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Re: (meteorobs) Question.......
John,
The Leonids are not unique in producing storms or outbursts from dust
trails. Reznikov has demonstrated this for dust trails of the Draconids
(comet Giacobini-Zinner), Andromedids (comet Beila) and the June Bootids
(comet Pons-Winnecke). The issue is not the age of the comet, but the age
of the dust trails. With all these comets studied, they are currently in,
or have recently gone through, periods of close approaches to the Earth's
orbit. The dust trails laid down during each orbit are then likely to
also pass close to the Earth's orbit. Whereas the comet can be
perturbed away from a close approach, the portions of the dust trails
separated from the comet can remain unperturbed and continue to give
outbursts when the comet no longer has close approaches. The converse is
also true; a portion of a dust trail can be perturbed into an Earth-
intersecting orbit and produce a shower or storm, when the parent comet is
not and may never have been in an Earth-intersecting orbit.
With time, the dust trails dissipate and merge into the background which
then becomes the annual streams.
Robert H. McNaught
rmn@aaocbn.aaodot gov.au
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