Sun | Definition, Composition, Properties, Temperature, & Facts

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border-right-sm border-left-sm open"> <div class="drawer d-flex flex-column open"> <div class="left-rail-section-content"> <div class="topic-left-rail-header text-truncate bg-gray-50 position-relative text-right d-flex align-items-center"> <div class="tlr-title px-20 py-15 text-left"> <em class="material-icons text-gray-400 d-lg-none" data-icon="toc"></em> <a class="font-serif font-weight-bold text-black link-blue" href="https://www.britannica.com/place/Sun">Sun</a> </div> <button aria-label="Close" class="js-sections-close-button btn-link btn-sm btn d-lg-none position-absolute top-0 p-10 right-0" > <em class="material-icons font-26" data-icon="close"></em> </button> </div> <div class="section-content pl-10 pr-20 pl-sm-50 pr-sm-60 pl-lg-5 pr-lg-10 pt-10 pt-lg-0 bg-gray-50 clear-catfish-ad"> <div class="toc mb-20"> <div class="font-serif font-14 font-weight-bold mx-15 mb-15 mt-20"> Table of Contents </div> <ul class="list-unstyled my-0" data-level="h1"><li data-target="#ref1"><div class="pl-25"><a class="link-gray-900 w-100" href="/place/Sun">Introduction</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref54136"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/place/Sun#ref54136">Physical properties</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref54137"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/place/Sun/Internal-structure">Internal structure</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref54138"><a class="w-100 link-gray-900" href="/place/Sun/Internal-structure#ref54138">Energy generation and transport</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref54139"><a class="w-100 link-gray-900" href="/place/Sun/Evolution">Evolution</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref54140"><a class="w-100 link-gray-900" href="/place/Sun/Evolution#ref54140">Helioseismology</a></li></ul></div></li><li data-target="#ref54141"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/place/Sun/Solar-atmosphere">Solar atmosphere</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref54142"><a class="w-100 link-gray-900" href="/place/Sun/Solar-atmosphere#ref54142">Photosphere</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref54143"><a class="w-100 link-gray-900" href="/place/Sun/Chromosphere-and-corona">Chromosphere and corona</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref54144"><a class="w-100 link-gray-900" href="/place/Sun/Chromosphere-and-corona#ref54144">Chromosphere</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref54145"><a class="w-100 link-gray-900" href="/place/Sun/Corona">Corona</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref54146"><a class="w-100 link-gray-900" href="/place/Sun/Corona#ref54146">Solar wind</a></li></ul></li></ul></div></li><li data-target="#ref54147"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/place/Sun/Solar-activity">Solar activity</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref54148"><a class="w-100 link-gray-900" href="/place/Sun/Solar-activity#ref54148">Sunspots</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref54149"><a class="w-100 link-gray-900" href="/place/Sun/Prominences">Prominences</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref54150"><a class="w-100 link-gray-900" href="/place/Sun/Flares">Flares</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref54151"><a class="w-100 link-gray-900" href="/place/Sun/Solar-terrestrial-effects">Solar-terrestrial effects</a></li></ul></div></li><li data-target="#ref54152"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/place/Sun/History-of-observation">History of observation</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li></ul> <a class="toc-extra-link link-gray-900" href="https://www.britannica.com/place/Sun/additional-info">References & Edit History</a> <a class="toc-extra-link link-gray-900" href="/facts/Sun">Related Topics</a> </div> <div class="tlr-media-slider pb-10 mb-30"> <a class="section-header link-gray-900 font-serif font-14 font-weight-bold mb-10 mx-10" href="https://www.britannica.com/place/Sun/images-videos">Images, Videos & Interactives</a> <div class="slider js-slider position-relative d-inline-flex align-items-center mw-100 "> <div class="slider-container js-slider-container overflow-hidden d-flex overflow-hidden text-nowrap ml-15"> <a href="https://cdn.britannica.com/64/94264-050-AAAB7996/Joshua-trees-Tree-National-Park-California.jpg" data-href="/media/1/573494/97735" class="media-overlay-link d-inline-block