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Spectra

TermDefinition
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.
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
Blackbody Radiators Radiate EM ration into space at all wavelengths irrespective of size, shape or composition
Max Planck BB equation His equation describes the energy flux of BB at a specific wavelength for a specified temperature
Temperature temperature is a measure of heat energy
The Kelvin Scale Equation T(Kelvin) = T(Centigrade) + 273
Wiens Law(temperature of any star anywhere in the universe) lamdamaxT = 2.8977 x 10^-3. Where lamdamax in meters, T in Kelvin
3 types of Spectra Continuous(blackbody) spectra, Emission spectra, Absorption Spectra
Continuous(Blackbody) spectra Hot solids, liquids of dense gases. EM radiation produced at all wavelengths
Emission Spectra Hot, low density gas. EM radiation at very specific wavelengths. Hot interstellar gas clouds produce such spectra.
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.
Spectra type graphs D4
Stellar absorption Lines Absorption line spectra produced by a blackbody radiator surrounded by a lower temperature gas envelope
Photosphere Cool, low density envelope where the absorption lines form.
Emission Lines In general, emission lines are associated with hot low density gases.
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
Photon Burst or packet of EM radiation with energy (E = hf)
Spectral analysis Each species of atom has a unique set of absorption/ emission lines
Spectral Classification Classify stars according to their spectral lines(key idea is to use 'strength' of hydrogen lines)
The spectral classification scheme OB AF G KM
OB >30,000(O) 10-30,000(B) hottest and most luminous stars (Blue)
AF 7500-10,000(A)6000-7500(F) Strongest hydrogen lines(blue-white)
G 5000-6000 (G)Sun = G2 star(yellow)
KM 3500-5000(K) <3500(M)Coolest and least luminous stars (red)
Created by: davidvachon1