="cite_note-71"><span class="mw-cite-backlink"><b><a href="#cite_ref-71">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMcGourty2005" class="citation news cs1">McGourty, C. (2005-12-14). <a rel="nofollow" class="external text" href="http://news.bbc.co.uk/2/hi/science/nature/4528586.stm">"Hubble finds mass of white dwarf"</a>. <i>BBC News</i><span class="reference-accessdate">. Retrieved <span class="nowrap">2010-01-01</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=BBC+News&rft.atitle=Hubble+finds+mass+of+white+dwarf&rft.date=2005-12-14&rft.aulast=McGourty&rft.aufirst=C.&rft_id=http%3A%2F%2Fnews.bbc.co.uk%2F2%2Fhi%2Fscience%2Fnature%2F4528586.stm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABinary+star" class="Z3988"></span></span> </li> <li id="cite_note-ApJ-20181105-72"><span class="mw-cite-backlink"><b><a href="#cite_ref-ApJ-20181105_72-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSchlaufmanThompsonCasey2018" class="citation journal cs1">Schlaufman, Kevin C.; Thompson, Ian B.; Casey, Andrew R. (5 November 2018). <a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F1538-4357%2Faadd97">"An Ultra Metal-poor Star Near the Hydrogen-burning Limit"</a>. <i><a href="/wiki/The_Astrophysical_Journal" title="The Astrophysical Journal">The Astrophysical Journal</a></i>. <b>867</b> (2): 98. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/1811.00549">1811.00549</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2018ApJ...867...98S">2018ApJ...867...98S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.3847%2F1538-4357%2Faadd97">10.3847/1538-4357/aadd97</a></span>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:54511945">54511945</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Astrophysical+Journal&rft.atitle=An+Ultra+Metal-poor+Star+Near+the+Hydrogen-burning+Limit&rft.volume=867&rft.issue=2&rft.pages=98&rft.date=2018-11-05&rft_id=info%3Aarxiv%2F1811.00549&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A54511945%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.3847%2F1538-4357%2Faadd97&rft_id=info%3Abibcode%2F2018ApJ...867...98S&rft.aulast=Schlaufman&rft.aufirst=Kevin+C.&rft.au=Thompson%2C+Ian+B.&rft.au=Casey%2C+Andrew+R.&rft_id=https%3A%2F%2Fdoi.org%2F10.3847%252F1538-4357%252Faadd97&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABinary+star" class="Z3988"></span></span> </li> <li id="cite_note-73"><span class="mw-cite-backlink"><b><a href="#cite_ref-73">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFElisa_V._QuintanaFred_C._AdamsJack_J._LissauerJohn_E._Chambers2007" class="citation journal cs1">Elisa V. Quintana; Fred C. Adams; Jack J. Lissauer; John E. Chambers (2007). "Terrestrial Planet Formation around Individual Stars within Binary Star Systems". <i>Astrophysical Journal</i>. <b>660</b> (1): 807–822. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0701266">astro-ph/0701266</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2007ApJ...660..807Q">2007ApJ...660..807Q</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F512542">10.1086/512542</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:14394432">14394432</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astrophysical+Journal&rft.atitle=Terrestrial+Planet+Formation+around+Individual+Stars+within+Binary+Star+Systems&rft.volume=660&rft.issue=1&rft.pages=807-822&rft.date=2007&rft_id=info%3Aarxiv%2Fastro-ph%2F0701266&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A14394432%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1086%2F512542&rft_id=info%3Abibcode%2F2007ApJ...660..807Q&rft.au=Elisa+V.+Quintana&rft.au=Fred+C.+Adams&rft.au=Jack+J.+Lissauer&rft.au=John+E.+Chambers&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABinary+star" class="Z3988"></span></span> </li> <li id="cite_note-74"><span class="mw-cite-backlink"><b><a href="#cite_ref-74">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHarmanecZascheBrožCatalan-Hurtado2022" class="citation journal cs1">Harmanec, P.; Zasche, P.; Brož, M.; Catalan-Hurtado, R.; Barlow, B. N.; Frondorf, W.; Wolf, M.; Drechsel, H.; Chini, R.; Nasseri, A.; Pigulski, A.; Labadie-Bartz, J.; Christie, G. W.; Walker, W. S. G.; Blackford, M. (2022-04-15). "Towards a consistent model of the hot quadruple system HD 93206 = QZ Carinae - I. Observations and their initial analyses". <i>Astronomy & Astrophysics</i>. <b>666</b>: A23. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://arxiv.org/abs/2204.07045">2204.07045</a></span>. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2022A&A...666A..23M">2022A&A...666A..23M</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1051%2F0004-6361%2F202142108">10.1051/0004-6361/202142108</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0004-6361">0004-6361</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Astronomy+%26+Astrophysics&rft.atitle=Towards+a+consistent+model+of+the+hot+quadruple+system+HD+93206+%3D+QZ+Carinae+-+I.