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Stellar Death High Mass Stars Nucleosynthesis Evolutionary Time Scales for a 15 M Star Fused Products H 4He 107 yrs. 40 X 106 K 4He 12C Few X 106 yrs 1 X 108 K 1000 yrs. 6 X 108 K 16O, 24Mg Few yrs. 1 X 109 K 28Si, 32S One year 2 X 109 K Days 3 X 109 K < 1 second > 3 X 109 K 16O, 20Ne, 12C 20Ne 24Mg, 4He + 16O 28Si + 56Fe 56Fe Neutrons Time Temperature Energy Budget H Used energy Released energy He C Fusion Stages Fe Animation The Final Second Fe fusion begins Energy debt results Core contracts - temperature increases Uncontrollable gravitational collapse vNuclei converted back into He He protons and neutrons proton + electron neutron + neutrino vCore Implodes Envelope Explodes Supernova Anazasi Pictographs The Crab Nebula Supernova 1987a Supernova 1998S in NGC 3877 Supernova Remnants Tycho’s SNR - 1572 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 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 PSR 0628-28 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 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. To Darken the Sun Time Delay = Radius/c 500,000 km/300,000 km/s = 1.67 sec Only candidates: White Dwarfs, Neutron Stars Pulse Mechanisms Binary Stars - How quickly can two stars orbit? o Two WD about 1m o Two NS about 1s. o Neutron Stars in orbit should emit gravity waves which should be detectable. Oscillations - Depends only on density o WD about ten seconds o NS about .001s Little variation permitted. Rotation - Until the object begins to break up. o WD about 1s o NS about .001s with large variation. The Crab Pulsar Rotating Neutron Star Lighthouse Model Synchrotron Radiation Radiation Magnetic lines of force Electron Glitches SS 433 Relative sizes Earth White Dwarf Neutron Star 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 Supermassive Stars If stellar core has more than three solar masses after supernova, then no known force can halt the collapse Black Hole Space-Time No mass Distortion caused by mass Predictions of General Relativity Advance of Mercury’s perihelion Bending of starlight Advance of Mercury’s Perihelion Advance in arcsec/cen 5599 total advance with respect to the geocenter. 5025 contribution of precession of Earth's equinoxes. 531 Classical or Newtonian contribution of the other planets. 43 General relativity correction (modern theory: 42.98) Bending of Starlight Apparent position of the star Sun Light from star bent by the gravity of the Sun Low Gravity Very small amount of bending Stronger Gravity Light at an angle is bent noticeably Exit Cone and Photon Sphere Photon Sphere Near a Black Hole Schwarzschild Black Hole Event Horizon Rs = 3(Mass) + Rs Singularity Mass Rs 3 M 9 km 5 15 10 30 What Can We Know? Mass gravity Charge Electric Fields Rotation Rate Co-rotation 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 Cygnus X-1