33-10 - Whats a black hole Stars die in 3 ways Mass smaller...

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What s a black hole? Stars die in 3 ways: Mass smaller that 1.4 Sun s mass: as nuclear fuel burns out, becomes a brown dwarf (blob of frozen gas) Mass between 1.4 and about 3 Msun : supernova explosion As fusion fuel runs out, star collapses under its own gravity Eventually density/temperature so great it reignites in a massive sudden explosion: supernova Most of its mass (heavy elements!) is expelled into its galaxy Remnant is a neutron star ( solid blob of neutrons * !!) or other compact object , typically radiates lots of energy ( pulsar ) Mass greater than about 3 Msun: collapses too quickly for the supernova stage, into a black hole General relativity says light is bent by strong gravity When density is so big, g field gets so intense that light cannot escape: black hole Black hole s intense g field sucks up all nearby matter… Most galaxies have a BH at their center
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from NY Times Artists conception of Black Hole with M=10 10 M sun What is required to make gravitational escape velocity = speed of light?
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Unformatted text preview: Recall from PHYS 114: v ESC = 2 GM EARTH R EARTH → c = 2 GM BH R BH R BH = 2 GM BH c 2 ? We used classical physics, but GR calculation gives the same result Schwarzschild radius: “ horizon ” of BH of mass M “ event horizon ” = radius such that nothing can escape (all light cones bend into the BH; “ future ” of any object there lies entirely inside the BH Most BHs have spin – stars spiral into them our solar system on the same scale 72 73 Unification of Fundamental Forces of Physics Electricity Magnetism Light Beta-decay Neutrinos Protons Neutrons Pions, etc. Earth Gravity Celestial Mech. Electromagnetism Weak Interaction Strong Interaction Universal Gravity Spacetime Geom. Electroweak Interaction “ Standard Model ” General Relativity ? 1864 Maxwell 1965 1971 Weinberg, Glashow & Salam 1973 1976-- 1687 Newton 1916 Einstein 2014? pre-20 th c. 20 th c. 1907 Einstein & Minkowski String theory? Supersymmetry? GUTs?...
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