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</div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to 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src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b6/STEREO_EUV_Feb10_rotating.gif/250px-STEREO_EUV_Feb10_rotating.gif" decoding="async" width="250" height="250" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/b/b6/STEREO_EUV_Feb10_rotating.gif 1.5x" data-file-width="256" data-file-height="256" /></a><figcaption>This is a rotating projection of the entire surface of the Sun on February 10, 2011, as seen by the twin STEREO satellites. Credit: NASA STEREO mission.</figcaption></figure> <p>As <a href="/wiki/Geography" title="Geography">geography</a> describes the features of the surface of the <a href="/wiki/Earth" title="Earth">Earth</a>, <b>heliography</b> describes the surface features of Helios or the Sun, Sol. </p> <div style="clear:both;"></div> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Helionomy">Helionomy</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=1" title="Edit section: Helionomy" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=1" title="Edit section's source code: Helionomy"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r2661592">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}</style><div role="note" class="hatnote navigation-not-searchable">Main resources: <a href="/w/index.php?title=Stars/Sun/Helionomy&action=edit&redlink=1" class="new" title="Stars/Sun/Helionomy (page does not exist)">Stars/Sun/Helionomy</a> and <a href="/w/index.php?title=Helionomy&action=edit&redlink=1" class="new" title="Helionomy (page does not exist)">Helionomy</a></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Stonyhurst_Disk_1893_Aug_9.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Stonyhurst_Disk_1893_Aug_9.gif/250px-Stonyhurst_Disk_1893_Aug_9.gif" decoding="async" width="250" height="231" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Stonyhurst_Disk_1893_Aug_9.gif/375px-Stonyhurst_Disk_1893_Aug_9.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/e/ea/Stonyhurst_Disk_1893_Aug_9.gif 2x" data-file-width="435" data-file-height="402" /></a><figcaption>Use of Stonyhurst disk is shown to determine the heliographic coordinates of sunspots. Credit: Cortie, A. L. 1908.</figcaption></figure> <p>The surface of the Sun is often described by features observed. These are located using heliographic coordinates based on heliographic north and south poles. The surface of the Sun rotates, has a rotational north and south pole, and there is a central meridian. </p><p>The Stonyhurst Disk is superimposed on an image of the Sun to determine the heliographic coordinates. These are constructed by analogy with the geographical and are characterized by two values, latitude (Φ) and longitude (λ).<sup id="cite_ref-Heliographic_1-0" class="reference"><a href="#cite_note-Heliographic-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Latitude is measured from the plane of the solar equator. The first longitude (λ1) is measured from the plane of the "central meridian" as it passes through the rotation axis of the Sun and the line connecting the center of the Sun to the observer.<sup id="cite_ref-Heliographic_1-1" class="reference"><a href="#cite_note-Heliographic-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The Carrington longitude (λ2) is measured from the central meridian as it passes through the ascending node of the solar equator at Greenwich noon on January 1, 1854 (JD 2398220.0) and rotating with the sidereal period of 25.38 Earth days.<sup id="cite_ref-Heliographic_1-2" class="reference"><a href="#cite_note-Heliographic-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>The two longitudes are associated approximately by the ratio </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \lambda _{2}=\left\{{\frac {\lambda _{1}}{360^{\circ }}}-{\frac {{\rm {JD}}-2398220}{27.2753}}\right\}\cdot 360^{\circ }}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>λ</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> <mo>=</mo> <mrow> <mo>{</mo> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msub> <mi>λ</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> <msup> <mn>360</mn> <mrow class="MJX-TeXAtom-ORD"> <mo>∘</mo> </mrow> </msup> </mfrac> </mrow> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">J</mi> <mi mathvariant="normal">D</mi> </mrow> </mrow> <mo>−</mo> <mn>2398220</mn> </mrow> <mn>27.2753</mn> </mfrac> </mrow> </mrow> <mo>}</mo> </mrow> <mo>⋅</mo> <msup> <mn>360</mn> <mrow class="MJX-TeXAtom-ORD"> <mo>∘</mo> </mrow> </msup> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \lambda _{2}=\left\{{\frac {\lambda _{1}}{360^{\circ }}}-{\frac {{\rm {JD}}-2398220}{27.2753}}\right\}\cdot 360^{\circ }}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ae0207947160e53c12fc817854d44989753a723f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:38.217ex; height:6.176ex;" alt="{\displaystyle \lambda _{2}=\left\{{\frac {\lambda _{1}}{360^{\circ }}}-{\frac {{\rm {JD}}-2398220}{27.2753}}\right\}\cdot 360^{\circ }}"></span>.<sup id="cite_ref-Heliographic_1-3" class="reference"><a href="#cite_note-Heliographic-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></dd></dl> <p>The Sun has an equatorial radius of 695,500 km<sup id="cite_ref-sse_2-0" class="reference"><a href="#cite_note-sse-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;"></div> <div class="mw-heading mw-heading2"><h2 id="Visual_radiation">Visual radiation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=2" title="Edit section: Visual radiation" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=2" title="Edit section's source code: Visual radiation"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r2661592"><div role="note" class="hatnote navigation-not-searchable">Main resources: <a href="/w/index.php?title=Radiation/Visuals&action=edit&redlink=1" class="new" title="Radiation/Visuals (page does not exist)">Radiation/Visuals</a>, <a href="/w/index.php?title=Visual_radiation&action=edit&redlink=1" class="new" title="Visual radiation (page does not exist)">Visual radiation</a>, and <a href="/w/index.php?title=Visuals&action=edit&redlink=1" class="new" title="Visuals (page does not exist)">Visuals</a></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Sun920607.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Sun920607.jpg/250px-Sun920607.jpg" decoding="async" width="250" height="248" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Sun920607.jpg/375px-Sun920607.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/a/aa/Sun920607.jpg 2x" data-file-width="466" data-file-height="463" /></a><figcaption>This is a visual image of the Sun with some sunspots visible on the photosphere. The two small spots in the middle have about the same diameter as our planet Earth. Credit: NASA.</figcaption></figure> <p><b>Def.</b> "[a] visible surface layer of a star, and especially that of a sun"<sup id="cite_ref-PhotosphereWikt_3-0" class="reference"><a href="#cite_note-PhotosphereWikt-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> is called a <b>photosphere</b>. </p><p>"When we speak of the surface of the Sun, we normally mean the photosphere."<sup id="cite_ref-Guidry_4-0" class="reference"><a href="#cite_note-Guidry-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> "[T]he photosphere may be thought of as the imaginary surface from which the solar light that we see appears to be emitted. The diameter quoted for the Sun usually refers to the diameter of the photosphere."<sup id="cite_ref-Guidry_4-1" class="reference"><a href="#cite_note-Guidry-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The photosphere emits visual, or visible, radiation. </p><p>Illumination of the Sun's photosphere is in part by gamma rays. Each gamma ray that interacts with the photosphere is converted into several million photons of visible light. At the visible surface of the Sun, the temperature has dropped to 5,700 K and the density to only 0.2 g/m<sup>3</sup> (about 1/6,000th the density of air at sea level).<sup id="cite_ref-NASA1_5-0" class="reference"><a href="#cite_note-NASA1-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>The tremendous power output of the Sun is not due to its high power per volume, but instead due to its large size. Above the photosphere visible sunlight is free to propagate into space, and its energy escapes the Sun entirely. The change in opacity is due to the decreasing amount of H<sup>−</sup> ions, which absorb visible light easily.<sup id="cite_ref-Abhyankar1977_6-0" class="reference"><a href="#cite_note-Abhyankar1977-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Conversely, the visible light we see is produced as electrons react with hydrogen atoms to produce H<sup>−</sup> ions.<sup id="cite_ref-Gibson_7-0" class="reference"><a href="#cite_note-Gibson-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Shu_8-0" class="reference"><a href="#cite_note-Shu-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> The photosphere has a particle density of ~10<sup>23</sup> m<sup>−3</sup> (this is about 0.37% of the particle number per volume of Earth's atmosphere at sea level; however, photosphere particles are electrons and protons, so the average particle in air is 58 times as heavy). </p> <div style="clear:both;"></div> <div class="mw-heading mw-heading2"><h2 id="Physical_features">Physical features</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=3" title="Edit section: Physical features" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=3" title="Edit section's source code: Physical features"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><b>Def.</b> a shape or surface that is round and flat in appearance (middle 17th century usage referring to the seemingly flat round form of the Sun) is called a <b>disc</b>, or <b>disk</b>. </p><p><b>Def.</b> "the radial distance <i>q</i> from the Sun's center such that the following finite Fourier transform is zero: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F(G;q,a)=\int _{-1/2}^{+1/2}G(q+a\sin \pi s)\cos(2\pi s)ds,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>F</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo>;</mo> <mi>q</mi> <mo>,</mo> <mi>a</mi> <mo stretchy="false">)</mo> <mo>=</mo> <msubsup> <mo>∫</mo> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> <mn>1</mn> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>+</mo> <mn>1</mn> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mn>2</mn> </mrow> </msubsup> <mi>G</mi> <mo stretchy="false">(</mo> <mi>q</mi> <mo>+</mo> <mi>a</mi> <mi>sin</mi> <mo>⁡</mo> <mi>π</mi> <mi>s</mi> <mo stretchy="false">)</mo> <mi>cos</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <mn>2</mn> <mi>π</mi> <mi>s</mi> <mo stretchy="false">)</mo> <mi>d</mi> <mi>s</mi> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle F(G;q,a)=\int _{-1/2}^{+1/2}G(q+a\sin \pi s)\cos(2\pi s)ds,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/9f8b190ba3d87164861e79f98c779afcbcb73108" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.671ex; width:46.344ex; height:6.676ex;" alt="{\displaystyle F(G;q,a)=\int _{-1/2}^{+1/2}G(q+a\sin \pi s)\cos(2\pi s)ds,}"></span></dd></dl> <p>where <i>s</i> is a dummy variable, <i>G</i> is the observed solar intensity as a function of the radius, and the parameter <i>a</i> determines the extent of the solar limb used"<sup id="cite_ref-Hill_9-0" class="reference"><a href="#cite_note-Hill-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> is called the <b>solar edge</b>. </p><p>"When <i>F</i>(<i>G</i>; <i>q</i>, <i>a</i>) = 0, the <i>a</i> dependence of <i>q</i> can be used to choose different points as the edge."<sup id="cite_ref-Hill_9-1" class="reference"><a href="#cite_note-Hill-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Theoretical_heliography">Theoretical heliography</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=4" title="Edit section: Theoretical heliography" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=4" title="Edit section's source code: Theoretical heliography"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><b>Def.</b> the "scientific study of the sun"<sup id="cite_ref-HeliographyWikt_10-0" class="reference"><a href="#cite_note-HeliographyWikt-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> is called <b>heliography</b>. </p><p>Here's a <a href="/wiki/Definitions/Theory#Theoretical_definition" title="Definitions/Theory">theoretical definition</a>: </p><p><b>Def.</b> the study of the physical features of the Sun and its atmosphere is called <b>heliography</b>. </p> <div class="mw-heading mw-heading2"><h2 id="Objects">Objects</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=5" title="Edit section: Objects" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=5" title="Edit section's source code: Objects"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r2661592"><div role="note" class="hatnote navigation-not-searchable">Main resources: <a href="/w/index.php?title=Objects/Astronomy&action=edit&redlink=1" class="new" title="Objects/Astronomy (page does not exist)">Objects/Astronomy</a>, <a href="/wiki/Object_astronomy" title="Object astronomy">Object astronomy</a>, and <a href="/w/index.php?title=Objects&action=edit&redlink=1" class="new" title="Objects (page does not exist)">Objects</a></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:SunSpotGranulation.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0f/SunSpotGranulation.jpg/250px-SunSpotGranulation.jpg" decoding="async" width="250" height="250" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0f/SunSpotGranulation.jpg/375px-SunSpotGranulation.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0f/SunSpotGranulation.jpg/500px-SunSpotGranulation.jpg 2x" data-file-width="1536" data-file-height="1536" /></a><figcaption>This visual image using the Vacuum Tower Telescope shows solar granulation around and outward from a sunspot or hole. Credit: Vacuum Tower Telescope, NASA.</figcaption></figure> <p>There is turbulence and granulation in the Sun's <a href="/w/index.php?title=Photosphere&action=edit&redlink=1" class="new" title="Photosphere (page does not exist)">photosphere</a>. A typical granule has a diameter on the order of 1,000 kilometers and lasts 8 to 20 minutes before dissipating. At any one time, the Sun's surface is covered by about 4 million granules. </p><p><b>Supergranulation</b> is a particular pattern of [granules] on the Sun's surface [that] was discovered in the 1950s by A.B.Hart using Doppler velocity measurements showing horizontal flows on the photosphere (flow speed about 300 to 500 m/s, a tenth of that in the smaller granules). Later work (1960s) by Leighton, Noyes and Simon established a typical size of about 30000 km for supergranules with a lifetime of about 24 hours.<sup id="cite_ref-Freedman_11-0" class="reference"><a href="#cite_note-Freedman-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;"></div> <div class="mw-heading mw-heading2"><h2 id="Emissions">Emissions</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=6" title="Edit section: Emissions" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=6" title="Edit section's source code: Emissions"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r2661592"><div role="note" class="hatnote navigation-not-searchable">Main resources: <a href="/w/index.php?title=Radiation_astronomy/Emissions&action=edit&redlink=1" class="new" title="Radiation astronomy/Emissions (page does not exist)">Radiation astronomy/Emissions</a>, <a href="/w/index.php?title=Emission_astronomy&action=edit&redlink=1" class="new" title="Emission astronomy (page does not exist)">Emission astronomy</a>, and <a href="/w/index.php?title=Emissions&action=edit&redlink=1" class="new" title="Emissions (page does not exist)">Emissions</a></div> <p>Solar faculae are bright spots that form in the canyons between solar granules. </p><p>The emission of higher than average amounts of radiation later were observed from the solar faculae.