From: Amara Graps (amara@amara.com)
Date: Wed Nov 20 2002 - 13:56:15 MST
Hal Finney:
>I don't know if it was just the bright moon washing out the dimmer meteors,
>or if the predicted rates of 3000-6000 per hour were vast exaggerations.
The moon was almost full, which had something to do with it. However 'vast
exaggerations' is not really fair. The scientists making the predictions had a
model that gave meteor rates. This year, the rates were 1/3, or less, of
the predictions. The (sophisticated) Leonids models had been getting better
and better at matching data, up to now.
Take a look at some of the differences in the models
http://leonid.arc.nasa.gov/1998.html
"WHY DO PREDICTIONS DIFFER?
Asher & McNaught assume mild ejection from comet at perihelion in
forward direction of motion - following Reznikov & Kondrat'eva.
Lyytinen assumes release at perihelion (no ejection), but continued
broadening and acceleration at perihelion due to radiation pressure
effects. Vaubaillon has built a theoretical model based on numerous
dynamically diverse meteoroids. Jenniskens derived trail positions
from recent Leonid MAC observations and finds systematic shifts
(ejection towards the Sun), and no significant broadening of showers
over time."
Therefore, while it is sad for all of the people who did not see a
show, it means that there _might_ be some new physics, that wasn't
included in the models before. That's really interesting.
Amara
-- through December 2002: Max-Planck-Institut für Kernphysik, Cosmic Dust Group, Heidelberg, Deutschland from January 2003: Consiglio Nazionale delle Ricerche, Istituto di Fisica dello Spazio Interplanetario, Roma, Italia
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