ASTR 1120ASTR 1120General Astronomy:General Astronomy:Stars & GalaxiesStars & Galaxies!NNOUNCEMENTSFIRST MIDTERMFIRST MIDTERM THIS THURSDAY, 09/17THIS THURSDAY, 09/17"ex# observing night Tue 09/22.$econd homework on mas%ring as&onomy due o' (UESDAY, 09/22, by 5pm.The SUNThe SUN!ast Tim"How far is the Sun?What is the Sun made of?How does the Sun produce its energy?(and how do we know?)Why is the Sun stable?What is the structure of the Sun?In the core, what is the mainIn the core, what is the main wavelengthwavelengthof photons present?of photons present?A.A.Radio wavesRadio wavesB.B.Gamma RaysGamma RaysC.C.VisibleVisibleD.D.InfraredInfraredE.E.X-raysX-raysClicker QuestionClicker QuestionIn the core, what is the mainIn the core, what is the main wavelengthwavelengthof photons present?of photons present?A.A.Radio wavesRadio wavesB.B.Gamma RaysGamma RaysC.C.VisibleVisibleD.D.InfraredInfraredE.E.X-raysX-raysClicker QuestionClicker QuestionAt the photosphere, what is the mainAt the photosphere, what is the mainwavelength of photons present?wavelength of photons present?A.A.Radio wavesRadio wavesB.B.Gamma RaysGamma RaysC.C.VisibleVisibleD.D.InfraredInfraredE.E.X-raysX-raysClicker QuestionClicker QuestionAt the photosphere, what is the mainAt the photosphere, what is the mainwavelength of photons present?wavelength of photons present?A.A.Radio wavesRadio wavesB.B.Gamma RaysGamma RaysC.C.VisibleVisibleD.D.InfraredInfraredE.E.X-raysX-raysClicker QuestionClicker QuestionHelioseismology:Helioseismology: Millions of soundMillions of soundwaves available to probe solar interiorwaves available to probe solar interiorACOUSTIC WAVESACOUSTIC WAVESSome waves bounceSome waves bouncejust below the surfacejust below the surfaceOthers almost make itOthers almost make itto the centerto the centerAll excited by turbulentAll excited by turbulentgranulation visible ingranulation visible inphotospherephotosphereHow do we know what’s inside the Sun?SOLARSOLAROSCILLATIONOSCILLATIONMODESMODESOne of millionsof modes, eachwith a differenttone!SunspotsSunspots••DarkerDarker = coolercooler– Still ~4,000 K• Sunspot pictured at thebottom left covers thearea of 15 Earths!– Taken with theSolar andHeliosphericObservatory(SOHO)Sunspots Caused By MagneticSunspots Caused By MagneticFieldsFields• Magnetic fields entrain gas in huge bubbling loops• Cooler areas at “liftoff” cause dark sunspotsBut What Causes the MagneticBut What Causes the MagneticFieldField Lines toLines to Stick Out Like That?Stick Out Like That?••Differential RotationDifferential Rotation– The Sun rotates differently at different latitudes.• The Sun winds itself upThis Solar This Solar ““Wind UpWind Up”” Leads LeadsTo The Sunspot CycleTo The Sunspot CycleDuring the Sunspot Cycle SunspotsDuring the Sunspot Cycle SunspotsForm At Different LatitudesForm At Different LatitudesComplex Interplay of Convection, Magnetism andComplex Interplay of Convection, Magnetism andDifferential Rotation.Differential Rotation.What is believed to be the main cause of theWhat is believed to be the main cause of thesunspot cycle?sunspot cycle?A. Temperature changes between the equator andpoles of the SunB. Twisting of magnetic fields lines in the Sun due to arotation rate varying with latitude.C. Variability in the Sun’s brightness every 11 yearsD. Interaction between the Sun and the orbits of theinnermost planetsE. A variation of the fusion rate occurring in the core ofthe Sun.Clicker QuestionClicker QuestionWhat is believed to be the main cause of theWhat is believed to be the main cause of thesunspot cycle?sunspot cycle?A. Temperature changes between the equator andpoles of the SunB. Twisting of magnetic fields lines in the Sun due to arotation rate varying with latitude.C. Variability in the Sun’s brightness every 11 yearsD. Interaction between the Sun and the orbits of theinnermost planetsE. A variation of the fusion rate occurring in the core ofthe Sun.Clicker QuestionClicker QuestionIf we see theIf we see thesunspot edge-on,sunspot edge-on,itit’’s called as called aPROMINENCEPROMINENCEWhen Prominences Go BadWhen Prominences Go Bad••Occasionally theOccasionally themagnetic field linesmagnetic field linesin a prominencein a prominence““snapsnap””– Energy & Light isreleased••FlaresFlares– Charged particlesare spewed out intospace••Coronal MassCoronal MassEjectionsEjectionsCoronal Coronal MASSMASS Ejections Ejections BlastBlastOut Charged ParticlesOut Charged Particles• PROTONS!– Can:• Damage satellites• Harm astronauts• Induce currents on Earth and destroy electrictransformers on the ground• Cause swelling in the Earth’s atmosphereCoronal Mass Ejections MovieCoronal Mass Ejections MoviefromfromSolar and Solar and Heliospheric Heliospheric ObservatoryObservatoryhttp://http://sohowwwsohowww..nascomnascom..nasanasa..govgov//Protons interacting with theProtons interacting with theEarthEarth’’s magnetic field produce auroras magnetic field produce auroraChromosphereChromosphere• Temperature goesback UP!• T ! 6,000-10,000 K6,000-10,000 K••Very thin densityVery thin density••Heated by energyHeated by energytwisting and spillingtwisting and spillingaround magnetic fieldaround magnetic fieldlineslinesOutside the Outside the chromosperechromospere, the, thetemperature spikes up again!temperature spikes up again!CoronaCorona• T ! 1,000,000 K1,000,000 K••Extremely thinExtremely thindensitydensity••X-raysX-rays••More magneticMore magneticheatingheatingX-ray image of the SunX-ray image of the SunSolar Eclipse: SunSolar Eclipse: Sun’’s lights lightblocked by the Moonblocked by the MoonCorona becomes clearer in visible light without glare from therest of the SunSolar WindSolar Wind••At the top of the corona,At the top of the corona,gas is hot enough (andgas is hot enough (andfar enough) to escapefar enough) to escapethe gravity of the Sunthe gravity of the Sun••In effect, the corona isIn effect, the corona is““evaporatingevaporating””––BuBut replenished fromt replenished frombelowbelow• Solar wind carries abouta million tons of solarmillion tons of solarmatter per secondmatter per second!!– Yet the sun has only lost0.1 percent of its