<sup id="cite_ref-Arctowski_12-0" class="reference"><a href="#cite_note-Arctowski-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p><p>Correlations are now known to exist with decreases in luminosity caused by sunspots (generally < - 0.3%) and increases (generally < + 0.05%) caused both by faculae that are associated with active regions as well as the magnetically active 'bright network'.<sup id="cite_ref-Willson81_13-0" class="reference"><a href="#cite_note-Willson81-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> Faculae in magnetically active regions are hotter and 'brighter' than the average photosphere and cause temporary increases in [total solar irradiance] TSI. Luminosity has also been found to decrease by as much as 0.3% on a 10 day timescale when large groups of sunspots rotate across the Earth's view and increase by as much as 0.05% for up to 6 months due to faculae associated with the large sunspot groups.<sup id="cite_ref-Willson81_13-1" class="reference"><a href="#cite_note-Willson81-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p>The net effect during periods of enhanced solar magnetic activity is increased radiant output of the sun because faculae are larger and persist longer than sunspots. </p><p>"Though sunspots themselves are darker, they form when there are particularly magnetically active regions, which is when larger, brighter, longer-duration Faculae are more common as well".<sup id="cite_ref-Sokavik_14-0" class="reference"><a href="#cite_note-Sokavik-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Reds">Reds</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=7" title="Edit section: Reds" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=7" title="Edit section's source code: Reds"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r2661592"><div role="note" class="hatnote navigation-not-searchable">Main resources: <a href="/w/index.php?title=Radiation_astronomy/Reds&action=edit&redlink=1" class="new" title="Radiation astronomy/Reds (page does not exist)">Radiation astronomy/Reds</a>, <a href="/w/index.php?title=Red_astronomy&action=edit&redlink=1" class="new" title="Red astronomy (page does not exist)">Red astronomy</a>, and <a href="/w/index.php?title=Reds&action=edit&redlink=1" class="new" title="Reds (page does not exist)">Reds</a></div> <p>"Naked sunspots are spots seen in Hα to be devoid of associated plage. In magnetograms and K-line little if any opposite polarity field is found, and in soft X-ray images a blank appears in the region of the spot. In almost all cases ... in which naked spots resulted the spot groups had emerged in unipolar regions of the same polarity as the naked spot. At least half of the naked spots are associated with coronal holes."<sup id="cite_ref-Liggett_15-0" class="reference"><a href="#cite_note-Liggett-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p><p>"[N]aked spots are long-lived and show rotation rates close to the Newton-Nunn curve. Most of the naked spots had bright rims in Hα"<sup id="cite_ref-Liggett_15-1" class="reference"><a href="#cite_note-Liggett-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup>. </p> <div class="mw-heading mw-heading2"><h2 id="Gaseous_objects">Gaseous objects</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=8" title="Edit section: Gaseous objects" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=8" title="Edit section's source code: Gaseous objects"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r2661592"><div role="note" class="hatnote navigation-not-searchable">Main resources: <a href="/wiki/Gases/Gaseous_objects" title="Gases/Gaseous objects">Gases/Gaseous objects</a> and <a href="/w/index.php?title=Gaseous_objects&action=edit&redlink=1" class="new" title="Gaseous objects (page does not exist)">Gaseous objects</a></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:ChroniclesofJohnofWorcester.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/3d/ChroniclesofJohnofWorcester.jpg/250px-ChroniclesofJohnofWorcester.jpg" decoding="async" width="250" height="140" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/3d/ChroniclesofJohnofWorcester.jpg/375px-ChroniclesofJohnofWorcester.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/3d/ChroniclesofJohnofWorcester.jpg/500px-ChroniclesofJohnofWorcester.jpg 2x" data-file-width="516" data-file-height="289" /></a><figcaption>The image shows a drawing of a sunspot in the Chronicles of John of Worcester. Credit: Original work by John of Worcester.</figcaption></figure> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Trouvelot_-_Group_of_sun_spots_-_1875.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1d/Trouvelot_-_Group_of_sun_spots_-_1875.jpg/250px-Trouvelot_-_Group_of_sun_spots_-_1875.jpg" decoding="async" width="250" height="195" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1d/Trouvelot_-_Group_of_sun_spots_-_1875.jpg/375px-Trouvelot_-_Group_of_sun_spots_-_1875.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1d/Trouvelot_-_Group_of_sun_spots_-_1875.jpg/500px-Trouvelot_-_Group_of_sun_spots_-_1875.jpg 2x" data-file-width="9295" data-file-height="7253" /></a><figcaption>This drawing of a group of sun spots and veiled spots is as observed on June 17, 1875, at 7 h 30 m a.m. Credit: Étienne Léopold Trouvelot.</figcaption></figure> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:PSM_V01_D167_Spiral_sun_spots.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/03/PSM_V01_D167_Spiral_sun_spots.jpg/250px-PSM_V01_D167_Spiral_sun_spots.jpg" decoding="async" width="250" height="202" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/03/PSM_V01_D167_Spiral_sun_spots.jpg/375px-PSM_V01_D167_Spiral_sun_spots.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/03/PSM_V01_D167_Spiral_sun_spots.jpg/500px-PSM_V01_D167_Spiral_sun_spots.jpg 2x" data-file-width="942" data-file-height="762" /></a><figcaption>This spiral sunspot was seen at Rome on May 5, 1857. Credit: Secchi.</figcaption></figure> <figure class="mw-halign-right" typeof="mw:Error mw:File/Thumb"><a href="/w/index.php?title=Special:Upload&wpDestFile=Sunspot_vtt1.jpg" class="new" title="File:Sunspot vtt1.jpg"><span class="mw-file-element mw-broken-media" data-width="250">File:Sunspot vtt1.jpg</span></a><figcaption>A sunspot is a depression on the Sun's face that is slightly cooler and less luminous than the rest of the Sun. Credit: Vacuum Tower Telescope, NSO, NOAO.</figcaption></figure> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Sunspot_swedish_label1.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Sunspot_swedish_label1.jpg/250px-Sunspot_swedish_label1.jpg" decoding="async" width="250" height="182" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Sunspot_swedish_label1.jpg/375px-Sunspot_swedish_label1.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Sunspot_swedish_label1.jpg/500px-Sunspot_swedish_label1.jpg 2x" data-file-width="665" data-file-height="483" /></a><figcaption>A planet-sized sunspot showing for the first time dark cores of the filaments extending into the sunspot. These filaments are thousands of km long by about 100 km wide. Recorded on July 15, 2002, using the Swedish Solar Telescope (SST). Solar active region AR 10030. Credit: SST, Royal Swedish Academy of Sciences.</figcaption></figure> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Solar-cycle-data.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Solar-cycle-data.png/250px-Solar-cycle-data.png" decoding="async" width="250" height="166" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Solar-cycle-data.png/375px-Solar-cycle-data.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Solar-cycle-data.png/500px-Solar-cycle-data.png 2x" data-file-width="700" data-file-height="466" /></a><figcaption>Measurements of solar cycle variation are included for the last 30 years. Credit: <a href="https://en.wikipedia.org/wiki/User:Dragons_flight" class="extiw" title="w:User:Dragons flight">Robert A. Rohde</a>.</figcaption></figure> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Sunspot-number.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Sunspot-number.png/250px-Sunspot-number.png" decoding="async" width="250" height="175" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Sunspot-number.png/375px-Sunspot-number.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Sunspot-number.png/500px-Sunspot-number.png 2x" data-file-width="1250" data-file-height="875" /></a><figcaption>History of the number of observed sunspots during the last 250 years shows the ~11-year solar cycle. Credit: <a href="https://en.wikipedia.org/wiki/User:Leland_McInnes" class="extiw" title="w:User:Leland McInnes">Leland McInnes</a>.</figcaption></figure> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Sunspot_Numbers.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/28/Sunspot_Numbers.png/250px-Sunspot_Numbers.png" decoding="async" width="250" height="105" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/28/Sunspot_Numbers.png/375px-Sunspot_Numbers.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/28/Sunspot_Numbers.png/500px-Sunspot_Numbers.png 2x" data-file-width="1813" data-file-height="762" /></a><figcaption>This figure summarizes sunspot number observations. Credit: <a href="https://en.wikipedia.org/wiki/User:Dragons_flight" class="extiw" title="w:User:Dragons flight">Robert A. Rohde</a>.</figcaption></figure> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Carbon-14_with_activity_labels.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/73/Carbon-14_with_activity_labels.png/250px-Carbon-14_with_activity_labels.png" decoding="async" width="250" height="101" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/73/Carbon-14_with_activity_labels.png/375px-Carbon-14_with_activity_labels.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/73/Carbon-14_with_activity_labels.png/500px-Carbon-14_with_activity_labels.png 2x" data-file-width="1000" data-file-height="402" /></a><figcaption>Changes in <sup>14</sup>C concentration in the Earth's atmosphere serve as a long term proxy of solar activity. Note the present day is on the right-hand side. Credit: USGS.</figcaption></figure> <p><b>Def.</b> "[a] hollow spot in a surface"<sup id="cite_ref-Hole_16-0" class="reference"><a href="#cite_note-Hole-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> is called a <b>hole</b>. </p><p><b>Def.</b> "[a]n opening in a solid[, liquid, gas, or plasma]"<sup id="cite_ref-Hole_16-1" class="reference"><a href="#cite_note-Hole-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> is called a <b>hole</b>. </p><p><b>Def.</b> "[a] round or irregular patch on [or apparently on] the surface of [an entity] having a different color, texture etc. and generally round in shape"<sup id="cite_ref-Spot_17-0" class="reference"><a href="#cite_note-Spot-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> is called a <b>spot</b>. </p><p><b>Def.</b> "[a]n opening through which [entities such as] gases ... can pass"<sup id="cite_ref-Vent_18-0" class="reference"><a href="#cite_note-Vent-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> is called a <b>vent</b>. </p><p><b>Sunspots</b> are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature. Like magnets, they also have two poles. Although they are at temperatures of roughly 3,000–4,500 K (2,727–4,227 °C), the contrast with the surrounding material at about 5,780 K leaves them clearly visible as dark spots, as the luminous intensity of a heated black body (closely approximated by the photosphere) is a function of temperature to the fourth power. If the sunspot were isolated from the surrounding photosphere it would be brighter than an electric arc. Sunspots expand and contract as they move across the surface of the Sun and can be as large as 80,000 kilometers (49,710 mi) in diameter, making the larger ones visible from Earth without the aid of a <a href="/w/index.php?title=Telescope&action=edit&redlink=1" class="new" title="Telescope (page does not exist)">telescope</a>.<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> They may also travel at relative speeds ("proper motions") of a few hundred m/s when they first emerge onto the solar photosphere. </p><p>"For the greater part of the sun-spot period there is practically but one zone of spots in each hemisphere. The departure from this condition of things near or at the time of minimum, when the spots of the dying cycle are approaching the equator, and the forerunners of the new cycle are beginning to appear in high latitudes, is the only case in which the solar spots are distinctly separated into more than a single zone in each hemisphere."<sup id="cite_ref-Maunder_20-0" class="reference"><a href="#cite_note-Maunder-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> "Spöerer's law ... involves that in a minimum year the zone about 15° should be entirely barren".<sup id="cite_ref-Maunder_20-1" class="reference"><a href="#cite_note-Maunder-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p><p>"First of all there were only fifteen groups seen during the entire year [1901], north and south put together. Of these, seven were in the north, and the mean latitude for the north was 8.6°, exactly the latitude of one spot of the seven, and this very naturally, seeing that it was by far the <b>greatest group</b> of the year, the celebrated "eclipse group.""<sup id="cite_ref-Maunder_20-2" class="reference"><a href="#cite_note-Maunder-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> Bold added. "Greatest group" and "eclipse group" are both relative synonyms for "<a href="/wiki/Dominant_group" title="Dominant group">dominant group</a>". </p><p>"[T]he spot-groups have been carefully examined for cases of return, and where it appeared clear that the same group has returned a second time or more frequently, without any temporary disappearance or subsidence, such a long-continued group has been treated as an <b>entity</b> throughout."<sup id="cite_ref-Maunder05_21-0" class="reference"><a href="#cite_note-Maunder05-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> Bold added. "It has been forgotten that, whatever the cause which produces this variation of rotation rate with latitude, the causes producing difference of rate within any given latitude are more effective still."<sup id="cite_ref-Maunder05_21-1" class="reference"><a href="#cite_note-Maunder05-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p><p>"[T]here is a slight retardation of the rotation period from the first cycle to the second, shown by both northern and southern hemispheres."<sup id="cite_ref-Maunder05_21-2" class="reference"><a href="#cite_note-Maunder05-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p><p>Studies of stratigraphic data have suggested that the solar cycles have been active for hundreds of millions of years, if not longer; measuring varves in precambrian sedimentary rock has revealed repeating peaks in layer thickness, with a pattern repeating approximately every eleven years. It is possible that the early atmosphere on Earth was more sensitive to changes in solar radiation than today, so that greater glacial melting (and thicker sediment deposits) could have occurred during years with greater sunspot activity.<sup id="cite_ref-Williams_22-0" class="reference"><a href="#cite_note-Williams-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Reed_23-0" class="reference"><a href="#cite_note-Reed-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> This would presume annual layering; however, alternate explanations (diurnal) have also been proposed.