+Observations+and+their+initial+analyses&rft.volume=666&rft.pages=A23&rft.date=2022-04-15&rft_id=info%3Aarxiv%2F2204.07045&rft.issn=0004-6361&rft_id=info%3Adoi%2F10.1051%2F0004-6361%2F202142108&rft_id=info%3Abibcode%2F2022A%26A...666A..23M&rft.aulast=Harmanec&rft.aufirst=P.&rft.au=Zasche%2C+P.&rft.au=Bro%C5%BE%2C+M.&rft.au=Catalan-Hurtado%2C+R.&rft.au=Barlow%2C+B.+N.&rft.au=Frondorf%2C+W.&rft.au=Wolf%2C+M.&rft.au=Drechsel%2C+H.&rft.au=Chini%2C+R.&rft.au=Nasseri%2C+A.&rft.au=Pigulski%2C+A.&rft.au=Labadie-Bartz%2C+J.&rft.au=Christie%2C+G.+W.&rft.au=Walker%2C+W.+S.+G.&rft.au=Blackford%2C+M.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ABinary+star" class="Z3988"></span></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Binary_star&action=edit&section=31" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output 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typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/45px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/59px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></span></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Binary_stars" class="extiw" title="commons:Category:Binary stars">Binary stars</a></span>.</div></div> </div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1235681985"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1237033735"><div class="side-box side-box-right plainlinks sistersitebox"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409"> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Wikibooks-logo-en-noslogan.svg/40px-Wikibooks-logo-en-noslogan.svg.png" decoding="async" width="40" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Wikibooks-logo-en-noslogan.svg/60px-Wikibooks-logo-en-noslogan.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/df/Wikibooks-logo-en-noslogan.svg/80px-Wikibooks-logo-en-noslogan.svg.png 2x" data-file-width="400" data-file-height="400" /></span></span></div> <div class="side-box-text plainlist">The Wikibook <i><a href="https://en.wikibooks.org/wiki/Glossary_of_Astronomical_Terms" class="extiw" title="wikibooks:Glossary of Astronomical Terms">Glossary of Astronomical Terms</a></i> has a page on the topic of: <i><b><a href="https://en.wikibooks.org/wiki/Glossary_of_Astronomical_Terms/binary_star" class="extiw" title="wikibooks:Glossary of Astronomical Terms/binary star">binary star</a></b></i></div></div> </div> <ul><li><a rel="nofollow" class="external text" href="https://www.eso.org/misc/iauG1/">IAU Commission G1: Binary and Multiple Star Systems</a></li> <li><a rel="nofollow" class="external text" href="http://www.ianridpath.com/binaries.html">List of the best visual binaries</a> for amateurs, with orbital elements</li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20180910000526/http://hubblesite.org/news/103-binary-stars">Pictures and news of binaries at Hubblesite.org</a></li> <li><a rel="nofollow" class="external text" href="http://chandra.harvard.edu/xray_sources/binary_stars.html">Chandra X-ray Observatory</a></li> <li><a rel="nofollow" class="external text" href="http://astroclub.tau.ac.il/ephem/VisualDoubleStars/">Selected visual double stars and their relative position as a function of time</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071016222552/http://astroclub.tau.ac.il/ephem/VisualDoubleStars/">Archived</a> 2007-10-16 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li> <li><a rel="nofollow" class="external text" href="https://www.aavso.org/aavso-eclipsing-binaries-section">AAVSO Eclipsing Binaries section</a></li> <li><a rel="nofollow" class="external text" href="https://ogle.astrouw.edu.pl/atlas/eclipsing_binaries.html">OGLE Atlas of Variable Star Light Curves - Eclipsing binaries</a></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 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href="/wiki/Template:Star" title="Template:Star"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Star" title="Template talk:Star"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Star" title="Special:EditPage/Template:Star"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Stars" style="font-size:114%;margin:0 4em"><a href="/wiki/Star" title="Star">Stars</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><a href="/wiki/Lists_of_stars" title="Lists of stars">List</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Star_formation" title="Star formation">Formation</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Accretion_(astrophysics)" title="Accretion (astrophysics)">Accretion</a></li> <li><a href="/wiki/Molecular_cloud" title="Molecular cloud">Molecular cloud</a></li> <li><a href="/wiki/Bok_globule" title="Bok globule">Bok globule</a></li> <li><a href="/wiki/Young_stellar_object" title="Young stellar object">Young stellar object</a> <ul><li><a href="/wiki/Protostar" title="Protostar">Protostar</a></li> <li><a href="/wiki/Pre-main-sequence_star" title="Pre-main-sequence star">Pre-main-sequence</a></li> <li><a href="/wiki/Herbig_Ae/Be_star" title="Herbig Ae/Be star">Herbig Ae/Be</a></li> <li><a href="/wiki/T_Tauri_star" title="T Tauri star">T Tauri</a></li></ul></li> <li><a href="/wiki/Herbig%E2%80%93Haro_object" title="Herbig–Haro object">Herbig–Haro object</a></li> <li><a href="/wiki/Hayashi_track" title="Hayashi track">Hayashi track</a></li> <li><a href="/wiki/Henyey_track" title="Henyey track">Henyey track</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Stellar_evolution" title="Stellar evolution">Evolution</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Main_sequence" title="Main sequence">Main sequence</a></li> <li><a href="/wiki/Red-giant_branch" title="Red-giant branch">Red-giant branch</a></li> <li><a href="/wiki/Horizontal_branch" title="Horizontal branch">Horizontal branch</a> <ul><li><a href="/wiki/Red_clump" title="Red clump">Red clump</a></li></ul></li> <li><a href="/wiki/Asymptotic_giant_branch" title="Asymptotic giant branch">Asymptotic giant branch</a> <ul><li><a href="/wiki/Post-AGB_star" title="Post-AGB star">post-AGB</a></li> <li><a href="/wiki/Super-AGB_star" title="Super-AGB star">super-AGB</a></li></ul></li> <li><a href="/wiki/Blue_loop" title="Blue loop">Blue loop</a></li> <li><a href="/wiki/Planetary_nebula" title="Planetary nebula">Planetary nebula</a> <ul><li><a href="/wiki/Protoplanetary_nebula" title="Protoplanetary nebula">Protoplanetary</a></li></ul></li> <li><a href="/wiki/Wolf-Rayet_nebula" class="mw-redirect" title="Wolf-Rayet nebula">Wolf-Rayet nebula</a></li> <li><a href="/wiki/PG_1159_star" title="PG 1159 star">PG1159</a></li> <li><a href="/wiki/Dredge-up" title="Dredge-up">Dredge-up</a></li> <li><a href="/wiki/OH/IR_star" title="OH/IR star">OH/IR</a></li> <li><a href="/wiki/Instability_strip" title="Instability strip">Instability strip</a></li> <li><a href="/wiki/Luminous_blue_variable" title="Luminous blue variable">Luminous blue variable</a></li> <li><a href="/wiki/Stellar_population" title="Stellar population">Stellar population</a></li> <li><a href="/wiki/Supernova" title="Supernova">Supernova</a> <ul><li><a href="/wiki/Superluminous_supernova" title="Superluminous supernova">Superluminous</a></li> <li><a href="/wiki/Hypernova" title="Hypernova">Hypernova</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Stellar_classification" title="Stellar classification">Classification</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><td colspan="2" class="navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Early-type_star" class="mw-redirect" title="Early-type star">Early</a></li> <li><a href="/wiki/Late-type_star" class="mw-redirect" title="Late-type star">Late</a></li> <li>Main sequence <ul><li><a href="/wiki/O-type_main-sequence_star" title="O-type main-sequence star">O</a></li> <li><a href="/wiki/B-type_main-sequence_star" title="B-type main-sequence star">B</a></li> <li><a href="/wiki/A-type_main-sequence_star" title="A-type main-sequence star">A</a></li> <li><a href="/wiki/F-type_main-sequence_star" title="F-type main-sequence star">F</a></li> <li><a href="/wiki/G-type_main-sequence_star" title="G-type main-sequence star">G</a></li> <li><a href="/wiki/K-type_main-sequence_star" title="K-type main-sequence star">K</a></li> <li><a href="/wiki/Red_dwarf" title="Red dwarf">M</a></li></ul></li> <li><a href="/wiki/Subdwarf" title="Subdwarf">Subdwarf</a> <ul><li><a href="/wiki/Subdwarf_O_star" title="Subdwarf O star">O</a></li> <li><a href="/wiki/Subdwarf_B_star" title="Subdwarf B star">B</a></li></ul></li> <li><a href="/wiki/Wolf%E2%80%93Rayet_star" title="Wolf–Rayet star">WR</a></li> <li><a href="/wiki/OB_star" title="OB star">OB</a></li> <li><a href="/wiki/Subgiant" title="Subgiant">Subgiant</a></li> <li><a href="/wiki/Giant_star" title="Giant star">Giant</a> <ul><li><a href="/wiki/Blue_giant" title="Blue giant">Blue</a></li> <li><a href="/wiki/Red_giant" title="Red giant">Red</a></li> <li><a href="/wiki/Yellow_giant" class="mw-redirect" title="Yellow giant">Yellow</a></li></ul></li> <li><a href="/wiki/Bright_giant" class="mw-redirect" title="Bright giant">Bright giant</a></li> <li><a href="/wiki/Supergiant" title="Supergiant">Supergiant</a> <ul><li><a href="/wiki/Blue_supergiant" title="Blue supergiant">Blue</a></li> <li><a href="/wiki/Red_supergiant" title="Red