Lec22 - Class News Mid-Term#2 Friday Oct. 4 Sample multiple...

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Class News • Mid-Term#2 Friday Oct. 4 • Sample multiple choice test on web page as – mt2-sample-mc.pdf • Will upload short answer sample later today or tonight. • HW#4 due classtime Wed. – HW help session Tuesday 5:15 p.m. in lecture room.
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18. The Bizarre Stellar Graveyard J. B. S. Haldane (1892 – 1964) from Possible Worlds , 1927 Now, my suspicion is that the Universe is not only queerer than we suppose, but queerer than we can suppose.
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Planetary Nebulae evolve to White Dwarf Stars
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Planetary Nebulae Ring Nebula Hourglass Nebula The collapsing core becomes a White Dwarf
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Degenerate Core Leftover • Central star of aPlanetary Nebula heats up as it collapses. • Star has insufficient mass to get hot enough to fuse Carbon. • Gravity is finally stopped by the force of electron degeneracy pressure . • The star is now stable…. ..
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Planetary Nebulae Cat’s Eye Nebula Twin Jet Nebula
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Degeneracy Pressure Two particles cannot occupy the same space with the same momentum (energy). For very dense solids, the electrons cannot be in their ground states, they become very energetic---approaching the speed of light. – the electrons play a game of musical chairs The pressure holding up the star no longer depends on temperature.
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White Dwarfs. .. • are stable: gravity vs. electron degeneracy pressure • generate no new energy. • slide down HR-diagram as they radiate their heat into space, getting cooler and fainter. • are very dense; 0.5 - 1.4 M packed into a sphere the size of the Earth!
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White Dwarfs • Degenerate matter obeys different laws of physics. • The more mass the star has, the smaller the star becomes! • increased gravity makes the star denser • greater density increases degeneracy pressure to balance gravity
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White Dwarfs Sirius A + B in X-rays Sirius B is the closest white dwarf to us
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• If WD in close binary: – matter from giant star can
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This note was uploaded on 02/01/2012 for the course PHYS 133 taught by Professor Staff during the Fall '08 term at University of Delaware.

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Lec22 - Class News Mid-Term#2 Friday Oct. 4 Sample multiple...

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