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What Is The Sun Made Of?. Absorption bands in the Solar Spectrum. 1802 Wollaston sees dark bands 1814 Fraunhofer records many lines and labels with letters these become known as Fraunhofer lines
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Absorption bands in the Solar Spectrum • 1802 Wollaston sees dark bands • 1814 Fraunhofer records many lines and labels with letters these become known as Fraunhofer lines • 1859 Kirchoff realizes the significance of dark lines as absorption lines coming from elements in the gas
Internal Structure • Core Temp ~ 270,000,000 °F Where nuclear fusion occurs Location of energy production in the Sun • Radiation Zone Temp ~12600000 °F – 3600000 °F Energy travels by radiation (photons) inner 2/3 of sun • Convective Zone Temp ~3600000 °F outer 1/3 of sun Energy travels by convection(bubbles of heated material) • Photosphere Temp ~9950 °F • Chromosphere Temp ~9950 °F
Energy Production • Hydrogen fuses in the core of the sun. • Fusion means 4H <-> 1He, • E=mc2 Energy is produced by this process because of the difference in binding energies between H and He • Conservation of Energy means energy is released each time a reaction occurs
Outer layers: Photosphere • Photosphere = visible layer of the sun! • Location of observed Blackbody Spectrum • Continuum tells us the Temperature T ~ 9950 °F
Effective Temperature • Blackbody curve from last week: Hot dense gas emits continuous emission. The wavelength of peak intensity determines the temperature Intensity vs wavelength
Outer layers: Chromosphere • Chromosphere observed in the H-alpha line • Looks red!! • Top layers hotter than photosphere • Lower layers cooler than photosphere • Cool gas in front of a Blackbody creates absorption lines...
Outer layers: Corona • Corona has a temperature much higher than lower layers(4,000,000 deg F), and much lower density • Not fully understood even now - magnetic fields are most probably involved... • Solar Flare clip
Spectral Typing • Stars of different spectral types have different absorption lines in their spectra • Different lines because different temperatures • Different temperatures because different masses
Sunspots • Sunspots are cooler places on the Photosphere where magnetic field lines break through the surface • Cooler spots look darker compared to their surroundings • The sun has an 11 year cycle from few sunspots to many. Currently we are moving towards a minimum
Today's lab A few notes to guide the discussion of the questions: • Q1 what is the response of the video detector to color? • Q5 video camera insensitive to these wavelengths, but photographic emulsions very sensitive to them, so much easier to see • Q6 think about Kirkoff's laws... • Q8 what do we breathe...? lines from Earth are called telluric lines • Q9 Heavy elements like Iron (Fe) need to be very very hot to turn into a gas and thus emit or absorb light at particular wavelengths. Even hotter temps lead to the loss of electrons – ionization...the corona has Fe XIV (Iron ionized 13 times!!)