Chapter 18, Problem 45EAP

To determine

Draw the graph that shows orbital speed depends on the distance from the galactic center for each of the following three hypothetical galaxies.

a. a galaxy with all its mass concentrated at its center

b. a galaxy with a constant mass density within 20,000 light- years of its center, and zero density beyond that distance

c. a galaxy with constant mass density within 20,000 light- years of its center, and beyond that an enclosed mass that increases proportionally to the distance from the center