The Sun:The Sun:Our StarOur StarPSC 203PSC 203OverviewOverviewIn this section:In this section:How is it structured?How is it structured?What does the surface look like?What does the surface look like?How is the sun “active”?How is the sun “active”?StructureStructureCoreCorevery center of sunvery center of sunenergy generated through fusion energy generated through fusion H->HeH->HeFusion = two atoms forced together to form Fusion = two atoms forced together to form a heavier atoma heavier atomRadiative ZoneRadiative Zoneoutside of coreoutside of coreenergy transferred through radiationenergy transferred through radiationradiation -> light of all wavelengthsradiation -> light of all wavelengthsConvection ZoneConvection Zoneoutside of radiative zoneoutside of radiative zoneenergy transferred through convectionenergy transferred through convectionconvection -> convection -> hot gas rises, cooler gas fallshot gas rises, cooler gas fallssimilar to boiling pot of watersimilar to boiling pot of waterPhotospherePhotospherevisible surface of sun visible surface of sun (in visible wavelengths)(in visible wavelengths)not solid surfacenot solid surfaceso bright it dominates view without so bright it dominates view without filtersfiltersChromosphereChromospherethe lower atmosphere of the sunthe lower atmosphere of the sunlocated above photospherelocated above photospherethis is where most activity occursthis is where most activity occursprominencesprominencesflaresflaresmagnetic loopsmagnetic loopsCoronaCoronathe outer atmosphere of the sunthe outer atmosphere of the sunlow density, high temperaturelow density, high temperaturenormally too faint to be seen normally too faint to be seen (photosphere is too bright)(photosphere is too bright)can be seen during solar eclipsecan be seen during solar eclipseSOHO sees by blocking out bright SOHO sees by blocking out bright photospherephotosphereInterior StructureInterior StructureWhat is the interior structure of the Sun?What is the interior structure of the Sun?DensityDensityThe density is highest at the centerThe density is highest at the centerDrops off rapidly toward surfaceDrops off rapidly toward surfaceTemperatureTemperatureThe temperature is highest at the centerThe temperature is highest at the centerDrops off rapidly toward surfaceDrops off rapidly toward surfaceAppearanceAppearanceLook at the following views of the sun and Look at the following views of the sun and describe what you seedescribe what you seePhotospherePhotosphereVery bright visible Very bright visible surfacesurfaceNeed filter to take Need filter to take picturepictureSun SpotsSun SpotsDarker cooler spots Darker cooler spots on the photosphereon the photosphereStill Still veryvery hot hotNeed filter to see Need filter to see themthemFeatures?Features?Other wavelengthsOther wavelengthsAs we look in other wavelengths, we see other As we look in other wavelengths, we see other features besides just the photospherefeatures besides just the photosphereWavelength related to temperatureWavelength related to temperaturespotchange.mpgspotchange.mpgChromosphereChromosphereLooking in UVLooking in UVFeatures?Features?ChromosphereChromosphereCoronaCoronaOuter edges of Outer edges of atmosphereatmosphereOverwhelmed by Overwhelmed by photospherephotosphereSeen in eclipses Seen in eclipses Features?Features?Activity on the SunActivity on the SunThe sun doesn’t stay the sameThe sun doesn’t stay the sameThe changes are referred to as “activity”The changes are referred to as “activity”Watch animations and movies and note Watch animations and movies and note changeschangesGranulationGranulationlight and dark speckling of the light and dark speckling of the photosphere photosphere caused by convection underneath caused by convection underneath very small scale and short timevery small scale and short timeSolar_Surface_Convection_SimulationSolar_Surface_Convection_SimulationHurricane-sized_whirlpools_spotted_on_SunHurricane-sized_whirlpools_spotted_on_SunChanges over monthChanges over monthPhotospherePhotospherecurrent_photocurrent_photoChromosphereChromospherecurrent_chromcurrent_chromNotice rotation and active regionsNotice rotation and active regionsChanges over yearsChanges over yearsTwosunsTwosunsactivity increases and decreases in 11 year activity increases and decreases in 11 year cyclecycleCalled “solar cycle”Called “solar cycle”Current statusCurrent statuscurrent_mdi_igrcurrent_mdi_igrAre we in high or low part of the cycleAre we in high or low part of the cycleMagnetic FieldMagnetic Fieldthe activity on the sun is caused by the the activity on the sun is caused by the magnetic fieldmagnetic fieldthe sun's magnetic field gets twisted and the sun's magnetic field gets twisted and knotted knotted dynamodynamoSunspot_Formation_and_FlareSunspot_Formation_and_FlareSun spotsSun spotstemporary cooler, darker spots on the temporary cooler, darker spots on the surfacesurfacecaused by magnetic field lines bunching caused by magnetic field lines bunching togethertogetherlast from hours to monthslast from hours to monthsSun spotsSun spotsProminencesProminencesGas extends above Gas extends above the photosphere the photosphere Most visible on the Most visible on the edgesedgesFeatures?Features?ProminencesProminencesProminencesProminencesGas flows along the magnetic field of the Gas flows along the magnetic field of the prominencesprominencesTraceZTraceZFlaresFlaresoutbursts of activity on the sun's surfaceoutbursts of activity on the sun's surfaceresulting in temporary brighteningresulting in temporary brighteningEITsub3EITsub3Movie clipMovie clipCMEsCMEsCoronal Mass Ejections Coronal Mass Ejections large amounts of gas thrown out into large amounts of gas thrown out into spacespacecaused by magnetic field breaking and caused by magnetic field breaking and