The Perseids celestial fireworks

A bright shooting star is one of the most breathtaking sights in the night sky. What makes it all the more delightful is the fact that the observer

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happened to be looking in the right place at the right time when the unexpected event occurred.

Centuries ago, however, a meteoric display was an unwelcome sight, especially to people in power, because in most cases, a meteor was considered an ill omen that reflected on kings and military leaders. SirJames Frazer in his book The Golden Bough tells us that the reign of many ancient Greekkingswas limited to eightyears. The practice was founded on the belief that at the end of every eight-year period 'a new consecration, a fresh outpouring of the divine grace, was regarded as necessaryin order to enable [kings] to discharge their civil and religious duties.' As part of the Spartan constitution, therefore, it was required that every eighth year, the ephors - the five Spartan magistrates who had power over the king - would choose a clear, moonless night to observe the sky.

If a meteor was seen during their vigil, they construed that the king had sinned against the deity, and suspended him from his functions.

Apparently, the practice lasted for centuries. Today few people would profess belief in the divinatory power of shooting stars. For those that do, however, the sky this week will be crisscrossed with celestial portents in the form of the Perseid meteor shower. This is probably not a good week to be king.

The after-midnight hours leading up to dawn on August 12 are usually the prime window to view the annual Perseid meteor shower. Hopefully, there won't be a bright Moon in the sky to interfere with the fainter meteors. But even if there is, you may still be able to see several of the the brighter ones flashing across the sky.

The Perseid shower is one of the most popular meteor displays of the year. One reason is because it occurs during high summer when people are more apt to be outside doing a little stargazing. The real reason for its popularity, however, is because of its activity. It was, in fact, once considered the finest of the annual meteor showers, although in recent years it has been edged out slightly by the Geminid shower, which occurs in December. (See December 6 - 12.) Nonetheless, the Perseids typically exhibit a large number of bright meteors, several of which may explode spectacularly or fragment and leave brief smoke trails (also known as smoke 'trains'). The brightest of the Perseids can be brighter than the brightest stars in the sky.

Given local sky conditions (the degree of light pollution and cloudiness) it's difficult to predict exactly how many meteors you may see. If there is no bright Moon in the sky at the time, you should be able to see between 20 and 30 meteors per hour in the predawn sky on the 12th. At that time, the radiant is overhead. If you trace the paths of these meteors backwards they should lead you to this location in the sky, which lies just northeast of the Double Cluster in the constellation Perseus.

The Perseids consist of the debris left over from Comet Swift-Tuttle, first seen in 1862. Astronomers determined that the comet had a period of 120 years, meaning that it should return to our part of the solar system every 120 years. Swift-Tuttle did not, however, return as expected in 1982, nor was it seen in the years following. In 1991, the Perseids put on a stronger showing than in previous years, leading some to speculate that the comet would return in 1992. Indeed, the comet passed near the Sun in December of that year and the August 1993 display was one of the most active of the century.

Don't be disappointed if your sky is cloudy the morning of the 12th. Because the shower is active over a period of about a month, the week before and the week after the peak should also be good for meteor watching. Go out in the early morning hours (4 a.m. to dawn may be the best time) and look overhead and toward the northeast. Use a reclining chair or sleeping bag, lie back, and catch a few falling stars.

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