研究発表

Analytical solution is derived for the secular motions of spin-down tops, which keep contact with a fixed point. It predicts the change of the spin-axis orientation and precession rate when the spin slows down due to frictions, which agree well with the numerical simulation of the full Euler’s angular-momentum equations. Especially, it finds their asymptotic limits when the spin rate goes to zero. Similar analytical solutions are also obtained for the secular motions of planets, whose oblatenesses are assumed to be the only factors to cause the moments by the gravity of Sun. According to them, their obliquities (the spin-axis orientations) are very stable for long time, as is true for the spinning tops.