Quote:
Originally Posted by grav
What is the speed of rotation of stars close to the center of a galaxy? Is the acceleration close to the center inversely proportional to the square of the distance from the center? Approximately how is the mass distributed across the radius?
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The small figure on the right on
this page answers all those questions, I think. It shows the rotation speed close to the center of a typical spiral is on or near what one would expect - based on what mass we can detect using the entire electromagnetic spectrum.... Then the observations, uh, diverge from that expectation.
The rotation curve traces how the mass is distributed across the radius, assuming that mass acts in an inverse-square fashion.