The structure of the Geminid meteor stream - I. The effect of planetary perturbations

The gravitational perturbations of the Geminid stream have been studied using a very simplified model in which Jupiter causes the only perturbation of an initially very well defined stream. In this way the effects of the gravitational perturbations are not obscured by the many other factors that influence the real stream. The results of extensive calculations of the evolution of the orbits of 71 meteoroids in Geminid-like orbits over a period of 5000 yr are presented. The complex of orbits so produced was found to lie on the surface of a torus flattened approximately parallel with the plane of the ecliptic. Visual observations of the shower show a strong suggestion of a secondary peak in the meteor activity curve at about $${0.8}^{\circ}$$ in solar longitude after the main shower maximum which would imply a probable age of about 6000 yr for the stream. The hollow stream resulting from planetary perturbations seems to provide an attractive explanation for the twin branches of the Taurid, delta-Aquarid and Piscid showers.