David J. Asher and Duncan I. Steel
Figure. 1. Orbit of 21P/Giacobini-Zinner showing the comet's position on 2011 October 8, and also the Minimum Orbit Intersection Distance between the cometary and Jovian orbits. The ellipse representing the comet's orbit is drawn as a thicker/thinner line above/below the ecliptic.
Outbursts and storms in the October Draconid meteor shower occur because meteroids from the parent periodic comet, 21P/Giacobini-Zinner, are not dispersed uniformly around the stream. The comet's orbital evolution has allowed meteoroidal material to be fed into the stream for the past few centuries and to be supplied for the next thousand years or more, but this depends on the nucleus continuing to be physically active. Various shower outbursts can be linked to the comet's observered activity during the past century.
Last Revised: 2012 October 10th