mr-5"> <img loading="lazy" src="https://cdn.britannica.com/64/94264-120-FD9463AB/Joshua-trees-Tree-National-Park-California.jpg" alt="Joshua Tree National Park" height="50" /> </a> <a 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Let us know if you have suggestions to improve this article (requires login). </div> <div class="type-menu"> <label for="feedback-type" class="label mb-10">Feedback Type</label> <select id="feedback-type" class="form-select mb-30" name="feedbackTypeId" required> <option value="" selected="selected">Select a type (Required)</option> <option value="1">Factual Correction</option> <option value="2">Spelling/Grammar Correction</option> <option value="3">Link Correction</option> <option value="4">Additional Information</option> <option value="5">Other</option> </select> </div> <label for="feedback" class="label mb-10">Your Feedback</label> <textarea id="feedback" class="form-control mb-30" name="feedback" maxlength="3000" rows="7" required></textarea> <button class="btn btn-blue" type="submit">Submit Feedback</button> </form> <div class="success-messaging d-none mt-30"> <div class="title">Thank you for your feedback</div> <p>Our editors will review what you’ve submitted and determine whether to revise the article.</p> </div> </div> </div> <div class="md-websites-modal size-lg d-none"> <div class="md-modal-body"> <div class="h2 font-serif pb-15 border-bottom font-weight-bold"> External Websites </div> <div class="pb-20"> <ul class="list-unstyled mt-20 lh-lg"> <li><a class="external" href="https://theplanets.org/the-sun/" target="_blank" rel="noopener ">The Planets - Sun Facts</a></li> <li><a class="external" href="https://www.livescience.com/what-is-the-sun" target="_blank" rel="noopener ">LiveScience - The sun: Facts about the bright star at the center of the solar system</a></li> <li><a class="external" href="https://hort.purdue.edu/newcrop/afcm/mustard.html" target="_blank" rel="noopener ">Purdue University - Mustard</a></li> <li><a class="external" href="https://solarsystem.nasa.gov/solar-system/sun/" target="_blank" rel="noopener ">NASA - Sun</a></li> </ul> </div> <div class="md-websites-ebk-title">Britannica Websites</div> <div class="md-websites-ebk-subtitle">Articles from Britannica Encyclopedias for elementary and high school students.</div> <ul class="list-unstyled bps-topic-web-sites lh-lg"> <li><a class="external" href="https://kids.britannica.com/kids/article/Sun/353824" target="_blank" rel="noopener">Sun - Children's Encyclopedia (Ages 8-11)</a></li> <li><a class="external" href="https://kids.britannica.com/students/article/Sun/276056" target="_blank" rel="noopener">Sun - Student Encyclopedia (Ages 11 and up)</a></li> </ul> </div> </div> </div> </div> <div class="toc-header-marker"></div> <button class="ai-ask-button btn btn-sm border-2 btn-outline-red-400 border-red-400 d-none mr-0 mr-lg-10 ml-5 ml-sm-10 ml-lg-0 p-10 px-sm-5 px-md-10 js-header-ai-ask-button"> Ask the Chatbot a Question </button> <div class="md-byline module-spacing "> <div class="font-serif font-12"> <span class="written-by text-gray-700"> Written by </span> <div class="editor-popover popover p-0"> <a class="d-block p-20 qa-editor-popup gtm-byline font-12 byline-contributor" href="/contributor/Kenneth-Lang/7799632" > <div class="editor-title font-16 font-weight-bold">Kenneth Lang</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Professor of astrophysics and radio astronomy, Tufts University. Prof. Lang is a world renowned author of popular and scholarly books in astronomy and astrophysics.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> Kenneth Lang</span>, <div class="editor-popover popover p-0"> <a class="d-block p-20 qa-editor-popup gtm-byline font-12 byline-contributor" href="/contributor/Harold-Zirin/4031" > <div class="editor-title font-16 font-weight-bold">Harold Zirin</div> <div class="editor-description font-12 font-serif mt-5 clamp-description text-black">Professor of Astrophysics, Emeritus; Director and Builder, Big Bear Solar Observatory, California Institute of Technology, Pasadena. Author of <i>Astrophysics of the Sun </i>and others.