Spectra
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| Magnitude | refers to the apparent brightness of a star and is not a fundamental property of the star. However, the greater the flux, the smaller and more negative the apparent magnitude.
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| Second law of thermodynamics | Heat flows from hot objects to cold objects -or , in other words, hot objects radiate more energy into space than colder ones
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| Blackbody Radiators | Radiate EM ration into space at all wavelengths irrespective of size, shape or composition
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| Max Planck BB equation | His equation describes the energy flux of BB at a specific wavelength for a specified temperature
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| Temperature | temperature is a measure of heat energy
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| The Kelvin Scale Equation | T(Kelvin) = T(Centigrade) + 273
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| Wiens Law(temperature of any star anywhere in the universe) | lamdamaxT = 2.8977 x 10^-3. Where lamdamax in meters, T in Kelvin
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| 3 types of Spectra | Continuous(blackbody) spectra, Emission spectra, Absorption Spectra
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| Continuous(Blackbody) spectra | Hot solids, liquids of dense gases. EM radiation produced at all wavelengths
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| Emission Spectra | Hot, low density gas. EM radiation at very specific wavelengths. Hot interstellar gas clouds produce such spectra.
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| Absorption Spectra | Produced when light from a continuous spectrum is viewed through a lower density, lower temperature gas. Absorption lines are seen at very specific wavelengths. Stars produce absorption line spectra.
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| Spectra type graphs | D4
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| Stellar absorption Lines | Absorption line spectra produced by a blackbody radiator surrounded by a lower temperature gas envelope
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| Photosphere | Cool, low density envelope where the absorption lines form.
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| Emission Lines | In general, emission lines are associated with hot low density gases.
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| Three processes are at work in Emission lines | 1.High temperature-many high energy collisions. 2.Collisions between atoms places them in an excited state. 3.Between repeat collisions an excited atom releases a photon which carries away their excitation energy and produces emission line
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| Photon | Burst or packet of EM radiation with energy (E = hf)
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| Spectral analysis | Each species of atom has a unique set of absorption/ emission lines
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| Spectral Classification | Classify stars according to their spectral lines(key idea is to use 'strength' of hydrogen lines)
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| The spectral classification scheme | OB AF G KM
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| OB | >30,000(O) 10-30,000(B) hottest and most luminous stars (Blue)
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| AF | 7500-10,000(A)6000-7500(F) Strongest hydrogen lines(blue-white)
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| G | 5000-6000 (G)Sun = G2 star(yellow)
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| KM | 3500-5000(K) <3500(M)Coolest and least luminous stars (red)
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davidvachon1
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