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Light and Stars Universe Ch.5 & 19, Astrophysics Ch.3 Physics of Astronomy, winter week 5 Star Date Star and Light pretest Overview of Universe Ch.5: Light Preview of Universe Ch.19: Stars Minilectures and workshops
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Universe Ch.5: The Nature of Light All light travels with speed c in vacuum Speed = wavelength * frequency Stars are nearly blackbodies (BB) The peak wavelength of a BB decreases with temperature: (m) = 3x10 -3 /T(K) The intensity of radiation from a star increases strongly with temperature: F= T 4 where = 5.67 X 10 -8 W m -2 K -4 Spectra can have emission and absorption lines due to quantum transitions in atoms Spectra from moving sources are Doppler-shifted
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Light as electromagnetic waves
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Elemental spectra
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Emission and Absorption lines
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Blackbodies and Stellar spectra Ch.5 # 43: Animation 5.1 Starry Night: Ch.5 # 46
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Universe Ch.19: The Nature of Stars Hotter stars are bluer Luminosity = power emitted by star Power = Energy/time Energy = mc 2 is released by fusion reactions Flux = intensity of emission = power/area F = T 4 = L/4 R 2, so L~ T 4 R 2 Hotter and bigger stars are more luminous Brightness depends on luminosity and distance Magnitude measures brightness logarithmically
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Distance and brightness of stars Ch.19 # 59: Animation 19.1, parallax Starry Night: Ch.19 #61 (colored pairs) #63: Use Starry Night to investigate the brightest stars. Turn on constellations. Which are most luminous? Which are most distant? What about six months later?
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Minilectures and workshops Mon.2.Feb: Universe Ch.5.1-3, #6, 11 (Jared + Tristen) Universe Ch.5.4-5, #25 (Brian + Jenni) Universe Ch.5.6-8, #27, 29 (Erin + Joey) Universe Ch.5.9, #34, 36 (Matt + Chelsea) Universe Ch.19.1, #25 (Annie + Mary) Tues.3.Feb: HW due on Physics Ch.6 Overview of CO Ch.3 and workshop on Ferguson Ex.19 (Spectra) Thus.5.Feb: HW due on Astrophysics (CO) Ch.2 Universe Ch.19.2-3, #34, 35 (Jared + Tristen) Universe Ch.19.4-5, Spectra -> T,Z, #43 (Erin + Joey) Universe Ch.19.6, L(R,T), #46, 50 (Annie + Mary) Universe Ch.19.7,8, HR, #52 (Brian + Jenni) Library workshop? Next week: Astrophysics (CO) Ch.3, Ferguson Ex. 21 (HR diagram) and Electromagnetism + Light
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