lec28 - Lecture 28 White Dwarfs and Supernovae Lecture 28...

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Lecture 28 White Dwarfs and Supernovae Purdue University, Astronomy 364 1 Lecture 28
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Are white dwarfs white? • White dwarfs have a range of temperatures (i.e. colors)
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Composition • Heavy nuclei are pulled below the surface, while hydrogen rises to the top, layered above the helium.
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Sirius B Wobble in the position of Sirius A led to the prediction of an unseen companion. Sirius B Sirius A M/M Sun 1.053 2.3 L/L Sun 0.03 23.5
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Density and Pressure Lecture 28 Purdue University, Astronomy 364 5 Sirius B has a radius R=0.0084R sun , so the average density of the star is ρ = M M R R 3 2 × 10 6 2 × 10 9 kgm 3 . For it to be in hydrostatic equilibrium, the central pressure must be P c 2 GM R 3 GM 2 2 π R 4 M M 2 R R 4 P c , 2 × 10 8 P c , 10 18 atm . It cannot be provided thermally, as it would require a central temperature T c ~ 6 x 10 9 K .
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Degenerate Electrons Heisenberg uncertainty principle: Δ x Δ p
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lec28 - Lecture 28 White Dwarfs and Supernovae Lecture 28...

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