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Stellar Death High Mass Stars

Stellar Death High Mass Stars. Nucleosynthesis. Evolutionary Time Scales for a 15 M  Star. Fe. C. H. He. Used energy. Released energy. Energy Budget. Energy. Fusion Stages. Animation. The Final Second. Fe fusion begins Energy debt results Core contracts - temperature increases.

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Stellar Death High Mass Stars

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  1. Stellar DeathHigh Mass Stars

  2. Nucleosynthesis Evolutionary Time Scales for a 15 M Star

  3. Fe C H He Used energy Released energy Energy Budget Energy Fusion Stages Animation

  4. The Final Second • Fe fusion begins • Energy debt results • Core contracts - temperature increases Uncontrollable gravitational collapse • Nuclei converted back into He • He  protons and neutrons • proton + electron  neutron + neutrino • Core Implodes  Envelope Explodes Supernova

  5. Anazasi Pictographs

  6. The Crab Nebula

  7. Supernova 1987a

  8. Supernova 1998S inNGC 3877

  9. Tycho’s SNR - 1572 Supernova Remnants

  10. Core Remnant • Too massive for electron degeneracy to halt collapse (> 1.4 M) • Neutron Degeneracy can halt collapse • M < 3 M • Strong nuclear force • Neutron Star

  11. Properties of a Neutron Star • Very small • Gravity balanced by strong nuclear force • R = 10 km • Very Faint • Rapid rotation • Conserve angular momentum • 1000 rotations/s • Intense Magnetic Field • One trillion gauss

  12. PSR 0628-28

  13. LGM? • Several more found at widely different places in the galaxy • Power of a power equals total power potential output of the Earth • No Doppler shifts PULSARS

  14. Light Time Argument • An object which varies its light can be no larger than the distance light can travel in the shortest period of variation.

  15. To Darken the Sun Time Delay = Radius/c 500,000 km/300,000 km/s = 1.67 sec

  16. Only candidates: White Dwarfs, Neutron Stars

  17. Pulse Mechanisms • Binary Stars - How quickly can two stars orbit? • Two WD about 1m • Two NS about 1s. • Neutron Stars in orbit should emit gravity waves which should be detectable. • Oscillations - Depends only on density • WD about ten seconds • NS about .001s Little variation permitted. • Rotation - Until the object begins to break up. • WD about 1s • NS about .001s with large variation.

  18. The Crab Pulsar

  19. Rotating Neutron Star

  20. Lighthouse Model

  21. Radiation Magnetic lines of force Electron Synchrotron Radiation

  22. Glitches

  23. SS 433

  24. Relative sizes Neutron Star Earth White Dwarf

  25. Mass Limits • Low mass stars • Less than 8 M on Main Sequence • Become White Dwarf (< 1.4 M) • Electron Degeneracy Pressure • High Mass Stars • Less than 40 M on Main Sequence • Become Neutron Stars (3 M < M <1.4 M) • Neutron Degeneracy Pressure

  26. Supermassive Stars • If stellar core has more than three solar masses after supernova, then no known force can halt the collapse Black Hole

  27. Space-Time No mass Distortion caused by mass

  28. Predictions of General Relativity • Advance of Mercury’s perihelion • Bending of starlight

  29. Advance of Mercury’s Perihelion Advance in arcsec/cen

  30. Apparent position of the star Sun Light from star bent by the gravity of the Sun Bending of Starlight

  31. Low Gravity Very small amount of bending

  32. Stronger Gravity Light at an angle is bent noticeably

  33. Exit Cone and Photon Sphere Photon Sphere

  34. Near a Black Hole

  35. Event Horizon Rs + Singularity Schwarzschild Black Hole Rs = 3(Mass) Mass Rs 3 M 9 km 5 15 10 30

  36. What Can We Know? • Mass • gravity • Charge • Electric Fields • Rotation Rate • Co-rotation

  37. How Can We Find Them? • Look for X-ray sources • Must come from compact source • White Dwarf • Neutron Star • Black Hole • Differentiate by Mass • WD - < 1.4 M • NS - between 1.4 and 3 M • BH - > 3 M

  38. Cygnus X-1

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