<sup id="cite_ref-Williams90_24-0" class="reference"><a href="#cite_note-Williams90-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p><p>Analysis of tree rings has revealed a detailed picture of past solar cycles: Dendrochronologically dated radiocarbon concentrations have allowed for a reconstruction of sunspot activity dating back 11,400 years, far beyond the four centuries of available, reliable records from direct solar observation.<sup id="cite_ref-pmid15510145_25-0" class="reference"><a href="#cite_note-pmid15510145-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> </p><p>The earliest surviving record of sunspot observation dates from 364 BC, based on comments by Chinese astronomer Gan De in a star catalogue.<sup id="cite_ref-NRICH_26-0" class="reference"><a href="#cite_note-NRICH-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> By 28 BC, Chinese astronomers were regularly recording sunspot observations in official imperial records.<sup id="cite_ref-UNESCO_27-0" class="reference"><a href="#cite_note-UNESCO-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> </p><p>The second drawing at right is of a group of sun spots and veiled spots. This group was observed on June 17, 1875, at 07:30 a.m. The interior of these spots appears to have a larger granule size than the outer surface of the photosphere itself. </p><p>The spiral sunspot in the third drawing at right is a vortex seen on May 5, 1857, at Rome. "[T]he substance of the photosphere is rushing with an eddying motion [into the spot]."<sup id="cite_ref-Youmans_28-0" class="reference"><a href="#cite_note-Youmans-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </p><p><b>Starspots</b> are equivalent to sunspots but located on other stars. Spots the size of sunspots are very hard to detect since they are too small to cause fluctuations in brightness. Observed starspots are in general much larger than those on the Sun, up to about 30 % of the stellar surface may be covered, corresponding to sizes 100 times greater than those on the Sun. </p><p>The distribution of starspots across the stellar surface varies analogous to the solar case, but differs for different types of stars, e.g., depending on whether the star is a binary or not. The same type of activity cycles that are found for the Sun can be seen for other stars, corresponding to the solar (2 times) 11-year cycle. Some stars have longer cycles, possibly analogous to the Maunder minima for the Sun. </p><p>Another activity cycle is the so called flip-flop cycle, which implies that the activity on either hemisphere shifts from one side to the other. The same phenomena can be seen on the Sun, with periods of 3.8 and 3.65 years for the northern and southern hemispheres. Flip-flop phenomena are observed for both binary [RS Canum Venaticorum variable] RS CVn stars and single stars although the extent of the cycles are different between binary and singular stars. </p><p>Manifesting intense magnetic activity, sunspots host secondary phenomena such as coronal loops (prominences) and reconnection events. Most solar flares and coronal mass ejections originate in magnetically active regions around visible sunspot groupings. Similar phenomena indirectly observed on stars are commonly called starspots and both light and dark spots have been measured.<sup id="cite_ref-strassmeier_29-0" class="reference"><a href="#cite_note-strassmeier-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </p><p>The sunspot itself can be divided into two parts: </p> <ul><li>The central <a href="https://en.wiktionary.org/wiki/umbra" class="extiw" title="wikt:umbra">umbra</a>, which is the darkest part, where the magnetic field is approximately vertical (normal to the Sun's surface).</li> <li>The surrounding penumbra, which is lighter, where the magnetic field is more inclined.</li></ul> <p>"[T]he rate of helicity change <i>dH</i>/<i>dt</i> due to horizontal motions is </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\frac {dH}{dt}}=-2\oint (\mathbf {v} \cdot \mathbf {A_{p}} )\mathbf {B_{n}} \mathrm {d} \mathbf {S} ,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mi>d</mi> <mi>H</mi> </mrow> <mrow> <mi>d</mi> <mi>t</mi> </mrow> </mfrac> </mrow> <mo>=</mo> <mo>−</mo> <mn>2</mn> <mo>∮</mo> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">v</mi> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <msub> <mi mathvariant="bold">A</mi> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">p</mi> </mrow> </msub> </mrow> <mo stretchy="false">)</mo> <mrow class="MJX-TeXAtom-ORD"> <msub> <mi mathvariant="bold">B</mi> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">n</mi> </mrow> </msub> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">d</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">S</mi> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {dH}{dt}}=-2\oint (\mathbf {v} \cdot \mathbf {A_{p}} )\mathbf {B_{n}} \mathrm {d} \mathbf {S} ,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/aed86a2d5f50c9859dc1f887332fe8a7a126823a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.338ex; width:27.575ex; height:5.843ex;" alt="{\displaystyle {\frac {dH}{dt}}=-2\oint (\mathbf {v} \cdot \mathbf {A_{p}} )\mathbf {B_{n}} \mathrm {d} \mathbf {S} ,}"></span></dd></dl> <p>where <i>B</i><sub>n</sub> is the vertical component of the magnetic field on the photosphere and <b>v</b> the photospheric horizontal velocity."<sup id="cite_ref-Nindos_30-0" class="reference"><a href="#cite_note-Nindos-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> </p><p>"Helicity [(H)] is a quantitative measure of the chiral properties of the structures observed in the solar atmosphere. ... [H]elicity [is] injected to the corona by photospheric horizontal shearing motions (other than differential rotation) or by [vertical] magnetic flux. ... [D]ifferential rotation cannot provide the required helicity to the [CME] field ejected to interplanetary space."<sup id="cite_ref-Nindos_30-1" class="reference"><a href="#cite_note-Nindos-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> </p><p>Solar active region AR 10030 contained a group of sunspots including the largest one partially included in the image at the right. It is a planet-sized sunspot showing for the first time the dark cores of the filaments extending into the sunspot. These filaments are thousands of km long by about 100 km wide. The image is recorded on July 15, 2002, using the Swedish Solar Telescope (SST). </p><p>The number of sunspots visible on the Sun is not constant, but varies over an 11-year cycle known as the solar cycle. At a typical solar minimum, few sunspots are visible, and occasionally none at all can be seen. Those that do appear are at high solar latitudes. As the sunspot cycle progresses, the number of sunspots increases and they move closer to the equator of the Sun, a phenomenon described by Spörer's law. Sunspots usually exist as pairs with opposite magnetic polarity. The magnetic polarity of the leading sunspot alternates every solar cycle, so that it will be a north magnetic pole in one solar cycle and a south magnetic pole in the next.<sup id="cite_ref-solarcycle_31-0" class="reference"><a href="#cite_note-solarcycle-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </p><p>HD 154345b has "a 9.2 year, circular orbit with radius 4.2 AU. ... We also detect a ~ 9 year activity cycle in this star [HD 154345] photometrically and in chromospheric emission. ... We note that the Sun's 11 year activity cycle has a period similar to that of Jupiter's orbit, and that the Mount Wilson survey demonstrated that decadal activity cycles are a common feature of old G stars (Baliunas et al. 1995)."<sup id="cite_ref-Wright_32-0" class="reference"><a href="#cite_note-Wright-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;"></div> <div class="mw-heading mw-heading2"><h2 id="Sun">Sun</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=9" title="Edit section: Sun" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=9" title="Edit section's source code: Sun"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r2661592"><div role="note" class="hatnote navigation-not-searchable">Main resources: <a href="/wiki/Stars/Sun" title="Stars/Sun">Stars/Sun</a> and <a href="/wiki/Sun_(star)" class="mw-redirect" title="Sun (star)">Sun (star)</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Zurich_sunspot_number_since_1750.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/78/Zurich_sunspot_number_since_1750.png/250px-Zurich_sunspot_number_since_1750.png" decoding="async" width="250" height="340" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/78/Zurich_sunspot_number_since_1750.png/375px-Zurich_sunspot_number_since_1750.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/78/Zurich_sunspot_number_since_1750.png/500px-Zurich_sunspot_number_since_1750.png 2x" data-file-width="768" data-file-height="1045" /></a><figcaption>This graph shows Wolf numbers since 1750. Credit: NASA.</figcaption></figure> <p>"[T]he longest data set, the Wolf sunspot number (R), is determined from visible wavelength observations of the solar surface."<sup id="cite_ref-Rybansky_33-0" class="reference"><a href="#cite_note-Rybansky-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> </p><p>"The <b>Wolf number</b> (also known as the <b>International sunspot number</b>, <b>relative sunspot number</b>, or <b>Zürich number</b>) is a quantity that measures the number of sunspots and groups of sunspots present on the surface of the sun."<sup id="cite_ref-WolfNumber_34-0" class="reference"><a href="#cite_note-WolfNumber-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p><p>"This number has been collected and tabulated by researchers for over 150 years."<sup id="cite_ref-WolfNumber_34-1" class="reference"><a href="#cite_note-WolfNumber-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p><p>The relative sunspot number <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>R</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle R}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4b0bfb3769bf24d80e15374dc37b0441e2616e33" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.764ex; height:2.176ex;" alt="{\displaystyle R}"></span> is computed using the formula (collected as a daily index of sunspot activity): </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R=k(10g+s)\,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>R</mi> <mo>=</mo> <mi>k</mi> <mo stretchy="false">(</mo> <mn>10</mn> <mi>g</mi> <mo>+</mo> <mi>s</mi> <mo stretchy="false">)</mo> <mspace width="thinmathspace" /> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle R=k(10g+s)\,}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/34864e89e2fc6d15271f166c7909be525ee42c33" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:15.642ex; height:2.843ex;" alt="{\displaystyle R=k(10g+s)\,}"></span></dd></dl> <p>where </p> <ul><li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle s}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>s</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle s}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/01d131dfd7673938b947072a13a9744fe997e632" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.09ex; height:1.676ex;" alt="{\displaystyle s}"></span> is the number of individual spots,</li> <li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle g}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>g</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle g}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d3556280e66fe2c0d0140df20935a6f057381d77" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.116ex; height:2.009ex;" alt="{\displaystyle g}"></span> is the number of sunspot groups, and</li> <li><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle k}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>k</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle k}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c3c9a2c7b599b37105512c5d570edc034056dd40" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.211ex; height:2.176ex;" alt="{\displaystyle k}"></span> is a factor that varies with location and instrumentation (also known as the <i>observatory factor</i> or the <i>personal reduction coefficient</i> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle K}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>K</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle K}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2b76fce82a62ed5461908f0dc8f037de4e3686b0" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.066ex; height:2.176ex;" alt="{\displaystyle K}"></span>).<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup></li></ul> <div style="clear:both;"></div> <div class="mw-heading mw-heading2"><h2 id="Hypotheses">Hypotheses</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=10" title="Edit section: Hypotheses" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=10" title="Edit section's source code: Hypotheses"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r2661592"><div role="note" class="hatnote navigation-not-searchable">Main resource: <a href="/wiki/Hypotheses" class="mw-redirect" title="Hypotheses">Hypotheses</a></div> <ol><li>As the surface of the Sun is bombarded by incoming electrons the rotational speed is decreased.</li> <li>The Sun rotates at its slowest during the peak of the solar cycle and fastest at the cycle minimum.</li> <li>As the rotational rate of the Sun is set by convention, the actual rate is detectably different.</li></ol> <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=Stars/Sun/Heliography&veaction=edit&section=11" title="Edit section: See also" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=11" title="Edit section's source code: See also"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r2670040">.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" style="column-width: 20em;"> <ul><li><a href="/wiki/Stars/Sun/Heliocentric_astronomy" title="Stars/Sun/Heliocentric astronomy">Heliocentric astronomy</a></li> <li><a href="/wiki/Stars/Sun/Heliogony" title="Stars/Sun/Heliogony">Heliogony</a></li> <li><a class="mw-selflink selflink">Heliography</a></li> <li><a href="/wiki/Stars/Sun/Heliology" title="Stars/Sun/Heliology">Heliology</a></li> <li><a href="/wiki/Stars/Sun/Heliometry" title="Stars/Sun/Heliometry">Heliometry</a></li> <li><a href="/wiki/Stars/Sun/Heliophysics" title="Stars/Sun/Heliophysics">Heliophysics</a></li> <li><a href="/wiki/Stars/Sun/Heliospheres" title="Stars/Sun/Heliospheres">Heliospheres</a></li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=12" title="Edit section: References" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=12" title="Edit section's source code: References"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r2661605">.mw-parser-output .reflist{font-size:90%;margin-bottom:0.5em;list-style-type:decimal}.