On the night of August 11th, turn off your TV, log off your PC, forget the presidential election, and head for the hills! If the skies are dark and clear, you will be treated to a grand celestial display: the Perseid meteor shower. Take your family or friends to a state park or a highway winding through the countryside, anywhere away from urban illumination. After 9pm, face northeast and look for streaks of light in the night firmament. If the conditions are right, you will see what is usually the Northern Hemisphere's best meteor shower of the year (also called the Perseids), in which shooting stars flash across the heavens at a rate of fifty to a hundred per hour. It is a spectacular show and, for those of us who are enthralled by the universe, a cosmic experience.
The Perseids occur every year at about this time, and gain their name from the Perseus constellation, as the shooting stars radiate from that area of the sky. In actuality, the meteors are born of the Swift-Tuttle comet, which passes through the inner solar system every 130 years or so (the last time in 1992), leaving a trail of grains of ice and rock in its wake. As the Earth crosses the debris trail of Swift-Tuttle, tiny fragments of metal and stone hit our atmosphere of speeds of 132,000 mph and burn up in vivid streaks of light.
The peak of the Perseids is the late night of the 11th and early morning of the 12th. When the constellation Perseus rises in the northeast at around 9pm, the show begins with "earthgrazers," meteors that "approach from the horizon and skim the atmosphere overhead like a stone skipping across the surface of a pond," according to the www.science.nasa.gov site. Earthgrazers trace long, colorful paths, and are considered by many to be the most beautiful of meteors. Alas, at 9pm this year the moon will still loom in the sky, so the earthgrazers will not be as impressive as on other occasions. In 2008, the best viewing time for the Perseids will be after the moon disappears below the horizon at 2am (this varies according to location; check your local time for the moon set on August 12). The best Perseid viewing will be from the Northern Hemisphere.
The earliest recorded accounts of Perseid activity come from Chinese annals two thousand years ago. In 1862, the America astronomers Lewis Swift and Horace Tuttle "discovered" what is now called the Swift-Tuttle comet; it was also known as "the Great Comet of 1862." Over the next two years, Italian astronomer Giovanni Schiaparelli correlated the orbit of the Perseid meteors with that of the Swift-Tuttle comet. We now know that most meteors have cometary origins (note: the rocks from space that hit the ground are called meteorites). And since comets are remnants of the formation of our solar system some 4 ½ billion years ago, the Perseids are an incandescent reminder of our world's origins.