lect 6 - The wavelength of a spectral line is affected by...

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The wavelength of a spectral line is affected by the relative motion between the source and the observer
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Doppler Shifts Red Shift : The object is moving away from the observer Blue Shift : The object is moving towards the observer ∆λ / λ o = v/ c ∆λ = wavelength shift λ o = wavelength if source is not moving v = velocity of source c = speed of light
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Our Star, the Sun
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What is the source of energy of the Sun? • Burning fuel? No! Burning chemical reactions release 10 -19 joule of energy per atom. All the atoms of the entire Sun will be consumed in 3x10 11 seconds = 10 4 years! • Gravitational contraction (Kelvin-Helmhotz)? No! If true, the Sun could have started contracting no more than 25 million years ago… impossible (Earth is much older, ~4.6 billion years).
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The Sun’s energy is generated by thermonuclear reactions in its core • The energy released in a nuclear reaction corresponds to a slight reduction of mass according to Einstein’s equation E = mc 2 • Thermonuclear fusion occurs only at very high temperatures; for example, hydrogen fusion occurs only at temperatures in excess of about 10 7 K • In the Sun, fusion occurs only in the dense, hot core
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Not to be mistaken… • Fusion with fission… • Chemical reactions with nuclear reactions…
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The Sun’s energy is produced by hydrogen fusion, not in a single step, but in a sequence of thermonuclear reactions in which four hydrogen nuclei combine to produce a single helium nucleus
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Thermonuclear fusion of Hydrogen (proton-proton chain)
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lect 6 - The wavelength of a spectral line is affected by...

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