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> Harold Zirin</span><span class="text-gray-700 mx-5">•</span><a class="see-all border-gray-700 gtm-byline" rel="nofollow" href="https://www.britannica.com/place/Sun/additional-info#contributors">All</a> </div> <div class="font-serif font-12 text-gray-700"> <span class="qa-fact-checked-by">Fact-checked by</span> <div class="editor-popover popover p-0"> <a class="d-block p-20 qa-editor-popup font-12" href="/editor/The-Editors-of-Encyclopaedia-Britannica/4419" > <div class="editor-title font-16 font-weight-bold">The Editors of Encyclopaedia Britannica</div> <div class="editor-description font-12 font-serif mt-5 text-black">Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link font-12 "> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <span class="text-gray-700"> Last Updated: <time datetime="2025-02-24T00:00:00CST" >Feb 24, 2025</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/place/Sun/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn btn-sm border-2 btn-outline-red-400 border-red-400 module-spacing js-inline-ai-ask-button p-10 ml-5"> Ask the Chatbot </button> </div> <div class="ai-top-questions-module module-spacing ai-tq collapsed font-sans-serif"> <div class="font-weight-bold font-14"> Top Questions </div> <ul class="mt-5"> <li class="ai-qa-item mb-5 bg-gray-50 rounded "> <div class="ai-top-question justify-content-between align-items-center font-14 px-10 py-5 rounded " data-qn="0"> <div>What is the Sun?</div> </div> <div class="answer p-10 ui-hidden" data-loaded="false"></div> <div class="ai-loader ui-hidden" /> </li> <li class="ai-qa-item mb-5 bg-gray-50 rounded "> <div class="ai-top-question justify-content-between align-items-center font-14 px-10 py-5 rounded " data-qn="1"> <div>What is the Sun made of?</div> </div> <div class="answer p-10 ui-hidden" data-loaded="false"></div> <div class="ai-loader ui-hidden" /> </li> <li class="ai-qa-item mb-5 bg-gray-50 rounded "> <div class="ai-top-question justify-content-between align-items-center font-14 px-10 py-5 rounded " data-qn="2"> <div>How does the Sun generate energy?</div> </div> <div class="answer p-10 ui-hidden" data-loaded="false"></div> <div class="ai-loader ui-hidden" /> </li> <li class="ai-qa-item mb-5 bg-gray-50 rounded af3"> <div class="ai-top-question justify-content-between align-items-center font-14 px-10 py-5 rounded " data-qn="3"> <div>What is the structure of the Sun?</div> </div> <div class="answer p-10 ui-hidden" data-loaded="false"></div> <div class="ai-loader ui-hidden" /> </li> <li class="ai-qa-item mb-5 bg-gray-50 rounded af3"> <div class="ai-top-question justify-content-between align-items-center font-14 px-10 py-5 rounded " data-qn="4"> <div>How does the Sun affect the Earth?</div> </div> <div class="answer p-10 ui-hidden" data-loaded="false"></div> <div class="ai-loader ui-hidden" /> </li> <li class="ai-qa-item mb-5 bg-gray-50 rounded af3"> <div class="ai-top-question justify-content-between align-items-center font-14 px-10 py-5 rounded " data-qn="5"> <div>What are sunspots and solar flares?</div> </div> <div class="answer p-10 ui-hidden" data-loaded="false"></div> <div class="ai-loader ui-hidden" /> </li> <li class="ai-qa-item mb-5 bg-gray-50 rounded af3"> <div class="ai-top-question justify-content-between align-items-center font-14 px-10 py-5 rounded " data-qn="6"> <div>How does the Sun compare to other stars in the universe?</div> </div> <div class="answer p-10 ui-hidden" data-loaded="false"></div> <div class="ai-loader ui-hidden" /> </li> <li class="ai-qa-item mb-5 bg-gray-50 rounded af3"> <div class="ai-top-question justify-content-between align-items-center font-14 px-10 py-5 rounded " data-qn="7"> <div>What is the life cycle of the Sun?</div> </div> <div class="answer p-10 ui-hidden" data-loaded="false"></div> <div class="ai-loader ui-hidden" /> </li> <li class="ai-qa-item mb-5 bg-gray-50 rounded af3"> <div class="ai-top-question justify-content-between align-items-center font-14 px-10 py-5 rounded " data-qn="8"> <div>How do scientists study the Sun?</div> </div> <div class="answer p-10 ui-hidden" data-loaded="false"></div> <div class="ai-loader ui-hidden" /> </li> <li class="ai-qa-item mb-5 bg-gray-50 rounded af3"> <div class="ai-top-question justify-content-between align-items-center font-14 px-10 py-5 rounded " data-qn="9"> <div>Why is the Sun important to life on Earth?</div> </div> <div class="answer p-10 ui-hidden" data-loaded="false"></div> <div class="ai-loader ui-hidden" /> </li> </ul> <button class="show-more btn btn-unstyled font-14 p-5 pr-10 mb-10 rounded-sm d-none"><em class="material-icons " data-icon="expand_more"></em> Show more</button> <button class="show-less btn btn-unstyled font-14 p-5 pr-10 mb-10 rounded-sm"><em class="material-icons " data-icon="expand_less"></em> Show less</button> </div><div class="bg-gray-50 p-15 rounded module-spacing recent-news d-flex flex-column float-false"> <div> <h2 class="font-weight-bold font-14 m-0 d-inline"> News <span class="text-gray-600">•</span> </h2> <div class="recent-news-item first-recent-news-item d-inline"> <a class="font-14 gtm-ap-news-link" href="https://www.techspot.com/news/106898-nasa-supercomputer-suggests-oort-cloud-may-spiral-like.html" rel="nofollow">NASA supercomputer suggests the Oort Cloud may be a spiral, like a miniature galaxy</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 24, 2025, 4:38 AM ET (TechSpot) <button class="btn btn-link d-inline p-0 font-12 js-toggle-recent-news"> <span class="text-gray-500">...