f10_nov23 - Interpretation of Hubbles Law The fact that we...

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Ast 307 - Nov. 23, 2010 • The fact that we see other (distant) galaxies moving away from us is not because we have a special location in the universe; we would see the same thing from any location. The idea that we are not in a privileged place in the universe is called the cosmological principle . Interpretation of Hubble’s Law Galaxies appear to be moving apart because the overall scale of the Universe is changing. (Exception: galaxies that are bound together by gravity do not obey Hubble’s Law!) Hubble’s constant tells us the age of universe because it relates the velocities and distances of all galaxies Age = ~ 1 / H 0 Distance Velocity The Age of the Universe
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Hubble’s Law: A Cosmological Redshift The last step: depends on the relation called “Hubble’s Law” Distances from Redshifts distance? Age and the Distance to Galaxies Notice that the linear distances between faraway galaxies change while the light is traveling. Furthermore, for extremely large distances, the simple redshift law breaks down and you have to use the relativistic version. To avoid confusion, astronomers often speak of lookback time or redshift rather than distance distance? Age and the Distance to Galaxies
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The Cosmic Neighborhood (“Local Group” of Galaxies) The Cosmic Neighborhood on a Larger Scale Distribution of Galaxies on the Sky Distribution of Galaxies in Space
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large structures: superclusters and voids Distribution of Galaxies in Space Galaxy Interactions: The M81 Group Sgr is a small galaxy that is interacting with, and apparently being disrupted
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This note was uploaded on 04/30/2011 for the course AST 317 taught by Professor Dinerstein during the Fall '10 term at University of Texas at Austin.

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f10_nov23 - Interpretation of Hubbles Law The fact that we...

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