supergiant">Red</a></li> <li><a href="/wiki/Yellow_supergiant" title="Yellow supergiant">Yellow</a></li></ul></li> <li><a href="/wiki/Hypergiant" title="Hypergiant">Hypergiant</a> <ul><li><a href="/wiki/Yellow_hypergiant" title="Yellow hypergiant">Yellow</a></li></ul></li> <li><a href="/wiki/Carbon_star" title="Carbon star">Carbon</a> <ul><li><a href="/wiki/S-type_star" title="S-type star">S</a></li> <li><a href="/wiki/CN_star" title="CN star">CN</a></li> <li><a href="/wiki/CH_star" title="CH star">CH</a></li></ul></li> <li><a href="/wiki/White_dwarf" title="White dwarf">White dwarf</a></li> <li><a href="/wiki/Chemically_peculiar_star" title="Chemically peculiar star">Chemically peculiar</a> <ul><li><a href="/wiki/Am_star" title="Am star">Am</a></li> <li><a href="/wiki/Ap_and_Bp_stars" title="Ap and Bp stars">Ap/Bp</a></li> <li><a href="/wiki/CEMP_star" title="CEMP star">CEMP</a></li> <li><a href="/wiki/Mercury-manganese_star" title="Mercury-manganese star">HgMn</a></li> <li><a href="/wiki/Helium-weak_star" title="Helium-weak star">He-weak</a></li> <li><a href="/wiki/Barium_star" title="Barium star">Barium</a></li> <li><a href="/wiki/Lambda_Bo%C3%B6tis_star" title="Lambda Boötis star">Lambda Boötis</a></li> <li><a href="/wiki/Lead_star" title="Lead star">Lead</a></li> <li><a href="/wiki/Technetium_star" title="Technetium star">Technetium</a></li></ul></li> <li><a href="/wiki/Be_star" title="Be star">Be</a> <ul><li><a href="/wiki/Shell_star" title="Shell star">Shell</a></li></ul></li> <li><a href="/wiki/B(e)_star" title="B(e) star">B[e]</a></li> <li><a href="/wiki/Helium_star" title="Helium star">Helium</a> <ul><li><a href="/wiki/Extreme_helium_star" title="Extreme helium star">Extreme</a></li></ul></li> <li><a href="/wiki/Blue_straggler" title="Blue straggler">Blue straggler</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Compact_star" class="mw-redirect" title="Compact star">Remnants</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Compact_star" class="mw-redirect" title="Compact star">Compact star</a></li> <li><a href="/wiki/IRAS_00500%2B6713" title="IRAS 00500+6713">Parker's star</a></li> <li><a href="/wiki/White_dwarf" title="White dwarf">White dwarf</a> <ul><li><a href="/wiki/Helium_planet" title="Helium planet">Helium planet</a></li></ul></li> <li><a href="/wiki/Neutron_star" title="Neutron star">Neutron</a> <ul><li><a href="/wiki/Radio-quiet_neutron_star" title="Radio-quiet neutron star">Radio-quiet</a></li> <li><a href="/wiki/Pulsar" title="Pulsar">Pulsar</a> <ul><li><a href="/wiki/Binary_pulsar" title="Binary pulsar">Binary</a></li> <li><a href="/wiki/X-ray_pulsar" title="X-ray pulsar">X-ray</a></li></ul></li> <li><a href="/wiki/Magnetar" title="Magnetar">Magnetar</a></li></ul></li> <li><a href="/wiki/Stellar_black_hole" title="Stellar black hole">Stellar black hole</a></li> <li><a href="/wiki/X-ray_binary" title="X-ray binary">X-ray binary</a> <ul><li><a href="/wiki/X-ray_burster" title="X-ray burster">Burster</a></li></ul></li> <li><a href="/wiki/Soft_gamma_repeater" title="Soft gamma repeater">SGR</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Hypothetical_star" title="Hypothetical star">Hypothetical</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Blue_dwarf_(red-dwarf_stage)" title="Blue dwarf (red-dwarf stage)">Blue dwarf</a></li> <li><a href="/wiki/Black_dwarf" title="Black dwarf">Black dwarf</a></li> <li><a href="/wiki/Exotic_star" title="Exotic star">Exotic</a> <ul><li><a href="/wiki/Boson_star" class="mw-redirect" title="Boson star">Boson</a></li> <li><a href="/wiki/Electroweak_star" class="mw-redirect" title="Electroweak star">Electroweak</a></li> <li><a href="/wiki/Strange_star" title="Strange star">Strange</a></li> <li><a href="/wiki/Preon_star" class="mw-redirect" title="Preon star">Preon</a></li> <li><a href="/wiki/Planck_star" title="Planck star">Planck</a></li> <li><a href="/wiki/Dark_star_(dark_matter)" title="Dark star (dark matter)">Dark</a></li> <li><a href="/wiki/Dark-energy_star" title="Dark-energy star">Dark-energy</a></li> <li><a href="/wiki/Quark_star" title="Quark star">Quark</a></li> <li><a href="/wiki/Q_star" title="Q star">Q</a></li></ul></li> <li>Black hole star <ul><li><a href="/wiki/Black_star_(semiclassical_gravity)" title="Black star (semiclassical gravity)">Black</a></li> <li>Hawking</li> <li><a href="/wiki/Quasi-star" title="Quasi-star">Quasi-star</a></li></ul></li> <li><a href="/wiki/Gravastar" title="Gravastar">Gravastar</a></li> <li><a href="/wiki/Thorne%E2%80%93%C5%BBytkow_object" title="Thorne–Żytkow object">Thorne–Żytkow object</a></li> <li><a href="/wiki/Iron_star" title="Iron star">Iron</a></li> <li><a href="/wiki/Blitzar" title="Blitzar">Blitzar</a></li> <li><a