</span><span>(Show more)</span> </button> </span> </div> </div> <div class="rest-of-recent-news-items"> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://www.nasa.gov/news-release/nasa-sets-launch-coverage-for-missions-studying-cosmic-origins-sun/" rel="nofollow">NASA Sets Launch Coverage for Missions Studying Cosmic Origins, Sun</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 19, 2025, 1:23 AM ET (NASA (.gov)) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://www.smh.com.au/business/consumer-affairs/sun-sets-over-minimum-payments-for-victorians-with-rooftop-solar-20250215-p5lcdu.html" rel="nofollow">Sun sets over minimum payments for Victorians with rooftop solar</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 15, 2025, 7:07 AM ET (Sydney Morning Herald) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://scitechdaily.com/solar-orbiter-just-solved-a-major-mystery-about-the-sun/" rel="nofollow">Solar Orbiter Just Solved a Major Mystery About the Sun</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 7, 2025, 5:48 AM ET (SciTechDaily) </span> </div> <button class="js-toggle-recent-news d-flex btn btn-unstyled font-14 pr-10 rounded-sm mt-10" aria-label="Toggle additional news items"> Show less <em class="material-icons" data-icon="expand_less"></em> </button> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref1027824"></span>Sun</strong>, <a href="https://www.britannica.com/science/star-astronomy" class="md-crosslink " data-show-preview="true">star</a> around which <a href="https://www.britannica.com/place/Earth" class="md-crosslink " data-show-preview="true">Earth</a> and the other components of the <a href="https://www.britannica.com/science/solar-system" class="md-crosslink " data-show-preview="true">solar system</a> revolve. It is the dominant body of the system, <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="constituting" href="https://www.merriam-webster.com/dictionary/constituting" data-type="MW">constituting</a> more than 99 percent of its entire mass. The Sun is the source of an enormous amount of <a href="https://www.britannica.com/science/energy" class="md-crosslink autoxref " data-show-preview="true">energy</a>, a portion of which provides Earth with the <a href="https://www.britannica.com/science/light" class="md-crosslink " data-show-preview="true">light</a> and <a href="https://www.britannica.com/science/heat" class="md-crosslink " data-show-preview="true">heat</a> necessary to support <a href="https://www.britannica.com/science/life" class="md-crosslink " data-show-preview="true">life</a>. It is part of the "<a href="https://www.britannica.com/topic/observable-universe" class="md-crosslink " data-show-preview="true">observable universe</a>," the region of space that humans can actually or theoretically observe with the aid of technology. Unlike the observable universe, the <a href="https://www.britannica.com/science/universe" class="md-crosslink " data-show-preview="true">universe</a> is possibly <a href="https://www.britannica.com/science/infinity-mathematics" class="md-crosslink " data-show-preview="true">infinite</a>.</p><span class="marker MOD1 mod-inline"></span><span class="marker PREMOD2 mod-inline"></span><p class="topic-paragraph"><em><a href="https://www.britannica.com/science/list-of-brightest-stars-2231574" class="md-crosslink " data-show-preview="true">(List of Brightest Stars as Seen from Earth)</a></em></p><span class="marker MOD2 mod-inline"></span><span class="marker PREMOD3 mod-inline"></span><p class="topic-paragraph">The Sun is classified as a <span id="ref959958"></span>G2 V star, with G2 standing for the second hottest stars of the yellow G class—of surface temperature about 5,800 <a href="https://www.britannica.com/science/kelvin" class="md-crosslink " data-show-preview="true">kelvins</a> (K)—and the V representing a main sequence, or <a href="https://www.britannica.com/science/dwarf-star" class="md-crosslink " data-show-preview="true">dwarf</a>, star, the typical star for this <a href="https://www.britannica.com/science/temperature" class="md-crosslink " data-show-preview="true">temperature</a> class. (G stars are so called