Transcript The Sun
The Sun – A typical Star Here’s the Story we’ll Unfold for you… • Nuclear power and the sun’s radiation • The layers of the sun; core, radiative zone, convective zone, photosphere, chromosphere, and corona • Sunspots and magnetic fields, the sunspot cycle • Solar activity and how it influences the Earth Gravity vs. pressure A Star: A Balance between Gravity and Pressure • Self-regulating… • Higher fusion rate would expand star, lowering core’s self-gravity and thence density, pressure, temperature and thus lowering fusion rate. And vice versa Solar spectrum (from eschelle spectrograph) The Sun – Nuclear Power’ed • Core: T>10M Kelvin, high speed protons moving so fast they approach to within 10-13 cm, leading to hydrogen fusion into helium • Fusion: the Strong Nuclear Force overcomes EM repulsion of protons • 4H → He + 2 gamma rays + 2 neutrinos • Gamma rays random-walk their way to the surface – takes ~50,000 years! distributing their energy along the way, wavelength lengthening to eventually become visible light at the surface Fusion Temp; strong vs em Layers of the sun Sun layers granulation granules Sun globe in Halpha Chromosphere all around chromosphere Eclipse chromosphere Diamond ring Total eclipse corona Eclipse composite Sunspots optical Sunspot group optical Sunspots • Zeeman Effect: splitting of spectral lines into triplets, due to the gas being imbedded within a magnetic field • Think of magnetic field lines like “sticky rubber bands” • Charged particles in a magnetic field feel a force sideways to their motion, binding the gas to the field. • Sunspots are like “magnetic scabs” of gas unable to be recirculated to lower, hotter levels. They are bound to the magnetic fields in the photosphere, cooling as they radiate to the cold universe, and hence cool and darken. • Vertical structure of a sunspot Babcock slide Differential Rotation intensified and concentrates magnetic field energy, producing sunspots Marching sunspots Sun pic at max,min Sunspot cycle #vs time Sunspot cycle 1760-1965 Ha loop Xray loops Xrays- chromospheric mag field loops Magnetic field spaghetti! Powerful solar flare Xray sun Total eclipse corona Eclipse corona2 solarwind Earth magnetosphere EarthOnionMagField Aurorae – GiNormous Flourescent Lights! • Caused when high speed solar wind particles impact the Earth’s atmosphere • Collisionally excites the nitrogen and oxygen atoms • These atoms then de-excite (electrons fall back down through the energy levels) giving off photons • Exactly the same as how flourescent lights work! greenpurpleAurora Aurora barn Aurorachu Alaska Aurora westlake Aurora lindersen Aurora hoffman Aurora c/IkeyaZhang Aurora ewoldt Aurora people Aurora tricolor Aurora tower Aurora from space iss Jupiter aurora Saturn aurorae cme Comet NEAT kinky tail SOHO wide angle SOHO+CMD+NEAT Sun Halpha + big prominence Sun halpha + big prom; later heliopause The Genesis Mission • (no, not the hokey StarTrek thing…) • Spacecraft spent months out in interplanetary space, capturing particles from the solar wind and from interstellar space • Then, brought them back to earth • But, there was this parachute problem… Genisis spacecraft crash site