Starship Asterisk*

Your understanding of the physics is correct (I'd say it a little differently, that the orbit radius is a function of orbital speed). The reason that Prometheus has a greater orbital speed than the F-ring is because it is closer to Saturn. In fact, the inner F-ring is orbiting faster than the outer...

Even though Prometheus is vastly larger than the particles that make up the F-ring I don't understand how it is that they orbit at different speeds. I thought that orbital speed was a function of altitude but not mass. Can somebody explain this to me? Thanks in advance. http://apod.nasa.gov/apod/ap0...