H - instability strip, the star becomes unstable and begins...

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H-R diagrams and observations of star clusters reveal how red giants evolve * The age of a star cluster can be estimated by plotting its stars on an H-R diagram * The cluster’s age is equal to the age of the main-sequence stars at the turnoff point (the upper end of the remaining main sequence) * As a cluster ages, the main sequence is “eaten away” from the upper left as stars of progressively smaller mass evolve into red giants Stellar evolution has produced two distinct populations of stars * Relatively young Population I stars are metal rich; ancient Population II stars are metal poor * The metals (heavy elements) in Population I stars were manufactured by thermonuclear reactions in an earlier generation of Population II stars, then ejected into space and incorporated into a later stellar generation * Many mature stars pulsate * When a star’s evolutionary track carries it through a region in the H-R diagram called the
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Unformatted text preview: instability strip, the star becomes unstable and begins to pulsate * Cepheid variables are high-mass pulsating variables * RR Lyrae variables are low-mass, metal-poor pulsating variables with short periods * Long-period variable stars also pulsate but in a fashion that is less well understood * There is a direct relationship between Cepheid periods of pulsation and their luminosities Mass transfer can affect the evolution of close binary star systems * Mass transfer in a close binary system occurs when one star in a close binary overflows its Roche lobe * Gas flowing from one star to the other passes across the inner Lagrangian point * This mass transfer can affect the evolutionary history of the stars that make up the binary system...
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This note was uploaded on 12/15/2011 for the course AST AST1002 taught by Professor Emilyhoward during the Fall '10 term at Broward College.

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