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QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. 1 ANNOUNCEMENTS 11/09/11 C.L.U.E. Thursday evening 11/10/11 There WILL be a question about massive star evolution, and we will answer it today in lecture. Survey still open for your indicating the topics you are most unsure of for Monday’s exam 3. You do have a textbook, and for most of your uncertainties with the various topics, reading the text will help! 2 Short visual review of evolution - sun-like star Death sequence of the Sun QuickTime™ and a decompressor are needed to see this picture. Understanding stages of low-mass star death Radius of the star turning into a red giant is increasing due to the great increase in luminosity being provided by the fusion occurring in a shell around the core. 3 Evolution of Stars Part II – MASSIVE STARS 4 Learning Goals: Explain why the much higher mass of some stars causes their evolution to be so different from the Sun. Outline the basic stages of the evolution of a massive star 5 Closer look at stars in Orion: QuickTime™ and a decompressor are needed to see this picture. 6 Betelgeuse ~20 x solar mass Can actually SEE this star’s surface! 7 How bright will Betelgeuse be when it goes supernova? m M 5log(d) 5 m M 5log(d) 5 msn 15 log 10.005 5 msn 15 log(200) 5 msn 17 QuickTime™ and a decompressor are needed to see this picture. m fullmoon 13 8 9 100+ times as massive as the Sun. Eta Carinae It is so massive that it can barely hold itself together. Some astronomers think Eta Carinae might die in a supernova blast within our lifetime. 10 http://www.spitzer.caltech.edu/Media/releases/ssc2005-12/ssc2005-12a.shtml 11 Some perspective CNO cycle 12 13 Evolution for a star > 10 times Sun’s mass No helium flash. Helium carbon fusion starts when temperature gets high enough (~100,000,000 K) Core does NOT become degenerate Rest of star expands Triple-alpha fusion of He to C needs extremely high T’s to operate. QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. 14 Core shrinks, heats Carbon oxygen fusion starts when temperature high enough Fusion continues to heavier and heavier nuclei QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. 15 Changes in temperature and luminosity for massive stars 16 17 Mass > 10 solar masses 18 Fusion to iron marks certain doom 19 20 21 What happens to the star? 22 23 24 Summary of the evolution of a high-mass star 25 Explain why the much higher mass of some stars causes their evolution to be so different from the Sun. Outline the basic stages of the evolution of a massive star 26