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(meteorobs) Smallest size of meteors
JeffGos@netzerodot net writes:
> Please define the size of shooting stars for me. I have a friend that
> believes they are large chunks of matter, whereas, I believe they are the
> size of grains of sand. Thanks for your help.
Jeff, you can tell Zinta that you are BOTH correct: if you are arguing about the
SMALLEST meteors which can be seen with the unaided eye from the ground, then
the answer is in fact "a smallish sand-grain". However, this depends very
heavily on other factors besides size! Read on...
First off, most meteoroids are far more likely to be the consistency of a tiny
dust-bunny (less dense than water) than a silicate grain. A bit of such fluff
the size of a sand grain would be invisible to the unaided eye if it were moving
SLOWLY relative to the earth - for example, 30 kilometers per second or less. In
that case, you might need a fist-sized ball of celestial cotton candy in order
for it to be large enough to be seen without enhancement.
However, if the debris were from say, the Leonid meteor stream, moving at *71*
kilometers per second relative to Earth, then a good grain-sized meteor would be
readily visible, while a fist-sized object from this stream might appear as
bright as the brighter stars in the sky!
By the same token, a bit of SOLID debris - denser than water, unlike most
"fluffy" cometary meteors - could be much smaller and still be seen: one
traveling 72 km/sec might be invisible without a microscope if found in space,
but would still cause a meteor bright enough to be seen on the ground!
So again, meteoroid size is just one determinant of meteor brightness: the other
important factors to consider are geocentric velocity and density!
Hope this settles your bet. :) Clear skies,
Lew Gramer <owner-meteorobs@jovian.com>
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