Slide 1Slide 2Slide 3Slide 4Slide 5The “evolutionary track” of a 1M starSlide 7Slide 8Slide 9Slide 10Slide 11Like all desperate measures, each fix is less successful than the first…Slide 13For a massive star…Slide 15Slide 16Slide 17Slide 18Iron has the least mass per nuclear particle. END OF THE LINE!Slide 20Slide 21The Death Throes of a High Mass StarWhen fusion stops:Uh oh…Supernovae in other galaxies can be as bright as the whole galaxy! Can see them at HUGE distances!PowerPoint PresentationSlide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33White Dwarfs are bizarre.How did they get so dense?“Electron Degeneracy Pressure”White dwarfs collapse until they are dense enough that “quantum mechanical” pressure takes over!Differences between thermal and degeneracy pressureSize of a White DwarfSlide 40Slide 41What happens as white dwarfs get more massive?How could white dwarf masses sometimes become higher than the 1.4M Chandrasekhar mass?Slide 44What happens to the core when fusion stops:Electrons just can’t handle it!The whole core becomes solid NEUTRONS!!!Dying massive stars form neutron starsObserving Neutron StarsSlide 50Slide 51Slide 52Rotation was the only reasonable mechanism for producing these pulsesPulsarsSlide 55Slide 56What happens if neutron degeneracy pressure can’t support the core either?All objects have an “Escape Velocity”Escape velocity depends on mass and size!So how smooshed do you have to get to be a black hole?What’s Your Schwarzschild Radius?Slide 62What about the Sun? Slide 64What does the Schwarzschild radius mean?Slide 66Slide 67Slide 68Slide 69Slide 70Stars orbiting a black hole in the center of the galaxy?Slide 72Summary of Star DeathSlide 74What are binary stars?Binaries can change with time:Before “mass transfer”After “mass transfer”The star ignites!If it weren’t degenerate:Slide 81Slide 82Slide 83Astronomy 101High-Mass Stars and then Stellar Graveyard7/16/09Astronomy 101Astronomy Picture of the DayAstronomy 101Something CoolBetelgeuseAstronomy 101Outline for TodayAstronomy Picture of the Day Something CoolBusinessReturn Lab 6Q&A session High Mass Star EvolutionWhite Dwarfs, Neutron Stars, & Black HolesMinute WritingBreakLab 8Astronomy 101Questions for TodayWhat happens to massive stars when they run out of Hydrogen?What happens when a star goes supernova?What supports white dwarfs and neutron stars?How do neutron stars pulse?What makes something a back hole?FadesCoolsThe “evolutionary track” of a 1M, starHydrogen FusionCore Collapse, Hydrogen Shell BurningOuter layers EjectedPlanetary NebulaWhite Dwarf Neutron Star Black HolesSupernova (type II)Iron CoreHelium Core Burning,Hydrogen Shell BurningHydrogen and Helium Shell Burning, Carbon CoreOnion Layer Shell BurningHydrogen FusionCore Collapse, Hydrogen Shell BurningOuter layers EjectedPlanetary NebulaWhite Dwarf Neutron Star Black HolesSupernova (type II)Iron CoreHelium Core Burning,Hydrogen Shell BurningHydrogen and Helium Shell Burning, Carbon CoreOnion Layer Shell BurningWhen Hydrogen Runs Out . . .Core contracts and heatsHelium fusion immediately sparkedHydrogen fusion continues in shellStar gets biggerH HHeWhen Helium Runs Out . . .Core contracts and heatsCarbon fusion immediately sparkedHelium and Hydrogen fusion continues in shellStar gets biggerH HHeHHeCOnion Layer BurningLike all desperate measures, each fix is less successful than the first…Core is hotter and hotter each time.Burn rate is faster and faster……but less and less energy is released per fusion reaction (i.e. energy difference between H and He is particularly large).Each Cycle is shorter than the one before!Like all desperate measures, each fix is less successful than the first…Core is hotter and hotter each time.Burn rate is faster and faster……but less and less energy is released per fusion reaction (i.e. energy difference between H and He is particularly large).Each Cycle is shorter than the one before!For a massive star…H-burning: 7 million years (107 K)He-burning: 500,000 years(109 K)C-burning: 600 years (1011 K)Ne-burning: 1 year (1012 K)O-burning: 6 months (1013 K)Si-burning: 1 day! (1014 K)What would happen if carbon had the smallest mass per nuclear particle?A) Supernovae would be more commonB) Supernovae would never occurC) High-mass stars would have hotter coresD) Iron would be more abundantWhat would happen if carbon had the smallest mass per nuclear particle?A) Supernovae would be more commonB) Supernovae would never occurC) High-mass stars would have hotter coresD) Iron would be more abundantHydrogen FusionCore Collapse, Hydrogen Shell BurningOuter layers EjectedPlanetary NebulaWhite Dwarf Neutron Star Black HolesSupernova (type II)Iron CoreHelium Core Burning,Hydrogen Shell BurningHydrogen and Helium Shell Burning, Carbon CoreOnion Layer Shell BurningHydrogen FusionCore Collapse, Hydrogen Shell BurningOuter layers EjectedPlanetary NebulaWhite Dwarf Neutron Star Black HolesSupernova (type II)Iron CoreHelium Core Burning,Hydrogen Shell BurningHydrogen and Helium Shell Burning, Carbon CoreOnion Layer Shell BurningIron has the least mass per nuclear particle. END OF THE LINE!Hydrogen FusionCore Collapse, Hydrogen Shell BurningOuter layers EjectedPlanetary NebulaWhite Dwarf Neutron Star Black HolesSupernova (type II)Iron CoreHelium Core Burning,Hydrogen Shell BurningHydrogen and Helium Shell Burning, Carbon CoreOnion Layer Shell BurningHydrogen FusionCore Collapse, Hydrogen Shell BurningOuter layers EjectedPlanetary NebulaWhite Dwarf Neutron Star Black HolesSupernova (type II)Iron CoreHelium Core Burning,Hydrogen Shell BurningHydrogen and Helium Shell Burning, Carbon CoreOnion Layer Shell BurningThe Death Throes of a High Mass StarIt really really really runs out of fuel.•Low mass stars run out because they don’t get hot enough to burn what they have left.•High mass stars run out because they’ve burned everythingeverything! Can’t burn iron!When fusion stops:Core cools.Pressure dropsStar collapses!This releases a huge amount of the star’s gravitational potential energy! Used to be Massive & Big!Now it’s Massive & Tiny!Uh oh…Over a solar mass of fuel burns in less than a DAY!HUGE LUMINOSITY!Supernovae in other galaxies can be as bright as the whole galaxy!Can see them at HUGE distances!We’re made of all the elements created while powering desperate stars or during supernova explosionsMore Fusion During ExplosionHydrogen FusionCore
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