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Re: (meteorobs) Fwd: How fast do Meteors go?
Kim Youmans wrote:
>I don't get how speed is the most important factor... In other words,
>all things being equal (read: speed) size/composition [really, mass]
>is the factor that influences brightness.
No, Kim, what you say is absolutely right. But the critical part of what you
wrote is "speed being equal". In other words, the point is that velocity IS
(usually) the most important factor in a meteor's intrinsic brightness. But
if two meteoroids are known to have the SAME velocity (as would be the case
if both are from the same stream), then mass is usually NEXT most important.
After all, to make a pi-Puppid as bright as a Leonid (at the same incidence
angle and observer distance), the pi-Puppid needs to be 16 times as massive!
HEAVY MATH ALERT...
Actually, the most correct statement from Marco's formula, seems to be that
mass is second most import, if we assume zenith distance isn't TOO close to
zero degrees! In the limit where h tends to 0, the value of log(sin(h)) will
become a large negative number after a while: then both the velocity & mass
will eventually become unimportant to luminosity! Marco, I assume from this
fact, that the equation you posted is actually an empirical approximation,
and must be replaced for meteoroids nearly parallel to Earth's atmosphere?
Or maybe my transcription of the original equation is just snafu!
I also notice that there are second order terms, i.e., the equation shows m
as a function of itself. I'll take a stab in the dark and say this term is
there to take into account the fact, among other things, that a "slow-ish"
meteor will NEVER actually be close to tangent with the Earth? Or in other
words, that slower meteors have more curved paths due to Earth's gravity??
END OF HEAVY MATH ALERT...
Well, like I said in the other post I just sent out, I'm gonna hope for
the meteor science "Bibles" at home to come to my rescue on this one! :)
Clear skies and clear equations,
Lew
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