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Light and Stars Universe Ch.5 & 19, Astrophysics Ch.3 Physics of Astronomy, winter week 5

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. Universe Ch.5: The Nature of Light.

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Light and Stars Universe Ch.5 & 19, Astrophysics Ch.3 Physics of Astronomy, winter week 5

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  1. Light and StarsUniverse Ch.5 & 19, Astrophysics Ch.3Physics 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

  2. 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: l(m) = 3x10-3/T(K) • The intensity of radiation from a star increases strongly with temperature: F=sT4 where s = 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

  3. Light as electromagnetic waves

  4. Elemental spectra

  5. Emission and Absorption lines

  6. Blackbodies and Stellar spectra • Ch.5 # 43: Animation 5.1 • Starry Night: Ch.5 # 46

  7. Universe Ch.19: The Nature of Stars • Hotter stars are bluer • Luminosity = power emitted by star • Power = Energy/time • Energy = mc2 is released by fusion reactions • Flux = intensity of emission = power/area • F = sT4 = L/4pR2, so L~ T4R2 • Hotter and bigger stars are more luminous • Brightness depends on luminosity and distance • Magnitude measures brightness logarithmically

  8. 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?

  9. 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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