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Re: (meteorobs) Excerpts from "CCNet 123/2001 - 22 November 2001"
Robert, let's walk through some numbers here. First, it should be obvious
that only the very largest Leonids that hit the moon are visible from Earth.
After all, an astronomer with a high-powered telescope can cover the entire
dark surface of the moon in a single view, which is several thousand square
miles of surface -- roughly ten times as much area as an observer on Earth
can cover. So, this person should be able to see ten times as many meteors.
Yet we know that he sees very few -- obviously he is seeing the very biggest
Leonids. Now, let's just say that the very biggest Leonid ever seen is about
magnitude -8. If it it were a hundred times further away than normal, it
would appear to be 10 magnitudes fainter -- about magnitude 2. This would be
visible in a telescope -- but it would be an extremely rare event. Of
course, I'm assuming that the conversion of energy into light with a lunar
impact is identical to the conversion of energy into light from an
atmospheric impact, which is unlikely. My hunch is, the lunar impact would
have a smaller percentage of its energy converted to visible light.
Therefore, the flash would be fainter than magnitude 2 -- but even with a
conversion efficiency of 1%, that Leonid would still be about magnitude 7,
definitely visible with a telescope. That gives us plenty of leeway to
believe that the lunar impacts are caused by regular old Leonids -- albeit
very big ones.
Chris
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