because of the prominence of a band of atomic and molecular spectral lines that the German physicist <a href="https://www.britannica.com/biography/Joseph-von-Fraunhofer" class="md-crosslink " data-show-preview="true">Joseph von Fraunhofer</a> <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="designated" href="https://www.britannica.com/dictionary/designated" data-type="EB">designated</a> G.) The Sun exists in the outer part of the <a href="https://www.britannica.com/place/Milky-Way-Galaxy" class="md-crosslink " data-show-preview="true">Milky Way Galaxy</a> and was formed from material that had been processed inside a <a href="https://www.britannica.com/science/supernova" class="md-crosslink " data-show-preview="true">supernova</a>. The Sun is not, as is often said, a small star. Although it falls midway between the biggest and smallest stars of its type, there are so many dwarf stars that the Sun falls in the top 5 percent of stars in the neighbourhood that immediately surrounds it.</p><span class="marker MOD3 mod-inline"></span></section> <span class="marker h2"></span><section data-level="1" id="ref54136"> <h2 class="h1">Physical properties</h2> <span class="marker PREMOD4 mod-inline"></span><div class="assemblies multiple medialist slider js-slider position-relative d-inline-flex align-items-center mw-100" data-type="other"><div class="slider-container js-slider-container overflow-hidden d-flex"><div class="rw-track d-flex align-items-center"><div class="position-relative rw-slide col-100 px-20 "><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="74702" data-asm-type="image"><div class="md-assembly-wrapper card-media" data-type="image"><a href="https://cdn.britannica.com/01/81401-050-8EB87030/planets-solar-system-Pluto-montage-images-Sun.jpg" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center media-overlay-link card-media" data-href="/media/1/573494/74702"><picture><source media="(min-width: 680px)" srcset="https://cdn.britannica.com/01/81401-050-8EB87030/planets-solar-system-Pluto-montage-images-Sun.jpg?w=300"><img src="https://cdn.britannica.com/01/81401-050-8EB87030/planets-solar-system-Pluto-montage-images-Sun.jpg?w=300" alt="solar system to scale" data-width="2020" data-height="660" loading="eager"></picture><div class="position-absolute top-10 left-10 assembly-slide-tag rounded-lg">1 of 3</div><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" href="https://cdn.britannica.com/01/81401-050-8EB87030/planets-solar-system-Pluto-montage-images-Sun.jpg" data-href="/media/1/573494/74702">solar system to scale</a><span>The eight planets of the solar system and Pluto, in a montage of images scaled to show the approximate sizes of the bodies relative to one another. Outward from the Sun, which is represented to scale by the yellow segment at the extreme left, are the four rocky terrestrial planets (Mercury, Venus, Earth, and Mars), the four hydrogen-rich giant planets (Jupiter, Saturn, Uranus, and Neptune), and icy, comparatively tiny Pluto.</span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div></figcaption></figure></div><div class="position-relative rw-slide col-100 px-20 "><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="120232" data-asm-type="image"><div class="md-assembly-wrapper card-media" data-type="image"><a href="https://cdn.britannica.com/25/126025-050-0FB12805/foreground-Inland-Sea-Seto-Great-Bridge.jpg" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center media-overlay-link card-media" data-href="/media/1/573494/120232"><picture><source media="(min-width: 680px)" srcset="https://cdn.britannica.com/25/126025-050-0FB12805/foreground-Inland-Sea-Seto-Great-Bridge.jpg?w=300"><img src="https://cdn.britannica.com/25/126025-050-0FB12805/foreground-Inland-Sea-Seto-Great-Bridge.jpg?w=300" alt="Inland Sea" data-width="650" data-height="488" loading="eager"></picture><div class="position-absolute top-10 left-10 assembly-slide-tag rounded-lg">2 of 3</div><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" href="https://cdn.britannica.com/25/126025-050-0FB12805/foreground-Inland-Sea-Seto-Great-Bridge.jpg" data-href="/media/1/573494/120232">Inland Sea</a><span>Sunset on the Inland Sea, with the Seto Great Bridge in the foreground.