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RE: (meteorobs) Xi Draconids' velocity
Hi meteor speed theorists,
>Thank you, Gary, for clarifying the velocity stuff. The radiant of the
>xi-Draconids is about 83 degrees from the apex. The fastest meteoroids producing
>a radiant at 90 degrees apex distance can have geocentric velocities up to 30
>km/s. sqrt(42^2-30^2). The xi-Draconids should be slightly faster (~33 km/s)
>when from this solar system. Hence, I would judge that George's and Bob's
>meteors are spurious alignments, but how to explain the outburst observed by
>Marco Langbroek who reports medium to fast speeds?
>
>Rainer
>
Here is one possible explanation: We are not used very well to shower radiants near the zenit (as
for the Ksi Draconids at 50 degrees northern latitude). For a radiant near the zenit, a meteor at 20
degrees from the radiant moves at a higher angular velocity than a meteor from a radiant at an
elevation of 40 degrees. Just because the meteor is closer to the observer. This could be an
explanation why observers of a possibly existing Ksi Draconid radiant overestimate the velocity of
its meteors.
Two further remarks:
1. My argument does not hold for meteors far from the radiant.
2. I say Ksi Draconids instead of Xi Draconids, because Xi could be misread for Chi.
Bye,
Marc
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Marc de Lignie
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Predicted progress always fails. Real progress is all the small
steps you realize to have made when looking back in time.
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