Chapter 12: The Deaths and Remnants of Stars
Chapter 12: The Deaths and Remnants of Stars 41087 - AST 115 - A
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This 2 page Bundle was uploaded by Ashley Notetaker on Friday November 6, 2015. The Bundle belongs to 41087 - AST 115 - A at Missouri State University taught by Robert S Patterson in Fall 2015. Since its upload, it has received 18 views. For similar materials see Basic Astronomy in Physics 2 at Missouri State University.
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Date Created: 11/06/15
White Dwarfs: Diameter :~ 10, 000 km (earth size) Mass: < 1.4 Solar Mass Avg. Density: 20 tons/in^3 Observations of Stellar Explosions: 1. Planetary Nebula *Bubble of gas expanding @ 100 km/sec *hot, low luminosity blue-white star @ center *1/2 Ly across 2. Nova *Gas from explosion expanding @ 1,000 km/sec *A star or stellar system that brightens suddenly b 100,000X its original value *After months it gradually fades back to obscurity. 3. Supernova Type Ia: Peak M = -19, Spectrum = no spectral lines Type II: Peak M = -17, Spectrum = spectral lines *Gas from explosion expanding @ 10,000 km/sec *A star or stellar system that brightens suddenly by 100 milX its original value *After months it gradually fades back to obscurity. Post-Main Sequence Evolution of High & Very High Mass Stars: 8 < mass < 25 Solar Mass = High Mass > 25 = Very High (@ 25 either high or very high) *High & Very High mass stars can achieve additional levels of fusion, bc their greater mass allows higher temps to be attained in the contracting core. Evolution Scenario for a 25 Solar Mass Star: *High mass makes core temp & fusion run faster *Carbon is fused into neon in just 600 years *Silicon is fused into iron in just 1 day Stellar Explosions: Explanations of Phenomena’s : White Dwarf & Planetary Nebula: *A low mass star loses its envelope as a “planetary nebula” after becoming a Red Giant for a 2 time. *The core is left behind as a “white dwarf” *Nebula fades after 100,000 years. *White Dwarf is done w/ fusion but the electrons in it have been squeezed into a “degenerate gas” & support. *Eventually white dwarf cools and turns into black dwarf Nova: *White Dwarf is in a close binary system w/ Red Giant *H from Red Giant overflows its “Roche Lobe” & falls into accretion disk *H eventually falls onto surface of White Dwarf, where it heats & explodes fro H fusion *Both stars Survive Supernova: Type Ia: *Same as Nova except, white dwarf is just under Chandrasekhar mass limit 1.4 Solar mass. *Accretion of H from companion causes entire white dwarf to gravitationally collapse & undergo huge explosion. Type II: *High mass star reaches end of evolution. *Iron core suffers gravitational collapse *Then a huge explosion of entire star. *Emission of tremendous E & huge #s of neutrinos
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