stellarexplosions

stellarexplosions - Stellar Explosions Supernovae...

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1 Novae (detonations on the surface of a star) Supernovae (detonations of a star) Gamma Ray Bursts (formation of a black hole?) Stellar Explosions Novae White dwarf in close binary system WD's tidal force stretches out companion, until parts of outer envelope spill onto WD. Surface gets hotter and denser. Eventually, a burst of fusion . Binary brightens by 10'000's! Some gas expelled into space. Whole cycle may repeat every few decades => recurrent novae . Nova V838Mon with Hubble, May – Dec 2002 4.2 pc ࣣ৭ֆרͷΑ͏ ! ࣣ৭ֆרͷΑ͏ Death of a High-Mass Star M > 8 M Sun Iron core Iron fusion doesn't produce energy (actually requires energy) => core shrinks and heats up Ejection speeds 1000’s to 10,000’s of km/sec! (see DEMO) Remnant is a “neutron star” or “black hole”. T ~ 10 10 K, radiation disrupts nuclei, p + e => n + neutrino Collapses until neutrons come into contact. Rebounds outward, violent shock ejects rest of star => A Core-collapse or Type II Supernova Such supernovae occur roughly every 50 years in Milky Way. Binding Energy per nucleon
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2 Example Supernova: 1994D in NGC 4526 Cassiopeia A: Supernova Remnant A Carbon-Detonation or “Type Ia” Supernova Despite novae, mass continues to build up on White Dwarf. If mass grows to 1.4 M Sun (the "Chandrasekhar limit"), gravity overwhelms the Pauli exclusion pressure supporting the WD, so it contracts and heats up. This starts carbon fusion everywhere at once.
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stellarexplosions - Stellar Explosions Supernovae...

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