Available from UMI in association with The British Library. Requires signed TDF. The aim of this work is to produce quite a detailed model, consistent with observations, of the evolution of the Taurid complex of interplanetary objects. The Taurids do not produce a spectacular meteor shower but the great breadth of the Taurid stream means that it is a major stream with regard to amount of material. The real size of the stream is evidenced by the fact that the activity lasts at least three months at both relevant times of year. As observations have been done over the years, new names have been given to showers coming from different longitudes in the sky, the Taurids not having as localised a radiant as many of the well-known and more compact streams. But despite the fact that the orbits of meteors in the various showers are comparatively spread out, they are still well enough aligned, and of similar size and shape, that they must be related (i.e. have a common origin). Around three quarters of meteors are sporadic rather than belonging to well-defined streams, although the dividing line is not clear-cut--perhaps 20% of meteors sometimes classified as sporadic actually occur as part of minor showers. The sporadic meteoroids move on similar orbits to meteoroids that are part of what is generally recognised as the Taurid stream, but there is a somewhat greater dispersion of elements in the sporadic stream. We point out the existence of an apex (AP) source which dominates for fainter (10th magnitude, say) meteors. There is a tendency for larger orbits in the Taurid stream to be at greater longitudes (cf. trends with longitude calculated by Stohl & Porubcan 1990). This is because of the differential effect of Jupiter on the rate of longitude precession on orbits of different sizes. We shall see that this dispersal in longitude is associated with a timescale of ~10 kyr (1 kyr = 1000 years). One of the main questions will be the mechanism for generating the range in size of orbits (which then undergo differential precession due to Jupiter). We shall see that the distribution of Taurid meteor orbits as detected by photography and radar is best explained by a model in which large cometary fragments split from the parent object (the Encke progenitor) at perihelion and these fragments then undergo catastrophic collisions with objects in the asteroid belt. (Abstract shortened by UMI.).
- Pub Date:
- Physics: Astronomy and Astrophysics;
- Sporadic Meteoroids;
- Taurid Meteoroids;