</span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div></figcaption></figure></div><div class="position-relative rw-slide col-100 px-20 "><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="120445" data-asm-type="image"><div class="md-assembly-wrapper card-media" data-type="image"><a href="https://cdn.britannica.com/91/118391-050-AB82752B/Photosphere-limb-image-Sun-Solar-and-Heliospheric-Oct-29-2003.jpg" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center media-overlay-link card-media" data-href="/media/1/573494/120445"><picture><source media="(min-width: 680px)" srcset="https://cdn.britannica.com/91/118391-050-AB82752B/Photosphere-limb-image-Sun-Solar-and-Heliospheric-Oct-29-2003.jpg?w=300"><img src="https://cdn.britannica.com/91/118391-050-AB82752B/Photosphere-limb-image-Sun-Solar-and-Heliospheric-Oct-29-2003.jpg?w=300" alt="photosphere of the Sun" data-width="1600" data-height="1600" loading="eager"></picture><div class="position-absolute top-10 left-10 assembly-slide-tag rounded-lg">3 of 3</div><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" href="https://cdn.britannica.com/91/118391-050-AB82752B/Photosphere-limb-image-Sun-Solar-and-Heliospheric-Oct-29-2003.jpg" data-href="/media/1/573494/120445">photosphere of the Sun</a><span>Photosphere of the Sun with sunspots, image taken by the Solar and Heliospheric Observatory satellite, Oct. 29, 2003. </span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div></figcaption></figure></div></div></div><button disabled="true" class="prev-button js-prev-button position-absolute btn btn-circle shadow btn-lg btn-blue-dark m-20"><span class="material-icons" data-icon="keyboard_arrow_left"></span></button><button disabled="true" class="next-button js-next-button position-absolute btn btn-circle shadow btn-lg btn-blue-dark m-20"><span class="material-icons" data-icon="keyboard_arrow_right"></span></button></div><p class="topic-paragraph">The radius of the Sun, <em>R</em><sub>☉</sub>, is 109 times that of <a href="https://www.britannica.com/place/Earth" class="md-crosslink " data-show-preview="true">Earth</a>, but its distance from Earth is 215 <em>R</em><sub>☉</sub>, so it subtends an angle of only <span class="md-fraction md-fraction-oblique"><span><span class="md-frac-num">1</span><span class="md-fraction-symbol">/</span><span class="md-frac-den">2</span></span></span>° in the sky, roughly the same as that of the <a href="https://www.britannica.com/place/Moon" class="md-crosslink " data-show-preview="true">Moon</a>. By comparison, <a href="https://www.britannica.com/place/Alpha-Centauri" class="md-crosslink " data-show-preview="true">Proxima Centauri</a>, the next closest <a href="https://www.britannica.com/science/star-astronomy" class="md-crosslink " data-show-preview="true">star</a> to Earth, is 250,000 times farther away, and its relative apparent brightness is reduced by the square of that ratio, or 62 billion times. The <a href="https://www.britannica.com/science/temperature" class="md-crosslink " data-show-preview="true">temperature</a> of the Sun’s surface is so high that no <a href="https://www.britannica.com/science/solid-state-of-matter" class="md-crosslink " data-show-preview="true">solid</a> or <a href="https://www.britannica.com/science/liquid-state-of-matter" class="md-crosslink " data-show-preview="true">liquid</a> can exist there; the <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="constituent" href="https://www.merriam-webster.com/dictionary/constituent" data-type="MW">constituent</a> materials are predominantly gaseous <a href="https://www.britannica.com/science/atom" class="md-crosslink " data-show-preview="true">atoms</a>, with a very small number of <a href="https://www.britannica.com/science/molecule" class="md-crosslink " data-show-preview="true">molecules</a>. As a result, there is no fixed surface. The surface viewed from Earth, called the <a href="https://www.britannica.com/science/photosphere" class="md-crosslink " data-show-preview="true">photosphere</a>, is the layer from which most of the <a href="https://www.britannica.com/science/radiation" class="md-crosslink autoxref " data-show-preview="true">radiation</a> reaches us; the radiation from below is absorbed and reradiated, and the emission from overlying layers drops sharply, by about a factor of six every 200 kilometres (124 miles). The Sun is so far from Earth that this slightly fuzzy surface cannot be resolved, and so the limb (the visible edge) appears sharp.