P GIACOBINI-ZINNER AND THE DRACONID METEOR-SHOWER/

The two most spectacular meteor showers in the present century were pr obably the Draconid showers of 1933 and 1946. Lesser showers were also observed in 1926, 1952 and 1985 but none in other years. All the obse rved showers occurred when the parent comet, comet Giacobini-Zinner wi th a period of about 6.5 yr, was close to the Earth, leading naturally to the suggestion that the stream is young with meteoroids mostly loc ated close to the parent comet. An interesting question remains, howev er-why showers only occurred in some of the years when the comet was c lose to the Earth and why a much higher level of activity occurred in 1933 and 1946. We analyse the data on the observed showers and investi gate the dynamical behaviour of the Draconid meteoroid stream by means of a computer simulation. Five hundred large meteoroids (0.25 cm) and 500 small meteoroids (0.03 cm) were ejected at each perihelion passag e of comet Giacobini-Zinner from 1900 to 1985 and their equations of m otion were integrated forward to 1985 (the last well recorded shower). The cross-section of the stream in the ecliptic and the profile of th e stream are analysed. We conclude that the best agreement between obs ervation and theory is obtained if the meteoroids producing the shower are very young, released from the comet at that apparition.