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(meteorobs) High-velocity meteors!
>I'm also trying to find out just which nite would there be an increase in
>sporadic activity...if there is any nites that would show a distinct upswing of
>activity?
This reminded me of a write-up I noticed in the August Sky&Telescope just before
I got sick last week... The AMOR group in New Zealand does radar meteor studies
that catch meteors down to equivalent visual magnitude 13. They found that some
*fourteen percent* of the observed meteors had heliocentric velocities in excess
of 72 km/s - fast enough for hyperbolic orbits!
They theorize that many of these hyperbolic-orbit meteoroids were entering the
solar system from streams related to nearby spectral-class-A stars, and others
were the result of the sun's motion around the galactic hub taking it into
clouds of particles associated with the local spiral arm. (Kind of neat, huh?)
I haven't been able to follow up the original article in _Nature_ yet, so I
don't know how these rates might theoretically compare to those for brighter
magnitude classes. (Is it valid to say that interstellar particles are of
generally smaller average size than interplanetary meteoroids??) But I wondered
how this activity might relate to seasonal variations in sporadic rates? Also
made me question the logic of assuming 72 km/s as a practical maximum for
visually observed meteors. Again, it may still be valid, if the number of these
super-fast meteors decreases fast enough with increasing size... Also, it may be
a moot point if no discernible streams can be distinguished among these
"extrasolar" particles. Made me ponder enough to post the question, though...
Clear skies,
Lew
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