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Re: (meteorobs) Ursids: no outburst seen from France



> I also had a little question: Why do Ursids outbursts hapenned six years
> after the comet Tuttle reached perihelion whereas the Leonids whose
> outbursts allways occured the year the comet passes closed the Sun?

Unlike the Leonid situation, fresh trails from  P/Tuttle are too far 
away from the earth orbit for any close encounter. However, with the 
centuries perturbations by the  large planets and tend to press them 
a bit inward, so that they can encounter earth. This takes about 6 
centuries. During this long time, even slow particles are nearly 
spread around the whole orbit, and it just requires one of these rare 
narrow encounters with a trail to get an outburst  - and it is not 
important that the comet is nearby . Many particles, including this 
year's, are also trapped in a resonance effect with Jupiter, which 
concentrates them a bit in a certain part of the trail. This part is 
nearly opposite of the current position of the comet in its orbit. 

Hartwig
H. Luethen
h.luthen@botanik.uni-hamburgdot de
priv: Behnstr. 13, D-22767 Hamburg
lab: Institut fuer Allgemeine Botanik, Ohnhorststr. 18
     D-22609 Hamburg, Germany
Tel: 0049 (0)40-3800551 priv
     0049 (0)40-428-16-346



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