Cosmogony of the asteroidal belt

WE have to derive the state of partial corotation in a way which, by being very simple, stresses its character as a basic state in cosmic plasma dynamics. We also substitute the mass density (m, a) for the number density (n, a) in the plot of asteroids, as a function of their semimajor axis a. This gives a better definition to the limits of the main belt, and demonstrates more clearly that the asteroids-like the Saturnian rings-have condensed from a partially corotating plasma.