112ANNOUNCEMENTS 11/09/11ANNOUNCEMENTS 11/09/11 C.L.U.E. Thursday evening 11/10/11 There WILL be a question about massive starevolution, and we will answer it today in lecture. Survey still open for your indicating the topicsyou are most unsure of for Monday’s exam 3. You do have a textbook, and for most of youruncertainties with the various topics, reading thetext will help!3Short visual review of evolution - sun-like starShort visual review of evolution - sun-like starDeath sequence of the SunUnderstanding stages oflow-mass star deathRadius of the star turning into ared giant is increasing due to thegreat increase in luminosity beingprovided by the fusion occurringin a shell around the core.4EvolutionEvolution of Stars of StarsPart II Part II –– MASSIVE STARS MASSIVE STARS25Learning Learning GoalsGoals:: Explain why the much higher mass of somestars causes their evolution to be so different fromthe Sun.Outline the basic stages of the evolution of amassive star6Closer look atCloser look atstars in Orion:stars in Orion:7Betelgeuse~20 x solar massCan actually SEEthis star’s surface!8How bright will Betelgeuse be when it goesHow bright will Betelgeuse be when it goessupernova?supernova?! m " M = 5log(d) " 5m = M + 5log(d) " 5msn= "15 + log10.005( )" 5msn= "15 + log(200) " 5msn# "17! mfull " moon# "133910Eta Carinae100+ timesas massiveas the Sun.It is somassive thatit can barelyhold itselftogether.Someastronomersthink EtaCarinaemight die ina supernovablast withinour lifetime.http://www.spitzer.caltech.edu/Media/releases/ssc2005-12/ssc2005-12a.shtml1112Some perspectiveCNO cycle41314 No helium flash. Helium carbon fusion starts whentemperature gets high enough(~100,000,000 K) Core does NOT become degenerate Rest of star expandsEvolution for a star >Evolution for a star > 10 times 10 times Sun Sun’’s masss massTriple-alpha fusion of He toC needs extremely high T’sto operate.15✗ Core shrinks, heats✗ Carbon oxygen fusion starts when temperature high enough✗ Fusion continues to heavier and heavier nuclei 16Changes in temperature and luminosity for massive starsChanges in temperature and luminosity for massive stars51718Mass >Mass > 10 10 solar masses solar masses19Fusion to iron marks certain doomFusion to iron marks certain doom2062122What happens to the star?What happens to the star?2324725Summary of the evolution of a high-mass starSummary of the evolution of a high-mass star26 Explain why the much higher mass of somestars causes their evolution to be so different fromthe Sun.Outline the basic stages of the evolution of amassive
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