11EvolutionEvolution of Stars of StarsPart II Part II –– MASSIVE STARS MASSIVE STARS2Learning Learning GoalsGoals::Outline the basic stages of the evolution of amassive starState what determines the fate of a star.Explain what a neutron star is and when it mightbe called a pulsar.Describe the events that would lead to yourbeing spaghettified.3Closer look atCloser look atstars in Orion:stars in Orion:4Betelgeuse~20 x solar massCan actually SEEthis star’s surface!256Eta 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.shtml78Some perspectiveCNO cycle3910 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 > 6 SunEvolution for a star > 6 Sun’’s masss massTriple-alpha fusion of He toC needs extremely high T’sto operate.11✗ Core shrinks, heats✗ Carbon oxygen fusion starts when temperature high enough✗ Fusion continues to heavier and heavier nuclei 12Changes in temperature and luminosity for massive starsChanges in temperature and luminosity for massive stars41314Mass > 6 solar massesMass > 6 solar masses15Fusion to iron marks certain doomFusion to iron marks certain doom1651718What happens to the star?What happens to the star?1920621Summary of the evolution of a high-mass starSummary of the evolution of a high-mass star22Bizarre Stellar GraveyardBizarre Stellar GraveyardCuriouser and Curiouser23Neutron Star•White dwarf limit is 1.4 timesthe mass of the Sun•If remnant is more massivethan ~1.4 solar masses --electron degeneracy cannotprovide support•Core collapses into a neutronstar; neutron degeneracyprovides support24Constellation Taurus (the bull)HyadesAldebaran72526http://www.jb.man.ac.uk/~pulsar/Education/Sounds/sounds.htmlConservation of angular momentum means these creatures spinextremely fast! Millisecond pulsars (1000 times per second)27All pulsars are neutron stars, but not all neutron stars are pulsars.Theoretically, what is a pulsar?Observationally, what is a pulsar?What are the characteristics of a neutron star ? How do we know these objects aren’t just white dwarfs?28829You entering a black hole: observer’s point of view.Entering a black hole: your personal point of view.Frames of referenceFrames of referenceDEATH BY BLACK HOLE Neil DeGrasse Tyson30Learning Learning GoalsGoals::Outline the basic stages of the evolution of amassive starState what determines the fate of a star.Explain what a neutron star is and when it mightbe called a pulsar.Describe the events that would lead to yourbeing
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