Lecture10 Black Hole1

# Lecture10 Black Hole1 - Black Holes I Stellar mass black...

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4/6/09 1 Black Holes – I Stellar mass black holes (Martin Gaskell & Milos Milosavljevic) (Hawley & Holcomb, Chapter 9) Astronomy 309R - Spring 2009

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4/6/09 2 Black Holes • Escape velocity: v 2 = 2 G M / R • What would happen if the escape velocity equaled the speed of light? – Light would not be able to escape from the object (this notion has been around since the 18th and the early 19th century: John Mitchell and Pierre-Simon Laplace) • Radius from which light cannot escape is called the Schwarzschild radius (Karl Schwarzschild 1873-1916 derived an exact solution of Einstein’s equation while serving in the German army in the WWI, just before he died). – R S = 2 G M / c 2 • ~3 km for the solar mass • ~9 mm for the Earth mass • six percent of the Sun-Earth distance for 3 million solar masses Astronomy 309R - Spring 2009
4/6/09 3 Causality near a Black Hole: The Event Horizon Schwarzschild radius is an event horizon! The event horizon is a geometric surface that particles, light, or information can traverse only in one direction. The event horizon is not an actual material surface; nothing special happens when passing the horizon as one is palling into a black hole. Space T ime future past Schwarzschild horizon outside the black hole inside the black hole Astronomy 309R - Spring 2009

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4/6/09 4 An Observer Falling into a Black Hole
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## This note was uploaded on 09/14/2009 for the course AST 309 taught by Professor Johnlacy during the Spring '08 term at University of Texas.

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Lecture10 Black Hole1 - Black Holes I Stellar mass black...

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