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Re: (meteorobs) An unknown meteor storm seen in Finland in the 1960's



In a message dated 12/10/02 1:25:00 AM Eastern Standard Time, 
Esko.Lyytinen@MINEDU.FI writes:

<< I now have received another observation of this strom. Also this has not
 a good timing, but most probably restricts the years to 1966 or 1967 and
 and would probably suit for the Draconids/Giacobinids. >>

In regard to the positioning of the Giacobinid parent comet 
(21P/Giacobini-Zinner), I find that in 1966, the Earth crossed the descending 
node of the comet on October 9.954 UT.  That's 190.7 days after the comet 
itself resided at the nodal crossing point. The distance between the Earth 
and comet orbit was -0.0621 a.u. (inside of the Earth's orbit).  

Looking at these figures, one would initially rule out a possible meteor 
outburst since the Earth 
1) Followed the parent comet at a distance greater than half a year to the 
descending node
2) The relatively large distance between the orbits of Earth and the comet; 
the largest, in fact since 1900 (when the gap was -0.0617 a.u.).

However . . . these things are based solely on the old "analog" method of 
predicting meteor outbursts.  

An old dust trail diverted into a slightly different orbit might easily have 
interacted with the Earth and produced a surprise outburst. 21P itself was 
perturbed several times in the 20th century . . . I find that in February 
1910 it approached to within 1 a.u. of Jupiter, causing its perihelion 
distance to increase, bringing its orbit close enough to Earth to make 
Giacobinid showers possible.  In January 1958 the comet swept to within 0.93 
a.u. of Jupiter, pulling its orbit away from Earth.  And in September 1969 it 
made its closest Jovian pass (to within 0.58 a.u.) bringing the comet's orbit 
back to our vicinity once again.  So who is to say what perturbations Jupiter 
might have had on a particular dust trail to perhaps push it toward Earth?

Perhaps 1966 was a possible year for an unexpected outburst; 1965 might also 
be worth considering, though the Moon was practically full at the time.

Keep in mind that the numbers I cited above probably would have kept all but 
the most assiduous meteor observers inside and not watching for possible 
Giacobinid activity.  Had there been knowledge of the predictive power of the 
theory of dust trails, perhaps many more people would have been out watching 
. . . and would have seen the outburst described by Esko.

After all . . . using the old analog method, who would have been outside in 
2001 and 2002 looking for enhanced Leonid activity, with the parent comet so 
far from its node, and a full day AFTER the Earth passed the nodal crossing 
point?

-- joe rao
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