rev.ex3.fall.11 - Astronomy Bizarre 309N Fall 2011 (47580)...

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Astronomy Bizarre Wheeler 309N Fall 2011 October 17, 2011 ( 47580) Review for Test #3 Supernovae (cont.), Supernova 1987A, Neutron Stars, Einstein’s Gravity Gravitational Radiation — A systematic "wiggling" of the curvature of space sends out gravitational waves of space curvature. Carry energy, angular momentum from a binary star system. Double white dwarfs — If the first white dwarf does not grow and explode, the second star can evolve to produce a white dwarf, resulting in two orbiting white dwarfs. These will spiral together by gravitational radiation, until smaller mass, larger radius white dwarf fills its Roche lobe. Mass transfer causes small white dwarf to be transferred essentially entirely to the larger one. May get larger white dwarf or, thermonuclear explosion. Light curves – brightness versus time of supernova. Type Ia brightest, Type Ib, Type Ic, Type II dimmer. Light curve mechanisms – shock energy plus radioactive decay. Ejecta must be large in radius before the matter is transparent enough for light to leak out. If the star is too small originally (Ia, Ib, Ic) all shock energy goes into energy of motion; light curve must be from radioactive decay. Explosion of carbon and oxygen or silicon – equal numbers of protons and neutrons, so first make nickel- 56. Weak force causes radioactive decay in 6 days (half-life) to cobalt-56 and then in 77 days (half- life) to iron-56. Heat from decay provides delayed source of light. Type Ia brighter, need more nickel than Ib, Ic, hence different mechanism.
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This note was uploaded on 11/13/2011 for the course AST 309N taught by Professor Wheeler during the Fall '11 term at University of Texas at Austin.

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rev.ex3.fall.11 - Astronomy Bizarre 309N Fall 2011 (47580)...

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