</p><span class="marker MOD4 mod-inline"></span> <span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">The mass of the Sun, <em>M</em><sub>☉</sub>, is 743 times the total mass of all the <a href="https://www.britannica.com/science/planet" class="md-crosslink " data-show-preview="true">planets</a> in the <a href="https://www.britannica.com/science/solar-system" class="md-crosslink " data-show-preview="true">solar system</a> and 330,000 times that of Earth. All the interesting planetary and interplanetary gravitational phenomena are <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="negligible" href="https://www.britannica.com/dictionary/negligible" data-type="EB">negligible</a> effects in comparison to the force exerted by the Sun. Under the force of <a href="https://www.britannica.com/science/gravity-physics" class="md-crosslink " data-show-preview="true">gravity</a>, the great mass of the Sun presses inward, and to keep the star from collapsing, the central <a href="https://www.britannica.com/science/pressure" class="md-crosslink " data-show-preview="true">pressure</a> outward must be great enough to support its weight. The <a href="https://www.britannica.com/science/density" class="md-crosslink autoxref " data-show-preview="true">density</a> at the Sun’s core is about 100 times that of <a href="https://www.britannica.com/science/water" class="md-crosslink " data-show-preview="true">water</a> (roughly six times that at the centre of Earth), but the temperature is at least 15,000,000 <a href="https://www.britannica.com/science/kelvin" class="md-crosslink autoxref " data-show-preview="true">K</a>, so the central pressure is at least 10,000 times greater than that at the centre of Earth, which is 3,500 kilobars. The nuclei of atoms are completely stripped of their <a href="https://www.britannica.com/science/electron" class="md-crosslink " data-show-preview="true">electrons</a>, and at this high temperature they collide to produce the <a href="https://www.britannica.com/science/nuclear-reaction" class="md-crosslink " data-show-preview="true">nuclear reactions</a> that are responsible for generating the energy <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="vital" href="https://www.britannica.com/dictionary/vital" data-type="EB">vital</a> to <a href="https://www.britannica.com/science/life" class="md-crosslink " data-show-preview="true">life</a> on Earth.</p><a class="link-module shadow-sm d-block qa-quiz-module" href="/quiz/36-questions-from-britannicas-most-popular-science-quizzes" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/05/215905-131-626D860A/Encyclopaedia-Britannica-thistle-graphic-logo.jpg" alt="Encyclopaedia Britannica thistle graphic to be used with a Mendel/Consumer quiz in place of a photograph." class="rounded-sm mr-15" width="70" /> <div class="line-clamp clamp-5"> <div class="module-title bg-green">Britannica Quiz</div> <div class="font-weight-semi-bold mt-5">36 Questions from Britannica’s Most Popular Science Quizzes</div> </div> </a><span class="marker MOD5 mod-inline"></span><div class="mb-20"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="276091" data-asm-type="infogram"><div class="md-assembly-wrapper card-media" data-type="infogram"><script id="infogram_0__/kq1AKnmJvA2RSNx54jy1" src="https://e.infogram.com/js/dist/embed.js?Itp" type="text/javascript" title="Planets of Our Solar System"></script></div></figure></div></div> <span class="marker PREMOD6 mod-inline"></span><div class="assemblies"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="280022" data-asm-type="video"><div class="md-assembly-wrapper card-media" data-type="video" video-id="240500"><a data-id="240500" class="gtm-assembly-link d-flex justify-content-center" style="--aspect-ratio: 16/9" href="/video/rarity-of-a-total-solar-eclipse/-280022"><img src="https://cdn.britannica.com/00/240500-138-9DA1E69A/rarity-of-a-total-solar-eclipse.jpg?w=800&h=450&c=crop" alt="How to watch a solar eclipse" loading="lazy"><script type="application/json"> { "sources": [ { "file" : "//content.jwplatform.com/manifests/rBdKG2j8.m3u8" } ], "image": "https://cdn.britannica.com/00/240500-138-9DA1E69A/rarity-of-a-total-solar-eclipse.jpg" ,"tracks": [ { "file" : "//assets-jpcust.jwpsrv.com/tracks/ucAN8Y2E", "label": "English" } ] ,"adfile": "//content.jwplatform.com/manifests/nzXcpYpT.m3u8" } </script><div class="btn btn-xl btn-white btn-circle position-absolute shadow" style="top: 50%; transform: translateY(-50%)"><em class="material-icons" data-icon="play_arrow"></em></div></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><span class="md-assembly-title font-weight-bold mr-5 d-inline font-sans-serif md-video-caption" video-control="240500">How to watch a solar eclipse</span><span>A solar eclipse is a celestial phenomenon occurring when the Moon appears to block out the Sun.