Astrophysics_of_Life

Astrophysics_of_Life - Astrophysics Astrophysics of Life :...

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Unformatted text preview: Astrophysics Astrophysics of Life : of Life : Stars Stars Wave Characteristics: Wavelength- Distance between successive wave peaks Period Time between passing wave peaks Frequency Number of wave peaks passing per unit time (1/Period) Wave Speed wavelength x frequency (follow a crest ) 2 Light Speed is 3x10 8 m/s Wavelength = C O L O R 400nm 500nm 600nm 700nm Visible light ranges in wavelength from ~400 to ~700 nanometers. 3 Electromagnetic Spectrum Electromagnetic Spectrum icrowav Microwav es, cooking heat sunburn most energetic 4 communication detected by our eyes penetrate tissue Blackbodies with different temperatures look like this: 5 Hotter blackbodies are brighter and bluer . Wiens Law Wiens Law Hotter bodies radiate more strongly at shorter wavelengths (i.e. eyre luer they re bluer ). max = 0.29 cm T (K) We can measure a stars temperature from its spectrum! 6 max = 0.29 cm T (K) (Flux) 7 Wien math fun Stefans Law Stefans Law Hotter blackbodies are brighter overall (at every wavelength). F = T 4 where: F = total radiative flux = constant 8 Emission Line Spectra 9 Each element produces its own unique pattern of lines Absorption Line Spectra Spectrum of the Sun Spectrum of the Sun: 10 Luminosity and Apparent Brightness Star B is more luminous, but they have the same brightness seen from as seen from Earth. Apparent Brightness and Inverse Square Law ight appears fainter Light appears fainter with increasing distance. If we increase our distance from the light source by 2, the light energy is spread out over four times the area. (area of sphere = 4 d 2 ) Luminosity Flux = 4 d 2 o know a stars luminosity we must measure its apparent To know a star s luminosity we must measure its apparent brightness (flux) and know its distance. Then, Luminosity = Flux *4 d 2 The Magnitude Scale d ntury BC Hipparchus Faintest Faintest 2 nd century BC, Hipparchus ranked all visible stars brightest = magnitude 1 faintest = magnitude 6....
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Astrophysics_of_Life - Astrophysics Astrophysics of Life :...

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