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 reflist-columns-2"> <ol class="references"> <li id="cite_note-Heliographic-1"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-Heliographic_1-0">1.0</a></sup> <sup><a href="#cite_ref-Heliographic_1-1">1.1</a></sup> <sup><a href="#cite_ref-Heliographic_1-2">1.2</a></sup> <sup><a href="#cite_ref-Heliographic_1-3">1.3</a></sup></span> <span class="reference-text"><span class="citation book"> <a class="external text" href="https://ru.wikipedia.org/wiki/Гелиографические_координаты"><i>Гелиографические координаты</i></a>. San Francisco, California: Wikimedia Foundation, Inc. October 19, 2012<span class="printonly">. <a class="external free" href="https://ru.wikipedia.org/wiki/Гелиографические_координаты">http://ru.wikipedia.org/wiki/Гелиографические_координаты</a></span><span class="reference-accessdate">. Retrieved 2012-11-19</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=%D0%93%D0%B5%D0%BB%D0%B8%D0%BE%D0%B3%D1%80%D0%B0%D1%84%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0%B8%D0%B5+%D0%BA%D0%BE%D0%BE%D1%80%D0%B4%D0%B8%D0%BD%D0%B0%D1%82%D1%8B&rft.date=October+19%2C+2012&rft.place=San+Francisco%2C+California&rft.pub=Wikimedia+Foundation%2C+Inc&rft_id=http%3A%2F%2Fru.wikipedia.org%2Fwiki%2F%D0%93%D0%B5%D0%BB%D0%B8%D0%BE%D0%B3%D1%80%D0%B0%D1%84%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0%B8%D0%B5_%D0%BA%D0%BE%D0%BE%D1%80%D0%B4%D0%B8%D0%BD%D0%B0%D1%82%D1%8B&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-sse-2"><span class="mw-cite-backlink"><a href="#cite_ref-sse_2-0">↑</a></span> <span class="reference-text"><span class="citation book"> <a rel="nofollow" class="external text" href="http://web.archive.org/web/20080102034758/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric"><i>Solar System Exploration: Planets: Sun: Facts & Figures</i></a>. NASA. 2008-01-02<span class="printonly">. <a rel="nofollow" class="external free" href="http://web.archive.org/web/20080102034758/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric">http://web.archive.org/web/20080102034758/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric</a></span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Solar+System+Exploration%3A+Planets%3A+Sun%3A+Facts+%26+Figures&rft.date=2008-01-02&rft.pub=NASA&rft_id=http%3A%2F%2Fweb.archive.org%2Fweb%2F20080102034758%2Fhttp%3A%2F%2Fsolarsystem.nasa.gov%2Fplanets%2Fprofile.cfm%3FObject%3DSun%26Display%3DFacts%26System%3DMetric&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-PhotosphereWikt-3"><span class="mw-cite-backlink"><a href="#cite_ref-PhotosphereWikt_3-0">↑</a></span> <span class="reference-text"><span class="citation book"> <a class="external text" href="https://en.wiktionary.org/wiki/photosphere"><i>photosphere</i></a>. San Francisco, California: Wikimedia Foundation, Inc. August 30, 2012<span class="printonly">. <a class="external free" href="https://en.wiktionary.org/wiki/photosphere">http://en.wiktionary.org/wiki/photosphere</a></span><span class="reference-accessdate">. Retrieved 2012-11-23</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=photosphere&rft.date=August+30%2C+2012&rft.place=San+Francisco%2C+California&rft.pub=Wikimedia+Foundation%2C+Inc&rft_id=http%3A%2F%2Fen.wiktionary.org%2Fwiki%2Fphotosphere&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Guidry-4"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-Guidry_4-0">4.0</a></sup> <sup><a href="#cite_ref-Guidry_4-1">4.1</a></sup></span> <span class="reference-text"><span class="citation book">Mike Guidry (1999-04-16). <a rel="nofollow" class="external text" href="http://csep10.phys.utk.edu/astr162/lect/sun/photosphere.html"><i>The Photosphere of the Sun</i></a>. University of Tennessee<span class="printonly">. <a rel="nofollow" class="external free" href="http://csep10.phys.utk.edu/astr162/lect/sun/photosphere.html">http://csep10.phys.utk.edu/astr162/lect/sun/photosphere.html</a></span><span class="reference-accessdate">. Retrieved 2006-10-12</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Photosphere+of+the+Sun&rft.aulast=Mike+Guidry&rft.au=Mike+Guidry&rft.date=1999-04-16&rft.pub=University+of+Tennessee&rft_id=http%3A%2F%2Fcsep10.phys.utk.edu%2Fastr162%2Flect%2Fsun%2Fphotosphere.html&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-NASA1-5"><span class="mw-cite-backlink"><a href="#cite_ref-NASA1_5-0">↑</a></span> <span class="reference-text"><span class="citation book"> <a rel="nofollow" class="external text" href="https://solarscience.msfc.nasa.gov/interior.shtml"><i>NASA/Marshall Solar Physics</i></a>. Solarscience.msfc.nasa.gov. 2007-01-18<span class="printonly">. <a rel="nofollow" class="external free" href="https://solarscience.msfc.nasa.gov/interior.shtml">http://solarscience.msfc.nasa.gov/interior.shtml</a></span><span class="reference-accessdate">. Retrieved 2009-07-11</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=NASA%2FMarshall+Solar+Physics&rft.date=2007-01-18&rft.pub=Solarscience.msfc.nasa.gov&rft_id=http%3A%2F%2Fsolarscience.msfc.nasa.gov%2Finterior.shtml&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Abhyankar1977-6"><span class="mw-cite-backlink"><a href="#cite_ref-Abhyankar1977_6-0">↑</a></span> <span class="reference-text"><span class="citation Journal">K.D. Abhyankar (1977). <a rel="nofollow" class="external text" href="http://prints.iiap.res.in/handle/2248/510">"A Survey of the Solar Atmospheric Models"</a>. <i>Bull. Astr. Soc. India</i> <b>5</b>: 40–44<span class="printonly">. <a rel="nofollow" class="external free" href="http://prints.iiap.res.in/handle/2248/510">http://prints.iiap.res.in/handle/2248/510</a></span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=A+Survey+of+the+Solar+Atmospheric+Models&rft.jtitle=Bull.+Astr.+Soc.+India&rft.aulast=K.D.+Abhyankar&rft.au=K.D.+Abhyankar&rft.date=1977&rft.volume=5&rft.pages=40%E2%80%9344&rft_id=http%3A%2F%2Fprints.iiap.res.in%2Fhandle%2F2248%2F510&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Gibson-7"><span class="mw-cite-backlink"><a href="#cite_ref-Gibson_7-0">↑</a></span> <span class="reference-text"><span class="citation book">E.G. Gibson (1973). <i>The Quiet Sun</i>. NASA.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Quiet+Sun&rft.aulast=E.G.+Gibson&rft.au=E.G.+Gibson&rft.date=1973&rft.pub=NASA&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Shu-8"><span class="mw-cite-backlink"><a href="#cite_ref-Shu_8-0">↑</a></span> <span class="reference-text"><span class="citation book">Shu, F.H. (1991). <i>The Physics of Astrophysics</i>. <b>1</b>. University Science Books. ISBN <a href="/wiki/Special:BookSources/0-935702-64-4" title="Special:BookSources/0-935702-64-4">0-935702-64-4</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Physics+of+Astrophysics&rft.aulast=Shu&rft.aufirst=F.H.&rft.au=Shu%2C%26%2332%3BF.H.&rft.date=1991&rft.volume=1&rft.pub=University+Science+Books&rft.isbn=0-935702-64-4&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Hill-9"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-Hill_9-0">9.0</a></sup> <sup><a href="#cite_ref-Hill_9-1">9.1</a></sup></span> <span class="reference-text"><span class="citation Journal">H. A. Hill & R. T. Stebbins (September 1, 1975). "The intrinsic visual oblateness of the sun". <i>The Astrophysical Journal</i> <b>200</b> (9): 471-7, 477-83. doi:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F153813">10.1086/153813</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+intrinsic+visual+oblateness+of+the+sun&rft.jtitle=The+Astrophysical+Journal&rft.aulast=H.+A.+Hill+%26+R.+T.+Stebbins&rft.au=H.+A.+Hill+%26+R.+T.+Stebbins&rft.date=September+1%2C+1975&rft.volume=200&rft.issue=9&rft.pages=471-7%2C+477-83&rft_id=info:doi/10.1086%2F153813&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-HeliographyWikt-10"><span class="mw-cite-backlink"><a href="#cite_ref-HeliographyWikt_10-0">↑</a></span> <span class="reference-text"><span class="citation book"> <a class="external text" href="https://en.wiktionary.org/wiki/heliography"><i>heliography</i></a>. San Francisco, California: Wikimedia Foundation, Inc<span class="printonly">. <a class="external free" href="https://en.wiktionary.org/wiki/heliography">https://en.wiktionary.org/wiki/heliography</a></span><span class="reference-accessdate">. Retrieved 2016-10-06</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=heliography&rft.place=San+Francisco%2C+California&rft.pub=Wikimedia+Foundation%2C+Inc&rft_id=https%3A%2F%2Fen.wiktionary.org%2Fwiki%2Fheliography&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Freedman-11"><span class="mw-cite-backlink"><a href="#cite_ref-Freedman_11-0">↑</a></span> <span class="reference-text"><span class="citation book">Roger A. Freedman, William J. Kaufmann III (2008). <i>Universe</i>. New York, USA: W. H. Freeman and Company. pp. 762. ISBN <a href="/wiki/Special:BookSources/978-0-7167-8584-2" title="Special:BookSources/978-0-7167-8584-2">978-0-7167-8584-2</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Universe&rft.aulast=Roger+A.+Freedman%2C+William+J.+Kaufmann+III&rft.au=Roger+A.+Freedman%2C+William+J.+Kaufmann+III&rft.date=2008&rft.pages=pp.%26nbsp%3B762&rft.place=New+York%2C+USA&rft.pub=W.+H.+Freeman+and+Company&rft.isbn=978-0-7167-8584-2&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Arctowski-12"><span class="mw-cite-backlink"><a href="#cite_ref-Arctowski_12-0">↑</a></span> <span class="reference-text"><span class="citation Journal">Henryk Arctowski (1940). <a rel="nofollow" class="external text" href="http://www.pnas.org/cgi/reprint/26/6/406.pdf">"On Solar Faculae and Solar Constant Variations"</a>. <i>Proc. Natl. Acad. Sci. U.S.A.</i> <b>26</b> (6): 406–11. doi:<a rel="nofollow" class="external text" href="https://doi.org/10.1073%2Fpnas.26.6.406">10.1073/pnas.26.6.406</a>. PMID <a rel="nofollow" class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/16588370">16588370</a>. PMC <a rel="nofollow" class="external text" href="http://www.pubmedcentral.gov/articlerender.fcgi?tool=pmcentrez&artid=1078196">1078196</a><span class="printonly">. <a rel="nofollow" class="external free" href="http://www.pnas.org/cgi/reprint/26/6/406.pdf">http://www.pnas.org/cgi/reprint/26/6/406.pdf</a></span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=On+Solar+Faculae+and+Solar+Constant+Variations&rft.jtitle=Proc.+Natl.+Acad.+Sci.+U.S.A.&rft.aulast=Henryk+Arctowski&rft.au=Henryk+Arctowski&rft.date=1940&rft.volume=26&rft.issue=6&rft.pages=406%E2%80%9311&rft_id=info:doi/10.1073%2Fpnas.26.6.406&rft_id=info:pmid/16588370&rft_id=http%3A%2F%2Fwww.pnas.org%2Fcgi%2Freprint%2F26%2F6%2F406.pdf&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Willson81-13"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-Willson81_13-0">13.0</a></sup> <sup><a href="#cite_ref-Willson81_13-1">13.1</a></sup></span> <span class="reference-text"><span class="citation Journal">Willson RC, Gulkis S, Janssen M, Hudson HS, Chapman GA (February 1981). <a rel="nofollow" class="external text" href="http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=17776650">"Observations of Solar Irradiance Variability"</a>. <i>Science</i> <b>211</b> (4483): 700–2. doi:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.211.4483.700">10.1126/science.211.4483.700</a>. PMID <a rel="nofollow" class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/17776650">17776650</a><span class="printonly">. <a rel="nofollow" class="external free" href="http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=17776650">http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=17776650</a></span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Observations+of+Solar+Irradiance+Variability&rft.jtitle=Science&rft.aulast=Willson+RC%2C+Gulkis+S%2C+Janssen+M%2C+Hudson+HS%2C+Chapman+GA&rft.au=Willson+RC%2C+Gulkis+S%2C+Janssen+M%2C+Hudson+HS%2C+Chapman+GA&rft.date=February+1981&rft.volume=211&rft.issue=4483&rft.pages=700%E2%80%932&rft_id=info:doi/10.1126%2Fscience.211.4483.700&rft_id=info:pmid/17776650&rft_id=http%3A%2F%2Fwww.sciencemag.org%2Fcgi%2Fpmidlookup%3Fview%3Dlong%26pmid%3D17776650&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Sokavik-14"><span class="mw-cite-backlink"><a href="#cite_ref-Sokavik_14-0">↑</a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r2527938">.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 a,.mw-parser-output .citation .cs1-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 a,.mw-parser-output .id-lock-registration a,.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-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 a,.mw-parser-output .citation .cs1-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}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:#d33}.mw-parser-output .cs1-visible-error{color:#d33}.mw-parser-output .cs1-maint{display:none;color:#3a3;margin-left:0.3em}.mw-parser-output .cs1-format{font-size:95%}.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}</style><cite id="CITEREFSokavik2011" class="citation web cs1"><a href="https://commons.wikimedia.org/wiki/User:Sokavik" class="extiw" title="commons:User:Sokavik">Sokavik</a> (June 3, 2011). <a class="external text" href="https://commons.wikimedia.org/w/index.php?title=File:NOAAsourcebutnotofficialsunclimate_3b.gif&oldid=55057393">"<span class="cs1-kern-left"></span>"File:NOAAsourcebutnotofficialsunclimate 3b.gif", In: <i>Wikimedia Commons</i>"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2012-11-19</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=%22File%3ANOAAsourcebutnotofficialsunclimate+3b.gif%22%2C+In%3A+Wikimedia+Commons&rft.date=2011-06-03&rft.au=Sokavik&rft_id=http%3A%2F%2Fcommons.wikimedia.org%2Fw%2Findex.php%3Ftitle%3DFile%3ANOAAsourcebutnotofficialsunclimate_3b.gif%26oldid%3D55057393&rfr_id=info%3Asid%2Fen.wikiversity.org%3AStars%2FSun%2FHeliography" class="Z3988"></span> <span class="cs1-visible-error citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_web" title="Template:Cite web">cite web</a>}}</code>: </span><span class="cs1-visible-error citation-comment"><code class="cs1-code">|author=</code> has generic name (<a href="/wiki/Help:CS1_errors#generic_name" title="Help:CS1 errors">help</a>)</span></span> </li> <li id="cite_note-Liggett-15"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-Liggett_15-0">15.0</a></sup> <sup><a href="#cite_ref-Liggett_15-1">15.1</a></sup></span> <span class="reference-text"><span class="citation Journal">Margaret Liggett and Harold Zirin (April 1983). "Naked Sunspots". <i>Solar Physics</i> <b>84</b> (04): 3-11. doi:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2FBF00157438">10.1007/BF00157438</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Naked+Sunspots&rft.jtitle=Solar+Physics&rft.aulast=Margaret+Liggett+and+Harold+Zirin&rft.au=Margaret+Liggett+and+Harold+Zirin&rft.date=April+1983&rft.volume=84&rft.issue=04&rft.pages=3-11&rft_id=info:doi/10.1007%2FBF00157438&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Hole-16"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-Hole_16-0">16.0</a></sup> <sup><a href="#cite_ref-Hole_16-1">16.1</a></sup></span> <span class="reference-text"><span class="citation book"> <a class="external text" href="https://en.wiktionary.org/wiki/hole"><i>hole</i></a>. San Francisco, California: Wikimedia Foundation, Inc. October 5, 2012<span class="printonly">. <a class="external free" href="https://en.wiktionary.org/wiki/hole">http://en.wiktionary.org/wiki/hole</a></span><span class="reference-accessdate">. Retrieved 2012-10-09</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=hole&rft.date=October+5%2C+2012&rft.place=San+Francisco%2C+California&rft.pub=Wikimedia+Foundation%2C+Inc&rft_id=http%3A%2F%2Fen.wiktionary.org%2Fwiki%2Fhole&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Spot-17"><span class="mw-cite-backlink"><a href="#cite_ref-Spot_17-0">↑</a></span> <span class="reference-text"><span class="citation book"> <a class="external text" href="https://en.wiktionary.org/wiki/spot"><i>spot</i></a>. San Francisco, California: Wikimedia Foundation, Inc. October 7, 2012<span class="printonly">. <a class="external free" href="https://en.wiktionary.org/wiki/spot">http://en.wiktionary.org/wiki/spot</a></span><span class="reference-accessdate">. Retrieved 2012-10-09</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=spot&rft.date=October+7%2C+2012&rft.place=San+Francisco%2C+California&rft.pub=Wikimedia+Foundation%2C+Inc&rft_id=http%3A%2F%2Fen.wiktionary.org%2Fwiki%2Fspot&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Vent-18"><span class="mw-cite-backlink"><a href="#cite_ref-Vent_18-0">↑</a></span> <span class="reference-text"><span class="citation book"> <a class="external text" href="https://en.wiktionary.org/wiki/vent"><i>vent</i></a>. San Francisco, California: Wikimedia Foundation, Inc. October 6, 2012<span class="printonly">. <a class="external free" href="https://en.wiktionary.org/wiki/vent">http://en.wiktionary.org/wiki/vent</a></span><span class="reference-accessdate">. Retrieved 2012-10-09</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=vent&rft.date=October+6%2C+2012&rft.place=San+Francisco%2C+California&rft.pub=Wikimedia+Foundation%2C+Inc&rft_id=http%3A%2F%2Fen.wiktionary.org%2Fwiki%2Fvent&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><a href="#cite_ref-19">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://articles.adsabs.harvard.edu//full/1989QJRAS..30...59M/0000060.000.html">harvard.edu</a></span> </li> <li id="cite_note-Maunder-20"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-Maunder_20-0">20.0</a></sup> <sup><a href="#cite_ref-Maunder_20-1">20.1</a></sup> <sup><a href="#cite_ref-Maunder_20-2">20.2</a></sup></span> <span class="reference-text"><span class="citation Journal">E. Walter Maunder (1903). "Spoerer's law of zones". <i>The Observatory</i> <b>26</b> (334): 329-30.