UT AST 309N - Review for Test 3 Neutron Stars and Black Holes (3 pages)

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Review for Test 3 Neutron Stars and Black Holes



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Review for Test 3 Neutron Stars and Black Holes

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Pages:
3
School:
University of Texas at Austin
Course:
Ast 309n - Lives and Deaths of Stars

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Astronomy Bizarre 309N FALL 2004 47855 Wheeler October 25 2004 Review for Test 3 Neutron Stars and Black Holes Neutron stars mass of sun radius 10km density like atomic nucleus huge gravity at surface Discovery of pulsars pulsating radio sources Interpretation of pulsars as rotating magnetized neutron stars Role of magnetic field to cause radiation misalignment of rotation axis magnetic axis Production of pulses probably related to strong electric magnetic fields at magnetic poles ejection of electrons annihilation of positrons About 600 pulsars known perhaps a billion neutron stars in the Galaxy Pressure support from quantum pressure of neutrons plus nuclear repulsion Maximum mass of neutron star about 2 solar masses Neutron stars as binary X rays sources X ray pulsars accreted gas channeled to magnetic poles neutron star spins faster as it accretes X ray transients 4 or 5 in Galaxy Outburst every few years for a month Probably a disk instability like a dwarf nova but with the white dwarf replaced by a neutron star X ray Bursters about 30 in the Galaxy Burst every few hours for minutes Probably the neutron star analog of a classical nova Matter accretes on surface of neutron star Hydrogen is supported by thermal pressure burns to helium Helium is supported by quantum pressure and is unregulated and explodes Often found in globular clusters Black Hole History Mitchell Laplace escape velocity Event Horizon Since nothing with velocity less than or equal to the speed of light can pass backward through an event horizon the information that an event occurred cannot pass through so an event on the wrong side of an event horizon can never be known to an observer on the opposite side hence the name Schwarzschild Radius the distance of the event horizon from the center of a black hole For a nonrotating non charged black hole the size of the event horizon is 3 kilometers x mass solar mass i e if the Sun were a black hole its event horizon would be 3 kilometers in radius the



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