The bone bleaching heat of August drives many of us indoors. Even the bravest only venture out of the cool comfort of air conditioning for a few moments; and it seems that the evenings offer little or no comfort. During such heat waves many people seek refreshment in the cool of a swimming pool, a bath tub or a shower. As it turns out, August is a perfect time to get outdoors and experience a shower of a different nature; in this case the 2008 Perseid meteor shower.
While meteors can be seen almost anytime, meteor showers are special occasions. Meteor showers occur when Earth passes through the debris trail left by a passing comet. In the case of the Perseid meteor shower, Earth is passing through the dusty trail left by Comet Swift-Tuttle. The comet itself is far beyond the orbit of Uranus, yet its debris trail stretches back as far as Earth. Earth passes through this trail every year in early to mid August. As Earth rotates through the debris field tiny bits of dust and rock slam into our atmosphere at over 130,000 miles per hour. As the meteors fall through the dense air they heat up and glow, leaving a bright streak behind them. The name of the meteor shower comes from the constellation from which the meteors appear to radiate, called the radiant; in this case the constellation Perseus the Hero. The point at which Earth passes through the greatest density of debris from the comet is called the peak.
The peak for the Perseid occurs on the night of August 11th and 12th; that is the greatest concentration of visible meteors will be seen before dawn on the morning of the 12th. Observers wanting to see the greatest number of meteors will want to find a nice, dark location away from city lights. Use lounge chairs or pic-nic blankets to avoid neck strain and look up. Perseus will rise above the northeastern horizon after 9:00 pm, but the best part of the show occurs after the gibbous moon has set, after 2:00 am.
The best meteors of the Perseid are the slow, colorful “Earthgrazers”. These are meteors that strike Earth’s atmosphere edge on, rather like skipping a rock across a lake. While these meteors are spectacular they are rare. Observers may see fewer than one of these an hour, but their brightness and long tails make them well worth the wait. Other meteors of the Perseid will appear as short lived, faint trails of light.
While watching for the Perseid peak there are plenty of other objects to occupy the observer. The most obvious is the planet Jupiter in the constellation Sagittarius. Jupiter is the very bright object almost due south to the left of the gibbous moon. Almost the same distance the right of the moon is the star Antares in the constellation Scorpius the Scorpion. Overhead, the stars Vega, Altair and Deneb outline the Summer Triangle. These stars are also the brightest stars in the constellations Lyra the Harp, Aquila the Eagle, and Cygnus the Swan.
August is sometimes called the “Dog Days of Summer” because of the stifling heat. Yet after the sun goes down and the land begins to cool the sky calls to us. It invites us to come out and look up at the stars, the planets, and most of all, the Perseid meteor shower.