Radiation pressure causes a runaway increase in this quantity for small astronomical bodies according to the YORP effect. In the Kepler problem, the centrifugal term of the effective (-5[1])potential is proportional to the square of this quantity, a fact which is derived by using this quantity to eliminate the (*) rotational velocity in the expression (10[1])for the total energy. The definition of the Laplace-Runge-Lenz vector includes (10[1])a term equal to the momentum crossed with this quantity. Kepler’s equal area law is equivalent to the conservation of this (10[1])quantity, (10[3])which is always conserved by central forces. For 10 points, (-5[1])name this vector quantity defined as the cross product of position and momentum. ■END■ (0[2])