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Spoerer%27s+law+of+zones&rft.jtitle=The+Observatory&rft.aulast=E.+Walter+Maunder&rft.au=E.+Walter+Maunder&rft.date=1903&rft.volume=26&rft.issue=334&rft.pages=329-30&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Maunder05-21"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-Maunder05_21-0">21.0</a></sup> <sup><a href="#cite_ref-Maunder05_21-1">21.1</a></sup> <sup><a href="#cite_ref-Maunder05_21-2">21.2</a></sup></span> <span class="reference-text"><span class="citation Journal">E. Walter Maunder and A. S. D. Maunder (June 1905). "The Solar Rotation Period from Greenwich Sun-spot Measures, 1879-1901". <i>Monthly Notices of the Royal Astronomical Society</i> <b>65</b> (8): 813-25.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Solar+Rotation+Period+from+Greenwich+Sun-spot+Measures%2C+1879-1901&rft.jtitle=Monthly+Notices+of+the+Royal+Astronomical+Society&rft.aulast=E.+Walter+Maunder+and+A.+S.+D.+Maunder&rft.au=E.+Walter+Maunder+and+A.+S.+D.+Maunder&rft.date=June+1905&rft.volume=65&rft.issue=8&rft.pages=813-25&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Williams-22"><span class="mw-cite-backlink"><a href="#cite_ref-Williams_22-0">↑</a></span> <span class="reference-text"><span class="citation Journal">Williams, G.E. (1985). "Solar affinity of sedimentary cycles in the late Precambrian Elatina Formation". <i>Australian Journal of Physics</i> <b>38</b>: 1027–1043.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Solar+affinity+of+sedimentary+cycles+in+the+late+Precambrian+Elatina+Formation&rft.jtitle=Australian+Journal+of+Physics&rft.aulast=Williams&rft.aufirst=G.E.&rft.au=Williams%2C%26%2332%3BG.E.&rft.date=1985&rft.volume=38&rft.pages=1027%E2%80%931043&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Reed-23"><span class="mw-cite-backlink"><a href="#cite_ref-Reed_23-0">↑</a></span> <span class="reference-text"><span class="citation Journal">Information, Reed Business (1981). <a rel="nofollow" class="external text" href="http://books.google.com/?id=4CpdD9YdMeoC&pg=PA147&lpg=PA147">"Digging down under for sunspots"</a>. <i>New Scientist</i> <b>91</b>: 147<span class="printonly">. <a rel="nofollow" class="external free" href="http://books.google.com/?id=4CpdD9YdMeoC&pg=PA147&lpg=PA147">http://books.google.com/?id=4CpdD9YdMeoC&pg=PA147&lpg=PA147</a></span><span class="reference-accessdate">. Retrieved 2010-07-14</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Digging+down+under+for+sunspots&rft.jtitle=New+Scientist&rft.aulast=Information%2C+Reed+Business&rft.au=Information%2C+Reed+Business&rft.date=1981&rft.volume=91&rft.pages=147&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3D4CpdD9YdMeoC%26pg%3DPA147%26lpg%3DPA147&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Williams90-24"><span class="mw-cite-backlink"><a href="#cite_ref-Williams90_24-0">↑</a></span> <span class="reference-text"><span class="citation Journal">Williams GE (1990). <a rel="nofollow" class="external text" href="http://adsabs.harvard.edu/abs/1990RSPTA.330..445W">"Precambrian Cyclic Rhythmites: Solar-Climatic or Tidal Signatures?"</a>. <i>Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences</i> <b>330</b>: 445<span class="printonly">. <a rel="nofollow" class="external free" href="http://adsabs.harvard.edu/abs/1990RSPTA.330..445W">http://adsabs.harvard.edu/abs/1990RSPTA.330..445W</a></span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Precambrian+Cyclic+Rhythmites%3A+Solar-Climatic+or+Tidal+Signatures%3F&rft.jtitle=Philosophical+Transactions+of+the+Royal+Society+of+London.+Series+A%2C+Mathematical+and+Physical+Sciences&rft.aulast=Williams+GE&rft.au=Williams+GE&rft.date=1990&rft.volume=330&rft.pages=445&rft_id=http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F1990RSPTA.330..445W&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-pmid15510145-25"><span class="mw-cite-backlink"><a href="#cite_ref-pmid15510145_25-0">↑</a></span> <span class="reference-text"><span class="citation Journal">Solanki SK, Usoskin IG, Kromer B, Schüssler M, Beer J (October 2004). <a rel="nofollow" class="external text" href="http://www.ncdc.noaa.gov/paleo/pubs/solanki2004/solanki2004.html">"Unusual activity of the Sun during recent decades compared to the previous 11,000 years"</a>. <i>Nature</i> <b>431</b> (7012): 1084–1087. doi:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fnature02995">10.1038/nature02995</a>. PMID <a rel="nofollow" class="external text" href="http://www.ncbi.nlm.nih.gov/pubmed/15510145">15510145</a><span class="printonly">. <a rel="nofollow" class="external free" href="http://www.ncdc.noaa.gov/paleo/pubs/solanki2004/solanki2004.html">http://www.ncdc.noaa.gov/paleo/pubs/solanki2004/solanki2004.html</a></span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Unusual+activity+of+the+Sun+during+recent+decades+compared+to+the+previous+11%2C000+years&rft.jtitle=Nature&rft.aulast=Solanki+SK%2C+Usoskin+IG%2C+Kromer+B%2C+Sch%C3%BCssler+M%2C+Beer+J&rft.au=Solanki+SK%2C+Usoskin+IG%2C+Kromer+B%2C+Sch%C3%BCssler+M%2C+Beer+J&rft.date=October+2004&rft.volume=431&rft.issue=7012&rft.pages=1084%E2%80%931087&rft_id=info:doi/10.1038%2Fnature02995&rft_id=info:pmid/15510145&rft_id=http%3A%2F%2Fwww.ncdc.noaa.gov%2Fpaleo%2Fpubs%2Fsolanki2004%2Fsolanki2004.html&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-NRICH-26"><span class="mw-cite-backlink"><a href="#cite_ref-NRICH_26-0">↑</a></span> <span class="reference-text"><span class="citation book"> <a rel="nofollow" class="external text" href="http://nrich.maths.org/6843"><i>Early Astronomy and the Beginnings of a Mathematical Science</i></a>. 2007<span class="printonly">. <a rel="nofollow" class="external free" href="http://nrich.maths.org/6843">http://nrich.maths.org/6843</a></span><span class="reference-accessdate">. Retrieved 2010-07-14</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Early+Astronomy+and+the+Beginnings+of+a+Mathematical+Science&rft.date=2007&rft_id=http%3A%2F%2Fnrich.maths.org%2F6843&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-UNESCO-27"><span class="mw-cite-backlink"><a href="#cite_ref-UNESCO_27-0">↑</a></span> <span class="reference-text"><span class="citation Journal"><a rel="nofollow" class="external text" href="http://archive.is/uKqG">"The Observation of Sunspots"</a>. <i>UNESCO Courier</i>. 1988. Archived from <a rel="nofollow" class="external text" href="http://findarticles.com/p/articles/mi_m1310/is_1988_Oct/ai_6955852/">the original</a> on 2012-06-28<span class="printonly">. <a rel="nofollow" class="external free" href="http://archive.is/uKqG">http://archive.is/uKqG</a></span><span class="reference-accessdate">. Retrieved 2010-07-14</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Observation+of+Sunspots&rft.jtitle=UNESCO+Courier&rft.date=1988&rft_id=http%3A%2F%2Farchive.is%2FuKqG&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Youmans-28"><span class="mw-cite-backlink"><a href="#cite_ref-Youmans_28-0">↑</a></span> <span class="reference-text"><span class="citation Journal">Edward Livingston Youmans (June 1872). <a class="external text" href="https://en.wikisource.org/wiki/Popular_Science_Monthly/Volume_1/June_1872/The_Spots_on_the_Sun">"The Spots on the Sun"</a>. <i>Popular Science Monthly</i> <b>1</b> (6): 144-58<span class="printonly">. <a class="external free" href="https://en.wikisource.org/wiki/Popular_Science_Monthly/Volume_1/June_1872/The_Spots_on_the_Sun">http://en.wikisource.org/wiki/Popular_Science_Monthly/Volume_1/June_1872/The_Spots_on_the_Sun</a></span><span class="reference-accessdate">. Retrieved 2012-11-19</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Spots+on+the+Sun&rft.jtitle=Popular+Science+Monthly&rft.aulast=Edward+Livingston+Youmans&rft.au=Edward+Livingston+Youmans&rft.date=June+1872&rft.volume=1&rft.issue=6&rft.pages=144-58&rft_id=http%3A%2F%2Fen.wikisource.org%2Fwiki%2FPopular_Science_Monthly%2FVolume_1%2FJune_1872%2FThe_Spots_on_the_Sun&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-strassmeier-29"><span class="mw-cite-backlink"><a href="#cite_ref-strassmeier_29-0">↑</a></span> <span class="reference-text"> <a rel="nofollow" class="external text" href="http://www.aip.de/groups/activity/presse/pressrelease990610.html">press release 990610</a>, K. G. Strassmeier, 1999-06-10, University of Vienna, "starspots vary on the same (short) time scales as Sunspots do", "HD 12545 had a warm spot (350 K above photospheric temperature; the white area in the picture)"</span> </li> <li id="cite_note-Nindos-30"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-Nindos_30-0">30.0</a></sup> <sup><a href="#cite_ref-Nindos_30-1">30.1</a></sup></span> <span class="reference-text"><span class="citation Journal">A. Nindos and H. Zhang (July 10, 2002). <a rel="nofollow" class="external text" href="http://iopscience.iop.org/1538-4357/573/2/L133">"Photospheric Motions and Coronal Mass Ejection Productivity"</a>. <i>The Astrophysical Journal</i> <b>573</b> (2): L133-6. doi:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F341937">10.1086/341937</a><span class="printonly">. <a rel="nofollow" class="external free" href="http://iopscience.iop.org/1538-4357/573/2/L133">http://iopscience.iop.org/1538-4357/573/2/L133</a></span><span class="reference-accessdate">. Retrieved 2012-11-24</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Photospheric+Motions+and+Coronal+Mass+Ejection+Productivity&rft.jtitle=The+Astrophysical+Journal&rft.aulast=A.+Nindos+and+H.+Zhang&rft.au=A.+Nindos+and+H.+Zhang&rft.date=July+10%2C+2002&rft.volume=573&rft.issue=2&rft.pages=L133-6&rft_id=info:doi/10.1086%2F341937&rft_id=http%3A%2F%2Fiopscience.iop.org%2F1538-4357%2F573%2F2%2FL133&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-solarcycle-31"><span class="mw-cite-backlink"><a href="#cite_ref-solarcycle_31-0">↑</a></span> <span class="reference-text"><span class="citation book"> <a rel="nofollow" class="external text" href="http://www.physorg.com/news119271347.html"><i>NASA Satellites Capture Start of New Solar Cycle</i></a>. PhysOrg. 4 January 2008<span class="printonly">. <a rel="nofollow" class="external free" href="http://www.physorg.com/news119271347.html">http://www.physorg.com/news119271347.html</a></span><span class="reference-accessdate">. Retrieved 2009-07-10</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=NASA+Satellites+Capture+Start+of+New+Solar+Cycle&rft.date=4+January+2008&rft.pub=PhysOrg&rft_id=http%3A%2F%2Fwww.physorg.com%2Fnews119271347.html&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Wright-32"><span class="mw-cite-backlink"><a href="#cite_ref-Wright_32-0">↑</a></span> <span class="reference-text"><span class="citation Journal">J. T. Wright, G. W. Marcy, R. P. Butler, S. S. Vogt, G. W. Henry, H. Isaacson, and A. W. Howard (August 10, 2008). <a rel="nofollow" class="external text" href="http://arxiv.org/pdf/0802.1731">"The Jupiter Twin HD 154345b"</a>. <i>The Astrophysical Journal</i> <b>683</b> (1): L63-6. doi:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F587461">10.1086/587461</a><span class="printonly">. <a rel="nofollow" class="external free" href="http://arxiv.org/pdf/0802.1731">http://arxiv.org/pdf/0802.1731</a></span><span class="reference-accessdate">. Retrieved 2013-01-06</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=The+Jupiter+Twin+HD+154345b&rft.jtitle=The+Astrophysical+Journal&rft.aulast=J.+T.+Wright%2C+G.+W.+Marcy%2C+R.+P.+Butler%2C+S.+S.+Vogt%2C+G.+W.+Henry%2C+H.+Isaacson%2C+and+A.+W.+Howard&rft.au=J.+T.+Wright%2C+G.+W.+Marcy%2C+R.+P.+Butler%2C+S.+S.+Vogt%2C+G.+W.+Henry%2C+H.+Isaacson%2C+and+A.+W.+Howard&rft.date=August+10%2C+2008&rft.volume=683&rft.issue=1&rft.pages=L63-6&rft_id=info:doi/10.1086%2F587461&rft_id=http%3A%2F%2Farxiv.org%2Fpdf%2F0802.1731&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-Rybansky-33"><span class="mw-cite-backlink"><a href="#cite_ref-Rybansky_33-0">↑</a></span> <span class="reference-text"><span class="citation Journal">M. Rybansky, V. Rusin, M. Minarovjech and P. Gaspar (1994). "Coronal index of solar activity: Years 1939-1963". <i>Solar Physics</i> <b>152</b> (1): 153-9. doi:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2FBF01473198">10.1007/BF01473198</a>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.atitle=Coronal+index+of+solar+activity%3A+Years+1939-1963&rft.jtitle=Solar+Physics&rft.aulast=M.+Rybansky%2C+V.+Rusin%2C+M.+Minarovjech+and+P.+Gaspar&rft.au=M.+Rybansky%2C+V.+Rusin%2C+M.+Minarovjech+and+P.+Gaspar&rft.date=1994&rft.volume=152&rft.issue=1&rft.pages=153-9&rft_id=info:doi/10.1007%2FBF01473198&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-WolfNumber-34"><span class="mw-cite-backlink">↑ <sup><a href="#cite_ref-WolfNumber_34-0">34.0</a></sup> <sup><a href="#cite_ref-WolfNumber_34-1">34.1</a></sup></span> <span class="reference-text"><span class="citation book"> <a class="external text" href="https://en.wikipedia.org/wiki/Wolf_number"><i>Wolf number</i></a>. San Francisco, California: Wikimedia Foundation, Inc. September 11, 2012<span class="printonly">. <a class="external free" href="https://en.wikipedia.org/wiki/Wolf_number">http://en.wikipedia.org/wiki/Wolf_number</a></span><span class="reference-accessdate">. Retrieved 2012-11-12</span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Wolf+number&rft.date=September+11%2C+2012&rft.place=San+Francisco%2C+California&rft.pub=Wikimedia+Foundation%2C+Inc&rft_id=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FWolf_number&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></span> </li> <li id="cite_note-35"><span class="mw-cite-backlink"><a href="#cite_ref-35">↑</a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://web.archive.org/web/20110727151005/http://www.sidc.be/news/106/sunspotnumberclarified.pdf">personal reduction coefficient K</a></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Stars/Sun/Heliography&veaction=edit&section=13" title="Edit section: Further reading" class="mw-editsection-visualeditor"><span>edit</span></a><span class="mw-editsection-divider"> | </span><a href="/w/index.php?title=Stars/Sun/Heliography&action=edit&section=13" title="Edit section's source code: Further reading"><span>edit source</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><span class="citation book"> <a rel="nofollow" class="external text" href="http://web.archive.org/web/20080102034758/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric"><i>Solar System Exploration: Planets: Sun: Facts & Figures</i></a>. NASA. 2008-01-02<span class="printonly">. <a rel="nofollow" class="external free" href="http://web.archive.org/web/20080102034758/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric">http://web.archive.org/web/20080102034758/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric</a></span>.