A Spectacular Memory

Sunday, August 12th, is the peak of the annual Perseid meteor shower. A really wonderful show is expected. The Moon will be new that night, so there will not be the glare that plagued us last year. The shower will follow the constellation of Perseus, beginning with its rising in the north-eastat about 9 P.M. This is the story of this shower:

All the time, we're being bombarded by stones falling from the sky. Most are pretty small, about the size of a grain of sand. We know theyıre so small because when we see a flash of light showing that theyıre burning up in our atmosphere and we say to a friend, ³Look, a shooting star,² and our friend asks ³Where?,² the answer is always, ³Too late. You missed it.² In that moment, the grain of sand has vaporized. That flash of light is called a meteor. Only rarely is one of these rocks large enough to survive the burning and land on the earth. Then itıs called a meteorite.

Most of these " shooting stars" are random and can be seen most any night, usually from any part of the sky.

However, " meteor showers" are predictable because they're the debris left by a comet. Comets are " dirty snowballs," balls of rock and ice a few miles across. When comets enter the warm inner part of the solar system, some of the ice evaporates. The sun's light, reflected from this mist, gives us the spectacular displays.

But the ice is also the glue that holds the comet together. As the ice begins to evaporate, some of the rock and dust of the comet falls off. The more spectacular the comet, the shorter is its life.

As the Earth passes through this stream of dust, we are treated to an annual meteor shower.

A comet passed the Earth in 1862. Known as comet Swift-Tuttle, it returned in 1992, a hundred thirty years later. It will not return until 2122. However, every year the dust it left in its trail gives us the annual Perseid meteor shower. A shower of lights in the sky -- what a memory to leave behind!

(08/08/07)