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(meteorobs) Radiant angular size: how come?
While just perusing the (snazzy, newly updated!) IMO Visual Meteor Observing
pages on the World Wide Web, I came on the following item:
"Due to perturbations and different ejection conditions from their parent
object, the individual particles of a meteor shower do not move on exactly the
same orbit. Thus they do not all enter the atmosphere exactly parallel to one
another. The result of this is that a radiant is not a point but an area of a
certain size whose dimensions depend on how widely the individual orbits are
spread, and on the geometrical conditions of how the stream encounters the
Earth, and thus differs from shower to shower (Kresak & Porubcan, 1970)."
What confuses me about this is that I know (from other AMS and IMO publications)
that meteoroids' orbits are actually GREATLY perturbed from their original
source body's orbit, due to solar wind, planetary perturbations, etc., etc.
So in spite of the fact that meteoroids may end up in "Apollo-like" orbits, even
when they originate from hyperbolic-orbit comets, does the tiny initial velocity
each one has relative to its parent body REALLY get preserved long enough to
show up as a radiant dispersion?! Or is there some other effect (like time
variations in solar output, or tiny-scale tidal effects on the stream, whatever)
that results in more like a poisson distribution over a given radiant area?
Just a curious question from a theoretical wannabe,
Lew