</span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Solar+System+Exploration%3A+Planets%3A+Sun%3A+Facts+%26+Figures&rft.date=2008-01-02&rft.pub=NASA&rft_id=http%3A%2F%2Fweb.archive.org%2Fweb%2F20080102034758%2Fhttp%3A%2F%2Fsolarsystem.nasa.gov%2Fplanets%2Fprofile.cfm%3FObject%3DSun%26Display%3DFacts%26System%3DMetric&rfr_id=info:sid/en.wikipedia.org:Stars/Sun/Heliography"><span style="display: none;"> </span></span></li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span 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class="mw-redirect" title="Binary Stars and Extrasolar Planets Learning Activity">Binary stars and extrasolar planets</a></li> <li><a href="/wiki/Activity:Cassiopeia_and_Ursa_Major" title="Activity:Cassiopeia and Ursa Major">Cassiopeia and Ursa Major</a></li> <li><a href="/wiki/Cosmogony/Laboratory" title="Cosmogony/Laboratory">Cosmogony laboratory</a></li> <li><a href="/w/index.php?title=Craters/Astronomy/Laboratory&action=edit&redlink=1" class="new" title="Craters/Astronomy/Laboratory (page does not exist)">Cratering laboratory</a></li> <li><a href="/wiki/Distance_to_the_Moon" title="Distance to the Moon">Distance to the Moon</a></li> <li><a href="/wiki/Electric_orbits" title="Electric orbits">Electric orbits</a></li> <li><a href="/wiki/Electron_beam_heating/Laboratory" title="Electron beam heating/Laboratory">Electron beam heating/Laboratory</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Empiricisms/Laboratory&action=edit&redlink=1" class="new" title="Radiation astronomy/Empiricisms/Laboratory (page does not exist)">Empirical radiation astronomy/Laboratory</a></li> <li><a href="/wiki/Stars/Galaxies/Laboratory" title="Stars/Galaxies/Laboratory">Galaxies/Laboratory</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Intergalactic_medium/Laboratory&action=edit&redlink=1" class="new" title="Radiation astronomy/Intergalactic medium/Laboratory (page does not exist)">Intergalactic medium/Laboratory</a></li> <li><a href="/wiki/International_Year_of_Astronomy" title="International Year of Astronomy">International Year of Astronomy</a></li> <li><a href="/wiki/Stars/Sun/Locating_the_Sun" title="Stars/Sun/Locating the Sun">Locating the Sun</a></li> <li><a href="/wiki/Stars/Sun/Neutrinos" title="Stars/Sun/Neutrinos">Neutrinos from the Sun</a></li> <li><a href="/wiki/Polar_reversals" title="Polar reversals">Polar reversals</a></li> <li><a href="/wiki/Stars/Vega/Spectrum" title="Stars/Vega/Spectrum">Spectrum of Vega</a></li> <li><a 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Stellar Astronomy">Solar System and Stellar Astronomy</a></li> <li><a href="/wiki/Changes_in_the_properties_of_matter_(mass_spectrometer_and_spectral_analysis_of_stars)" class="mw-redirect" title="Changes in the properties of matter (mass spectrometer and spectral analysis of stars)">Spectral analysis of stars</a></li> <li><a href="/wiki/Stargazing" title="Stargazing">Stargazing</a></li> <li><a href="/wiki/The_visible_sky" title="The visible sky">The visible sky</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="background:#21ABCD;;width:1%;background:#21ABCD; color:#000000;">Categories</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0;background:#ACE5EE;"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Category:Astronomy/Laboratories" title="Category:Astronomy/Laboratories">Astronomy laboratories</a></li> <li><a href="/wiki/Category:Astrophysics" title="Category:Astrophysics">Astrophysics</a></li> <li><a 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href="/wiki/Category:Galaxy_images" title="Category:Galaxy images">Galaxy images</a></li> <li><a href="/wiki/Category:Milky_Way_images" title="Category:Milky Way images">Milky Way images</a></li> <li><a href="/wiki/Category:Plasma_images" title="Category:Plasma images">Plasma images</a></li> <li><a href="/wiki/Category:Solar_System" title="Category:Solar System">Solar System</a></li> <li><a href="/wiki/Category:Solar_system_images" title="Category:Solar system images">Solar system images</a></li> <li><a href="/wiki/Category:Star-forming_regions" title="Category:Star-forming regions">Star-forming regions</a></li> <li><a href="/wiki/Category:Stars_images" title="Category:Stars images">Stars images</a></li> <li><a href="/wiki/Category:Sun_images" title="Category:Sun images">Sun images</a></li> <li><a href="/wiki/Category:Superluminal_images" title="Category:Superluminal images">Superluminal images</a></li> <li><a href="/w/index.php?title=Category:Supernova_Images&action=edit&redlink=1" class="new" title="Category:Supernova Images (page does not exist)">Supernova Images</a></li> <li><a href="/w/index.php?title=Category:Vega_images&action=edit&redlink=1" class="new" title="Category:Vega images (page does not exist)">Vega images</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="background:#21ABCD;;width:1%;background:#21ABCD; color:#000000;">Courses</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0;background:#BCD4E6;"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Introduction_to_astrophysics" class="mw-redirect" title="Introduction to astrophysics">Introduction to astrophysics</a></li> <li><a href="/wiki/Astrochemistry" title="Astrochemistry">Introduction to Astrochemistry</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Courses&action=edit&redlink=1" class="new" title="Radiation astronomy/Courses (page does not exist)">Radiation astronomy/Courses</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Courses/Principles&action=edit&redlink=1" class="new" title="Radiation astronomy/Courses/Principles (page does not exist)">Principles of radiation astronomy</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Courses/Principles/Syllabus&action=edit&redlink=1" class="new" title="Radiation astronomy/Courses/Principles/Syllabus (page does not exist)">Principles of radiation astronomy/Syllabus</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Courses/Principles/Syllabus/Fall&action=edit&redlink=1" class="new" title="Radiation astronomy/Courses/Principles/Syllabus/Fall (page does not exist)">Principles of radiation astronomy/Syllabus/Fall</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Courses/Principles/Syllabus/Spring&action=edit&redlink=1" class="new" title="Radiation astronomy/Courses/Principles/Syllabus/Spring (page does not exist)">Principles of radiation astronomy/Syllabus/Spring</a></li> <li><a href="/wiki/Stars/Sun/Astronomy/Course" title="Stars/Sun/Astronomy/Course">Solar astronomy</a></li> <li><a href="/wiki/Solar_System" class="mw-disambig" title="Solar System">Solar System</a></li> <li><a href="/wiki/Stars/Courses" title="Stars/Courses">Stars/Courses</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/X-rays/Course&action=edit&redlink=1" class="new" title="Radiation astronomy/X-rays/Course (page does not exist)">X-ray astronomy</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="background:#21ABCD;;width:1%;background:#21ABCD; color:#000000;">Glossaries</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0;background:#ACE5EE;"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cosmic_View:_Glossary_of_Terms" class="mw-redirect" title="Cosmic View: Glossary of Terms">Cosmic View: Glossary of Terms</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="background:#21ABCD;;width:1%;background:#21ABCD; color:#000000;">Lectures</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0;background:#BCD4E6;"><div style="padding:0 0.25em"> <ul><li><a href="/w/index.php?title=Radiation_astronomy/Active_galactic_nuclei&action=edit&redlink=1" class="new" title="Radiation astronomy/Active galactic nuclei (page does not exist)">Active galactic nuclei astronomy</a></li> <li><a href="/wiki/Astrophysics" title="Astrophysics">Astrophysics</a></li> <li><a href="/wiki/Plasmas/Plasma_objects/Auroras" title="Plasmas/Plasma objects/Auroras">Auroras</a></li> <li><a href="/w/index.php?title=Stars/Betelgeuse&action=edit&redlink=1" class="new" title="Stars/Betelgeuse (page does not exist)">Betelgeuse</a></li> <li><a href="/wiki/Stars/Binaries" title="Stars/Binaries">Binaries</a></li> <li><a href="/wiki/Stars/Blues" title="Stars/Blues">Blue stars</a></li> <li><a href="/wiki/Plasmas/Plasma_objects/Coronal_clouds" title="Plasmas/Plasma objects/Coronal clouds">Coronal clouds</a></li> <li><a href="/wiki/Radiation/Cosmic_rays" title="Radiation/Cosmic rays">Cosmic radiation astronomy</a></li> <li><a href="/wiki/Theory/Cosmogony" title="Theory/Cosmogony">Cosmogony</a></li> <li><a href="/wiki/Stars/Cyans" title="Stars/Cyans">Cyan stars</a></li> <li><a href="/wiki/Stars/Dwarfs" title="Stars/Dwarfs">Dwarf stars</a></li> <li><a href="/wiki/Stars/Flares" title="Stars/Flares">Flare stars</a></li> <li><a href="/wiki/Stars/Galaxies/Evolution" title="Stars/Galaxies/Evolution">Galactic evolution</a></li> <li><a href="/wiki/Stars/Galaxies" title="Stars/Galaxies">Galaxies</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Galaxies&action=edit&redlink=1" class="new" title="Radiation astronomy/Galaxies (page does not exist)">Galaxy astronomy</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Galaxy_clusters&action=edit&redlink=1" class="new" title="Radiation astronomy/Galaxy clusters (page does 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href="/wiki/Stars/Sun/Heliometry" title="Stars/Sun/Heliometry">Heliometry</a></li> <li><a href="/wiki/Stars/Sun/Heliophysics" title="Stars/Sun/Heliophysics">Heliophysics</a></li> <li><a href="/w/index.php?title=Stars/Sun/Helioseismology&action=edit&redlink=1" class="new" title="Stars/Sun/Helioseismology (page does not exist)">Helioseismology</a></li> <li><a href="/wiki/Stars/Sun/Heliospheres" title="Stars/Sun/Heliospheres">Heliospheres</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/High-velocity_galaxies&action=edit&redlink=1" class="new" title="Radiation astronomy/High-velocity galaxies (page does not exist)">High-velocity galaxy astronomy</a></li> <li><a href="/w/index.php?title=Stars/Hypergiants&action=edit&redlink=1" class="new" title="Stars/Hypergiants (page does not exist)">Hypergiant stars</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Hypervelocity_stars&action=edit&redlink=1" class="new" title="Radiation astronomy/Hypervelocity stars (page does not exist)">Hypervelocity stellar astronomy</a></li> <li><a href="/wiki/Stars/Infrareds" title="Stars/Infrareds">Infrared stars</a></li> <li><a href="/wiki/Intergalactic_medium" class="mw-redirect" title="Intergalactic medium">Intergalactic medium</a></li> <li><a href="/wiki/Interstellar_medium" class="mw-redirect" title="Interstellar medium">Interstellar medium</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Lightnings&action=edit&redlink=1" class="new" title="Radiation astronomy/Lightnings (page does not exist)">Lightning astronomy</a></li> <li><a href="/wiki/Plasmas/Magnetohydrodynamics" title="Plasmas/Magnetohydrodynamics">Magnetohydrodynamics</a></li> <li><a href="/w/index.php?title=Stars/Main-sequences&action=edit&redlink=1" class="new" title="Stars/Main-sequences (page does not exist)">Main-sequence stars</a></li> <li><a href="/wiki/Radiation/Meteors" title="Radiation/Meteors">Meteor astronomy</a></li> <li><a href="/wiki/Radiation/Meteors" title="Radiation/Meteors">Meteor radiation</a></li> <li><a href="/wiki/Stars/Galaxies/Milky_Way" title="Stars/Galaxies/Milky Way">Milky Way</a></li> <li><a href="/wiki/Stars/Nova-likes" title="Stars/Nova-likes">Nova-like stars</a></li> <li><a href="/wiki/Stars/Novas" title="Stars/Novas">Novas</a></li> <li><a href="/wiki/Plasmas/Plasma_objects/Nucleosynthesis" title="Plasmas/Plasma objects/Nucleosynthesis">Nucleosynthesis</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Oort_clouds&action=edit&redlink=1" class="new" title="Radiation astronomy/Oort clouds (page does not exist)">Oort cloud astronomy</a></li> <li><a href="/wiki/Stars/Oranges" title="Stars/Oranges">Orange stars</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Plasmas&action=edit&redlink=1" class="new" title="Radiation astronomy/Plasmas (page does not exist)">Plasma-meteor astronomy</a></li> <li><a href="/wiki/Plasmas/Plasma_objects/Astronomy" title="Plasmas/Plasma objects/Astronomy">Plasma-object astronomy</a></li> <li><a href="/wiki/Stars/Quasars" title="Stars/Quasars">Quasars</a></li> <li><a href="/wiki/Stars/Radiative_dynamo" title="Stars/Radiative dynamo">Radiative dynamo</a></li> <li><a href="/wiki/Stars/Reds" title="Stars/Reds">Red stars</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Scattered_disks&action=edit&redlink=1" class="new" title="Radiation astronomy/Scattered disks (page does not exist)">Scattered disk astronomy</a></li> <li><a href="/wiki/Stars/Sirius" title="Stars/Sirius">Sirius</a></li> <li><a href="/wiki/Stars/Sun/Astronomy" title="Stars/Sun/Astronomy">Solar astronomy</a></li> <li><a href="/wiki/Stars/Sun/Solar_binary" title="Stars/Sun/Solar binary">Solar binary</a></li> <li><a href="/wiki/Stars/Solar_systems" title="Stars/Solar systems">Solar systems</a></li> <li><a href="/wiki/Stars/Galaxies/Spirals" title="Stars/Galaxies/Spirals">Spiral galaxies</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Standard_candles&action=edit&redlink=1" class="new" title="Radiation astronomy/Standard candles (page does not exist)">Standard candle astronomy</a></li> <li><a href="/wiki/Stars/Sun/Standard_models" title="Stars/Sun/Standard models">Standard solar models</a></li> <li><a href="/wiki/Stars/Star_fissions" title="Stars/Star fissions">Star fission</a></li> <li><a href="/wiki/Stars/Star-forming_regions" title="Stars/Star-forming regions">Star-forming region</a></li> <li><a href="/wiki/Stars" title="Stars">Stars</a></li> <li><a href="/wiki/Stars/Active_regions" title="Stars/Active regions">Stellar active regions</a></li> <li><a href="/wiki/Stars/Astronomy" title="Stars/Astronomy">Stellar astronomy</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Stars&action=edit&redlink=1" class="new" title="Radiation astronomy/Stars (page does not exist)">Stellar radiation astronomy</a></li> <li><a href="/wiki/Stars/Evolutions" title="Stars/Evolutions">Stellar evolution</a></li> <li><a href="/wiki/Stars/Sciences" title="Stars/Sciences">Stellar science</a></li> <li><a href="/wiki/Stars/Surface_fusion" title="Stars/Surface fusion">Stellar surface fusion</a></li> <li><a href="/wiki/Stars/Sun/X-ray_sources" title="Stars/Sun/X-ray sources">Sun as an X-ray source</a></li> <li><a href="/wiki/Stars/Sun" title="Stars/Sun">Sun</a></li> <li><a href="/w/index.php?title=Sun-synchronous_astronomy&action=edit&redlink=1" class="new" title="Sun-synchronous astronomy (page does not exist)">Sun-synchronous astronomy</a></li> <li><a href="/w/index.php?title=Stars/Supergiants&action=edit&redlink=1" class="new" title="Stars/Supergiants (page does not exist)">Supergiant stars</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Superluminals&action=edit&redlink=1" class="new" title="Radiation astronomy/Superluminals (page does not exist)">Superluminal astronomy</a></li> <li><a href="/wiki/Stars/Supernovas" title="Stars/Supernovas">Supernovas</a></li> <li><a href="/w/index.php?title=Supernova_X-rays&action=edit&redlink=1" class="new" title="Supernova X-rays (page does not exist)">Supernova X-rays</a></li> <li><a href="/wiki/Stars/Ultraviolets" title="Stars/Ultraviolets">Ultraviolet stars</a></li> <li><a href="/wiki/Stars/Variables" title="Stars/Variables">Variable stars</a></li> <li><a href="/wiki/Stars/Vega" title="Stars/Vega">Vega</a></li> <li><a href="/wiki/Stars/Violets" title="Stars/Violets">Violet stars</a></li> <li><a href="/w/index.php?title=Wanderers&action=edit&redlink=1" class="new" title="Wanderers (page does not exist)">Wanderers</a></li> <li><a href="/wiki/Stars/X-ray_classification" title="Stars/X-ray classification">X-ray classification of stars</a></li> <li><a href="/wiki/Stars/X-rays" title="Stars/X-rays">X-ray stars</a></li> <li><a href="/wiki/Stars/Yellows" title="Stars/Yellows">Yellow stars</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="background:#21ABCD;;width:1%;background:#21ABCD; color:#000000;">Lessons</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0;background:#ACE5EE;"><div style="padding:0 0.25em"> <ul><li><a href="/w/index.php?title=Portal:Astronomy/Courses&action=edit&redlink=1" class="new" title="Portal:Astronomy/Courses (page does not exist)">Astronomy/Lessons</a></li> <li><a href="/w/index.php?title=First_blue_source_in_Andromeda&action=edit&redlink=1" class="new" title="First blue source in Andromeda (page does not exist)">First blue source in Andromeda</a></li> <li><a href="/wiki/First_blue_source_in_Bo%C3%B6tes" class="mw-redirect" title="First blue source in Boötes">First blue source in Boötes</a></li> <li><a href="/w/index.php?title=First_blue_source_in_Columba&action=edit&redlink=1" class="new" title="First blue source in Columba (page does not exist)">First blue source in Columba</a></li> <li><a href="/w/index.php?title=First_blue_source_in_Lynx&action=edit&redlink=1" class="new" title="First blue source in Lynx (page does not exist)">First blue source in Lynx</a></li> <li><a href="/w/index.php?title=First_blue_source_in_Sextans&action=edit&redlink=1" class="new" title="First blue source in Sextans (page does not exist)">First blue source in Sextans</a></li> <li><a href="/w/index.php?title=First_cosmic-ray_source_in_Coma_Berenices&action=edit&redlink=1" class="new" title="First cosmic-ray source in Coma Berenices (page does not exist)">First cosmic-ray source in Coma Berenices</a></li> <li><a href="/w/index.php?title=First_cosmic-ray_source_in_Lyra&action=edit&redlink=1" class="new" title="First cosmic-ray source in Lyra (page does not exist)">First cosmic-ray source in Lyra</a></li> <li><a href="/w/index.php?title=First_cosmic-ray_source_in_Scorpius&action=edit&redlink=1" class="new" title="First cosmic-ray source in Scorpius (page does not exist)">First cosmic-ray source in Scorpius</a></li> <li><a href="/w/index.php?title=First_cosmic-ray_source_in_Taurus&action=edit&redlink=1" class="new" title="First cosmic-ray source in Taurus (page does not exist)">First cosmic-ray source in Taurus</a></li> <li><a href="/w/index.php?title=First_cyan_source_in_Antlia&action=edit&redlink=1" class="new" title="First cyan source in Antlia (page does not exist)">First cyan source in Antlia</a></li> <li><a href="/wiki/First_cyan_source_in_Caelum" class="mw-redirect" title="First cyan source in Caelum">First cyan source in Caelum</a></li> <li><a href="/w/index.php?title=First_cyan_source_in_Corona_Australis&action=edit&redlink=1" class="new" title="First cyan source in Corona Australis (page does not exist)">First cyan source in Corona Australis</a></li> <li><a href="/w/index.php?title=First_cyan_source_in_Mensa&action=edit&redlink=1" class="new" title="First cyan source in Mensa (page does not exist)">First cyan source in Mensa</a></li> <li><a href="/w/index.php?title=First_cyan_source_in_Telescopium&action=edit&redlink=1" class="new" title="First cyan source in Telescopium (page does not exist)">First cyan source in Telescopium</a></li> <li><a href="/w/index.php?title=First_electron_source_in_Apus&action=edit&redlink=1" class="new" title="First electron source in Apus (page does not exist)">First electron source in Apus</a></li> <li><a href="/w/index.php?title=First_electron_source_in_Corona_Borealis&action=edit&redlink=1" class="new" title="First electron source in Corona Borealis (page does not exist)">First electron source in Corona Borealis</a></li> <li><a href="/w/index.php?title=First_electron_source_in_Microscopium&action=edit&redlink=1" class="new" title="First electron source in Microscopium (page does not exist)">First electron source in Microscopium</a></li> <li><a href="/w/index.php?title=First_electron_source_in_Triangulum&action=edit&redlink=1" class="new" title="First electron source in Triangulum (page does not exist)">First electron source in Triangulum</a></li> <li><a href="/w/index.php?title=First_gamma-ray_source_in_Aquarius&action=edit&redlink=1" class="new" title="First gamma-ray source in Aquarius (page does not exist)">First gamma-ray source in Aquarius</a></li> <li><a href="/w/index.php?title=First_gamma-ray_source_in_Aquarius&action=edit&redlink=1" class="new" title="First gamma-ray source in Aquarius (page does not exist)">First gamma-ray source in Aquarius</a></li> <li><a href="/w/index.php?title=First_gamma-ray_source_in_Corvus&action=edit&redlink=1" class="new" title="First gamma-ray source in Corvus (page does not exist)">First gamma-ray source in Corvus</a></li> <li><a href="/w/index.php?title=First_gamma-ray_source_in_Monoceros&action=edit&redlink=1" class="new" title="First gamma-ray source in Monoceros (page does not exist)">First gamma-ray source in Monoceros</a></li> <li><a href="/w/index.php?title=First_gamma-ray_source_in_Scutum&action=edit&redlink=1" class="new" title="First gamma-ray source in Scutum (page does not exist)">First gamma-ray source in Scutum</a></li> <li><a href="/w/index.php?title=First_gamma-ray_source_in_Triangulum_Australe&action=edit&redlink=1" class="new" title="First gamma-ray source in Triangulum Australe (page does not exist)">First gamma-ray source in Triangulum Australe</a></li> <li><a href="/w/index.php?title=First_green_source_in_Crater&action=edit&redlink=1" class="new" title="First green source in Crater (page does not exist)">First green source in Crater</a></li> <li><a href="/w/index.php?title=First_green_source_in_Musca&action=edit&redlink=1" class="new" title="First green source in Musca (page does not exist)">First green source in Musca</a></li> <li><a href="/w/index.php?title=First_green_source_in_Tucana&action=edit&redlink=1" class="new" title="First green source in Tucana (page does not exist)">First green source in Tucana</a></li> <li><a href="/w/index.php?title=First_infrared_source_in_Ara&action=edit&redlink=1" class="new" title="First infrared source in Ara (page does not exist)">First infrared source in Ara</a></li> <li><a href="/w/index.php?title=First_infrared_source_in_Crux&action=edit&redlink=1" class="new" title="First infrared source in Crux (page does not exist)">First infrared source in Crux</a></li> <li><a href="/w/index.php?title=First_infrared_source_in_Norma&action=edit&redlink=1" class="new" title="First infrared source in Norma (page does not exist)">First infrared source in Norma</a></li> <li><a href="/w/index.php?title=First_infrared_source_in_Ursa_Major&action=edit&redlink=1" class="new" title="First infrared source in Ursa Major (page does not exist)">First infrared source in Ursa Major</a></li> <li><a href="/w/index.php?title=First_meteor_source_in_Aries&action=edit&redlink=1" class="new" title="First meteor source in Aries (page does not exist)">First meteor source in Aries</a></li> <li><a href="/w/index.php?title=First_meteor_source_in_Cygnus&action=edit&redlink=1" class="new" title="First meteor source in Cygnus (page does not exist)">First meteor source in Cygnus</a></li> <li><a href="/w/index.php?title=First_meteor_source_in_Octans&action=edit&redlink=1" class="new" title="First meteor source in Octans (page does not exist)">First meteor source in Octans</a></li> <li><a href="/w/index.php?title=First_meteor_source_in_Ursa_Minor&action=edit&redlink=1" class="new" title="First meteor source in Ursa Minor (page does not exist)">First meteor source in Ursa Minor</a></li> <li><a href="/w/index.php?title=First_microwave_source_in_Canis_Major&action=edit&redlink=1" class="new" title="First microwave source in Canis Major (page does not exist)">First microwave source in Canis Major</a></li> <li><a href="/w/index.php?title=First_microwave_source_in_Cepheus&action=edit&redlink=1" class="new" title="First microwave source in Cepheus (page does not exist)">First microwave source in Cepheus</a></li> <li><a href="/w/index.php?title=First_microwave_source_in_Hercules&action=edit&redlink=1" class="new" title="First microwave source in Hercules (page does not exist)">First microwave source in Hercules</a></li> <li><a href="/w/index.php?title=First_microwave_source_in_Piscis_Austrinus&action=edit&redlink=1" class="new" title="First microwave source in Piscis Austrinus (page does not exist)">First microwave source in Piscis Austrinus</a></li> <li><a href="/w/index.php?title=First_muon_source_in_Auriga&action=edit&redlink=1" class="new" title="First muon source in Auriga (page does not exist)">First muon source in Auriga</a></li> <li><a href="/w/index.php?title=First_muon_source_in_Delphinus&action=edit&redlink=1" class="new" title="First muon source in Delphinus (page does not exist)">First muon source in Delphinus</a></li> <li><a href="/w/index.php?title=First_muon_source_in_Ophiuchus&action=edit&redlink=1" class="new" title="First muon source in Ophiuchus (page does not exist)">First muon source in Ophiuchus</a></li> <li><a href="/w/index.php?title=First_muon_source_in_Vela&action=edit&redlink=1" class="new" title="First muon source in Vela (page does not exist)">First muon source in Vela</a></li> <li><a href="/w/index.php?title=First_neutrino_source_in_Bo%C3%B6tes&action=edit&redlink=1" class="new" title="First neutrino source in Boötes (page does not exist)">First neutrino source in Boötes</a></li> <li><a href="/w/index.php?title=First_neutrino_source_in_Dorado&action=edit&redlink=1" class="new" title="First neutrino source in Dorado (page does not exist)">First neutrino source in Dorado</a></li> <li><a href="/w/index.php?title=First_neutrino_source_in_Orion&action=edit&redlink=1" class="new" title="First neutrino source in Orion (page does not exist)">First neutrino source in Orion</a></li> <li><a href="/w/index.php?title=First_neutrino_source_in_Virgo&action=edit&redlink=1" class="new" title="First neutrino source in Virgo (page does not exist)">First neutrino source in Virgo</a></li> <li><a href="/w/index.php?title=First_neutron_source_in_Caelum&action=edit&redlink=1" class="new" title="First neutron source in Caelum (page does not exist)">First neutron source in Caelum</a></li> <li><a href="/w/index.php?title=First_neutron_source_in_Draco&action=edit&redlink=1" class="new" title="First neutron source in Draco (page does not exist)">First neutron source in Draco</a></li> <li><a href="/w/index.php?title=First_neutron_source_in_Pavo&action=edit&redlink=1" class="new" title="First neutron source in Pavo (page does not exist)">First neutron source in Pavo</a></li> <li><a href="/w/index.php?title=First_neutron_source_in_Volans&action=edit&redlink=1" class="new" title="First neutron source in Volans (page does not exist)">First neutron source in Volans</a></li> <li><a href="/w/index.php?title=First_optical_source_in_Camelopardalis&action=edit&redlink=1" class="new" title="First optical source in Camelopardalis (page does not exist)">First optical source in Camelopardalis</a></li> <li><a href="/w/index.php?title=First_optical_source_in_Equuleus&action=edit&redlink=1" class="new" title="First optical source in Equuleus (page does not exist)">First optical source in Equuleus</a></li> <li><a href="/w/index.php?title=First_optical_source_in_Pegasus&action=edit&redlink=1" class="new" title="First optical source in Pegasus (page does not exist)">First optical source in Pegasus</a></li> <li><a href="/w/index.php?title=First_optical_source_in_Vulpecula&action=edit&redlink=1" class="new" title="First optical source in Vulpecula (page does not exist)">First optical source in Vulpecula</a></li> <li><a href="/wiki/First_orange_source_in_Cancer" class="mw-redirect" title="First orange source in Cancer">First orange source in Cancer</a></li> <li><a href="/w/index.php?title=First_orange_source_in_Eridanus&action=edit&redlink=1" class="new" title="First orange source in Eridanus (page does not exist)">First orange source in Eridanus</a></li> <li><a href="/w/index.php?title=First_orange_source_in_Perseus&action=edit&redlink=1" class="new" title="First orange source in Perseus (page does not exist)">First orange source in Perseus</a></li> <li><a href="/w/index.php?title=First_positron_source_in_Cancer&action=edit&redlink=1" class="new" title="First positron source in Cancer (page does not exist)">First positron source in Cancer</a></li> <li><a href="/w/index.php?title=First_positron_source_in_Fornax&action=edit&redlink=1" class="new" title="First positron source in Fornax (page does not exist)">First positron source in Fornax</a></li> <li><a href="/w/index.php?title=First_positron_source_in_Phoenix&action=edit&redlink=1" class="new" title="First positron source in Phoenix (page does not exist)">First positron source in Phoenix</a></li> <li><a href="/w/index.php?title=First_proton_source_in_Canes_Venatici&action=edit&redlink=1" class="new" title="First proton source in Canes Venatici (page does not exist)">First proton source in Canes Venatici</a></li> <li><a href="/w/index.php?title=First_proton_source_in_Gemini&action=edit&redlink=1" class="new" title="First proton source in Gemini (page does not exist)">First proton source in Gemini</a></li> <li><a href="/w/index.php?title=First_proton_source_in_Pictor&action=edit&redlink=1" class="new" title="First proton source in Pictor (page does not exist)">First proton source in Pictor</a></li> <li><a href="/w/index.php?title=First_radio_source_in_Canis_Minor&action=edit&redlink=1" class="new" title="First radio source in Canis Minor (page does not exist)">First radio source in Canis Minor</a></li> <li><a href="/w/index.php?title=First_radio_source_in_Grus&action=edit&redlink=1" class="new" title="First radio source in Grus (page does not exist)">First radio source in Grus</a></li> <li><a href="/w/index.php?title=First_radio_source_in_Pisces&action=edit&redlink=1" class="new" title="First radio source in Pisces (page does not exist)">First radio source in Pisces</a></li> <li><a href="/wiki/First_red_source_in_Canis_Major" class="mw-redirect" title="First red source in Canis Major">First red source in Canis Major</a></li> <li><a href="/w/index.php?title=First_red_source_in_Horologium&action=edit&redlink=1" class="new" title="First red source in Horologium (page does not exist)">First red source in Horologium</a></li> <li><a href="/w/index.php?title=First_red_source_in_Puppis&action=edit&redlink=1" class="new" title="First red source in Puppis (page does not exist)">First red source in Puppis</a></li> <li><a href="/w/index.php?title=First_source_in_Capricornus&action=edit&redlink=1" class="new" title="First source in Capricornus (page does not exist)">First source in Capricornus</a></li> <li><a href="/w/index.php?title=First_source_in_Hydra&action=edit&redlink=1" class="new" title="First source in Hydra (page does not exist)">First source in Hydra</a></li> <li><a href="/w/index.php?title=First_source_in_Pyxis&action=edit&redlink=1" class="new" title="First source in Pyxis (page does not exist)">First source in Pyxis</a></li> <li><a href="/wiki/First_submillimeter_source_in_Carina" class="mw-redirect" title="First submillimeter source in Carina">First submillimeter source in Carina</a></li> <li><a href="/w/index.php?title=First_submillimeter_source_in_Hydrus&action=edit&redlink=1" class="new" title="First submillimeter source in Hydrus (page does not exist)">First submillimeter source in Hydrus</a></li> <li><a href="/w/index.php?title=First_submillimeter_source_in_Reticulum&action=edit&redlink=1" class="new" title="First submillimeter source in Reticulum (page does not exist)">First submillimeter source in Reticulum</a></li> <li><a href="/w/index.php?title=First_superluminal_source_in_Cassiopeia&action=edit&redlink=1" class="new" title="First superluminal source in Cassiopeia (page does not exist)">First superluminal source in Cassiopeia</a></li> <li><a href="/wiki/First_superluminal_source_in_Indus" class="mw-redirect" title="First superluminal source in Indus">First superluminal source in Indus</a></li> <li><a href="/w/index.php?title=First_superluminal_source_in_Sagitta&action=edit&redlink=1" class="new" title="First superluminal source in Sagitta (page does not exist)">First superluminal source in Sagitta</a></li> <li><a href="/w/index.php?title=First_ultraviolet_source_in_Centaurus&action=edit&redlink=1" class="new" title="First ultraviolet source in