</span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div><a class="font-14 mt-10 d-inline-block" href="/place/Sun/images-videos">See all videos for this article</a></figcaption></figure></div></div><p class="topic-paragraph">While the temperature of the Sun drops from 15,000,000 K at the centre to 5,800 K at the photosphere, a surprising reversal occurs above that point; the temperature drops to a minimum of 4,000 K, then begins to rise in the <a href="https://www.britannica.com/science/chromosphere" class="md-crosslink " data-show-preview="true">chromosphere</a>, a layer about 7,000 kilometres high at a temperature of 8,000 K. During a total eclipse the chromosphere appears as a pink ring. Above the chromosphere is a dim, extended <a href="https://www.britannica.com/science/halo-atmospheric-phenomenon" class="md-crosslink autoxref " data-show-preview="true">halo</a> called the <a href="https://www.britannica.com/science/corona-Sun" class="md-crosslink " data-show-preview="true">corona</a>, which has a temperature of 1,000,000 K and reaches far past the planets. Beyond a distance of 5<em>R</em><sub>☉</sub> from the Sun, the corona flows outward at a speed (near Earth) of 400 kilometres per second (km/s); this flow of charged particles is called the <a href="https://www.britannica.com/science/solar-wind" class="md-crosslink " data-show-preview="true">solar wind</a>.</p><div class="one-good-fact-module"> </div><span class="marker MOD6 mod-inline"></span> <span class="marker PREMOD7 mod-inline"></span><p class="topic-paragraph">The Sun is a very stable source of energy; its radiative output, called the <span id="ref1027834"></span><a href="https://www.britannica.com/science/solar-constant" class="md-crosslink " data-show-preview="true">solar constant</a>, is 1.366 kilowatts per square metre at Earth and varies by no more than 0.1 percent. Superposed on this stable star, however, is an interesting 11-year cycle of magnetic activity <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="manifested" href="https://www.merriam-webster.com/dictionary/manifested" data-type="MW">manifested</a> by regions of <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="transient" href="https://www.merriam-webster.com/dictionary/transient" data-type="MW">transient</a> strong <a href="https://www.britannica.com/science/magnetic-field" class="md-crosslink " data-show-preview="true">magnetic fields</a> called <a href="https://www.britannica.com/science/sunspot" class="md-crosslink " data-show-preview="true">sunspots</a>.</p><div class="module-spacing"> <DIV class="marketing-INLINE_SUBSCRIPTION marketing-content" data-marketing-id="INLINE_SUBSCRIPTION"><style> .student-promo-banner-wrapper { container-type: inline-size; margin-bottom: 15px; } @container (min-width: 475px) { .student-promo-banner { flex-direction: row; } .student-promo-banner-img-wrapper { margin-bottom: 0; margin-right: 10px; justify-content: flex-start; } .student-promo-banner-text-wrapper { text-align: left; margin-bottom: 0px; margin-left: 10px; } .student-promo-banner-button-wrapper { margin-right: 0; } }</style> <div class="student-promo-banner-wrapper"> <div class="student-promo-banner d-flex flex-column align-items-center bg-blue rounded p-20"> <div class="student-promo-banner-img-wrapper mb-20 mr-0 d-flex justify-content-center"> <img class="rounded" style="max-width: 100px; min-width: 80px" src="https://cdn.britannica.com/marketing/BlueThistle.webp" /> </div> <div class="student-promo-banner-text-wrapper ml-0 mb-10 text-center text-white"> <div class="h2 mb-10">Get Unlimited Access</div> <div class="h4 font-weight-semi-bold">Try Britannica Premium for free and discover more.</div> </div> <div class="student-promo-banner-button-wrapper d-flex justify-content-center align-items-center ml-auto mr-auto"> <a class="btn btn-m btn-orange" href="https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=inline-cta&utm_campaign=august-2024">Subscribe</a> </div> </div> </div> </DIV></div><span class="marker MOD7 mod-inline"></span> </section> <span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-simplify-root"></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article> </div> </div> </div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":11,"pageId":573494,"pageLength":807,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-133/js/libs/jquery-3.5.0.min.js?v=3.133.36"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-133/dist/topic-page.js?v=3.133.36' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"D","adLeg":"C","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"PAGINATED","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":true} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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Sun | Definition, Composition, Properties, Temperature, & Facts | Britannica