THE LEONID METEOR-SHOWER - WHY ARE THERE STORMS BUT NO REGULAR ANNUALACTIVITY

The Leonid meteor shower is the most famous meteor shower of all time. The main characteristics of the stream are well known, being very spe ctacular displays of meteors occurring on numerous occasions when the parent comet, 55P/Tempel-Tuttle, is close to perihelion. Since there i s a perihelion passage of the comet due on 1998 February 28, it is a t opic of intense interest to predict whether or not a spectacular displ ay will be seen in 1998 or 1999. It is not, however, the primary purpo se of this presentation to make predictions regarding this event, but rather to address an equally interesting problem related to the Leonid s, which is: why do we not see even a moderate display like those of t he Orionids or the Geminids in years when the parent comet is far from perihelion? We suggest that the gravitational perturbations from the planet Uranus, resulting from a particular set of geometrical circumst ances that have been present over the last two thousand years, but whi ch will come to an end in AD 2160, have been responsible.