Unit 10 The Death of Stars.pdf - Thursday, November 15,...

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Thursday, November 15, 2018Unit 10: The Death of StarsGlobular Clusters-Hundreds of thousands of members, all very old and generally metal-poor-Spherical symmetry-Age of a cluster can be judged by theturnoffpoint on the main sequence of itsHertzsprung-Russell Diagram-Turning point: The top of the surviving portion of the main sequence on the clustersH-R diagramPopulation I stars:stars like the Sun which were formed out of interstellar gas anddust that had been seeded with debris from an earlier population of stars-This earlier population have gone through their life cycle and put their material backinto the interstellar medium-Their spectra show strong lines of the heavier elements (metal-rich)-All stars in the irregular, galactic clusters are of this type-Relatively youngPopulation II stars:stars are an earlier generation of stars condensed out of gasclouds that were not enriched with the debris of exploding stars-Spectra show only very weak indications of the heavier elements (metal-poor).-All stars in globular clusters are of this type-Relatively old1
Thursday, November 15, 2018Variable Stars: Mature, pulsating stars-Pulsating variable stars are actually evolved, post-main sequence starsLong Period Variables:-Cool red giants that vary in brightness by a factor of 100 or more over a period ofmonths or years-Occupy upper right side of HR diagram-Many eject large amounts of gas and dust into spaceCepheid Variables:-Recognized by how its light output varies - rapid brightening, followed by gradualdimming-Occupy upper middle of HR diagram-A Cepheid variable brightens and fades because the stars outer envelope cyclicallyexpands and contracts-Region between the upper main sequence and the red-giant branch =instabilitystrip-

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Term
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Tags
Stellar Evolution, Supernova, White dwarf

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