3. Mass Enclosed (11 points): The Earth is travelling around the center of the Milky Way (which is -8200 parsecs away) w

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3 Mass Enclosed 11 Points The Earth Is Travelling Around The Center Of The Milky Way Which Is 8200 Parsecs Away W 1 (400.91 KiB) Viewed 37 times

3. Mass Enclosed (11 points): The Earth is travelling around the center of the Milky Way (which is -8200 parsecs away) with an orbital speed of around 220 km/s. Estimate the mass enclosed out to the position of the Earth if the Milky Way system is described by: a. A Kuzmin disk with a scale radius of a=5000 parsecs. b. A massless disk in a spherically symmetric dark matter halo. C. Given that the total mass of the stars and gas in the Milky Way within the Earth's orbit is about 4x1010 solar masses, about what fraction of the Milky Way's mass within Earth's orbit is dark matter? You may use either of your answers to part a or b, both of which are hopefully larger than 4x1010 solar masses. [Extra credit for 1 point: explain which model from parts a & b is the better one to use.]