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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gsenviro eNotes educator| Certified Educator

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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.