href="/wiki/White_hole" title="White hole">White hole</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Stellar_nucleosynthesis" title="Stellar nucleosynthesis">Nucleosynthesis</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Deuterium_fusion" title="Deuterium fusion">Deuterium burning</a></li> <li><a href="/wiki/Lithium_burning" title="Lithium burning">Lithium burning</a></li> <li><a href="/wiki/Proton%E2%80%93proton_chain" title="Proton–proton chain">Proton–proton chain</a></li> <li><a href="/wiki/CNO_cycle" title="CNO cycle">CNO cycle</a></li> <li><a href="/wiki/Helium_flash" title="Helium flash">Helium flash</a></li> <li><a href="/wiki/Triple-alpha_process" title="Triple-alpha process">Triple-alpha process</a></li> <li><a href="/wiki/Alpha_process" title="Alpha process">Alpha process</a></li> <li><a href="/wiki/Carbon-burning_process" title="Carbon-burning process">C burning</a></li> <li><a href="/wiki/Neon-burning_process" title="Neon-burning process">Ne burning</a></li> <li><a href="/wiki/Oxygen-burning_process" title="Oxygen-burning process">O burning</a></li> <li><a href="/wiki/Silicon-burning_process" title="Silicon-burning process">Si burning</a></li> <li><a href="/wiki/S-process" title="S-process">s-process</a></li> <li><a href="/wiki/R-process" title="R-process">r-process</a></li> <li><a href="/wiki/P-process" title="P-process">p-process</a></li> <li><a href="/wiki/Fusor_(astronomy)" title="Fusor (astronomy)">Fusor</a></li> <li><a href="/wiki/Nova" title="Nova">Nova</a> <ul><li><a href="/wiki/Symbiotic_nova" title="Symbiotic nova">Symbiotic</a></li> <li><a href="/wiki/Nova_remnant" title="Nova remnant">Remnant</a></li> <li><a href="/wiki/Luminous_red_nova" title="Luminous red nova">Luminous red nova</a></li> <li><a href="/wiki/Nova#Recurrent_novae" title="Nova">Recurrent</a></li> <li><a href="/wiki/Micronova" title="Micronova">Micronova</a></li></ul></li> <li><a href="/wiki/Supernova_nucleosynthesis" title="Supernova nucleosynthesis">Supernova</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Stellar_structure" title="Stellar structure">Structure</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Stellar_core" title="Stellar core">Core</a></li> <li><a href="/wiki/Convection_zone" title="Convection zone">Convection zone</a> <ul><li><a href="/wiki/Microturbulence" title="Microturbulence">Microturbulence</a></li> <li><a href="/wiki/Solar-like_oscillations" title="Solar-like oscillations">Oscillations</a></li></ul></li> <li><a href="/wiki/Radiation_zone" class="mw-redirect" title="Radiation zone">Radiation zone</a></li> <li><a href="/wiki/Stellar_atmosphere" title="Stellar atmosphere">Atmosphere</a> <ul><li><a href="/wiki/Photosphere" title="Photosphere">Photosphere</a></li> <li><a href="/wiki/Starspot" title="Starspot">Starspot</a></li> <li><a href="/wiki/Chromosphere" title="Chromosphere">Chromosphere</a></li> <li><a href="/wiki/Stellar_corona" title="Stellar corona">Stellar corona</a></li> <li><a href="/wiki/Alfv%C3%A9n_surface" title="Alfvén surface">Alfvén surface</a></li></ul></li> <li><a href="/wiki/Stellar_wind" title="Stellar wind">Stellar wind</a> <ul><li><a href="/wiki/Stellar-wind_bubble" title="Stellar-wind bubble">Bubble</a></li> <li><a href="/wiki/Bipolar_outflow" title="Bipolar outflow">Bipolar outflow</a></li></ul></li> <li><a href="/wiki/Accretion_disk" title="Accretion disk">Accretion disk</a> <ul><li><a href="/wiki/Protoplanetary_disk" title="Protoplanetary disk">Protoplanetary disk</a></li> <li><a href="/wiki/Proplyd" title="Proplyd">Proplyd</a></li></ul></li> <li><a href="/wiki/Asteroseismology" title="Asteroseismology">Asteroseismology</a> <ul><li><a href="/wiki/Helioseismology" title="Helioseismology">Helioseismology</a></li></ul></li> <li><a href="/wiki/Circumstellar_dust" title="Circumstellar dust">Circumstellar dust</a></li> <li><a href="/wiki/Cosmic_dust" title="Cosmic dust">Cosmic dust</a></li> <li><a href="/wiki/Circumstellar_envelope" title="Circumstellar envelope">Circumstellar envelope</a></li> <li><a href="/wiki/Eddington_luminosity" title="Eddington luminosity">Eddington luminosity</a></li> <li><a href="/wiki/Kelvin%E2%80%93Helmholtz_mechanism" title="Kelvin–Helmholtz mechanism">Kelvin–Helmholtz mechanism</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Properties</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Stellar_designations_and_names" title="Stellar designations and names">Designation</a></li> <li><a href="/wiki/Stellar_dynamics" title="Stellar dynamics">Dynamics</a></li> <li><a href="/wiki/Effective_temperature" title="Effective temperature">Effective temperature</a></li> <li><a href="/wiki/Luminosity" title="Luminosity">Luminosity</a></li> <li><a href="/wiki/Stellar_kinematics" title="Stellar