Stuff already at Lagrangia?

Good question. A friend of mine with a Masters degree in astronomy had
this to say about your question:

"
My back-of-the-envelope calculation goes like this:

The full moon has a visible-light magnitude = -12.
HST can detect objects as faint as magnitude 28 (maybe fainter, but this
is a reasonable limit).
Magnitude differential = 40 magnitudes.
5 magnitudes = factor of 100 intensity difference, so 40 magnitudes =
100^8 = 10^16.
Assume the reflectivities of the moon and the small rock are the same.
This gives Moon Cross-Section/Rock Cross-Section = pi*R^2/pi*r^2 = (R/r)
^2
= 10^16.
Therefore, R/r = 10^8
R = 1086 miles. so r = 1.086(10^3)(10^-8)= 1.086(10^-5) mile = 0.69
inch.

So, the limit of visibility would seem to be about 1-2 inches in
diameter.
This calculation assumes that you could track the rock perfectly for
several
hours to build up enough photons to achieve the mag 28 detection limit.
If this is not possible, then the required object size could be an order
of magnitude larger. In this case, 1-2 feet would be a reasonable
detection
limit.

"

That is, if there were rocks 1-2 feet in diameter floating about in those
bean-shaped orbits about L4 or L5, then we should be able to detect them
with Hubble.

But whether or not Hubble has ever been tasked to address this question , I
do not know.

Ron Menich

"Xenophile"
ssi_list@...
08/29/01 01:26
AM
Please respond
to ssi_list

It seems reasonable that, from time to time, something soars through
one or another of the L points. And since anything put at L4 or L5
tends to stay there, some of it may be there waiting for us. Sure,
if it came in at 100,000 KmPH, it wouldn't stick around, but might
things arrive more gently at times? This could be a wonderful
resourse (or the mother of all traffic hazards).

So is there stuff already there that can be used? Is it worth trying
to find out, or would we already know if it were there? Could there
be only a collection of things smaller than rice grains, in which
case it may not be worth it to track it down, much less recover it,
even if it all adds up to hundreds of thousands of tons? Or could
there be 10,000 ton chunks of metal and silicates and volatiles?

Xenophile (who likes the ida a lot)