Slide 1

YSS - Intro. to Observational Astrophysics (ASTR 205). Class #10 The Bizarre Stellar Graveyard (Chapter 13) Professor: Jos Maza June 20, 2011 Professor: Jos Maza June 20, 2011 Slide 2 White Dwarfs Degeneracy pressure Electron degeneracy pressure A teaspoon of white dwarf matter would weigh several tons. Degeneracy pressure Electron degeneracy pressure A teaspoon of white dwarf matter would weigh several tons. Slide 3 Slide 4 Slide 5 What can happen to a white dwarf in a close binary system? The white dwarf would generate an accretion disk. What can happen to a white dwarf in a close binary system? The white dwarf would generate an accretion disk. Slide 6 Slide 7 Novae Slide 8 Slide 9 Slide 10 White dwarf supernovae Chandrasekhars limit 1.4 M When a carbon WD reaches a mass near 1.4 M its temperature rises high enough for carbon fusion to ignite. White Dwarf Supernova Chandrasekhars limit 1.4 M When a carbon WD reaches a mass near 1.4 M its temperature rises high enough for carbon fusion to ignite. White Dwarf Supernova Slide 11 Slide 12 Neutron Stars Radius 10 km Neutron degeneracy pressure supports neutron stars. Density 10 15 g/cm 3 Radius 10 km Neutron degeneracy pressure supports neutron stars. Density 10 15 g/cm 3 Slide 13 Slide 14 In 1967 graduate student Jocelyn Bell working at Cambridge discovered a new type of radio source. These sources emitted a periodic pulse with a very short period 1.337 seconds. These sources were named PULSARS. In 1967 graduate student Jocelyn Bell working at Cambridge discovered a new type of radio source. These sources emitted a periodic pulse with a very short period 1.337 seconds. These sources were named PULSARS. Slide 15 Slide 16 Crab Pulsar Slide 17 Crab Nebula Slide 18 Slide 19 Slide 20 Slide 21 Black Holes Escape velocity grows if the radius decreases. There is a radius at which the escape velocity approaches the speed of light. Schwarzschild radius. Escape velocity grows if the radius decreases. There is a radius at which the escape velocity approaches the speed of light. Schwarzschild radius. Slide 22 Slide 23 Slide 24 Event horizon Schwarzschild radius Event horizon Schwarzschild radius Slide 25 Slide 26 Slide 27 Slide 28 Gamma-Ray Bursts In 1973 the first Gamma Ray Burst was announced. At first it was thought these were just a variation of the X-Ray burst that can arise from neutron stars in close binary systems. In 1973 the first Gamma Ray Burst was announced. At first it was thought these were just a variation of the X-Ray burst that can arise from neutron stars in close binary systems. Slide 29 Slide 30 Slide 31 Afterglow: hypernova