# If measuring out to the last datapoint, what is the total mass of the galaxies NGC 2403, UGC 128, and M33.

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At enotes, the educators can not solve the assignments for you, rather we provide a helping hand and enough information to get you started on the right path. Following the same ethics, I will solve one of the parts for you, so that you can use it as an example and solve the rest of the question yourself.

The total mass of the galaxies can be calculated by the following equation:

Mass, M = r x v^2 / G,

where, M: mass of galaxy

r: distance from the center

v: orbital velocity

To calculate total mass to the last datapoint, we need the rotation curves of each of these galaxies. The rotation curve of NGC2403 is available here (http://burro.astr.cwru.edu/JavaLab/RotcurveWeb/main_BACK.html) and we get the parameters:

r = 15,000 pc; and v ~ 135 km/s and G = 4.43 x 10^-3, we get,

M (NGC2403) = 15000 x 135 x 135/(4.43 x 10^-3) = **6.17 x 10^10 Solar MassesĀ **

Hope this helps.