Estimating Mass of the Milky Way Galaxy

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Homework Help Overview

The discussion revolves around estimating the mass of the Milky Way galaxy based on the sun's rotation around its center. The original poster provides specific parameters such as the distance from the sun to the center of the galaxy and the time taken for one complete rotation, while also assuming a uniform mass distribution.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to set up the problem using gravitational equations and questions whether their setup is correct, particularly regarding unit conversions. Other participants raise concerns about the accuracy of the equations used and suggest clarifications on the mass terms involved.

Discussion Status

The discussion is ongoing, with participants providing feedback on the original poster's approach and equations. Some guidance has been offered regarding unit conversions and the correct application of gravitational principles, but no consensus has been reached on the exact method to use.

Contextual Notes

Participants are navigating through the complexities of gravitational equations and the implications of mass distribution assumptions. There is an emphasis on ensuring proper unit consistency, particularly in converting years to seconds.

myoplex11
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Homework Statement


The sun rotates around the center of the milky way galaxy at a distance of about 30,000 light years (1ly= 9.5*10^15m). if it takes about 200 million years to make one rotation, estimate the mass of our galaxy. Assume that the mass distribution of galaxy is concentrated mostly in a central uniform sphere.


Homework Equations



G Msun Mgalamy / r^2 = Mgalaxy v^2/ r


The Attempt at a Solution


r= (30000 * (9.5 * 10^5) ) m
v= 2 * pi * r / 200 million years
i know i have to convert the years into seconds is my setup right?
 
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You have the equations slighty wrong. Your's would cancel the mass of the galaxy leaving only the mass of the sun.

And yes - you should work in m/kg/s
 
i am not sure what equation to use
 

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