AST-L20-ch1213__3

AST-L20-ch1213__3 - AST 1002 Today's Lecture: purpose &...

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1 1) Review: main sequence lives of low mass stars Red Giant formation 2) Hotter, more Massive stars CNO cycle nucleosynthesis – creation of the heavier elements 3) Supernova 4) Split class: “ the li fe and t i me s of A l bert E n te (Planetarium) Today’s Lecture: purpose & goals S upernova 1987a E n Memor a , Nat ona A c ademy of en e s, Wa h ngton D . C 2005 is the Einstein Centennial! Stellar Midlife/Death large stars “live fast, die young” AST 1002 Planets, Stars and Galaxies Review t MS = 1/M 2.5 x 10 10 years Stellar Lifetimes Most luminous stars live shortest lives also, largest (most massive ) stars 80-100M Blue giants few tens of thousands of years Very few recent young still here. Less luminous stars live longer which are the less massive, smaller stars 0.08-0.12M Red dwarf stars over a trillion years ALL still here!! (age of the universe 15 billion years) Formation of Red Giants remember: Stefan-Boltzmann Law: L = 4 π R 2 . σ T 4 The e are the ame tarat d fferent tage of fe!! Review2: Lives of Less Massive Stars Low mass stars follow a pattern: protostar main sequence star stable when gravity and pressure balance. star dies when hydrogen used up at core. Small stars no mixing @core degenerate helium ashe. red giant hydrogen shell and helium core burning shrinks core which gets hotter ; expands outer surface which gets cooler high luminosity Red giant Planetary nebula Blow off outer surface (stellar wind) leaving behind bare core white dwarf (no fusion, very hot, very small
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This note was uploaded on 10/13/2011 for the course AST 1002 taught by Professor Gerstein during the Spring '08 term at FSU.

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AST-L20-ch1213__3 - AST 1002 Today's Lecture: purpose &...

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