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By Nash Black
We see them in the night sky as meteorite showers (falling stars), especially if we have a telescope to hand. Early on when they were first discovered by Giuseppe Piazzi on January 1, 1801 they were referred to as minor planets. He named his discovery Ceres after the Greek goddess of motherhood and agriculture.
Over the next eighty-five or so years the number of the originally so called new planets had risen to over 100,000. After 1845 they were no longer spoken of as minor planets but as asteroids. Nor were they named after classical goddesses.
Today they are closely monitored because it is recognized that earth-crossed asteroids pose a threat to life here. Off the coast of North & South Caroline there is evidence of a large hole where an ancient asteroid vanished into the sea. The same is true of the beautiful Crater Lake in Oregon. There is strong evidence to support the theory that the dinosaurs vanished due to an asteroid colliding with the earth.
What is an asteroid? The best description is a ‘hunk of rock.’ They exist in a Belt orbit mainly between Jupiter and Mars. Are they the remains of a former planet that exploded back millions of years ago – no one knows. The major part of the belt is empty space. Their distance from the sun is 2.06 to 3.37 AUs. An AU equals an Astronomical Unit or the average distance of the sun to the earth or about 93 million miles.
Asteroids take many shapes, few are round and those are small bits. Some are shaped like potatoes with craters. Hundreds have moons like ours, about seventy so around the main belt of asteroids including five that have two satellites.
Amor and its brethren asteroids, of which about 1200 are know, pack the greatest danger to earth. The famous Amor, 433 Eros was the first asteroid to be orbited. In 2001 it was landed upon by NASA’s Near Shoemaker probe.
Apollo asteroids move mainly outside the earth’s orbit, but their belt does cross our path from the outside in. One entering our atmosphere caused the Great Daylight Fireball of 1972 meteor.
For a short time in December 2004 an Aten asteroid seemed to posed a threat of hitting the earth or moon on Friday, April 13th. A small probability for the next estimated date is in 2036. These are projections from astronomers, what will happen remains to be seen as the orbits of asteroids are seldom static, but vary for a considerable distance.
On the up side is the idea that millions of years ago cosmic collisions may have created our protective, stabilizing moon and made life possible here on earth.