Shooting stars are not, of course, really stars.
They are actually small bits of rock and metal that collide with Earth’s
upper atmosphere and, because of friction, burn up. On rare occasions,
man-made satellites and spacecraft parts fall into the atmosphere and burn
up the same way. The flash of tight from this incineration is correctly
called a meteor. A meteor is formed when an object, usually the size of
a marble or a piece of popcorn, hits the atmosphere at an altitude of 80
to 100 kilometers (50 to 62 miles). The air at that height is very thin
but the objects are moving at tens of thousands of kilometers per hour.
Larger objects do not burn up completely. Surviving fragments fall
through the atmosphere and land on Earth. Once one of these objects lands
it is called a meteorite. Most meteorites fall into Earths oceans. Meteorites
can be either rock, metal (nickel and iron) or a mixture of both. Stony
meteorites are difficult to identify. They do not glow or give off radioactivity.
Stones outnumber metals.
But metallic meteorites are easier to find. Rarely
are chunks of metal found lying about. A metal detector can be used to
search for metallic meteorites. Dry barren areas where there is little
vegetation to cover up the ground and turn over the soil are the best.
Dry lake beds are good places to search because wind can blow dust off
of the surface, leaving the meteorites exposed. Many meteorites are found
on the Antarctic ice sheet.
There is an easy way to collect meteorites, but
we must be satisfied with finding small metal ones. They are actually microscopic
and are known as micrometeorites. Tons of these fall on Earth each day.
To collect micrometeorites you need to find a place where they can become
concentrated. The drains of a house or building work well since rainwater
can wash particles off of an entire roof and collect them at the drain
spout. Tile roofs are best since they drain very well and do not produce
many’ other sorts of particles or debris.
But dust, plants. pieces of window screens and all other sorts of airborne
material also collect there. To find the metallic micrometeorites, collect
and dry some of the material from a deep howl at the base of the drain
spout. After removing leaves and other debris, place the remaining material
on a piece of paper and place a magnet under the paper. Tilt and tap the
paper so that all of the non-metallic particles fall off Many of the remaining
metallic particles are pieces of space dust! To examine them, place the
paper under a microscope. High power will be required to see them clearly.
Most of the particles are not from space, but the micrometeorites will
show signs of their fiery trip through the atmosphere. They will be rounded
and may have small pits on their surfaces.
Much of what you are observing are particles that date from the formation
of the solar system around 4.6 billion years ago! They are the debris remaining
from the raw materials that formed into the nine known planets and the
asteroids. Most particles have been broken off or ground down from larger
objects.