lecture_tan32 - Key Concepts: Lecture 32: Towards Cosmology...

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Key Concepts: Lecture 32: Towards Cosmology The Distribution of Galaxies: towards a large scale view of the cosmos Why is the sky dark? Implications for the cosmos The Expanding Universe The Age of the Universe since the Big Bang The Distribution of Galaxies Galaxies tend to group together on many scales Gravity is the glue that tries to bind all galaxies together • The group of galaxies of which the Milky Way is a part. • 3 million LY across • 30 total members • Three large spirals Milky Way • Total mass 5x10 12 M sun Groups: The Local Group Clusters of Galaxies Some galaxies are found in dense groups of 100 to 10000 galaxies Few spiral galaxies in clusters Typical sizes 10 million LY across Galaxy collisions are frequent: note galaxies can be changed in a collision, but the existing stars are not affected (stars do not collide). Nearest Galaxy Cluster: Virgo Distance = 50 million LY The Rich Cluster Abell 2218
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C L 0 0 2 4 + 1 6 5 4 Gravitational Lensing Images of distant galaxy Cluster of Galaxies Light from distant galaxies is deflected by the gravitational influence of the intervening cluster o galaxies, analogous to light being deflected by a lens. The amount of deflection tells us about the mass of the cluster or cluster of galaxies The Masses of Clusters • Clusters are bound together by gravity – Using the Doppler shift we can measure the orbital velocities of the galaxies – We can the apply Newton’s version of Kepler’s law to find the mass – They typically have 300x more mass than can
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This note was uploaded on 09/07/2011 for the course AST 1002 taught by Professor Dr.haywoodsmith,jr during the Spring '07 term at University of Florida.

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lecture_tan32 - Key Concepts: Lecture 32: Towards Cosmology...

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