astronomy homework 4 - are sensitive to masses between...

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1. Discuss whether or not dark matter could be black holes of any mass. Give both observational and theoretical reasons for the possibility. Dark Matter can be anything that gives off no light. The full range of possible masses of the dark matter particle go from 1/10^(71) of the Sun (axions) to 10^4 times the Sun (black holes). Baryonic candidates fall in the category of MACHOs. MACHOs are Jupiters, brown dwarfs, white dwarfs, and black holes, they are very dark but have a large mass. There are observational and theoretical constraints for most of these. The observational reasons behind this come from the MACHO Project which is designed to find microlensing events that would reveal massive objects. This happens when an object passes in front of a star and causes it to brighten for a moment, which rarely happens. However, there is also evidence and numbers suggest that there are not enough of these objects to make up for all of the dark matter, but only 20%. The MACHO searches
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Unformatted text preview: are sensitive to masses between brown dwarfs and 100 solar masses black holes. The theoretical considerations as to why black holes would not be considered dark matter, one example is: if Jupiter were dark matter then there would have to be a lot of them, and that means that planet formation must be very efficient and there is constraints on that based on the number of brown dwarfs. 2. Calculate the velocity difference that the Hubble Expansion imparts between one side of the Earth to the other side. Why is the Earth not being ripped apart? The earth is not being affected because gravity is to strong in short distances to be ripped apart by the velocity. 3. Same as 2, but do the calculation for the edges of the Milky Way galaxy. Now, do the same for the effect between the Milky Way Galaxy and the Coma Cluster of Galaxies. This will have a greater affect than on earth because gravity is not as strong in large distances,...
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This note was uploaded on 09/13/2011 for the course AST 301 taught by Professor Harvey during the Spring '07 term at University of Texas at Austin.

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astronomy homework 4 - are sensitive to masses between...

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