Move over, Barnum & Bailey. The Greatest Show this summer is in the night sky.
Perseid, the granddaddy of meteor showers, is in the midst of a month-long run and will reach a peak rate of some 60 meteors per hour this weekend.
"The Perseids is the most faithful meteor shower every year; you are guaranteed to see some," says Brian Marsden, a cometary scientist at the Harvard-Smithsonian Center for Astrophysics. "And it has the advantage of occurring in August, when it's warm. You don't have to go out in the middle of winter as you do in order to see the Leonid meteors."
Indeed, the Perseid meteor shower is one of summer's cheap thrills. All you need to enjoy it is a lawn chair, bug spray, and, preferably, a good night's sleep the evening before, since the best viewing hours are between midnight and dawn's early light.
The Perseids (pronounced purr-see-ids) are named after the constellation Perseus, from which the bright streaks of light appear to originate, although the meteors have nothing to do with the distant star formation.
The meteors are attributable instead to the comet Swift-Tuttle, which takes a hairpin turn around the sun every 130 years. When Earth intersects the orbital path of Swift-Tuttle, it runs into debris from the cosmic litterbug that has accumulated over eons.
The term meteor "shower" can be a bit deceptive. "They're not going to be coming down like snowflakes," says Mr. Marsden, over the phone from an office about 30 feet from the spot where Horace Tuttle co-discovered Swift-Tuttle on the Harvard campus in 1862.
Meteors aren't exactly the kind of oversize rock Bruce Willis might lead a crack team of demolition experts into space to destroy. In the case of Perseids, the "meteor" part of meteor showers can be a bit deceptive, too. They are generally the size of a fleck of dust and rarely larger than a pea.
It is believed that no Perseids particle has ever reached Earth's surface.
Nevertheless, speeds of up to 13 to 14 miles per second (50,000 miles per hour), combined with friction from contact with the earth's atmosphere, turns the comet dust into nature's version of fireworks.
Although the meteors will likely average one per minute at their peak, astronomers warn that many are faint and that they often clump, so that 15 meteors might appear in a five-minute stretch.
Gary Kronk, a serious amateur astronomer from St. Louis, has written three books on comets and meteors and observed Perseids each year since 1974.
He recommends first-time viewers pick a spot that is free from intrusive lights and buildings or trees which might block the sky, and then lay a lounge chair flat in order to see as much of the cosmos as possible.
Mr. Kronk advises against looking directly at the constellation of Perseus in the northeast sky, which is known as the "radiant," the apparent source of the meteors. Focusing there, observers have a tendency to miss faint meteors elsewhere in the broad sky. The solar system's chief source of light pollution - our moon - will be three-quarters tomorrow night and brighten the sky enough to set connoisseurs to complaining.
"The Perseids are probably the best meteor shower to introduce anybody to," says Kronk. "The reason why is they're consistent from year to year. If you get outside the city, you're going to see 60 to 80 meteors per hour pretty easily."
"The peak of the shower is a little different this year," he adds. "It will actually occur over the United States, so that will help people catch a few more meteors than normal."