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lecture20 - 5/16/08 Globular Clusters Stellar lifetimes...

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Unformatted text preview: 5/16/08 Globular Clusters Stellar lifetimes Learning from star clusters Life after the main sequence He burning Red giants Open Clusters Note the blue stars Note the haze: blue light scattered by dust still in the open cluster Globular Clusters Globular clusters are denser groups of stars Up to 10 6 stars Gravitationally bound do not evaporate over 10 9 years This means we see some globular clusters that formed a long time ago. Laboratories of stellar Globular Clusters Appear very red Have very little gas and dust in them Stars are densely packed! Stellar Lifetimes More massive stars are hotter at the center They burn H to He at the center at a higher rate And thus emit more energy Stars on the main sequence follow a mass-luminosity relation: L ~ M 3.5 Meanwhile: a stars lifetime depends on its mass and luminosity how much mass it has to fuse H to He how quickly its fusing H to He Note: a star spends most of its lifetime on the main sequence the red giant phase afterwards is much shorter Stellar Lifetimes We can roughly compare stellar lifetimes of stars, given their M or L on the main sequence Remember that Luminosity (or power) is Energy/time: L = E/t Meanwhile, the energy produced by a star comes from the fusing of H into He in the core....
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This note was uploaded on 06/11/2008 for the course ASTRO 1 taught by Professor Antonucci during the Spring '08 term at UCSB.

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lecture20 - 5/16/08 Globular Clusters Stellar lifetimes...

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