kinematics">Kinematics</a></li> <li><a href="/wiki/Stellar_magnetic_field" title="Stellar magnetic field">Magnetic field</a></li> <li><a href="/wiki/Absolute_magnitude" title="Absolute magnitude">Absolute magnitude</a></li> <li><a href="/wiki/Stellar_mass" title="Stellar mass">Mass</a></li> <li><a href="/wiki/Metallicity" title="Metallicity">Metallicity</a></li> <li><a href="/wiki/Stellar_rotation" title="Stellar rotation">Rotation</a></li> <li><a href="/wiki/Starlight" title="Starlight">Starlight</a></li> <li><a href="/wiki/Variable_star" title="Variable star">Variable</a></li> <li><a href="/wiki/Photometric_system" title="Photometric system">Photometric system</a></li> <li><a href="/wiki/Color_index" title="Color index">Color index</a></li> <li><a href="/wiki/Hertzsprung%E2%80%93Russell_diagram" title="Hertzsprung–Russell diagram">Hertzsprung–Russell diagram</a></li> <li><a href="/wiki/Color%E2%80%93color_diagram" title="Color–color diagram">Color–color diagram</a></li> <li><a href="/wiki/Str%C3%B6mgren_sphere" title="Strömgren sphere">Strömgren sphere</a></li> <li><a href="/wiki/Kraft_break" title="Kraft break">Kraft break</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Star_system" title="Star system">Star systems</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a class="mw-selflink selflink">Binary</a> <ul><li><a href="/wiki/Contact_binary" title="Contact binary">Contact</a></li> <li><a href="/wiki/Common_envelope" title="Common envelope">Common envelope</a></li> <li><a href="/wiki/Eclipsing_binary" class="mw-redirect" title="Eclipsing binary">Eclipsing</a></li> <li><a href="/wiki/Symbiotic_binary" title="Symbiotic binary">Symbiotic</a></li></ul></li> <li><a href="/wiki/Star_system#Multiple_star_systems" title="Star system">Multiple</a></li> <li><a href="/wiki/Star_cluster" title="Star cluster">Cluster</a> <ul><li><a href="/wiki/Open_cluster" title="Open cluster">Open</a></li> <li><a href="/wiki/Globular_cluster" title="Globular cluster">Globular</a></li> <li><a href="/wiki/Super_star_cluster" title="Super star cluster">Super</a></li></ul></li> <li><a href="/wiki/Planetary_system" title="Planetary system">Planetary system</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Earth-centric<br />observations</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Sun" title="Sun">Sun</a> <ul><li><a href="/wiki/Solar_eclipse" title="Solar eclipse">Solar eclipse</a></li> <li><a href="/wiki/Solar_radio_emission" title="Solar radio emission">Solar radio emission</a></li> <li><a href="/wiki/Solar_System" title="Solar System">Solar System</a></li> <li><a href="/wiki/Sunlight" title="Sunlight">Sunlight</a></li></ul></li> <li><a href="/wiki/Pole_star" title="Pole star">Pole star</a></li> <li><a href="/wiki/Circumpolar_star" title="Circumpolar star">Circumpolar</a></li> <li><a href="/wiki/Constellation" title="Constellation">Constellation</a></li> <li><a href="/wiki/Asterism_(astronomy)" title="Asterism (astronomy)">Asterism</a></li> <li><a href="/wiki/Magnitude_(astronomy)" title="Magnitude (astronomy)">Magnitude</a> <ul><li><a href="/wiki/Apparent_magnitude" title="Apparent magnitude">Apparent</a></li> <li><a href="/wiki/Extinction_(astronomy)" title="Extinction (astronomy)">Extinction</a></li> <li><a href="/wiki/Photographic_magnitude" title="Photographic magnitude">Photographic</a></li></ul></li> <li><a href="/wiki/Radial_velocity" title="Radial velocity">Radial velocity</a></li> <li><a href="/wiki/Proper_motion" title="Proper motion">Proper motion</a></li> <li><a href="/wiki/Stellar_parallax" title="Stellar parallax">Parallax</a></li> <li><a href="/wiki/Photometric-standard_star" title="Photometric-standard star">Photometric-standard</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Lists_of_stars" title="Lists of stars">Lists</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/List_of_proper_names_of_stars" title="List of proper names of stars">Proper names</a> <ul><li><a href="/wiki/List_of_Arabic_star_names" title="List of Arabic star names">Arabic</a></li> <li><a href="/wiki/Chinese_star_names" class="mw-redirect" title="Chinese star names">Chinese</a></li></ul></li> <li><a href="/wiki/List_of_star_extremes" title="List of star extremes">Extremes</a> <ul><li><a href="/wiki/List_of_most_massive_stars" title="List of most massive stars">Most massive</a></li> <li><a href="/wiki/List_of_hottest_stars" title="List of hottest stars">Highest temperature</a></li> <li><a href="/wiki/List_of_coolest_stars" title="List of coolest stars">Lowest temperature</a></li> <li><a href="/wiki/List_of_largest_known_stars" class="mw-redirect" title="List of largest known stars">Largest volume</a></li> <li><a href="/wiki/List_of_smallest_known_stars" title="List