Centaurus (page does not exist)">First ultraviolet source in Centaurus</a></li> <li><a href="/w/index.php?title=First_ultraviolet_source_in_Lacerta&action=edit&redlink=1" class="new" title="First ultraviolet source in Lacerta (page does not exist)">First ultraviolet source in Lacerta</a></li> <li><a href="/w/index.php?title=First_ultraviolet_source_in_Sagittarius&action=edit&redlink=1" class="new" title="First ultraviolet source in Sagittarius (page does not exist)">First ultraviolet source in Sagittarius</a></li> <li><a href="/w/index.php?title=First_violet_source_in_Cepheus&action=edit&redlink=1" class="new" title="First violet source in Cepheus (page does not exist)">First violet source in Cepheus</a></li> <li><a href="/w/index.php?title=First_violet_source_in_Leo&action=edit&redlink=1" class="new" title="First violet source in Leo (page does not exist)">First violet source in Leo</a></li> <li><a href="/w/index.php?title=First_violet_source_in_Sculptor&action=edit&redlink=1" class="new" title="First violet source in Sculptor (page does not exist)">First violet source in Sculptor</a></li> <li><a href="/w/index.php?title=First_visual_source_in_Cetus&action=edit&redlink=1" class="new" title="First visual source in Cetus (page does not exist)">First visual source in Cetus</a></li> <li><a href="/w/index.php?title=First_visual_source_in_Leo_Minor&action=edit&redlink=1" class="new" title="First visual source in Leo Minor (page does not exist)">First visual source in Leo Minor</a></li> <li><a href="/w/index.php?title=First_visual_source_in_Scutum&action=edit&redlink=1" class="new" title="First visual source in Scutum (page does not exist)">First visual source in Scutum</a></li> <li><a href="/w/index.php?title=First_X-ray_source_in_Andromeda&action=edit&redlink=1" class="new" title="First X-ray source in Andromeda (page does not exist)">First X-ray source in Andromeda</a></li> <li><a href="/w/index.php?title=First_X-ray_source_in_Antlia&action=edit&redlink=1" class="new" title="First X-ray source in Antlia (page does not exist)">First X-ray source in Antlia</a></li> <li><a href="/w/index.php?title=First_X-ray_source_in_Apus&action=edit&redlink=1" class="new" title="First X-ray source in Apus (page does not exist)">First X-ray source in Apus</a></li> <li><a href="/w/index.php?title=First_X-ray_source_in_Aquarius&action=edit&redlink=1" class="new" title="First X-ray source in Aquarius (page does not exist)">First X-ray source in Aquarius</a></li> <li><a href="/w/index.php?title=First_X-ray_source_in_Centaurus&action=edit&redlink=1" class="new" title="First X-ray source in Centaurus (page does not exist)">First X-ray source in Centaurus</a></li> <li><a href="/w/index.php?title=First_X-ray_source_in_Chamaeleon&action=edit&redlink=1" class="new" title="First X-ray source in Chamaeleon (page does not exist)">First X-ray source in Chamaeleon</a></li> <li><a href="/w/index.php?title=First_X-ray_source_in_Lepus&action=edit&redlink=1" class="new" title="First X-ray source in Lepus (page does not exist)">First X-ray source in Lepus</a></li> <li><a href="/w/index.php?title=First_X-ray_source_in_Serpens_Caput&action=edit&redlink=1" class="new" title="First X-ray source in Serpens Caput (page does not exist)">First X-ray source in Serpens Caput</a></li> <li><a href="/w/index.php?title=First_yellow_source_in_Aquila&action=edit&redlink=1" class="new" title="First yellow source in Aquila (page does not exist)">First yellow source in Aquila</a></li> <li><a href="/w/index.php?title=First_yellow_source_in_Circinus&action=edit&redlink=1" class="new" title="First yellow source in Circinus (page does not exist)">First yellow source in Circinus</a></li> <li><a href="/w/index.php?title=First_yellow_source_in_Lupus&action=edit&redlink=1" class="new" title="First yellow source in Lupus (page does not exist)">First yellow source in Lupus</a></li> <li><a href="/w/index.php?title=First_yellow_source_in_Serpens_Cauda&action=edit&redlink=1" class="new" title="First yellow source in Serpens Cauda (page does not exist)">First yellow source in Serpens Cauda</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Radios/Lessons&action=edit&redlink=1" class="new" title="Radiation astronomy/Radios/Lessons (page does not exist)">Radio astronomy/Lessons</a></li> <li><a href="/w/index.php?title=X-ray_astronomy/Lessons&action=edit&redlink=1" class="new" title="X-ray astronomy/Lessons (page does not exist)">X-ray astronomy/Lessons</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="background:#21ABCD;;width:1%;background:#21ABCD; color:#000000;">Lists</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0;background:#BCD4E6;"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Asteroid_Surveys" title="Asteroid Surveys">Asteroid Surveys</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="background:#21ABCD;;width:1%;background:#21ABCD; color:#000000;">Portals</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0;background:#ACE5EE;"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Portal:Astrophysics" title="Portal:Astrophysics">Astrophysics</a></li> <li><a href="/wiki/Portal:Cosmology" title="Portal:Cosmology">Cosmology</a></li> <li><a href="/wiki/Portal:General_relativity" title="Portal:General relativity">General relativity</a></li> <li><a href="/wiki/School:Geophysics" title="School:Geophysics">Geophysics</a></li> <li><a href="/wiki/Portal:Radiation_astronomy" title="Portal:Radiation astronomy">Radiation astronomy</a></li> <li><a href="/wiki/Portal:Special_relativity" title="Portal:Special relativity">Special relativity</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="background:#21ABCD;;width:1%;background:#21ABCD; color:#000000;">Problem sets</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0;background:#BCD4E6;"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Angular_momentum_and_energy" title="Angular momentum and energy">Angular momentum and energy</a></li> <li><a href="/wiki/Column_densities" title="Column densities">Column densities</a></li> <li><a href="/w/index.php?title=Cosmic_circuits&action=edit&redlink=1" class="new" title="Cosmic circuits (page does not exist)">Cosmic circuits</a></li> <li><a href="/wiki/Energy_phantoms" title="Energy phantoms">Energy phantoms</a></li> <li><a href="/wiki/Furlongs_per_fortnight" title="Furlongs per fortnight">Furlongs per fortnight</a></li> <li><a href="/wiki/Lenses_and_focal_length" title="Lenses and focal length">Lenses and focal length</a></li> <li><a href="/w/index.php?title=Neutrino_emissions&action=edit&redlink=1" class="new" title="Neutrino emissions (page does not exist)">Neutrino emissions</a></li> <li><a href="/wiki/Planck%27s_equation" title="Planck's equation">Planck's equation</a></li> <li><a href="/wiki/Spectrographs" title="Spectrographs">Spectrographs</a></li> <li><a href="/wiki/Star_jumping" title="Star jumping">Star jumping</a></li> <li><a href="/wiki/Synchrotron_radiation/Problem_set" title="Synchrotron radiation/Problem set">Synchrotron radiation</a></li> <li><a href="/wiki/Telescopes_and_cameras" title="Telescopes and cameras">Telescopes and cameras</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="background:#21ABCD;;width:1%;background:#21ABCD; color:#000000;">Projects</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0;background:#ACE5EE;"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Neutrinos_from_the_Sun" class="mw-redirect" title="Neutrinos from the Sun">Neutrinos from the Sun</a></li> <li><a href="/wiki/Stars/Star_fissions" title="Stars/Star fissions">Stellar fission as a source of binary stars</a></li> <li><a href="/wiki/Stars/Sun/Solar_binary" title="Stars/Sun/Solar binary">The Sun as a binary star</a></li> <li><a href="/wiki/Stars/X-ray_classification" title="Stars/X-ray classification">X-ray classification of stars</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="background:#21ABCD;;width:1%;background:#21ABCD; color:#000000;">Quizzes</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0;background:#BCD4E6;"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Plasmas/Plasma_objects/Auroras/Quiz" title="Plasmas/Plasma objects/Auroras/Quiz">Auroras/Quiz</a></li> <li><a href="/wiki/Stars/Betelgeuse/Quiz" title="Stars/Betelgeuse/Quiz">Betelgeuse/Quiz</a></li> <li><a href="/wiki/Plasmas/Plasma_objects/Coronal_clouds/Quiz" title="Plasmas/Plasma objects/Coronal clouds/Quiz">Coronal cloud/Quiz</a></li> <li><a href="/wiki/Stars/Galaxies/Quiz" title="Stars/Galaxies/Quiz">Galaxies/Quiz</a></li> <li><a href="/wiki/Gases/Gaseous_objects/Astronomy/Quiz" title="Gases/Gaseous objects/Astronomy/Quiz">Gaseous-object astronomy/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Heliocentric_astronomy/Quiz" title="Stars/Sun/Heliocentric astronomy/Quiz">Heliocentric astronomy/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Heliognosy/Quiz" title="Stars/Sun/Heliognosy/Quiz">Heliognosy/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Heliogony/Quiz" title="Stars/Sun/Heliogony/Quiz">Heliogony/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Heliography/Quiz" title="Stars/Sun/Heliography/Quiz">Heliography/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Heliology/Quiz" title="Stars/Sun/Heliology/Quiz">Heliology/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Heliometry/Quiz" title="Stars/Sun/Heliometry/Quiz">Heliometry/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Heliophysics/Quiz" title="Stars/Sun/Heliophysics/Quiz">Heliophysics/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Heliospheres/Quiz" title="Stars/Sun/Heliospheres/Quiz">Heliospheres/Quiz</a></li> <li><a href="/wiki/Interstellar_medium/Quiz" title="Interstellar medium/Quiz">Interstellar medium/Quiz</a></li> <li><a href="/wiki/Plasmas/Magnetohydrodynamics/Quiz" title="Plasmas/Magnetohydrodynamics/Quiz">Magnetohydrodynamics/Quiz</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Meteors/Quiz&action=edit&redlink=1" class="new" title="Radiation astronomy/Meteors/Quiz (page does not exist)">Meteor astronomy/Quiz</a></li> <li><a href="/wiki/Radiation/Meteors/Quiz" title="Radiation/Meteors/Quiz">Meteor radiation/Quiz</a></li> <li><a href="/wiki/Stars/Galaxies/Milky_Way/Quiz" title="Stars/Galaxies/Milky Way/Quiz">Milky Way/Quiz</a></li> <li><a href="/wiki/Stars/Nova-likes/Quiz" title="Stars/Nova-likes/Quiz">Nova-like stars/Quiz</a></li> <li><a href="/wiki/Plasmas/Plasma_objects/Nucleosynthesis/Quiz" title="Plasmas/Plasma objects/Nucleosynthesis/Quiz">Nucleosynthesis/Quiz</a></li> <li><a href="/w/index.php?title=Oort_clouds/Quiz&action=edit&redlink=1" class="new" title="Oort clouds/Quiz (page does not exist)">Oort clouds/Quiz</a></li> <li><a href="/wiki/Plasmas/Plasma_objects/Astronomy/Quiz" title="Plasmas/Plasma objects/Astronomy/Quiz">Plasma-object astronomy/Quiz</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Courses/Principles/Hourly_1&action=edit&redlink=1" class="new" title="Radiation astronomy/Courses/Principles/Hourly 1 (page does not exist)">Principles of radiation astronomy/Hourly 1</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Courses/Principles/Hourly_2&action=edit&redlink=1" class="new" title="Radiation astronomy/Courses/Principles/Hourly 2 (page does not exist)">Principles of radiation astronomy/Hourly 2</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Courses/Principles/Hourly_3&action=edit&redlink=1" class="new" title="Radiation astronomy/Courses/Principles/Hourly 3 (page does not exist)">Principles of radiation astronomy/Hourly 3</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Courses/Principles/Midterm_quiz&action=edit&redlink=1" class="new" title="Radiation astronomy/Courses/Principles/Midterm quiz (page does not exist)">Principles of radiation astronomy/Midterm quiz</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Courses/Principles/Final_quiz&action=edit&redlink=1" class="new" title="Radiation astronomy/Courses/Principles/Final quiz (page does not exist)">Principles of radiation astronomy/Final quiz</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Detectors/Quiz&action=edit&redlink=1" class="new" title="Radiation astronomy/Detectors/Quiz (page does not exist)">Radiation detectors/Quiz</a></li> <li><a href="/wiki/Stars/Radiative_dynamo/Quiz" title="Stars/Radiative dynamo/Quiz">Radiative dynamo/Quiz</a></li> <li><a href="/w/index.php?title=Scattered_discs/Quiz&action=edit&redlink=1" class="new" title="Scattered discs/Quiz (page does not exist)">Scattered discs/Quiz</a></li> <li><a href="/wiki/Serpens_X-1/Quiz" title="Serpens X-1/Quiz">Serpens X-1/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Astronomy/Quiz" title="Stars/Sun/Astronomy/Quiz">Solar astronomy/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Solar_binary/Quiz" title="Stars/Sun/Solar binary/Quiz">Solar binary/Quiz</a></li> <li><a href="/wiki/Stars/Galaxies/Spirals/Quiz" title="Stars/Galaxies/Spirals/Quiz">Spiral galaxies/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Standard_models/Quiz" title="Stars/Sun/Standard models/Quiz">Standard solar model/Quiz</a></li> <li><a href="/wiki/Stars/Star_fissions/Quiz" title="Stars/Star fissions/Quiz">Star fission/Quiz</a></li> <li><a href="/wiki/Stars/Star-forming_regions/Quiz" title="Stars/Star-forming regions/Quiz">Star-forming region/Quiz</a></li> <li><a href="/wiki/Stars/Quiz" title="Stars/Quiz">Stars/Quiz</a></li> <li><a href="/wiki/Stars/Active_regions/Quiz" title="Stars/Active regions/Quiz">Stellar active region/Quiz</a></li> <li><a href="/wiki/Stars/Astronomy/Quiz" title="Stars/Astronomy/Quiz">Stellar astronomy/Quiz</a></li> <li><a href="/wiki/Stars/Sciences/Quiz" title="Stars/Sciences/Quiz">Stellar science/Quiz</a></li> <li><a href="/wiki/Stars/Surface_fusion/Quiz" title="Stars/Surface fusion/Quiz">Stellar surface fusion/Quiz</a></li> <li><a href="/wiki/Stars/Sun/X-ray_sources/Quiz" title="Stars/Sun/X-ray sources/Quiz">Sun as an X-ray source/Quiz</a></li> <li><a href="/wiki/Stars/Sun/Quiz" title="Stars/Sun/Quiz">Sun/Quiz</a></li> <li><a href="/w/index.php?title=Sun-synchronous_astronomy/Quiz&action=edit&redlink=1" class="new" title="Sun-synchronous astronomy/Quiz (page does not exist)">Sun-synchronous astronomy/Quiz</a></li> <li><a href="/w/index.php?title=Radiation_astronomy/Superluminals/Quiz&action=edit&redlink=1" class="new" title="Radiation astronomy/Superluminals/Quiz (page does not exist)">Superluminal astronomy/Quiz</a></li> <li><a href="/wiki/Stars/Supernovas" title="Stars/Supernovas">Supernovas/Quiz</a></li> <li><a href="/wiki/Supernova_X-rays/Quiz" title="Supernova X-rays/Quiz">Supernova X-rays/Quiz</a></li> <li><a href="/wiki/Stars/Vega/Quiz" title="Stars/Vega/Quiz">Vega/Quiz</a></li> <li><a href="/w/index.php?title=Vela_X-1/Quiz&action=edit&redlink=1" class="new" title="Vela X-1/Quiz (page does not exist)">Vela X-1/Quiz</a></li> <li><a href="/wiki/Stars/X-ray_classification/Quiz" title="Stars/X-ray classification/Quiz">X-ray classification of stars/Quiz</a></li></ul> </div></td></tr></tbody></table></div><style data-mw-deduplicate="TemplateStyles:r2415560"></style><table class="plainlinks metadata ambox ambox-notice" role="presentation" style="width:250px; float:right; clear:right; margin-left:10px; margin-right:0px;"><tbody><tr><td class="mbox-empty-cell"></td><td class="mbox-text"><div class="mbox-text-span"><div style="padding:0px 10px; white-space:nowrap"> <p><span typeof="mw:File"><a href="https://en.wikibooks.org/wiki/Special:Search/Heliography" title="Wikibooks"><img alt="Wikibooks logo" src="//upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikibooks-logo.svg/24px-Wikibooks-logo.svg.png" decoding="async" width="24" height="24" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikibooks-logo.svg/36px-Wikibooks-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikibooks-logo.svg/48px-Wikibooks-logo.svg.png 2x" data-file-width="300" data-file-height="300" /></a></span>  <span 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