set3-06-sol - the properties of stars Let M and R be the...

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Astro 346, Spring Semester 2006 Homework, 3rd set, solutions Problem 1: Classifcation oF stars The distance in parsec is just the inverse of the parallax in arcsec. Therefore a) D=50 pc b) D=12.5 pc c) D=300 pc To derive the evolutionary state, we calculate the absolute brightness and then use table 9.2 in the textbook to estimate the star’s position in the H-R-diagram and to determine its spectral type and eFective temperature. a) M V = 12 . 5 White Dwarf, type A0, T e 10 . 000 K b) M V = 3 . 7 dwarf or main sequence star, type ±5, T e 6 . 500 K c) M V = - 1 . 5 giant, type G5, T e 4 . 700 K Problem 2: The Jeans-criterion The starting point is the violation of the hydrostatic stability criterion that we used to calculate
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Unformatted text preview: the properties of stars. Let M and R be the mass and radius of the gas cloud P = n kT . G M m p n R ⇒ kT . G M m p R Next, replace the radius by the density and mass to derive M ’ m p n R 3 ⇒ M & 1 √ m p n kT m p G ! 3 / 2 Using the numbers given for the density and temperature, we obtain M & 3 · 10 36 g ’ 1500 M ¯ Most stars are formed with less than one solar mass, so that thousands of stars are produced, when one of these clouds collapses....
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This note was uploaded on 02/29/2012 for the course PHYS 227 taught by Professor Rabe during the Fall '08 term at Rutgers.

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