of smallest known stars">Smallest volume</a></li> <li><a href="/wiki/List_of_brightest_stars" title="List of brightest stars">Brightest</a></li> <li><a href="/wiki/Historical_brightest_stars" title="Historical brightest stars">Historical brightest</a></li> <li><a href="/wiki/List_of_most_luminous_stars" title="List of most luminous stars">Most luminous</a></li> <li><a href="/wiki/List_of_nearest_stars" title="List of nearest stars">Nearest</a> <ul><li><a href="/wiki/List_of_nearest_bright_stars" title="List of nearest bright stars">bright</a></li></ul></li> <li><a href="/wiki/List_of_the_most_distant_astronomical_objects#List_of_most_distant_objects_by_type" title="List of the most distant astronomical objects">Most distant</a></li></ul></li> <li><a href="/wiki/List_of_stars_with_resolved_images" title="List of stars with resolved images">With resolved images</a></li> <li><a href="/wiki/List_of_multiplanetary_systems" title="List of multiplanetary systems">With multiple exoplanets</a></li> <li><a href="/wiki/List_of_brown_dwarfs" title="List of brown dwarfs">Brown dwarfs</a></li> <li><a href="/wiki/List_of_red_dwarfs" title="List of red dwarfs">Red dwarfs</a></li> <li><a href="/wiki/List_of_white_dwarfs" title="List of white dwarfs">White dwarfs</a></li> <li><a href="/wiki/List_of_novae_in_the_Milky_Way_galaxy" title="List of novae in the Milky Way galaxy">Milky Way novae</a></li> <li><a href="/wiki/List_of_supernovae" title="List of supernovae">Supernovae</a> <ul><li><a href="/wiki/List_of_supernova_candidates" title="List of supernova candidates">Candidates</a></li> <li><a href="/wiki/List_of_supernova_remnants" title="List of supernova remnants">Remnants</a></li></ul></li> <li><a href="/wiki/List_of_planetary_nebulae" title="List of planetary nebulae">Planetary nebulae</a></li> <li><a href="/wiki/Timeline_of_stellar_astronomy" title="Timeline of stellar astronomy">Timeline of stellar astronomy</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Substellar_object" title="Substellar object">Substellar object</a> <ul><li><a href="/wiki/Brown_dwarf" title="Brown dwarf">Brown dwarf</a> <ul><li><a href="/wiki/Brown-dwarf_desert" title="Brown-dwarf desert">Desert</a></li> <li><a href="/wiki/Sub-brown_dwarf" title="Sub-brown dwarf">Sub</a></li></ul></li> <li><a href="/wiki/Planet" title="Planet">Planet</a></li></ul></li> <li><a href="/wiki/Galactic_year" title="Galactic year">Galactic year</a></li> <li><a href="/wiki/Galaxy" title="Galaxy">Galaxy</a></li> <li><a href="/wiki/Guest_star_(astronomy)" title="Guest star (astronomy)">Guest</a></li> <li><a href="/wiki/Gravity" title="Gravity">Gravity</a></li> <li><a href="/wiki/Intergalactic_star" title="Intergalactic star">Intergalactic</a></li> <li><a href="/wiki/Planet-hosting_stars" class="mw-redirect" title="Planet-hosting stars">Planet-hosting stars</a></li> <li><a href="/wiki/Tidal_disruption_event" title="Tidal disruption event">Tidal disruption event</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:Stars" title="Category:Stars">Category</a></li> <li><span class="nowrap"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:He1523a.jpg" class="mw-file-description"><img alt="icon" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/He1523a.jpg/14px-He1523a.jpg" decoding="async" width="14" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5f/He1523a.jpg/21px-He1523a.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5f/He1523a.jpg/28px-He1523a.jpg 2x" data-file-width="180" data-file-height="207" /></a></span> </span><a href="/wiki/Portal:Stars" title="Portal:Stars">Stars portal</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Stellar_systems" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Stellar_system" title="Template:Stellar system"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Stellar_system" title="Template talk:Stellar system"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Stellar_system" title="Special:EditPage/Template:Stellar system"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Stellar_systems" style="font-size:114%;margin:0 4em"><a href="/wiki/Star" title="Star">Stellar</a> <a href="/wiki/Star_system" title="Star system">systems</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Bound</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Galaxy" title="Galaxy">Galaxy</a></li> <li><a href="/wiki/Dwarf_galaxy" title="Dwarf galaxy">Dwarf galaxy</a></li> <li><a href="/wiki/Star_cluster" title="Star cluster">Star cluster</a> <ul><li><a href="/wiki/Hypercompact_stellar_system" title="Hypercompact stellar system">Hypercompact stellar system</a></li> <li><a href="/wiki/Globular_cluster" title="Globular cluster">Globular cluster</a></li> <li><a