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1	Astro 1050 Wed. Oct. 15, 2003 Today: Chapter 8, Properties of Stars
2	L, T, R, and the H-R diagram L = 4 p R² sT⁴ The main sequence consists very roughly of similar size stars The giants, supergiants, and white dwarfs are much larger or smaller
3	Lines of constant R in the H-R diagram
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5	Different “types” of H-R diagrams
6	Luminosity Classes
7	Spectra of Different Luminosity Classes
8	Spectroscopic “Parallax”
9	What fundamental property of a star varies along the main sequence?
10	What fundamental property of a star varies along the main sequence?
11	Masses of Binary stars
12	Masses of Binary stars
13	Masses of Binary stars
14	Measuring a and P of binaries Two types of binary stars Visual binaries: See separate stars a large, P long Can’t directly measure component of a along line of sight Spectroscopic binaries: See Doppler shifts in spectra a small, P short Can’t directly measure component of a in plane of sky If star is visual and spectroscopic binary get get full set of information and then get M
15	Masses and the HR Diagram Main Sequence position: M: 0.5 M_Sun G: 1 M_Sun B: 40 M_sun Luminosity Class Must be controlled by something else
16	The Mass-Luminosity Relationship L = M^3.5
17	Eclipsing Binary Stars System seen “edge-on” Stars pass in front of each other Brightness drops when either is hidden Used to measure: size of stars (relative to orbit) relative “surface brightness” area hidden is same for both eclipses drop bigger when hotter star hidden tells us system is edge on useful for spectroscopic binaries