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Lecture march 18

# Lecture march 18 - Less than 1 of stars in solar...

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Majority of stars have p in range 1/10 < p/pwater < 10 White dwarfs have R = 10^-2 R(sun) Mass star = Mass (sun) P(white dwarf) = 10^6 p (sun) Red giants have Radius of star = 10^2 Radius of sun Mass of star = Mass of Sun P (red giant) = 10^-6 p (sun) O stars (the most luminous stars) are so rare that there are no O stars within a sphere containing the nearest 10^6 pc^3 (i.e. radius r=62 pc) There are 50,000 Main Sequence stars Only about 20 M Giant stars Most common are white dwarfs and Main Sequence M stars Only 0.03 Main Sequence O stars (i.e. have to search 30x 10^6 pc ^3 to find even one) Only 1 star in 4x10^6 is an O star 90% of all stars lie in Main Sequence 10% of stars in solar neighborhood are white dwarfs
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Unformatted text preview: Less than 1% of stars in solar neighborhood are giants and super giants 1913 Henry Norris Russell (American Astronomer) had parallax distances to these stars in the solar neighborhood and plotted them on this diagram. o Could determine their luminosities from inverse sqare law and apparent brightness o He missed stars of high L because there are too few nearby o Still saw M-S pattern o 1911: E. Hertsprung, Danish astronomer studied stars in star clusters plotting brightness vs. color index. Star cluster all stars roughly same distance from earth implies all F, for stars yield L’s by same inverse square law Color index was consistent with surface temperature and spectral type o...
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