href="/wiki/Dark_globular_cluster" title="Dark globular cluster">Dark globular cluster</a></li> <li><a href="/wiki/Open_cluster" title="Open cluster">Open cluster</a></li> <li><a href="/wiki/List_of_most_massive_star_clusters" title="List of most massive star clusters">List of most massive star clusters</a></li> <li><a href="/wiki/List_of_largest_star_clusters" title="List of largest star clusters">List of largest star clusters</a></li></ul></li> <li><a href="/wiki/Hypercompact_stellar_system" title="Hypercompact stellar system">Hypercompact stellar system</a></li> <li><a href="/wiki/Star_system" title="Star system">Star system</a></li> <li><a class="mw-selflink selflink">Binary star</a></li> <li><a href="/wiki/Planetary_system" title="Planetary system">Planetary system</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Unbound</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Stellar_stream" class="mw-redirect" title="Stellar stream">Stellar stream</a></li> <li><a href="/wiki/Stellar_association" title="Stellar association">Stellar association</a></li> <li><a href="/wiki/Stellar_kinematics" title="Stellar kinematics">Moving group</a></li> <li><a href="/wiki/Runaway_star" class="mw-redirect" title="Runaway star">Runaway star</a></li> <li><a href="/wiki/Stellar_kinematics#Hypervelocity_stars" title="Stellar kinematics">Hypervelocity star</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Visual grouping</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Double_star" title="Double star">Double star</a></li> <li><a href="/wiki/Multiple_star" class="mw-redirect" title="Multiple star">Multiple star</a></li> <li><a href="/wiki/Star_cloud" class="mw-redirect" title="Star cloud">Star cloud</a></li> <li><a href="/wiki/Asterism_(astronomy)" title="Asterism (astronomy)">Asterism</a></li> <li><a href="/wiki/Constellation" title="Constellation">Constellation</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow hlist" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, 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0;column-gap:1em;align-items:baseline;margin:0;list-style:none}.mw-parser-output .portal-bar-content-related{margin:0;list-style:none}.mw-parser-output .portal-bar-item{display:inline-block;margin:0.15em 0.2em;min-height:24px;line-height:24px}@media screen and (max-width:768px){.mw-parser-output .portal-bar{font-size:88%;font-weight:bold;display:flex;flex-flow:column wrap;align-items:baseline}.mw-parser-output .portal-bar-header{text-align:center;flex:0;padding-left:0.5em;margin:0 auto}.mw-parser-output .portal-bar-related{font-size:100%;align-items:flex-start}.mw-parser-output .portal-bar-content{display:flex;flex-flow:row wrap;align-items:center;flex:0;column-gap:1em;border-top:1px solid #a2a9b1;margin:0 auto;list-style:none}.mw-parser-output .portal-bar-content-related{border-top:none;margin:0;list-style:none}}.mw-parser-output .navbox+link+.portal-bar,.mw-parser-output .navbox+style+.portal-bar,.mw-parser-output .navbox+link+.portal-bar-bordered,.mw-parser-output .navbox+style+.portal-bar-bordered,.mw-parser-output .sister-bar+link+.portal-bar,.mw-parser-output .sister-bar+style+.portal-bar,.mw-parser-output .portal-bar+.navbox-styles+.navbox,.mw-parser-output .portal-bar+.navbox-styles+.sister-bar{margin-top:-1px}</style><div class="portal-bar noprint metadata noviewer portal-bar-bordered" role="navigation" aria-label="Portals"><span class="portal-bar-header"><a href="/wiki/Wikipedia:Contents/Portals" title="Wikipedia:Contents/Portals">Portals</a>:</span><ul class="portal-bar-content"><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/19px-Crab_Nebula.jpg" decoding="async" width="19" height="19" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/29px-Crab_Nebula.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/38px-Crab_Nebula.jpg 2x" data-file-width="3864" data-file-height="3864" /></span></span> </span><a href="/wiki/Portal:Astronomy" title="Portal:Astronomy">Astronomy</a></li><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/RocketSunIcon.svg/19px-RocketSunIcon.svg.png" decoding="async" width="19" height="19" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/RocketSunIcon.svg/29px-RocketSunIcon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d6/RocketSunIcon.svg/38px-RocketSunIcon.svg.png 2x" data-file-width="128" data-file-height="128" /></span></span> </span><a href="/wiki/Portal:Spaceflight" title="Portal:Spaceflight">Spaceflight</a></li><li class="portal-bar-item"><span class="nowrap"><span typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Earth-moon.jpg/21px-Earth-moon.jpg" decoding="async" width="21" height="17" class="mw-file-element" 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