lecture10 - Lecture 10: White Dwarfs, Neutron Stars, and...

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Unformatted text preview: Lecture 10: White Dwarfs, Neutron Stars, and Black Holes White Dwarfs Review: end states of low (<2M sun ) and intermediate (2-9 M sun ) mass stars outer layers are thrown off into a planetary nebula remaining core is carbon for low-mass stars, mostly oxygen for intermediate mass remaining core is initially very hot! (~30,000 degrees) What wavelength would you use to look for white dwarfs? A. Radio B. Infrared C. Visible D. Ultraviolet Sirius is a double star consisting of a main sequence star of spectral type A (T=9000 degrees) and a white dwarf. Which one is the white dwarf in this HST image? A. Upper right B. Lower left A. Upper right B. Lower left Sirius is a double star consisting of a main sequence star of spectral type A (T=9000 degrees) and a white dwarf. Which one is the white dwarf in this X-ray image*? A. Upper right B. Lower left *The HST and X- ray images were taken years apart, so don't assume they are in the same position as before. White Dwarf Cooling WD has no energy source, so it must cool as it radiates its existing energy takes 1-10 billion years to slip off the HR diagram More massive white dwarfs are: A. Larger than less massive ones B. Smaller than less massive ones C. The same size D. Size does not depend on mass More massive white dwarfs are: A. Hotter than less massive ones B. Cooler than less massive ones C. The same temperature D. Temperature does not depend on mass White Dwarf Support electron degeneracy pressure roughly a million times denser than than an ordinary star* (5 tons per teaspoon)* typically 1 Msun packed into the size of the Earth! more mass makes it smaller *Note: R sun = 100 R earth How strong is a 1 M sun white dwarf's surface gravity, relative to Earth's surface gravity?* A. more than 3x10 5 times stronger B. 3x10 5 times stronger C. the same, because the WD and the Earth are the same size D. 3x10 5 times weaker E. More than 3x10 5 times weaker *Note: M sun = 3x10 5 M earth White Dwarf Support theory: electron degeneracy can't support >1.4 M sun (Chandrasekhar limit) observation: every WD ever observed has mass <1.4 M sun Subramanyan Chandrasekhar (Nobel Prize 1984) Accreting Binaries Big star is stretched. Why?...
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This note was uploaded on 02/16/2010 for the course BIS 34957 taught by Professor Britt during the Spring '10 term at UC Davis.

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lecture10 - Lecture 10: White Dwarfs, Neutron Stars, and...

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